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To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2010.09.024 Byline: Yiwei Wang, James F. Martin, C. Brian Bai Keywords: Gli1; Gli2; Gli3; Shh; Mouse; Pituitary; Patterning; Proliferation Abstract: Induction of early pituitary progenitors is achieved through combined activities of signals from adjacent embryonic tissues. Previous studies have identified a requirement for oral ectoderm derived Sonic Hedgehog (Shh) in specification and/or proliferation of early pituitary progenitors, however how different Gli genes mediate Shh signaling to control pituitary progenitor development has not yet been determined. Here we show that Gli2, which encodes a major Gli activator, is required for proliferation of specific groups of pituitary progenitors but not for initial dorsoventral patterning. We further show that the action of Gli2 occurs prior to the closure of Rathke' pouch. Lastly, we show that Shh/Gli2 signaling controls the diencephalic expression of Bone morphogenetic protein 4 (Bmp4) and Fibroblast growth factor 8 (Fgf8), two genes that are known to play critical roles in patterning and growth of Rathke's pouch. Our results therefore suggest both cell-autonomous and non-cell-autonomous requirements for Gli2 in regulation of pituitary progenitor specification, proliferation and differentiation. Article History: Received 30 June 2010; Revised 21 September 2010; Accepted 30 September 2010

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2006.03.013 Byline: Dmitry A. Ovchinnikov (a), Jennifer Selever (b), Ying Wang (a), You-Tzung Chen (a), Yuji Mishina (c), James F. Martin (b), Richard R. Behringer (a) Keywords: Bone morphogenetic protein receptor; Limb development; Pattern formation; Conditional knockout; Prx1 Abstract: The mesenchyme of the developing vertebrate limb responds to inductive signals, giving rise to skeletal elements that define limb shape and size. Several signals emanate from the limb ectoderm and in particular from the specialized epithelium of the apical ectodermal ridge (AER), including three members of the bone morphogenetic protein (BMP) family of signaling molecules, BMP2, BMP4 and BMP7. Using the Cre/loxP system in mice, we rendered limb bud mesenchyme insensitive to BMP signals through the type I receptor, BMPR-IA. Conditional mutants had shortened limbs and almost complete agenesis of the autopod because of reduced cell proliferation. Reduced expression of downstream BMP signaling targets, Msx1, Msx2 and gremlin in the distal mesenchyme (progress zone) correlated with decreased levels of cyclin D1 and Wnt5a. Ectopic anterior activation of sonic hedgehog (SHH) signaling and Hox expression revealed alterations in anterior-posterior (AP) patterning. Abnormal localization of Lmx1b-expressing cells in the ventral mesenchyme, along with histological alterations and an abnormal melanization pattern of the limb, indicate altered dorsal-ventral (DV) boundaries. These findings suggest that signