90 results on '"Andrew B. Lassar"'
Search Results
2. Creb5 establishes the competence for Prg4 expression in articular cartilage
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Cheng-Hai Zhang, Yao Gao, Unmesh Jadhav, Han-Hwa Hung, Kristina M. Holton, Alan J. Grodzinsky, Ramesh A. Shivdasani, and Andrew B. Lassar
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Biology (General) ,QH301-705.5 - Abstract
Zhang et al. identify Creb5 as a transcription factor that is required for induction of Prg4 expression by TGFβ and EGFR ligands. They show that Creb5 directly binds to two Prg4 promoter-proximal regulatory elements, working together with a more distal regulatory element to drive induction of Prg4 by TGFβ. These findings provide new insight into the molecular regulation of Prg4 expression in superficial zone articular chondrocytes.
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- 2021
- Full Text
- View/download PDF
3. Fibroblast Growth Factor Maintains Chondrogenic Potential of Limb Bud Mesenchymal Cells by Modulating DNMT3A Recruitment
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Deepak Kumar and Andrew B. Lassar
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Biology (General) ,QH301-705.5 - Abstract
The formation of cartilage is restricted to the core of the limb bud mesenchyme by ectodermal Wnts, which can irreversibly silence expression of the prochondrogenic transcription factor Sox9. In contrast, fibroblast growth factor (FGF) signals from the apical ectodermal ridge maintain the competence of chondrogenic precursors to undergo chondrogenesis once these cells go out of the range of ectodermal Wnt signals. We have found that Wnt signals induce both a repressive chromatin mark (H3K27me3) and DNA methylation over the Sox9 promoter and that Wnt-induced irreversible silencing of the Sox9 gene requires DNA methylation of this locus, which is specifically countered by FGF signals. FGF blocks the recruitment of the de novo DNA methyltransferase, DNMT3A, to the Sox9 promoter by inducing the interaction and phosphorylation of DNMT3A by ERK1/ERK2 and thereby controls whether expression of Sox9 is either irreversibly or reversibly silenced by Wnt signals in limb bud mesenchymal cells.
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- 2014
- Full Text
- View/download PDF
4. Foxc1andFoxc2function in osteochondral progenitors for the progression through chondrocyte hypertrophy and mineralization of the primary ossification center
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Asra Almubarak, Qiuwan Zhang, Cheng-Hai Zhang, Andrew B. Lassar, Tsutomu Kume, and Fred B Berry
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Article - Abstract
The forkhead box transcription factor genesFoxc1andFoxc2are expressed in the condensing mesenchyme of the developing skeleton prior to the onset of chondrocyte differentiation. To determine the roles of these transcription factors in limb development we deleted bothFoxc1andFoxc2in lateral plate mesoderm using the Prx1-cre mouse line. Resulting compound homozygous mice died shortly after birth with exencephaly, and malformations to this sternum and limb skeleton. Notably distal limb structures were preferentially affected, with the autopods displaying reduced or absent mineralization. The radius and tibia bowed and the ulna and fibula were reduced to an unmineralized rudimentary structure. Molecular analysis revealed reduced expression of Ihh leading to reduced proliferation and delayed chondrocyte hypertrophy at E14.5. At later ages, Prx1-cre;Foxc1Δ/Δ;Foxc2Δ/Δembryos exhibited restored Ihh expression and an expanded COLX-positive hypertrophic chondrocyte region, indicating a delayed exit and impaired remodeling of the hypertrophic chondrocytes. Osteoblast differentiation and mineralization were disrupted at the osteochondral junction and in the primary ossification center (POC). Levels of OSTEOPONTIN were elevated in the POC of compound homozygous mutants, while expression of Phex was reduced, indicating that impaired OPN processing by PHEX may underlie the mineralization defect we observe. Together our findings suggest that Foxc1 and Foxc2 act at different stages of endochondral ossification. Initially these genes act during the onset of chondrogenesis leading to the formation of hypertrophic chondrocytes. At later stages Foxc1 and Foxc2 are required for remodeling of HC and for Phex expression required for mineralization of the POC.
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- 2023
5. Colchicine protects against cartilage degeneration by inhibiting MMP13 expression via PLC-γ1 phosphorylation
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Akira Hara, Haruhiko Akiyama, Andrew B. Lassar, Kentaro Takeuchi, Kazu Matsumoto, Hiroyasu Ogawa, Norishige Kuramitsu, Atsushi Goto, Keisuke Akaike, Yoshiyuki Suehara, and Hitomi Aoki
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Biomedical Engineering ,Inflammation ,Pharmacology ,Article ,Chondrocyte ,chemistry.chemical_compound ,Chondrocytes ,Rheumatology ,Matrix Metalloproteinase 13 ,Osteoarthritis ,medicine ,Animals ,Colchicine ,Orthopedics and Sports Medicine ,RNA, Messenger ,Phosphorylation ,Phospholipase C gamma ,Synovial Membrane ,Mice, Inbred C57BL ,Blot ,medicine.anatomical_structure ,chemistry ,Synovial membrane ,medicine.symptom ,Signal transduction ,Signal Transduction ,Proto-oncogene tyrosine-protein kinase Src - Abstract
Summary Objective Low molecular weight compounds that reduce the expression of MMP13 at the mRNA level might serve as disease-modifying osteoarthritis (OA) drugs (DMOADs). The objective of this study was to identify a candidate DMOAD that targets MMP13 expression. Design High-throughput screening was performed to identify compounds that suppress inflammatory cytokine-induced MMP13 expression. Ingenuity pathway analysis (IPA) using isobaric tags for relative and absolute quantification (iTRAQ)-based proteomic analysis was conducted to identify signaling pathways related to cytokines. MMP13 expression in chondrocytes was evaluated through RT-qPCR and western blotting analyses. Additionally, 10-week-old mice were subjected to destabilization of the medial meniscus (DMM) surgery to induce OA and were sacrificed 12 weeks post-surgery for pathological examination. OA was evaluated using the OARSI scoring system. Results Colchicine was identified as a DMOAD candidate as it inhibited inflammatory cytokine-induced MMP13 expression in vitro, and the colchicine-administered mice with DMM presented significantly lower OARSI scores (adjusted P: 0.0242, mean difference: 1.6, 95% confidence interval (CI) of difference: 0.1651–3.035) and significantly lower synovial membrane inflammation scores (adjusted P: 0.0243, mean difference: 0.6, 95% CI of difference: 0.06158–1.138) than mice with DMM. IPA further revealed that components of the Rho signaling pathways are regulated by cytokines and colchicine. IL-1β and TNF-α activate RAC1 and SRC signals, respectively, leading to the phosphorylation of PLC-γ1 and synergistic induction of MMP13 expression. Most notably, colchicine abrogates inflammatory cytokine-induced phosphorylation of PLC-γ1, leading to the induction of MMP13 expression. Conclusions Colchicine is a potential DMOAD candidate that inhibits MMP13 expression and consequent cartilage degradation by disrupting the SRC/RAC1-phospho-PLCγ1-Ca2+ signaling pathway.
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- 2021
6. Overexpression of transcription factor FoxA2 in the developing skeleton causes an enlargement of the cartilage hypertrophic zone, but it does not trigger ectopic differentiation in immature chondrocytes
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Nicole Bell, Sanket Bhagat, Shanmugam Muruganandan, Ryunhyung Kim, Kailing Ho, Rachel Pierce, Elena Kozhemyakina, Andrew B. Lassar, Laura Gamer, Vicki Rosen, and Andreia M. Ionescu
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Histology ,Physiology ,Endocrinology, Diabetes and Metabolism ,Cell Differentiation ,Core Binding Factor Alpha 1 Subunit ,Hypertrophy ,Alkaline Phosphatase ,Bone and Bones ,Article ,Mice ,Cartilage ,Chondrocytes ,Matrix Metalloproteinase 13 ,Hepatocyte Nuclear Factor 3-beta ,Animals ,Transcription Factors - Abstract
We previously found that FoxA factors are necessary for chondrocyte differentiation. To investigate whether FoxA factors alone are sufficient to drive chondrocyte hypertrophy, we build a FoxA2 transgenic mouse in which FoxA2 cDNA is driven by a reiterated Tetracycline Response Element (TRE) and a minimal CMV promoter. This transgenic line was crossed with a col2CRE;Rosa26(rtTA/+) mouse line to generate col2CRE;Rosa26(rtTA/+);TgFoxA2(+/−) mice for inducible expression of FoxA2 in cartilage using doxycycline treatment. Ectopic expression of FoxA2 in the developing skeleton reveals skeletal defects and shorter skeletal elements in E17.5 mice. The chondro-osseous border was frequently mis-shaped in mutant mice, with small islands of col.10+ hypertrophic cells extending in the metaphyseal bone. Even though overexpression of FoxA2 causes an accumulation of hypertrophic chondrocytes, it did not trigger ectopic hypertrophy in the immature chondrocytes. This suggests that FoxA2 may need transcriptional co-factors (such as Runx2), whose expression is restricted to the hypertrophic zone, and absent in the immature chondrocytes. To investigate a potential FoxA2/Runx2 interaction in immature chondrocytes versus hypertrophic cells, we separated these two subpopulations by FACS to obtain CD24(+)CD200(+) hypertrophic chondrocytes and CD24(+)CD200(−) immature chondrocytes and we ectopically expressed FoxA2 alone or in combination with Runx2 via lentiviral gene delivery. In CD24(+)CD200(+) hypertrophic chondrocytes, FoxA2 enhanced the expression of chondrocyte hypertrophic markers collagen 10, MMP13, and alkaline phosphatase. In contrast, in the CD24(+)CD200(−) immature chondrocytes, neither FoxA2 nor Runx2 overexpression could induce ectopic expression of hypertrophic markers MMP13, alkaline phosphatase, or PTH/PTHrP receptor. Overall these findings mirror our in vivo data, and suggest that induction of chondrocyte hypertrophy by FoxA2 may require other factors in addition to Runx2 (i.e., Hif2α, MEF2C, or perhaps unknown factors), whose expression/activity is rate-limiting in immature chondrocytes.
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- 2021
7. Creb5 establishes the competence forPrg4expression in articular cartilage
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Ramesh A. Shivdasani, Han-Hwa Hung, Kristina Holton, Alan J. Grodzinsky, Unmesh Jadhav, Cheng-Hai Zhang, Yao Gao, and Andrew B. Lassar
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Chemistry ,Regulator ,medicine ,Chromatin conformation ,Arthritis ,Articular cartilage ,Egfr signaling ,medicine.disease ,Beta (finance) ,Gene ,Transcription factor ,Cell biology - Abstract
A hallmark of cells comprising the superficial zone of articular cartilage is their expression of lubricin, encoded by thePrg4gene, that lubricates the joint and protects against the development of arthritis. Here, we identify Creb5 as a transcription factor that is specifically expressed in superficial zone articular chondrocytes and is required for TGF-β and EGFR signaling to inducePrg4expression. Notably, forced expression of Creb5 in chondrocytes derived from the deep zone of the articular cartilage confers the competence for TGF-β and EGFR signals to inducePrg4expression. Chromatin-IP and ATAC-Seq analyses have revealed that Creb5 directly binds to twoPrg4promoter-proximal regulatory elements, that display an open chromatin conformation specifically in superficial zone articular chondrocytes; and which work in combination with a more distal regulatory element to drive induction ofPrg4by TGF-β. Our results indicate that Creb5 is a critical regulator ofPrg4/lubricin expression in the articular cartilage.
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- 2020
8. Creb5 coordinates synovial joint formation with the genesis of articular cartilage
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Cheng-Hai Zhang, Yao Gao, Han-Hwa Hung, Zhu Zhuo, Alan J. Grodzinsky, and Andrew B. Lassar
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Cartilage, Articular ,Multidisciplinary ,Chondrocytes ,Gene Expression Regulation ,Musculoskeletal Physiological Phenomena ,General Physics and Astronomy ,Proteoglycans ,General Chemistry ,General Biochemistry, Genetics and Molecular Biology - Abstract
While prior work has established that articular cartilage arises from Prg4-expressing perichondrial cells, it is not clear how this process is specifically restricted to the perichondrium of synovial joints. We document that the transcription factor Creb5 is necessary to initiate the expression of signaling molecules that both direct the formation of synovial joints and guide perichondrial tissue to form articular cartilage instead of bone. Creb5 promotes the generation of articular chondrocytes from perichondrial precursors in part by inducing expression of signaling molecules that block a Wnt5a autoregulatory loop in the perichondrium. Postnatal deletion of Creb5 in the articular cartilage leads to loss of both flat superficial zone articular chondrocytes coupled with a loss of both Prg4 and Wif1 expression in the articular cartilage; and a non-cell autonomous up-regulation of Ctgf. Our findings indicate that Creb5 promotes joint formation and the subsequent development of articular chondrocytes by driving the expression of signaling molecules that both specify the joint interzone and simultaneously inhibit a Wnt5a positive-feedback loop in the perichondrium.
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- 2020
9. Creb5 establishes the competence for Prg4 expression in articular cartilage
- Author
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Andrew B. Lassar, Alan J. Grodzinsky, Han-Hwa Hung, Kristina Holton, Yao Gao, Ramesh A. Shivdasani, Unmesh Jadhav, and Cheng-Hai Zhang
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0301 basic medicine ,Cartilage, Articular ,QH301-705.5 ,Molecular biology ,Regulator ,Medicine (miscellaneous) ,Arthritis ,Articular cartilage ,Stem cells ,Biology ,Cyclic AMP Response Element-Binding Protein A ,General Biochemistry, Genetics and Molecular Biology ,Article ,03 medical and health sciences ,Transforming Growth Factor beta2 ,0302 clinical medicine ,Chondrocytes ,Developmental biology ,medicine ,Animals ,Egfr signaling ,Biology (General) ,Phosphorylation ,Promoter Regions, Genetic ,Transcription factor ,Gene ,Cells, Cultured ,Binding Sites ,Transforming Growth Factor alpha ,medicine.disease ,Cell biology ,030104 developmental biology ,Gene Expression Regulation ,Cattle ,Proteoglycans ,Stem cell ,Mitogen-Activated Protein Kinases ,General Agricultural and Biological Sciences ,030217 neurology & neurosurgery - Abstract
A hallmark of cells comprising the superficial zone of articular cartilage is their expression of lubricin, encoded by the Prg4 gene, that lubricates the joint and protects against the development of arthritis. Here, we identify Creb5 as a transcription factor that is specifically expressed in superficial zone articular chondrocytes and is required for TGF-β and EGFR signaling to induce Prg4 expression. Notably, forced expression of Creb5 in chondrocytes derived from the deep zone of the articular cartilage confers the competence for TGF-β and EGFR signals to induce Prg4 expression. Chromatin-IP and ATAC-Seq analyses have revealed that Creb5 directly binds to two Prg4 promoter-proximal regulatory elements, that display an open chromatin conformation specifically in superficial zone articular chondrocytes; and which work in combination with a more distal regulatory element to drive induction of Prg4 by TGF-β. Our results indicate that Creb5 is a critical regulator of Prg4/lubricin expression in the articular cartilage., Zhang et al. identify Creb5 as a transcription factor that is required for induction of Prg4 expression by TGFβ and EGFR ligands. They show that Creb5 directly binds to two Prg4 promoter-proximal regulatory elements, working together with a more distal regulatory element to drive induction of Prg4 by TGFβ. These findings provide new insight into the molecular regulation of Prg4 expression in superficial zone articular chondrocytes.
- Published
- 2020
10. Superficial cells are self‐renewing chondrocyte progenitors, which form the articular cartilage in juvenile mice
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Hong Qian, Matthew L. Warman, Jozef Kaiser, Thibault Bouderlique, Lei Li, Phillip T Newton, Andrei S. Chagin, Andrew B. Lassar, Marie Šejnohová, Igor Adameyko, Elena Kozhemyakina, Meng Xie, Vyacheslav Dyachuk, Björn Barenius, Tomáš Zikmund, and Jan Krivanek
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Cartilage, Articular ,0301 basic medicine ,Population ,Osteoarthritis ,Biology ,Biochemistry ,Chondrocyte ,Mice ,03 medical and health sciences ,Chondrocytes ,Genetics ,medicine ,Animals ,Regeneration ,Progenitor cell ,education ,Molecular Biology ,education.field_of_study ,Research ,Cartilage ,Regeneration (biology) ,Mesenchymal stem cell ,medicine.disease ,Cell biology ,Adult Stem Cells ,030104 developmental biology ,medicine.anatomical_structure ,Chondrogenesis ,Biotechnology ,Adult stem cell - Abstract
Articular cartilage has little regenerative capacity. Recently, genetic lineage tracing experiments have revealed chondrocyte progenitors at the articular surface. We further characterized these progenitors by using in vivo genetic approaches. Histone H2B–green fluorescent protein retention revealed that superficial cells divide more slowly than underlying articular chondrocytes. Clonal genetic tracing combined with immunohistochemistry revealed that superficial cells renew their number by symmetric division, express mesenchymal stem cell markers, and generate chondrocytes via both asymmetric and symmetric differentiation. Quantitative analysis of cellular kinetics, in combination with phosphotungstic acid–enhanced micro–computed tomography, showed that superficial cells generate chondrocytes and contribute to the growth and reshaping of articular cartilage. Furthermore, we found that cartilage renewal occurs as the progeny of superficial cells fully replace fetal chondrocytes during early postnatal life. Thus, superficial cells are self-renewing progenitors that are capable of maintaining their own population and fulfilling criteria of unipotent adult stem cells. Furthermore, the progeny of these cells reconstitute adult articular cartilage de novo, entirely substituting fetal chondrocytes.—Li, L., Newton, P. T., Bouderlique, T., Sejnohova, M., Zikmund, T., Kozhemyakina, E., Xie, M., Krivanek, J., Kaiser, J., Qian, H., Dyachuk, V., Lassar, A. B., Warman, M. L., Barenius, B., Adameyko, I., Chagin, A. S. Superficial cells are self-renewing chondrocyte progenitors, which form the articular cartilage in juvenile mice.
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- 2016
11. PTHrP targets HDAC4 and HDAC5 to repress chondrocyte hypertrophy
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Forest Lai, Mieno Shiraishi, Tso-Pang Yao, Shigeki Nishimori, Elena Kozhemyakina, Andrew B. Lassar, Henry M. Kronenberg, and Tatsuya Kobayashi
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musculoskeletal diseases ,0301 basic medicine ,Mef2 ,Core Binding Factor Alpha 1 Subunit ,Ribs ,Chondrocyte hypertrophy ,Biology ,Histone Deacetylases ,Chondrocyte ,Mice ,03 medical and health sciences ,Chondrocytes ,0302 clinical medicine ,Osteogenesis ,medicine ,Animals ,Humans ,RNA, Messenger ,Phosphorylation ,Transcription factor ,Cell Proliferation ,Mice, Knockout ,Histone deacetylase 5 ,MEF2 Transcription Factors ,Parathyroid Hormone-Related Protein ,Hypertrophy ,General Medicine ,musculoskeletal system ,HDAC4 ,Cell biology ,Mice, Inbred C57BL ,RUNX2 ,Disease Models, Animal ,Cartilage ,Phenotype ,030104 developmental biology ,medicine.anatomical_structure ,Gene Expression Regulation ,030220 oncology & carcinogenesis ,Transcriptome ,hormones, hormone substitutes, and hormone antagonists ,Research Article ,Signal Transduction - Abstract
During endochondral bone formation, chondrocyte hypertrophy represents a crucial turning point from chondrocyte differentiation to bone formation. Both parathyroid hormone-related protein (PTHrP) and histone deacetylase 4 (HDAC4) inhibit chondrocyte hypertrophy. Using multiple mouse genetics models, we demonstrate in vivo that HDAC4 is required for the effects of PTHrP on chondrocyte differentiation. We further show in vivo that PTHrP leads to reduced HDAC4 phosphorylation at the 14-3-3-binding sites and subsequent HDAC4 nuclear translocation. The Hdac4-KO mouse shares a similar but milder phenotype with the Pthrp-KO mouse, indicating the possible existence of other mediators of PTHrP action. We identify HDAC5 as an additional mediator of PTHrP signaling. While the Hdac5-KO mouse has no growth plate phenotype at birth, the KO of Hdac5 in addition to the KO of Hdac4 is required to block fully PTHrP action on chondrocyte differentiation at birth in vivo. Finally, we show that PTHrP suppresses myocyte enhancer factor 2 (Mef2) action that allows runt-related transcription factor 2 (Runx2) mRNA expression needed for chondrocyte hypertrophy. Our results demonstrate that PTHrP inhibits chondrocyte hypertrophy and subsequent bone formation in vivo by allowing HDAC4 and HDAC5 to block the Mef2/Runx2 signaling cascade. These results explain the phenotypes of several genetic abnormalities in humans.
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- 2019
12. Transcription of Class III Genes: Formation of Preinitiation Complexes
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Andrew B. Lassar, Paul L. Martin, and Robert G. Roeder
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- 2019
13. The role of FoxA2 transcription factor as potential regulator of articular cartilage hypertrophy and OA progression
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Vicki Rosen, Laura W. Gamer, K. Ho, Yang Li, Andrew B. Lassar, D. Astari Teguh, Andreia M. Ionescu, R. Kim, L. Xu, Klaus H. Kaestner, Malcolm Whitman, R. Fuente Perez, and Elena Kozhemyakina
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Rheumatology ,business.industry ,Biomedical Engineering ,Regulator ,Medicine ,Orthopedics and Sports Medicine ,Articular cartilage ,FOXA2 ,business ,Transcription factor ,Muscle hypertrophy ,Cell biology - Published
- 2019
14. Identification of aPrg4-Expressing Articular Cartilage Progenitor Cell Population in Mice
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Matthew L. Warman, Minjie Zhang, Andrew B. Lassar, Elena Kozhemyakina, Noriaki Ono, Akio Kobayashi, Henry M. Kronenberg, Andreia M. Ionescu, and Ugur M. Ayturk
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education.field_of_study ,Extramural ,Cartilage ,Immunology ,Population ,Cre recombinase ,Locus (genetics) ,Articular cartilage ,Biology ,Cell biology ,medicine.anatomical_structure ,Rheumatology ,medicine ,Immunology and Allergy ,Stem cell ,Progenitor cell ,education - Abstract
Objective We generated knock-in mice that express a tamoxifen-inducible Cre recombinase from the Prg4 locus (Prg4GFPCreERt2), and used these animals to fate-map the progeny of Prg4-positive articular cartilage cells at various ages.
- Published
- 2015
15. Finding MyoD and lessons learned along the way
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Andrew B. Lassar
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0301 basic medicine ,Genetics ,Cognitive science ,Gene Expression Regulation, Developmental ,Cell Differentiation ,Cell Biology ,Biology ,Fibroblasts ,MyoD ,Muscle Development ,Article ,03 medical and health sciences ,Wright ,Mice ,030104 developmental biology ,0302 clinical medicine ,Animals ,Cell Lineage ,Muscle, Skeletal ,030217 neurology & neurosurgery ,Developmental Biology ,MyoD Protein - Abstract
In 1987, Robert Davis, Hal Weintraub and I reported the identification of MyoD, a transcription factor that could reprogram fibroblasts into skeletal muscle cells. In this recollection, I both summarize the prior work of Helen Blau, Woody Wright, Peter Jones and Charlie Emerson that inspired my entry into this field, and the subsequent events that led to finding MyoD. Lastly, I highlight some of the principles in developmental biology that have emerged during the past 30 years, which are particularly relevant to skeletal muscle biology.
- Published
- 2017
16. BMP-mediated induction of GATA4/5/6 blocks somitic responsiveness to SHH
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Andreia M. Ionescu, Elena Kozhemyakina, Andrew B. Lassar, Deepak Kumar, Tamara Holowacz, Hervé Kempf, Dae Won Kim, Georges Daoud, Harvard Medical School [Boston] (HMS), Ingénierie Moléculaire et Physiopathologie Articulaire (IMoPA), Université de Lorraine (UL)-Centre National de la Recherche Scientifique (CNRS), and Centre National de la Recherche Scientifique (CNRS)-Université de Lorraine (UL)
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animal structures ,GATA5 Transcription Factor ,Kruppel-Like Transcription Factors ,Bone morphogenetic protein ,Zinc Finger Protein GLI1 ,Mice ,Chondrocytes ,GLI1 ,GATA6 Transcription Factor ,Paraxial mesoderm ,Animals ,Hedgehog Proteins ,[SDV.BBM.BC]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Biochemistry [q-bio.BM] ,Molecular Biology ,Research Articles ,Homeodomain Proteins ,biology ,GATA4 ,Gene Expression Profiling ,Lateral plate mesoderm ,GATA2 ,Gene Expression Regulation, Developmental ,Nuclear Proteins ,GATA4 Transcription Factor ,Bone Morphogenetic Proteins ,embryonic structures ,NIH 3T3 Cells ,Cancer research ,biology.protein ,GATA transcription factor ,[SDV.MHEP]Life Sciences [q-bio]/Human health and pathology ,Transcription Factors ,Developmental Biology - Abstract
International audience; The relative timing of SHH and BMP signals controls whether presomitic mesoderm (PSM) cells will adopt either a chondrogenic or lateral plate mesoderm fate. Here we document that SHH-mediated induction of Nkx3.2 maintains the competence of somitic cells to initiate chondrogenesis in response to subsequent BMP signals by repressing BMP-dependent induction of GATA genes. Conversely, administration of BMP signals to PSM or forced expression of GATA family members in chick PSM explants blocks induction of hedgehog-dependent gene expression. We demonstrate that GATA factors can interact with Gli factors and can recruit the transcriptional co-factor FOG1 (ZFPM1) to the regulatory region of the mouse Gli1 gene, repressing the induction of Gli1 by SHH by binding to both GATA and Gli binding sites. Knockdown of FOG1 reverses the ability of GATA factors to repress Gli1 expression. Our findings uncover a novel role for GATA transcription factors as repressors of hedgehog signaling, and document that NKX3.2 maintains the ability of sclerotomal cells to express SHH transcriptional targets in the presence of BMP signals by repressing the induction of Gata4/5/6.
- Published
- 2014
17. Evolutionary conservation of Nkx2.5 autoregulation in the second heart field
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Benjamin Lee, Kyu-Ho Lee, Samuel I. Evans, Andrew B. Lassar, Christopher D. Clark, and Boding Zhang
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Second heart field ,Gene regulatory network ,Transgenic ,Mice ,0302 clinical medicine ,Autoregulation ,MEF2C ,Genetics ,0303 health sciences ,Heart development ,Stem Cells ,Gene Expression Regulation, Developmental ,Heart ,Nkx2.5 ,respiratory system ,Cell biology ,Enhancer Elements, Genetic ,embryonic structures ,Homeobox Protein Nkx-2.5 ,cardiovascular system ,Transcription ,Genetic Vectors ,Molecular Sequence Data ,Mice, Transgenic ,Biology ,Article ,Homeobox protein Nkx-2.5 ,03 medical and health sciences ,stomatognathic system ,Sequence Homology, Nucleic Acid ,Animals ,Outflow tract ,Enhancer ,Molecular Biology ,Congenital heart disease ,030304 developmental biology ,Heart Failure ,Homeodomain Proteins ,Muscle Cells ,Base Sequence ,Gene Expression Profiling ,Myocardium ,Cell Biology ,Mef2c ,Gene expression profiling ,Myocyte ,Homeobox ,Chickens ,030217 neurology & neurosurgery ,Transcription Factors ,Progenitor ,Developmental Biology - Abstract
The cardiac homeobox gene Nkx2.5 plays a key and dosage-sensitive role in the differentiation of outflow tract and right ventricle from progenitors of the second heart field (SHF) and Nkx2.5 mutation is strongly associated with human outflow tract congenital heart disease (OFT CHD). Therefore defining the regulatory mechanisms controlling Nkx2.5 expression in SHF populations serves an important function in understanding the etiology of complex CHD. Through a comparative analysis of regulatory elements controlling SHF expression of Nkx2.5 in the chicken and mouse, we have found evidence that Nkx2.5 autoregulation is important for maintaining Nkx2.5 expression during SHF differentiation in both species. However the mechanism of Nkx2.5 maintenance differs between placental mammals and non-mammalian vertebrates: in chick Nkx2.5 binds directly to a genomic enhancer element that is required to maintain Nkx2.5 expression in the SHF. In addition, it is likely that this is true in other non-mammalian vertebrates given that they possess a similar genomic organization. By contrast, in placental mammals, Nkx2.5 autoregulation in the SHF functions indirectly through Mef2c. These data underscore a tight relationship in mammals between Nkx2.5 and Mef2c in SHF transcriptional regulation, and highlight the potential for evolutionary cis-regulatory analysis to identify core, conserved components of the gene networks controlling heart development.
- Published
- 2013
18. The Transcriptional Activity of Sox9 in Chondrocytes Is Regulated by RhoA Signaling and Actin Polymerization
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Andrew B. Lassar and Deepak Kumar
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animal structures ,RHOA ,Transcription, Genetic ,Polymers ,Blotting, Western ,Fluorescent Antibody Technique ,Chick Embryo ,Chondrocyte ,Gene expression ,medicine ,Animals ,Phosphorylation ,Protein kinase A ,Protein Kinase Inhibitors ,Molecular Biology ,Cells, Cultured ,Actin ,Sulfonamides ,Binding Sites ,biology ,Reverse Transcriptase Polymerase Chain Reaction ,SOX9 Transcription Factor ,Articles ,Cell Biology ,Cell Dedifferentiation ,Isoquinolines ,Chondrogenesis ,Cyclic AMP-Dependent Protein Kinases ,Molecular biology ,Actins ,Cell biology ,medicine.anatomical_structure ,embryonic structures ,Mutation ,biology.protein ,Protein Multimerization ,Signal transduction ,rhoA GTP-Binding Protein ,Signal Transduction - Abstract
In this study, we demonstrate that dedifferentiation of round primary chondrocytes into a fibroblast morphology correlates with a profound induction of RhoA protein and stress fibers. Culture of dedifferentiated chondrocytes in alginate gel induces a precipitous loss of RhoA protein and a loss of stress fibers concomitant with the reexpression of the chondrocyte differentiation program. We have found that chondrogenesis in limb bud micromass cultures similarly entails a loss of RhoA protein and that expression of dominant negative RhoA in such cultures can markedly enhance chondrogenesis. Consistent with these results, expression of the Rho antagonist C3 transferase can restore chondrocyte gene expression in dedifferentiated chondrocytes grown on plastic. Transfection of cells with agents that block actin polymerization enhance the ability of either exogenous Sox9 or a Gal4 DBD-Sox9 fusion protein to activate gene expression. Interestingly, the enhancement of Sox9 function by actin depolymerization requires both protein kinase A (PKA) activity and a PKA phosphorylation site in Sox9 (S181) that is known to enhance Sox9 transcriptional activity. Lastly, we demonstrate that RhoA-mediated modulation of actin polymerization regulates the ability of Sox9 to both activate chondrocyte-specific markers and maintain its own expression in chondrocytes via a positive feedback loop.
- Published
- 2009
19. A pathway to bone: signaling molecules and transcription factors involved in chondrocyte development and maturation
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Elazar Zelzer, Elena Kozhemyakina, and Andrew B. Lassar
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medicine.medical_specialty ,Cell signaling ,Mesenchymal stem cell ,Chondrocyte hypertrophy ,SOX9 ,Review ,Biology ,Chondrogenesis ,Chondrocyte ,Cell biology ,medicine.anatomical_structure ,Endocrinology ,Chondrocytes ,Internal medicine ,medicine ,Animals ,Humans ,Growth Plate ,Signal transduction ,Molecular Biology ,Transcription factor ,Developmental Biology ,Transcription Factors - Abstract
Decades of work have identified the signaling pathways that regulate the differentiation of chondrocytes during bone formation, from their initial induction from mesenchymal progenitor cells to their terminal maturation into hypertrophic chondrocytes. Here, we review how multiple signaling molecules, mechanical signals and morphological cell features are integrated to activate a set of key transcription factors that determine and regulate the genetic program that induces chondrogenesis and chondrocyte differentiation. Moreover, we describe recent findings regarding the roles of several signaling pathways in modulating the proliferation and maturation of chondrocytes in the growth plate, which is the ‘engine’ of bone elongation.
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- 2015
20. Dissimilar regulation of cell differentiation in mesencephalic (cranial)and sacral (trunk) neural crest cells in vitro
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Clifford J. Tabin, Andrew B. Lassar, Arhat Abzhanov, and Eldad Tzahor
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Cell type ,animal structures ,Cell Survival ,Cellular differentiation ,Bone Morphogenetic Protein 2 ,Chick Embryo ,Cell fate determination ,Biology ,Transforming Growth Factor beta1 ,Cranial neural crest ,Mesencephalon ,Transforming Growth Factor beta ,Morphogenesis ,Extracellular ,Animals ,Hox gene ,Molecular Biology ,Cells, Cultured ,In Situ Hybridization ,beta Catenin ,Body Patterning ,Homeodomain Proteins ,Neurons ,Neural fold ,Neural crest ,Cell Differentiation ,Anatomy ,Cell biology ,Rhombencephalon ,Cytoskeletal Proteins ,Neural Crest ,Bone Morphogenetic Proteins ,embryonic structures ,Trans-Activators ,Fibroblast Growth Factor 2 ,Chondrogenesis ,Developmental Biology - Abstract
During development neural crest cells give rise to a wide variety of specialized cell types in response to cytokines from surrounding tissues. Depending on the cranial-caudal level of their origin, different populations of neural crest cells exhibit differential competence to respond to these signals as exemplified by the unique ability of cranial neural crest to form skeletal cell types. We show that in addition to differences in whether they respond to particular signals, cranial neural crest cells differ dramatically from the trunk neural crest cells in how they respond to specific extracellular signals, such that under identical conditions the same signal induces dissimilar cell fate decisions in the two populations in vitro. Conversely, the same differentiated cell types are induced by different signals in the two populations. These in vitro differences in neural crest response are consistent with in vivo manipulations. We also provide evidence that these differences in responsiveness are modulated, at least in part, by differential expression of Hox genes within the neural crest.
- Published
- 2003
21. Characterization of Nkx3.2 DNA Binding Specificity and Its Requirement for Somitic Chondrogenesis
- Author
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Dae Won Kim, Raymond E. Chen, Hervé Kempf, Andrew B. Lassar, Department of Biological Chemistry and Molecular Pharmacology [Boston] (DBCMP), and Harvard Medical School [Boston] (HMS)
- Subjects
Transcription, Genetic ,Glutamine ,Amino Acid Motifs ,Chick Embryo ,urologic and male genital diseases ,Biochemistry ,Mice ,chemistry.chemical_compound ,Genes, Reporter ,[SDV.BC.IC]Life Sciences [q-bio]/Cellular Biology/Cell Behavior [q-bio.CB] ,Cloning, Molecular ,ComputingMilieux_MISCELLANEOUS ,Glutathione Transferase ,0303 health sciences ,Reverse Transcriptase Polymerase Chain Reaction ,030302 biochemistry & molecular biology ,3T3 Cells ,Recombinant Proteins ,[SDV.MHEP.RSOA]Life Sciences [q-bio]/Human health and pathology/Rhumatology and musculoskeletal system ,Asparagine ,Plasmids ,Protein Binding ,Binding domain ,HMG-box ,Recombinant Fusion Proteins ,Molecular Sequence Data ,Mutation, Missense ,Biology ,03 medical and health sciences ,Chondrocytes ,[SDV.MHEP.CSC]Life Sciences [q-bio]/Human health and pathology/Cardiology and cardiovascular system ,Sequence Homology, Nucleic Acid ,Animals ,Binding site ,Molecular Biology ,030304 developmental biology ,Homeodomain Proteins ,Reporter gene ,Binding Sites ,Base Sequence ,urogenital system ,[SDV.BDD.MOR]Life Sciences [q-bio]/Development Biology/Morphogenesis ,[SDV.BBM.BM]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology ,DNA ,Cell Biology ,Chondrogenesis ,Molecular biology ,Protein Structure, Tertiary ,DNA binding site ,Retroviridae ,[SDV.BDD.EO]Life Sciences [q-bio]/Development Biology/Embryology and Organogenesis ,chemistry ,Homeobox ,Transcription Factors - Abstract
We have previously shown that Nkx3.2, a member of the NK class of homeoproteins, functions as a transcriptional repressor to promote somitic chondrogenesis. However, it has not been addressed whether Nkx3.2 can bind to DNA in a sequence-specific manner and whether DNA binding by Nkx3.2 is required for its biological activity. In this work, we employed a DNA binding site selection assay, which identified TAAGTG as a high affinity Nkx3.2 binding sequence. Sequence-specific binding of Nkx3.2 to the TAAGTG motif in vitro was confirmed by electrophoretic mobility shift assays, and mutagenesis of this sequence revealed that HRAGTG (where H represents A, C, or T, and R represents A or G) comprises the consensus DNA binding site for Nkx3.2. Consistent with these findings, the expression of a reporter gene containing reiterated Nkx3.2 binding sites was repressed in vivo by Nkx3.2 co-expression. In addition, we have generated a DNA nonbinding point mutant of Nkx3.2 (Nkx3.2-N200Q), which contains an asparagine to glutamine missense mutation in the homeodomain. Interestingly, despite being defective in DNA binding, Nkx3.2-N200Q still retains its intrinsic transcriptional repressor function. Finally, we demonstrate that unlike wild-type Nkx3.2, Nkx3.2-N200Q is unable to activate the chondrocyte differentiation program in somitic mesoderm, indicating that DNA binding by Nkx3.2 is critical for this factor to induce somitic chondrogenesis.
- Published
- 2003
22. Shh establishes an Nkx3.2/Sox9 autoregulatory loop that is maintained by BMP signals to induce somitic chondrogenesis
- Author
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Mie Elissa Sato, Li Zeng, L. Charles Murtaugh, Andrew B. Lassar, Hervé Kempf, Department of Biological Chemistry and Molecular Pharmacology [Boston] (DBCMP), and Harvard Medical School [Boston] (HMS)
- Subjects
Transcription, Genetic ,Cellular differentiation ,Bone Morphogenetic Protein 2 ,Apoptosis ,Chick Embryo ,Mesoderm ,0302 clinical medicine ,Transforming Growth Factor beta ,Cricetinae ,[SDV.BC.IC]Life Sciences [q-bio]/Cellular Biology/Cell Behavior [q-bio.CB] ,0303 health sciences ,High Mobility Group Proteins ,Gene Expression Regulation, Developmental ,Cell Differentiation ,SOX9 Transcription Factor ,Cell biology ,medicine.anatomical_structure ,Somites ,[SDV.MHEP.RSOA]Life Sciences [q-bio]/Human health and pathology/Rhumatology and musculoskeletal system ,Bone Morphogenetic Proteins ,embryonic structures ,Research Paper ,animal structures ,CHO Cells ,Biology ,Bone morphogenetic protein ,Feedback ,03 medical and health sciences ,Cricetulus ,Organ Culture Techniques ,[SDV.MHEP.CSC]Life Sciences [q-bio]/Human health and pathology/Cardiology and cardiovascular system ,Notochord ,Genetics ,medicine ,Paraxial mesoderm ,Animals ,Cell Lineage ,Hedgehog Proteins ,030304 developmental biology ,Floor plate ,Homeodomain Proteins ,Proteins ,[SDV.BDD.MOR]Life Sciences [q-bio]/Development Biology/Morphogenesis ,[SDV.BBM.BM]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology ,Chondrogenesis ,Antigens, Differentiation ,Molecular biology ,Repressor Proteins ,Somite ,Cartilage ,[SDV.BDD.EO]Life Sciences [q-bio]/Development Biology/Embryology and Organogenesis ,Culture Media, Conditioned ,Trans-Activators ,Carrier Proteins ,030217 neurology & neurosurgery ,Transcription Factors ,Developmental Biology - Abstract
International audience; Prior work has established that transient Shh signals from the notochord and floor plate confer a competence in somitic tissue for subsequent BMP signals to induce chondrogenesis. We have therefore proposed that Shh induces a factor(s) that renders somitic cells competent to chondrify in response to subsequent BMP signals. Recently, we have shown that forced expression of Nkx3.2, a transcriptional repressor induced by Shh, is able to confer chondrogenic competence in somites. In this work, we show that administration of Shh or forced Nkx3.2 expression induces the expression of the transcription factor Sox9 in the somitic tissue. Forced expression of Sox9 can, in turn, induce robust chondrogenesis in somitic mesoderm, provided that BMP signals are present. We have found that in the presence of BMP signals, Sox9 and Nkx3.2 induce each other's expression. Thus, Nkx3.2 may promote axial chondrogenesis by derepressing the expression of Sox9 in somitic mesoderm. Furthermore, forced expression of either Sox9 or Nkx3.2 not only activates expression of cartilage-specific genes in somitic mesoderm, but also promotes the proliferation and survival of the induced chondrocytes in the presence of BMP signals. However, unlike Nkx3.2, Sox9 is able to induce de novo cartilage formation in non-cartilage-forming tissues. Our findings suggest that Shh and BMP signals work in sequence to establish a positive regulatory loop between Sox9 and Nkx3.2, and that Sox9 can subsequently initiate the chondrocyte differentiation program in a variety of cellular environments.
- Published
- 2002
23. Erythropoietin and Retinoic Acid Signaling in the Epicardium Is Required for Cardiac Myocyte Proliferation
- Author
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Ingo Stuckmann and Andrew B. Lassar
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Cell Survival ,Retinoic acid ,Cell Differentiation ,Tretinoin ,Biology ,Biochemistry ,Cell biology ,chemistry.chemical_compound ,chemistry ,Erythropoietin ,Genetics ,medicine ,Animals ,Cardiac myocyte proliferation ,Myocytes, Cardiac ,Mitogens ,Pericardium ,Molecular Biology ,Cell Division ,Signal Transduction ,medicine.drug - Published
- 2002
24. GATA6 is a crucial regulator of Shh in the limb bud
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Elena Kozhemyakina, Andreia M. Ionescu, and Andrew B. Lassar
- Subjects
Apical ectodermal ridge ,Cancer Research ,endocrine system ,animal structures ,Limb Buds ,lcsh:QH426-470 ,Embryonic Development ,Hindlimb ,Mice ,Limb bud ,GATA6 Transcription Factor ,Forelimb ,Genetics ,medicine ,Animals ,Limb development ,Hedgehog Proteins ,Sonic hedgehog ,Biology ,Molecular Biology ,Genetics (clinical) ,Ecology, Evolution, Behavior and Systematics ,Body Patterning ,biology ,Gene Expression Regulation, Developmental ,Embryo, Mammalian ,Molecular biology ,GATA4 Transcription Factor ,Polydactyly ,lcsh:Genetics ,medicine.anatomical_structure ,Zone of polarizing activity ,embryonic structures ,biology.protein ,Ectopic expression ,Research Article ,Developmental Biology ,Signal Transduction - Abstract
In the limb bud, patterning along the anterior-posterior (A-P) axis is controlled by Sonic Hedgehog (Shh), a signaling molecule secreted by the “Zone of Polarizing Activity”, an organizer tissue located in the posterior margin of the limb bud. We have found that the transcription factors GATA4 and GATA6, which are key regulators of cell identity, are expressed in an anterior to posterior gradient in the early limb bud, raising the possibility that GATA transcription factors may play an additional role in patterning this tissue. While both GATA4 and GATA6 are expressed in an A-P gradient in the forelimb buds, the hindlimb buds principally express GATA6 in an A-P gradient. Thus, to specifically examine the role of GATA6 in limb patterning we generated Prx1-Cre; GATA6fl/fl mice, which conditionally delete GATA6 from their developing limb buds. We found that these animals display ectopic expression of both Shh and its transcriptional targets specifically in the anterior mesenchyme of the hindlimb buds. Loss of GATA6 in the developing limbs results in the formation of preaxial polydactyly in the hindlimbs. Conversely, forced expression of GATA6 throughout the limb bud represses expression of Shh and results in hypomorphic limbs. We have found that GATA6 can bind to chromatin (isolated from limb buds) encoding either Shh or Gli1 regulatory elements that drive expression of these genes in this tissue, and demonstrated that GATA6 works synergistically with FOG co-factors to repress expression of luciferase reporters driven by these sequences. Most significantly, we have found that conditional loss of Shh in limb buds lacking GATA6 prevents development of hindlimb polydactyly in these compound mutant embryos, indicating that GATA6 expression in the anterior region of the limb bud blocks hindlimb polydactyly by repressing ectopic expression of Shh., Author Summary Sonic Hedgehog (Shh) is a crucial regulator of the growth and anterior-posterior patterning of the developing limb bud, and is produced in the “Zone of Polarizing Activity” in the posterior of the limb bud. Here, we demonstrate that GATA4 and GATA6 (members of the GATA family of transcription factors) are expressed in the anterior mesenchyme of mouse limb buds and that limb bud-specific deletion of GATA6 results in ectopic expression of Shh and its target genes (such as Gli1) in the anterior limb bud mesenchyme, resulting in preaxial polydactyly. Conversely, over-expression of GATA6 in limb buds causes down-regulation of Shh and its target genes, resulting in a decreased number of digits. We also show that GATA6 binds to the sequences that regulate expression of either Shh or Gli1, and that simultaneous deletion of both GATA6 and Shh genes in developing limb buds rescues the polydactylous hindlimb phenotype of GATA6 mutants. Our findings indicate that GATA6 is necessary to repress ectopic expression of both Shh and hedgehog transcriptional targets in the anterior region of the mouse hindlimb bud, and thus demonstrate that GATA transcription factors, in addition to being regulators of cell identity, are important negative regulators of ectopic Shh expression in the limb bud.
- Published
- 2014
25. The origin of skeletal muscle stem cells in the embryo and the adult
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Peter Bailey, Tamara Holowacz, and Andrew B. Lassar
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Cell Survival ,Cellular differentiation ,Biology ,Models, Biological ,medicine ,Animals ,Muscle, Skeletal ,Body Patterning ,Stem cell transplantation for articular cartilage repair ,Myogenesis ,Stem Cells ,Cell Cycle ,Gene Expression Regulation, Developmental ,Skeletal muscle ,Cell Differentiation ,Cell Biology ,Anatomy ,Neural stem cell ,Cell biology ,Somite ,medicine.anatomical_structure ,Myogenic Regulatory Factors ,Stem cell ,Cell Division ,Signal Transduction ,Transcription Factors ,Adult stem cell - Abstract
Skeletal muscle progenitors are specified during embryogenesis and in addition have recently been found to be generated from either mesenchymal or neural stem cells in the adult. We review recent progress in identifying the signals and transcription factors that control skeletal muscle formation during embryogenesis and in the adult.
- Published
- 2001
26. Gizzard Formation and the Role of Bapx1
- Author
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Andrew B. Lassar, Drucilla J. Roberts, Corinne M. Nielsen, Jay C. Chyung, and Lewis C. Murtaugh
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animal structures ,Bone Morphogenetic Protein 4 ,Chick Embryo ,Biology ,medicine ,Animals ,Paired Box Transcription Factors ,Gizzard ,Molecular Biology ,Homeodomain Proteins ,Stomach ,Nuclear Proteins ,Midgut ,Proventriculus ,Hindgut ,Foregut ,Cell Biology ,Anatomy ,medicine.anatomical_structure ,Bone morphogenetic protein 4 ,Bone Morphogenetic Proteins ,Gizzard, Avian ,embryonic structures ,Ectopic expression ,Transcription Factors ,Developmental Biology - Abstract
The anterior-posterior gut pattern is formed from three broad domains: fore-, mid-, and hindgut that have distinct functional, morphological, and molecular boundaries. The stomach demarcates the posterior boundary of the foregut. Avian stomachs are composed of two chambers: the anterior chamber (proventriculus) and the thick muscular posterior chamber (gizzard). Expression of candidate pattern formation control factors are restricted in the chick stomach regions such that Bmp4 and Wnt5a are not expressed in the gizzard. We previously implicated Bmp4 as controlling growth and differentiation of the gut musculature. Bmp4 is not expressed in the developing gizzard but is expressed in the rest of the gut including the adjacent proventriculus and midgut. Bapx1 (Nkx3.2) is expressed in the gizzard musculature but not in the proventriculus or midgut. We show ectopic expression of Bapx1 in the proventriculus results in a gizzard-like morphology and inhibits the normal proventricular expression of Bmp4 and Wnt5a. Overexpression of a reverse-function Bapx1 construct can result in a small stomach and ectopic extension of Bmp4 and Wnt5a expression into the gizzard. We suggest the role of Bapx1 is to regulate the expression of Bmp4 and Wnt5a to pattern the avian stomach.
- Published
- 2001
27. Inhibition of Wnt activity induces heart formation from posterior mesoderm
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Aaron Gardiner, Giuliana Di Rocco, Andrew B. Lassar, Sara M. Bush, and Martha J. Marvin
- Subjects
medicine.medical_specialty ,Mesoderm ,animal structures ,Chick Embryo ,Germ layer ,Xenopus Proteins ,Biology ,FGF and mesoderm formation ,Proto-Oncogene Proteins ,Internal medicine ,Genetics ,medicine ,Paraxial mesoderm ,Animals ,Embryonic Induction ,Myocardium ,Lateral plate mesoderm ,Endoderm ,Proteins ,Heart ,Zebrafish Proteins ,Cell biology ,Wnt Proteins ,Endocrinology ,medicine.anatomical_structure ,embryonic structures ,Intercellular Signaling Peptides and Proteins ,NODAL ,Intermediate mesoderm ,Signal Transduction ,Research Paper ,Developmental Biology - Abstract
In the chick, heart mesoderm is induced by signals from the anterior endoderm. Although BMP-2 is expressed in the anterior endoderm, BMP activity is necessary but not sufficient for heart formation. Previous work from our lab has suggested that one or more additional factors from anterior endoderm are required. Crescent is a Frizzled-related protein that inhibits Wnt-8c and is expressed in anterior endoderm during gastrulation. At the same stages, expression of Wnt-3a and Wnt-8c is restricted to the primitive streak and posterior lateral plate, and is absent from the anterior region where crescent is expressed. Posterior lateral plate mesoderm normally forms blood, but coculture of this tissue with anterior endoderm or infection with RCAS–crescent induces formation of beating heart muscle and represses formation of blood. Dkk-1, a Wnt inhibitor of a different protein family, similarly induces heart-specific gene expression in posterior lateral plate mesoderm. Furthermore, we have found that ectopic Wnt signals can repress heart formation from anterior mesoderm in vitro and in vivo and that forced expression of either Wnt-3a or Wnt-8c can promote development of primitive erythrocytes from the precardiac region. We conclude that inhibition of Wnt signaling promotes heart formation in the anterior lateral mesoderm, whereas active Wnt signaling in the posterior lateral mesoderm promotes blood development. We propose a model in which two orthogonal gradients, one of Wnt activity along the anterior-posterior axis and the other of BMP signals along the dorsal-ventral axis, intersect in the heart-forming region to induce cardiogenesis in a region of high BMP and low Wnt activity.
- Published
- 2001
28. Wnt signals from the neural tube block ectopic cardiogenesis
- Author
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Andrew B. Lassar and Eldad Tzahor
- Subjects
Mesoderm ,animal structures ,Bone Morphogenetic Protein 2 ,CHO Cells ,Chick Embryo ,Wnt1 Protein ,Biology ,Bone morphogenetic protein ,Research Communication ,Transforming Growth Factor beta ,Cricetinae ,Proto-Oncogene Proteins ,Genetics ,medicine ,Paraxial mesoderm ,Animals ,Humans ,Cells, Cultured ,Embryonic Induction ,Neural tube ,Wnt signaling pathway ,Heart ,Anatomy ,Zebrafish Proteins ,Cell biology ,Wnt Proteins ,medicine.anatomical_structure ,Bone Morphogenetic Proteins ,embryonic structures ,Ectopic expression ,Neural plate ,Signal Transduction ,Developmental Biology - Abstract
It has long been observed that repressive signals from the neural tube block cardiogenesis in vertebrates. Here we show that a signal from the neural tube that blocks cardiogenesis in the adjacent anterior paraxial mesoderm of stage 8–9 chick embryos can be mimicked by ectopic expression of either Wnt-3a or Wnt-1, both of which are expressed in the dorsal neural tube. Repression of cardiogenesis by the neural tube can be overcome by ectopic expression of a secreted Wnt antagonist. On the basis of both in vitro and in vivo results, we propose that Wnt signals from the neural tube normally act to block cardiogenesis in the adjacent anterior paraxial mesendoderm.
- Published
- 2001
29. Mechanical motion promotes expression of Prg4 in articular cartilage via multiple CREB-dependent, fluid flow shear stress-induced signaling pathways
- Author
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Elena Kozhemyakina, Alan J. Grodzinsky, Han-Hwa Hung, Andrew B. Lassar, Hiroyasu Ogawa, Massachusetts Institute of Technology. Department of Biological Engineering, Hung, Han-Hwa K., and Grodzinsky, Alan J.
- Subjects
Cartilage, Articular ,Male ,Cell signaling ,Osteoarthritis ,Motor Activity ,CREB ,Mice ,Adenosine Triphosphate ,Chondrocytes ,Stress, Physiological ,Genetics ,medicine ,Extracellular ,Animals ,CREB-binding protein ,Alleles ,Cells, Cultured ,Recombination, Genetic ,Regulation of gene expression ,biology ,medicine.disease ,CREB-Binding Protein ,Molecular biology ,Cell biology ,Gene Expression Regulation ,Proteoglycan ,Gene Knockdown Techniques ,biology.protein ,Calcium ,Female ,Proteoglycans ,Signal transduction ,Signal Transduction ,Research Paper ,Developmental Biology - Abstract
Lubricin is a secreted proteoglycan encoded by the Prg4 locus that is abundantly expressed by superficial zone articular chondrocytes and has been noted to both be sensitive to mechanical loading and protect against the development of osteoarthritis. In this study, we document that running induces maximal expression of Prg4 in the superficial zone of knee joint articular cartilage in a COX-2-dependent fashion, which correlates with augmented levels of phospho-S133 CREB and increased nuclear localization of CREB-regulated transcriptional coactivators (CRTCs) in this tissue. Furthermore, we found that fluid flow shear stress (FFSS) increases secretion of extracellular PGE2, PTHrP, and ATP (by epiphyseal chondrocytes), which together engage both PKA- and Ca++-regulated signaling pathways that work in combination to promote CREB-dependent induction of Prg4, specifically in superficial zone articular chondrocytes. Because running and FFSS both boost Prg4 expression in a COX-2-dependent fashion, our results suggest that mechanical motion may induce Prg4 expression in the superficial zone of articular cartilage by engaging the same signaling pathways activated in vitro by FFSS that promote CREB-dependent gene expression in this tissue., National Institute of Arthritis and Musculoskeletal and Skin Diseases (U.S.) (Grant AR60331)
- Published
- 2013
30. The p38 MAPK family, a pushmi-pullyu of skeletal muscle differentiation
- Author
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Andrew B. Lassar
- Subjects
Transcription, Genetic ,Cellular differentiation ,Reviews ,Biology ,Muscle Development ,MyoD ,Cell Line ,Epigenesis, Genetic ,Histones ,Mice ,Mitogen-Activated Protein Kinase 12 ,MyoD Protein ,medicine ,Animals ,Regeneration ,Gene Silencing ,Phosphorylation ,Muscle, Skeletal ,Promoter Regions, Genetic ,Transcription factor ,Myogenin ,Cell Proliferation ,Genetics ,Myogenesis ,Comment ,Skeletal muscle ,Cell Differentiation ,Cell Biology ,Cell biology ,Mice, Inbred C57BL ,medicine.anatomical_structure ,Gene Expression Regulation ,Histone methyltransferase ,Signal Transduction - Abstract
The mitogen-activated protein kinase p38-gamma is highly expressed in skeletal muscle and is associated with the dystrophin glycoprotein complex; however, its function remains unclear. After induced damage, muscle in mice lacking p38-gamma generated significantly fewer myofibers than wild-type muscle. Notably, p38-gamma-deficient muscle contained 50% fewer satellite cells that exhibited premature Myogenin expression and markedly reduced proliferation. We determined that p38-gamma directly phosphorylated MyoD on Ser199 and Ser200, which results in enhanced occupancy of MyoD on the promoter of myogenin together with markedly decreased transcriptional activity. This repression is associated with extensive methylation of histone H3K9 together with recruitment of the KMT1A methyltransferase to the myogenin promoter. Notably, a MyoD S199A/S200A mutant exhibits markedly reduced binding to KMT1A. Therefore, p38-gamma signaling directly induces the assembly of a repressive MyoD transcriptional complex. Together, these results establish a hitherto unappreciated and essential role for p38-gamma signaling in positively regulating the expansion of transient amplifying myogenic precursor cells during muscle growth and regeneration.
- Published
- 2009
31. pRb is required for MEF2-dependent gene expression as well as cell-cycle arrest during skeletal muscle differentiation
- Author
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Paul S. Kim, Douglas B. Spicer, Andrew B. Lassar, Bennett G. Novitch, and Wang L. Cheung
- Subjects
Transcriptional Activation ,Mef2 ,Cell cycle checkpoint ,Recombinant Fusion Proteins ,Biology ,MyoD ,Resting Phase, Cell Cycle ,Retinoblastoma Protein ,General Biochemistry, Genetics and Molecular Biology ,Mice ,Serine ,Animals ,Myocyte ,Muscle, Skeletal ,Promoter Regions, Genetic ,E2F ,Creatine Kinase ,Transcription factor ,MyoD Protein ,Cell Nucleus ,Binding Sites ,Agricultural and Biological Sciences(all) ,MEF2 Transcription Factors ,Biochemistry, Genetics and Molecular Biology(all) ,Myogenesis ,Cell Cycle ,Cell Differentiation ,Herpes Simplex Virus Protein Vmw65 ,DNA ,Cell cycle ,DNA-Binding Proteins ,Gene Expression Regulation ,Myogenic Regulatory Factors ,Cancer research ,General Agricultural and Biological Sciences ,Transcription Factors - Abstract
Background: The onset of differentiation-specific gene expression in skeletal muscle is coupled to permanent withdrawal from the cell cycle. The retinoblastoma tumor-suppressor protein (pRb) is a critical regulator of this process, required for both cell-cycle arrest in G0 phase and high-level expression of late muscle-differentiation markers. Although the cell-cycle defects that are seen in pRb-deficient myocytes can be explained by the well-described function of pRb as a negative regulator of the transition from G1 to S phase, it remains unclear how pRb positively affects late muscle-gene expression. Results: Here, we show that the myogenic defect in Rb −/− cells corresponds to a deficiency in the activity of the transcription factor MEF2. Without pRb, MyoD induces the accumulation of nuclear-localized MEF2 that is competent to bind DNA yet transcriptionally inert. When pRb is present, MyoD stimulates the function of the MEF2C transcriptional activation domain and the activity of endogenous MEF2-type factors. Co-transfection of MyoD together with an activated form of MEF2C containing the Herpesvirus VP16 transcriptional activation domain partially bypasses the requirement for pRb and induces late muscle-gene expression in replicating cells. This ectopic myogenesis is nevertheless significantly augmented by co-expression of an E2F1–pRb chimeric protein that blocks the cell cycle. Conclusion: These findings indicate that pRb promotes the expression of late-stage muscle-differentiation markers by both inhibiting cell-cycle progression and cooperating with MyoD to promote the transcriptional activation activity of MEF2.
- Published
- 1999
32. Identification of a novel target, FoxA2, in the onset and development of osteoarthritis
- Author
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L. Xu, Andreia M. Ionescu, Elena Kozhemyakina, Vicki Rosen, Klaus H. Kaestner, Malcolm Whitman, Y. Li, and Andrew B. Lassar
- Subjects
medicine.diagnostic_test ,business.industry ,Cartilage ,Biomedical Engineering ,Magnetic resonance imaging ,Osteoarthritis ,Cartilage metabolism ,Meniscus (anatomy) ,Knee Joint ,medicine.disease ,Bone remodeling ,medicine.anatomical_structure ,Rheumatology ,medicine ,Femur ,Orthopedics and Sports Medicine ,Nuclear medicine ,business - Abstract
s / Osteoarthritis and Cartilage 23 (2015) A82eA416 A303 cartilage damage with more lesions on the articular cartilage (OARSI score 2.63±0.43). Conclusions: We have found that conditional deletion of FoxA2 in a murine model of osteoarthritis prevents disease progression, while overexpression of FoxA2 accelerates progression of the disease. Taken together these preliminary results suggest that inhibiting FoxA factors could represent a potential therapeutic intervention to ameliorate the progression of OA. 476 CHARACTERIZATION OF RAT OSTEOARTHRITIS MODEL: CORRELATION BETWEEN WEIGHT BEARING, SERUM BIOMARKERS, IMAGING AND HISTOLOGY C.M. Bagi. Pfizer, Inc, Groton, CT, USA Purpose: The objectives of this work were to assess the pathophysiology of articular cartilage and subchondral bone in the rat medial meniscal tear model (MMT) of osteoarthritis and to evaluate the application of various endpoints and assessment techniques. Standard methods, including histology and serum biomarkers were compared and contrasted with weight bearing and microCT assessment to determine the diagnostic and prognostic value of such endpoints for in studies designed to evaluate efficacy and safety of anti-arthritis medicines. Methods: MMT surgery was performed on male Lewis rats were to induce OA. Biomarkers of bone and cartilage metabolism (Osteocalcin, P1NP, CTX I, TRAP5b, CTX-II) were evaluated in the serum. A Dynamic Weight Bearing (DWB) system was utilized to measure functional capacity of the musculoskeletal system and 3-point bending method was used to assess femur strength. Micro-CT (mCT) and contrast (EPIC) mCT were used to evaluate bone geometry and articular cartilage morphology. Fluorescent labels (calcein and alizarin red-S) were used to assess bone remodeling by histomorphometry in undemineralized bone sections. Articular cartilage and bone morphology was evaluated using histology (HE bone loss at tibial metaphysis and bone formation of the subchondral bone at tibial epiphysis. Contrast enhanced EPIC-mCT imaging provides a reproducible method to assess 3D distribution of GAGs in the articular cartilage of laboratory rats. Contrast imaging data are complementary to histological findings and can be utilized to guide histological assessment. Serum biomarkers along with imaging have abundant translational value when preclinical data are extrapolated to the clinical milieu. 477 MEDIAL CARTILAGE LESIONS DETECTED BY 3.0-TESLA MRI ARE THE RISK FACTOR FOR THE PROGRESSION OF EARLY-STAGE MEDIAL KNEE OSTEOARTHRITIS R. Sadatsuki y, H. Kaneko y, L. Liu z, S. Hada y, M. Kinoshita y, A. Yusup y, Y. Kobayashi y, Y. Saita y, Y. Takazawa y, K. Kaneko yz, M. Ishijima yz. yDept. of Med. for Orhtopaedics and Motor Organ, Juntendo Univ. Graduate Sch. of Med., Tokyo, Japan; z Sportology Ctr., Juntendo Univ. Graduate Sch. of Med., Tokyo, Japan Purpose: It is currently impossible to prevent the progression of the knee osteoarthritis (OA). OA has been believed that cartilage is the primary and most important source of lesions that lead to the disease. However, in addition to cartilage, the importance of all parts of the joint, including the bone, meniscus, ligaments, muscle, and synovium and the crucial role of inflammation in these parts that were previously considered to be irrelevant in this condition are now recognized to be important for OA. The symptoms, especially pain, are also known to be one of the risk factor for the progression of OA. It is impossible to detect the OA-related early changes of the cartilage using radiograph. A magnetic resonance imaging (MRI) is currently underway to facilitate the understanding the pathophysiology of the early stage of knee OA, as it can detect not only bone but also other structural changes occurred in OA. In this study, we examined the factors in patients with early-stage knee OA among the radiographicand MRI-detected structural changes of the knee joint and the clinical symptoms which were associated with the radiographic OA progression after three years of follow up. Methods: Among the one-hundred thirty-two early stage medial knee OA patients with K/L grade 1 or 2 who visited our hospital from January 2009 to December 2011 for medial knee pain, thirty-five patients who were able to follow up for three years were registered. At baseline, the knee radiographs, JKOM score, a patient-oriented outcome measure, and 3.0-Tesla knee MRI were performed. The progression of knee OA was evaluated by radiographs taken at three years from the baseline. OA-related structural changes in the knee joint evaluated by MRI were semi-quantified using the Whole-Organ Magnetic Resonance Imaging Score (WORMS). The subjects were divided into two groups by the presence or absence of the progression of the disease (P; progress group, n1⁄422; NP; non-progression group, n1⁄413). When the K/L grade of the patients were progressed one or more grades after 3 years, they were defined as P. Difference between the two groups was determined by Mann-Whitney U test, and logistic regression analysis was performed using SPSS ver.19.0. Results: No significant differences of the medial knee joint space width (JSW) and femoro-tibial angle (FTA) by radiographs at baseline were observed between NP and P (p1⁄40.73 and 0.31, respectively). Among the MRI-detected joint changes induced by knee OA and evaluated by WORMS, the medial cartilage lesion score in P (4.70) was only significantly increased in comparison to that in NP group (1.62) at baseline (p1⁄40.01). At three years after follow up, the JSWs of the patients in P were significantly decreased in comparison to those of the patients in NP (p1⁄40.007). The MRI-detected medial cartilage lesions showed the significant negative association with the radiographic medial knee joint space width (JSW) after three years of follow up (r1⁄4-0.382, p1⁄40.02). The logistic regression analysis adjusted for age and BMI revealed that among the radiographic OA-related parameters, such as JSW and FTA, pain VAS, JKOM score and the MRI-detected eight parameters, the medial cartilage lesion was only associated with the knee OA progression (OR; 5.02, 95%CI: 1.05 to 23.96, p1⁄40.043). Conclusions: When the structural changes of knee OA were precisely evaluated by 3TMRI andWORMS, the cartilage damage was found to be the most important factor for the progression of the early-stage knee
- Published
- 2015
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33. Ectopic Pax-3 Activates MyoD and Myf-5 Expression in Embryonic Mesoderm and Neural Tissue
- Author
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Martyn Goulding, Susan E. Koester, Andrew B. Lassar, Miguel Maroto, Andrea Münsterberg, and Ram Reshef
- Subjects
medicine.medical_specialty ,animal structures ,Notochord ,Muscle Proteins ,MyoD ,Nervous System ,General Biochemistry, Genetics and Molecular Biology ,Mesoderm ,Mice ,Internal medicine ,Proto-Oncogene Proteins ,Ectoderm ,medicine ,Animals ,Paired Box Transcription Factors ,Hedgehog Proteins ,Sonic hedgehog ,Muscle, Skeletal ,PAX3 Transcription Factor ,Myogenin ,Floor plate ,MyoD Protein ,Embryonic Induction ,biology ,PITX2 ,Myogenesis ,Biochemistry, Genetics and Molecular Biology(all) ,Gene Expression Regulation, Developmental ,Proteins ,Cell Differentiation ,Fibroblasts ,Zebrafish Proteins ,Cell biology ,DNA-Binding Proteins ,Wnt Proteins ,Endocrinology ,medicine.anatomical_structure ,Spinal Cord ,Myogenic regulatory factors ,embryonic structures ,biology.protein ,Trans-Activators ,Myogenic Regulatory Factor 5 ,Mitogens ,Biomarkers ,Signal Transduction ,Transcription Factors - Abstract
Summary induce myogenic precursors or to maintain and expand a population of already specified cells (see Munsterberg To understand how the skeletal muscle lineage is in- and Lassar, 1995, and references therein). We have duced during vertebrate embryogenesis, we have shown that myogenesis of explanted presegmental sought to identify the regulatory molecules that medi- plate mesoderm (isolated from a stage 10 chick embryo) ate induction of the myogenic regulatory factors MyoD requires two signals from axial tissues, one emanating and Myf-5. In this work, we demonstrate that either from the floor plate-notochord complex and the other signals from the overlying ectoderm or Wnt and Sonic from more dorsal regions of the neural tube (Mun- hedgehog signals can induce somitic expression of sterberg and Lassar, 1995). Consistent with these find- the paired box transcription factors, Pax-3 and Pax-7, ings, Emerson and colleagues recently reported that concomitant with expression of Myf-5 and prior to that signals from the notochord are required to initiate quail of MyoD. Moreover, infection of embryonic tissues in MyoD expression and that signals from the neural tube vitro with a retrovirus encoding Pax-3 is sufficient to are required to maintain MyoD expression in ovo (Pow- induce expression of MyoD, Myf-5, and myogenin in nall et al., 1996). both paraxial and lateral plate mesoderm in the ab- The muscle-promoting signal from the floor plate- sence of inducing tissues as well as in the neural tube. notochord complex can be mimicked by the signaling Together, these findings imply that Pax-3 may mediate molecule Sonic hedgehog (Shh), and the muscle-pro- activation of MyoD and Myf-5 in response to muscle- moting signal from the neural tube can be mimicked by inducing signals from either the axial tissues or overly- cell lines programmed to express either Wnt-1 or Wnt-3 ing ectoderm and identify Pax-3 as a key regulator of (Munsterberg et al., 1995; Stern et al., 1995). Because somitic myogenesis.
- Published
- 1997
- Full Text
- View/download PDF
34. [Untitled]
- Author
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Andrew B. Lassar and Thomas M. Schultheiss
- Subjects
Bone morphogenetic protein 8A ,Bone morphogenetic protein 10 ,Anatomy ,Biology ,Bone morphogenetic protein ,Biochemistry ,Bone morphogenetic protein 2 ,Cell biology ,Bone morphogenetic protein 7 ,Bone morphogenetic protein 6 ,Bone morphogenetic protein 5 ,GDF6 ,Genetics ,Molecular Biology - Published
- 1997
35. Skeletal muscle cells lacking the retinoblastoma protein display defects in muscle gene expression and accumulate in S and G2 phases of the cell cycle
- Author
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G J Mulligan, Bennett G. Novitch, Andrew B. Lassar, and Tyler Jacks
- Subjects
Cellular differentiation ,MyoD ,Medical and Health Sciences ,Retinoblastoma Protein ,S Phase ,Mice ,Myocyte ,Phosphorylation ,Cells, Cultured ,Mice, Knockout ,Cultured ,Myogenesis ,Cell Cycle ,Retinoblastoma protein ,Cell Differentiation ,Skeletal ,Articles ,Biological Sciences ,Cell cycle ,Mutant Strains ,medicine.anatomical_structure ,Embryo ,embryonic structures ,Muscle ,Myogenin ,biological phenomena, cell phenomena, and immunity ,Chloramphenicol O-Acetyltransferase ,G2 Phase ,Cells ,Knockout ,Recombinant Fusion Proteins ,Biology ,Transfection ,Thymidine Kinase ,Caffeine ,Cyclins ,CDC2 Protein Kinase ,medicine ,Animals ,Muscle, Skeletal ,MyoD Protein ,Myosin Heavy Chains ,Mammalian ,Skeletal muscle ,DNA ,Cell Biology ,Fibroblasts ,Embryo, Mammalian ,Molecular biology ,Mice, Mutant Strains ,biology.protein ,Developmental Biology - Abstract
Viral oncoproteins that inactivate the retinoblastoma tumor suppressor protein (pRb) family both block skeletal muscle differentiation and promote cell cycle progression. To clarify the dependence of terminal differentiation on the presence of the different pRb-related proteins, we have studied myogenesis using isogenic primary fibroblasts derived from mouse embryos individually deficient for pRb, p107, or p130. When ectopically expressed in fibroblasts lacking pRb, MyoD induces an aberrant skeletal muscle differentiation program characterized by normal expression of early differentiation markers such as myogenin and p21, but attenuated expression of late differentiation markers such as myosin heavy chain (MHC). Similar defects in MHC expression were not observed in cells lacking either p107 or p130, indicating that the defect is specific to the loss of pRb. In contrast to wild-type, p107-deficient, or p130-deficient differentiated myocytes that are permanently withdrawn from the cell cycle, differentiated myocytes lacking pRb accumulate in S and G2 phases and express extremely high levels of cyclins A and B, cyclin-dependent kinase (Cdk2), and Cdc2, but fail to readily proceed to mitosis. Administration of caffeine, an agent that removes inhibitory phosphorylations on inactive Cdc2/cyclin B complexes, specifically induced mitotic catastrophe in pRb-deficient myocytes, consistent with the observation that the majority of pRb-deficient myocytes arrest in S and G2. Together, these findings indicate that pRb is required for the expression of late skeletal muscle differentiation markers and for the inhibition of DNA synthesis, but that a pRb-independent mechanism restricts entry of differentiated myocytes into mitosis.
- Published
- 1996
36. Induction of avian cardiac myogenesis by anterior endoderm
- Author
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Andrew B. Lassar, Steve Xydas, and Thomas M. Schultheiss
- Subjects
Genetic Markers ,medicine.medical_specialty ,Mesoderm ,animal structures ,Xenopus ,Molecular Sequence Data ,Chick Embryo ,Biology ,Polymerase Chain Reaction ,Quail ,Internal medicine ,medicine ,Animals ,Myocyte ,Cell Lineage ,Amino Acid Sequence ,Heart formation ,Molecular Biology ,DNA Primers ,Embryonic Induction ,Base Sequence ,Sequence Homology, Amino Acid ,Myogenesis ,Primitive streak ,Endoderm ,Cardiac myocyte ,Cardiac muscle ,Heart ,Gastrula ,Cell biology ,Endocrinology ,medicine.anatomical_structure ,embryonic structures ,Developmental Biology - Abstract
An experimental system was devised to study the mecha-nisms by which cells become committed to the cardiac myocyte lineage during avian development. Chick tissues from outside the fate map of the heart (in the posterior primitive streak {PPS} of a Hamburger & Hamilton stage 4 embryo) were combined with potential inducing tissues from quail embryos and cultured in vitro. Species-specific RT-PCR was employed to detect the appearance of the cardiac muscle markers chick Nkx-2.5 (cNkx-2.5), cardiac troponin C and ventricular myosin heavy chain in the chick responder tissues. Using this procedure, we found that stage 4-5 anterior lateral (AL) endoderm and anterior central (AC) mesendoderm, but not AL mesoderm or posterior lateral mesendoderm, induced cells of the PPS to differentiate as cardiac myocytes. Induction of cardiogen-esis was accompanied by a marked decrease in the expression of ρ-globin, implying that PPS cells were being induced by anterior endoderm to become cardiac myocytes instead of blood-forming tissue. These results suggest that anterior endoderm contains signaling molecules that can induce cardiac myocyte specification of early primitive streak cells. One of the cardiac muscle markers induced by anterior endoderm, cNkx-2.5, is here described for the first time. cNkx-2.5 is a chick homeobox-containing gene that shares extensive sequence similarity with the Drosophila gene tinman, which is required for Drosophila heart formation. The mesodermal component of cNkx-2.5 expression from stage 5 onward, as determined by in situ hybridization, is strikingly in accord with the fate map of the avian heart. By the time the myocardium and endocardium form distinct layers, cNkx-2.5 is found only in the myocardium. cNkx-2.5 thus appears to be the earliest described marker of avian mesoderm fated to give rise to cardiac muscle.
- Published
- 1995
37. Correlation of Terminal Cell Cycle Arrest of Skeletal Muscle with Induction of p21 by MyoD
- Author
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David Beach, Douglas B. Spicer, Gregory J. Hannon, Andrew B. Lassar, James Rhee, Stephen X. Skapek, Orna Halevy, and Bennett G. Novitch
- Subjects
medicine.medical_specialty ,Multidisciplinary ,Cell cycle checkpoint ,biology ,Cellular differentiation ,Cell cycle ,MyoD ,Cell biology ,Endocrinology ,Cyclin-dependent kinase ,Internal medicine ,biology.protein ,medicine ,Myocyte ,Cell Cycle Protein ,CDK inhibitor - Abstract
Skeletal muscle differentiation entails the coordination of muscle-specific gene expression and terminal withdrawal from the cell cycle. This cell cycle arrest in the G0 phase requires the retinoblastoma tumor suppressor protein (Rb). The function of Rb is negatively regulated by cyclin-dependent kinases (Cdks), which are controlled by Cdk inhibitors. Expression of MyoD, a skeletal muscle-specific transcriptional regulator, activated the expression of the Cdk inhibitor p21 during differentiation of murine myocytes and in nonmyogenic cells. MyoD-mediated induction of p21 did not require the tumor suppressor protein p53 and correlated with cell cycle withdrawal. Thus, MyoD may induce terminal cell cycle arrest during skeletal muscle differentiation by increasing the expression of p21.
- Published
- 1995
38. Finding MyoD with a little help from my friends
- Author
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Andrew B. Lassar
- Subjects
MEF2 Transcription Factors ,Cellular differentiation ,Cell Differentiation ,Cell Biology ,Transfection ,Biology ,Fibroblasts ,MyoD ,Cell biology ,Cell Line ,Myogenic Regulatory Factors ,Cell culture ,Animals ,Myogenin ,Muscle, Skeletal ,MyoD Protein - Published
- 2012
39. Wiring diagrams: regulatory circuits and the control of skeletal myogenesis
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Andrea Münsterberg and Andrew B. Lassar
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Mutagenesis (molecular biology technique) ,Context (language use) ,Regulatory Sequences, Nucleic Acid ,Biology ,Fibroblast growth factor ,MyoD ,Precursor cell ,medicine ,Animals ,Humans ,Genetics ,MEF2 Transcription Factors ,Myogenesis ,Muscles ,Helix-Loop-Helix Motifs ,Embryogenesis ,Skeletal muscle ,Cell Differentiation ,DNA ,Cell Biology ,Cell biology ,DNA-Binding Proteins ,medicine.anatomical_structure ,Gene Expression Regulation ,Myogenic Regulatory Factors ,Transcription Factors - Abstract
During the past year, targeted mutagenesis in mice has begun to clarify the roles of individual members of the MyoD family of myogenic regulators in vertebrate development. In this review, we discuss these studies both in the context of tissue interactions necessary to induce skeletal muscle precursor cells during embryogenesis and the molecular circuitry that regulates the terminal differentiation of these cells.
- Published
- 1994
40. FoxA family members are crucial regulators of the hypertrophic chondrocyte differentiation program
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Andrew B. Lassar, Claudia M. Nicolae, Klaus H. Kaestner, Elena Kozhemyakina, Bjorn R. Olsen, and Andreia M. Ionescu
- Subjects
medicine.medical_specialty ,Cellular differentiation ,Chondrocyte hypertrophy ,Core Binding Factor Alpha 1 Subunit ,Dwarfism ,Chick Embryo ,Biology ,Cell Enlargement ,General Biochemistry, Genetics and Molecular Biology ,Article ,Smad1 Protein ,Mice ,Chondrocytes ,Genes, Reporter ,Internal medicine ,Matrix Metalloproteinase 13 ,medicine ,Animals ,Growth Plate ,Enhancer ,Molecular Biology ,Endochondral ossification ,Cells, Cultured ,Metatarsal Bones ,Binding Sites ,Cell Differentiation ,Cell Biology ,Fibroblasts ,Chondrogenesis ,Alkaline Phosphatase ,Embryo, Mammalian ,Mice, Mutant Strains ,Cell biology ,Endocrinology ,Myogenic Regulatory Factors ,Myogenic regulatory factors ,Hepatocyte Nuclear Factor 3-beta ,FOXA3 ,FOXA2 ,Hepatocyte Nuclear Factor 3-gamma ,Developmental Biology ,Collagen Type X - Abstract
SummaryDuring endochondral ossification, small, immature chondrocytes enlarge to form hypertrophic chondrocytes, which express collagen X. In this work, we demonstrate that FoxA factors are induced during chondrogenesis, bind to conserved binding sites in the collagen X enhancer, and can promote the expression of a collagen X-luciferase reporter in both chondrocytes and fibroblasts. In addition, we demonstrate by both gain- and loss-of-function analyses that FoxA factors play a crucial role in driving the expression of both endogenous collagen X and other hypertrophic chondrocyte-specific genes. Mice engineered to lack expression of both FoxA2 and FoxA3 in their chondrocytes display defects in chondrocyte hypertrophy, alkaline phosphatase expression, and mineralization in their sternebrae and, in addition, exhibit postnatal dwarfism that is coupled to significantly decreased expression of both collagen X and MMP13 in their growth plates. Our findings indicate that FoxA family members are crucial regulators of the hypertrophic chondrocyte differentiation program.
- Published
- 2011
41. Promotion of avian endothelial cell differentiation by GATA transcription factors
- Author
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Georges Daoud, Hervé Kempf, Ronit Yelin, Richard G. James, Andrew B. Lassar, Clifford J. Tabin, Thomas M. Schultheiss, Caramai N. Kamei, Department of Biological Chemistry and Molecular Pharmacology [Boston] (DBCMP), Harvard Medical School [Boston] (HMS), and Department of Genetics, Harvard Medical School, Boston, MA 02115, USA
- Subjects
Mesoderm ,Cellular differentiation ,Bone Morphogenetic Protein 2 ,Apoptosis ,Chick Embryo ,Coturnix ,Biology ,Endothelial cell differentiation ,GATA Transcription Factors ,Article ,Avian Proteins ,03 medical and health sciences ,0302 clinical medicine ,Vasculogenesis ,[SDV.MHEP.CSC]Life Sciences [q-bio]/Human health and pathology/Cardiology and cardiovascular system ,[SDV.BC.IC]Life Sciences [q-bio]/Cellular Biology/Cell Behavior [q-bio.CB] ,medicine ,Animals ,Molecular Biology ,ComputingMilieux_MISCELLANEOUS ,030304 developmental biology ,0303 health sciences ,GATA4 ,GATA2 ,Endothelial Cells ,[SDV.BDD.MOR]Life Sciences [q-bio]/Development Biology/Morphogenesis ,[SDV.BBM.BM]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology ,Cell Differentiation ,Cell Biology ,Molecular biology ,VEGF ,Somite ,medicine.anatomical_structure ,[SDV.BDD.EO]Life Sciences [q-bio]/Development Biology/Embryology and Organogenesis ,[SDV.MHEP.RSOA]Life Sciences [q-bio]/Human health and pathology/Rhumatology and musculoskeletal system ,embryonic structures ,GATA transcription factor ,030217 neurology & neurosurgery ,Developmental Biology - Abstract
In the avian embryo, endothelial cells originate from several sources, including the lateral plate and somite mesoderm. In this study, we show that Gata transcription factors are expressed in the lateral plate and in vasculogenic regions of the avian somite and are able to promote a vascular endothelial fate when ectopically expressed in somite precursors. A fusion of GATA4 to the transcriptional activator VP16 promoted endothelium formation, indicating that GATA transcription factors promote vasculogenesis via activation of downstream targets, while a fusion of GATA4 to the transcriptional repressor engrailed repressed expression of Vascular Endothelial Growth Factor Receptor 2, a marker of endothelial precursors. These findings indicate a role for GATA transcription factors in the differentiation of the endothelium.
- Published
- 2011
42. Cell differentiation: Plasticity and commitment — developmental decisions in the life of a cell
- Author
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Stuart H. Orkin and Andrew B. Lassar
- Subjects
medicine.anatomical_structure ,Cellular differentiation ,Cell ,medicine ,Cell Biology ,Biology ,Plasticity ,Neuroscience - Published
- 2001
43. A Novel Myoblast Enhancer Element Mediates MyoD Transcription
- Author
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Andrew B. Lassar, H Weintraub, and Stephen J. Tapscott
- Subjects
TATA box ,Molecular Sequence Data ,CAAT box ,Muscle Proteins ,Chick Embryo ,Biology ,MyoD ,Mice ,MyoD Protein ,Animals ,Cloning, Molecular ,Enhancer ,Molecular Biology ,Regulation of gene expression ,Base Sequence ,Myogenesis ,Muscles ,Cell Differentiation ,DNA ,Cell Biology ,Molecular biology ,Long terminal repeat ,DNA-Binding Proteins ,Enhancer Elements, Genetic ,Gene Expression Regulation ,Organ Specificity ,CCAAT-Enhancer-Binding Proteins ,Transcription Factors ,Research Article - Abstract
The MyoD gene can orchestrate the expression of the skeletal muscle differentiation program. We have identified the regions of the gene necessary to reproduce transcription specific to skeletal myoblasts and myotubes. A proximal regulatory region (PRR) contains a conserved TATA box, a CCAAT box, and a GC-rich region that includes a consensus SP1 binding site. The PRR is sufficient for high levels of skeletal muscle-specific activity in avian muscle cells. In murine cells the PRR alone has only low levels of activity and requires an additional distal regulatory region to achieve high levels of muscle-specific activity. The distal regulatory region differs from a conventional enhancer in that chromosomal integration appears necessary for productive interactions with the PRR. While the Moloney leukemia virus long terminal repeat can enhance transcription from the MyoD PRR in both transient and stable assays, the simian virus 40 enhancer cannot, suggesting that specific enhancer-promoter interactions are necessary for PRR function.
- Published
- 1992
44. Parathyroid hormone-related peptide represses chondrocyte hypertrophy through a protein phosphatase 2A/histone deacetylase 4/MEF2 pathway
- Author
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Tso-Pang Yao, Elena Kozhemyakina, Andrew B. Lassar, and Todd J. Cohen
- Subjects
Transcription, Genetic ,Recombinant Fusion Proteins ,Phosphatase ,Chondrocyte hypertrophy ,Core Binding Factor Alpha 1 Subunit ,Biology ,Histone Deacetylases ,Smad1 Protein ,chemistry.chemical_compound ,Mice ,Chondrocytes ,Genes, Reporter ,Okadaic Acid ,Colforsin ,Animals ,Protein Phosphatase 2 ,Phosphorylation ,Luciferases ,Molecular Biology ,Smad4 Protein ,Cell Nucleus ,Forskolin ,Parathyroid hormone-related protein ,MEF2 Transcription Factors ,Parathyroid Hormone-Related Protein ,Cell Differentiation ,Cell Biology ,Protein phosphatase 2 ,Hypertrophy ,Articles ,musculoskeletal system ,HDAC4 ,Molecular biology ,Enzyme Activation ,chemistry ,14-3-3 Proteins ,Myogenic Regulatory Factors ,embryonic structures ,Chickens ,Collagen Type X ,Protein Binding ,Signal Transduction - Abstract
The maturation of immature chondrocytes to hypertrophic chondrocytes is regulated by parathyroid hormone-related peptide (PTHrP). We demonstrate that PTHrP or forskolin administration can block induction of collagen X-luciferase by exogenous Runx2, MEF2, and Smad1 in transfected chondrocytes. We have found that PTHrP/forskolin administration represses the transcriptional activity of MEF2 and that forced expression of MEF2-VP16 can restore expression of the collagen X reporter in chondrocytes treated with these agents. PTHrP/forskolin induces dephosphorylation of histone deacetylase 4 (HDAC4) phospho-S246, which decreases interaction of HDAC4 with cytoplasmic 14-3-3 proteins and promotes nuclear translocation of HDAC4 and repression of MEF2 transcriptional activity. We have found that forskolin increases the activity of an HDAC4 phospho-S246 phosphatase and that forskolin-induced nuclear translocation of HDAC4 was reversed by the protein phosphatase 2A (PP2A) antagonist, okadaic acid. Finally, we demonstrate that knockdown of PP2A inhibits forskolin-induced nuclear translocation of HDAC4 and attenuates the ability of this signaling molecule to repress collagen X expression in chondrocytes, indicating that PP2A is critical for PTHrP-mediated regulation of chondrocyte hypertrophy.
- Published
- 2009
45. Id3 Is a Direct Transcriptional Target of Pax7 in Quiescent Satellite Cells
- Author
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Jennifer L. Shadrach, Deepak Kumar, Amy J. Wagers, and Andrew B. Lassar
- Subjects
Satellite Cells, Skeletal Muscle ,Transcription, Genetic ,Molecular Sequence Data ,Biology ,Models, Biological ,Cell Line ,Mice ,Genes, Reporter ,Myocyte ,Animals ,Paired Box Transcription Factors ,RNA, Small Interfering ,Luciferases ,Promoter Regions, Genetic ,Molecular Biology ,PAX3 Transcription Factor ,Conserved Sequence ,Inhibitor of Differentiation Protein 2 ,Regulation of gene expression ,Gene knockdown ,Binding Sites ,Base Sequence ,Myogenesis ,PAX7 Transcription Factor ,Cell Biology ,Articles ,musculoskeletal system ,Molecular biology ,Gene Expression Regulation ,Cell culture ,Gene Knockdown Techniques ,Ectopic expression ,Inhibitor of Differentiation Proteins ,Stem cell ,Chromatin immunoprecipitation ,tissues ,Protein Binding - Abstract
Pax7 is a key regulator of skeletal muscle stem cells and is required along with Pax3 to generate skeletal muscle precursors. We have identified a collection of genes induced by either Pax3 or Pax7 in C2C12 muscle cells. Two notable Pax3/7 targets are the inhibitory helix-loop-helix (HLH) proteins inhibitor of DNA binding (Id) 2 and Id3, both of which are coordinately expressed with Pax7 in quiescent satellite cells and are induced in quiescent C2C12 myogenic cells after ectopic expression of either Pax3 or Pax7. Ectopic Pax7 activates expression of a luciferase reporter driven by the Id3 promoter, and maximal induction of this reporter requires a conserved Pax7 binding site located upstream of the Id3 gene. Chromatin immunoprecipitation indicated that Pax7 is bound upstream of the Id3 promoter in quiescent satellite cells. In addition, short hairpin RNA-mediated knockdown of Pax7 expression in cultured satellite cells coordinately decreased both Id2 and Id3 expression. Together, these findings indicate that Id3 is a direct transcriptional target for Pax7 in quiescent satellite cells, and they suggest that Pax7 acts to block premature differentiation of quiescent satellite cells by inducing the expression of Id2 and Id3, which in turn may act to block either the precocious induction of myogenic basic (b)HLH proteins, the activity of myogenic bHLH proteins, or both.
- Published
- 2009
46. Functional activity of myogenic HLH proteins requires hetero-oligomerization with E12/E47-like proteins in vivo
- Author
-
Anna Voronova, Cornelis Murre, Robert L. Davis, David Baltimore, Harold Weintraub, Woodring E. Wright, Tom Kadesch, and Andrew B. Lassar
- Subjects
Transcription, Genetic ,Macromolecular Substances ,Transcription Factor 7-Like 1 Protein ,Muscle Proteins ,Biology ,Transfection ,MyoD ,DNA-binding protein ,General Biochemistry, Genetics and Molecular Biology ,Cell Line ,MyoD Protein ,Animals ,Myocyte ,Phosphorylation ,Myogenin ,Immunoassay ,Reporter gene ,PITX2 ,Myogenesis ,Immune Sera ,Muscles ,Adenovirus Early Proteins ,Oncogene Proteins, Viral ,musculoskeletal system ,Molecular biology ,DNA-Binding Proteins ,Mutagenesis, Site-Directed ,Oligonucleotide Probes ,TCF Transcription Factors ,tissues ,Transcription Factors - Abstract
In this report we provide four lines of evidence indicating that E12/E47-like proteins interact in vivo with the myogenic HLH proteins MyoD and myogenin. First, cotransfection of MyoD and E47 in COS cells indicates that these factors synergistically enhance transcription of a reporter gene containing an oligomerized MyoD-binding site. Second, mobility-shift assays of muscle cell nuclear extracts, "double shifted" with specific antisera, have identified complexes binding to the MEF1 site that contain either MyoD or myogenin in association with E12/E47-like proteins. Third, association with E47 alters the phosphorylation state of MyoD. Fourth, C3H10T1/2 cells expressing antisense E2A transcripts contain low levels of E2A gene products and display less terminal muscle differentiation when infected with retroviral MyoD or when challenged to differentiate with 5-azacytidine treatment. In addition we demonstrate that MyoD, in conjunction with E12/E47-like proteins, is functioning as a regulatory nodal point for activation of several other downstream muscle regulators.
- Published
- 1991
47. A gradient of Shh establishes mutually repressing somitic cell fates induced by Nkx3.2 and Pax3
- Author
-
Philip G. Lee, Dana M. Cairns, Li Zeng, Andrew B. Lassar, and Mie Elissa Sato
- Subjects
animal structures ,PAX3 ,Chick Embryo ,Models, Biological ,Shh ,Article ,Wnt3 Protein ,03 medical and health sciences ,0302 clinical medicine ,Myotome ,Wnt3A Protein ,Ectoderm ,medicine ,Paraxial mesoderm ,Animals ,Humans ,Paired Box Transcription Factors ,Cell Lineage ,Hedgehog Proteins ,Somite ,Sonic hedgehog ,10. No inequality ,Molecular Biology ,030304 developmental biology ,Body Patterning ,Regulation of gene expression ,Homeodomain Proteins ,0303 health sciences ,Pax3 ,biology ,Wnt signaling pathway ,Gene Expression Regulation, Developmental ,Nkx3.2 ,SOX9 Transcription Factor ,Cell Biology ,Rats ,Wnt Proteins ,medicine.anatomical_structure ,Somites ,embryonic structures ,Cancer research ,biology.protein ,Chondrogenesis ,030217 neurology & neurosurgery ,WNT3A ,Biomarkers ,Developmental Biology ,Signal Transduction - Abstract
Wnt and Sonic Hedgehog (Shh) signals are known to pattern the somite into dermomyotomal, myotomal and sclerotomal cell fates. By employing explants of presomitic mesoderm cultured with constant levels of Wnt3a conditioned medium and increasing levels of Shh, we found that differing levels of Shh signaling elicit differing responses from somitic cells: the lowest level of Shh signaling allows dermomyotomal gene expression, intermediate levels induce loss of dermomyotomal markers and activation of myogenic differentiation, and higher levels induce loss of myotomal markers and activation of sclerotomal gene expression. In addition, we have found that in the presence of high levels of Wnt signaling, instead of inducing sclerotomal markers, Shh signals act to maintain the expression of dermomyotomal and myotomal markers. One of the sclerotomal genes induced by high levels of Shh signaling is Nkx3.2. Forced expression of Nkx3.2 blocks somitic expression of the dermomyotomal marker Pax3 both in vitro and in vivo. Conversely, forced expression of Pax3 in somites can block Shh-mediated induction of sclerotomal gene expression and chondrocyte differentiation in vitro. Thus we propose that varying levels of Shh signaling act in a morphogen-like manner to elicit differing responses from somitic cells, and that Pax3 and Nkx3.2 set up mutually repressing cell fates that promote either dermomyotome/myotome or sclerotome differentiation, respectively.
- Published
- 2008
48. Id: A Negative Regulator of Helix-Loop-Helix DNA Binding Proteins
- Author
-
Daniel Lockshon, Robert L. Davis, Robert Benezra, Stephen J. Tapscott, Mathew J. Thayer, Andrew B. Lassar, and Harold Weintraub
- Subjects
Myogenic differentiation ,HMG-box ,Basic helix-loop-helix ,Chemistry ,Muscles ,General Neuroscience ,Molecular Sequence Data ,Muscle Proteins ,Cell Differentiation ,DNA ,DNA-binding protein ,General Biochemistry, Genetics and Molecular Biology ,Negative regulator ,Cell biology ,History and Philosophy of Science ,Terminal (electronics) ,Multigene Family ,Sequence Homology, Nucleic Acid ,Animals ,Myogenin ,Amino Acid Sequence ,MyoD Protein - Published
- 1990
49. Prochondrogenic signals induce a competence for Runx2 to activate hypertrophic chondrocyte gene expression
- Author
-
Hervé Kempf, Aaron M. Udager, Andreia M. Ionescu, Andrew B. Lassar, Department of Biological Chemistry and Molecular Pharmacology [Boston] (DBCMP), and Harvard Medical School [Boston] (HMS)
- Subjects
animal structures ,Chondrocyte hypertrophy ,Core Binding Factor Alpha 1 Subunit ,SOX9 ,Chick Embryo ,Biology ,Bone morphogenetic protein ,Chondrocyte ,Mesoderm ,03 medical and health sciences ,0302 clinical medicine ,Chondrocytes ,stomatognathic system ,[SDV.MHEP.CSC]Life Sciences [q-bio]/Human health and pathology/Cardiology and cardiovascular system ,[SDV.BC.IC]Life Sciences [q-bio]/Cellular Biology/Cell Behavior [q-bio.CB] ,medicine ,Animals ,Transcription factor ,ComputingMilieux_MISCELLANEOUS ,030304 developmental biology ,Regulation of gene expression ,0303 health sciences ,Gene Expression Regulation, Developmental ,[SDV.BDD.MOR]Life Sciences [q-bio]/Development Biology/Morphogenesis ,[SDV.BBM.BM]Life Sciences [q-bio]/Biochemistry, Molecular Biology/Molecular biology ,Chondrogenesis ,Cell biology ,RUNX2 ,medicine.anatomical_structure ,[SDV.BDD.EO]Life Sciences [q-bio]/Development Biology/Embryology and Organogenesis ,[SDV.MHEP.RSOA]Life Sciences [q-bio]/Human health and pathology/Rhumatology and musculoskeletal system ,embryonic structures ,Immunology ,030217 neurology & neurosurgery ,Developmental Biology ,Signal Transduction - Abstract
Whereas Runx2 is necessary for bone formation and cartilage hypertrophy, it is unclear why Runx2 induces markers of chondrocyte hypertrophy only in chondrocytes. We document that chondrocytes either contain a cofactor, which can be induced in somitic cells by prochondrogenic signals, that is necessary for Runx2 to induce chondrocyte hypertrophy or, alternatively, lack a repressor of this maturation program. Sequential Shh and bone morphogenetic protein (BMP) signals or forced expression of either Nkx3.2 or Sox9 (plus BMP signals) induces chondrogenesis in presomitic mesoderm and simultaneously induces a competence for Runx2 to activate the chondrocyte maturation program. The ability of either sequential Shh and BMP signals or retrovirus-encoded Nkx3.2 or Sox9 to induce this competence correlates with their ability to activate chondrogenesis in various embryonic tissues. Consistent with these findings in embryonic tissues, we have found that cotransfected Runx2 and Smad1 are able to induce the expression of a reporter construct driven by the collagen X regulatory sequences in chondrocytes but not in fibroblasts. In contrast, both Runx2 and Smad1 are competent to activate reporters driven by either reiterated Runx or Smad binding sites, respectively, in both cell types. As Sox9 and Nkx3.2 have previously been shown to block chondrocyte maturation in vivo, our findings suggest that these transcription factors can, in addition, either induce the expression or activity of a factor in chondrocytes that is required for Runx2 to activate the chondrocyte maturation program, or alternatively that these transcription factors block the expression or activity of a repressor of this maturation program.
- Published
- 2007
50. Asymmetric localization of Numb in the chick somite and the influence of myogenic signals
- Author
-
Andrew B. Lassar, Li Zeng, and Tamara Holowacz
- Subjects
animal structures ,Transcription, Genetic ,Notch signaling pathway ,Dermomyotome ,Chick Embryo ,Biology ,MyoD ,Muscle Development ,Article ,Wnt3 Protein ,MyoD Protein ,Myotome ,medicine ,Animals ,Hedgehog Proteins ,RNA, Messenger ,Receptors, Notch ,Myogenesis ,Membrane Proteins ,Cell Differentiation ,Cell biology ,Wnt Proteins ,Somite ,medicine.anatomical_structure ,Biochemistry ,Somites ,embryonic structures ,NUMB ,Trans-Activators ,Carrier Proteins ,hormones, hormone substitutes, and hormone antagonists ,Developmental Biology - Abstract
Whereas Notch signaling is known to play an essential role in the formation of somites, its role during later stages of somite maturation is less well understood. Here, we examine the signals and transcription factors that control the expression of the Notch antagonist, Numb, during somite maturation in the chick embryo. Numb mRNA is present in the epithelial somite and is increased in expression in the forming myotome. Numb protein displays a very specific subcellular localization and dynamic expression during somite maturation. Numb protein is asymmetrically localized in a cortical crescent on the basal side of dividing cells in the dorsomedial lip of the dermomyotome and is subsequently uniformly distributed throughout differentiated myotomal cells. Treatment of somites with either the combination of Wnt-3a and Shh, or ectodermal signals plus noggin, both of which induce somitic myogenesis, did not significantly affect Numb transcript levels but did lead to a dramatic increase in the levels of Numb protein, which was uniformly distributed throughout the cytoplasm of the resultant myotubes. Forced expression of MyoD in somites similarly induced high levels of Numb protein throughout the cytoplasm, without affecting Numb mRNA levels. We also found that signals that promote somitic myogenesis or forced MyoD expression induced expression of the Notch ligand, Serrate-2. Our findings suggest that Notch signals are specifically repressed in the myotome and that asymmetric expression of Numb in dividing cells of the dorsomedial lip of the dermomyotome may modulate whether these cells continue to divide or differentiate into myotomal cells.
- Published
- 2006
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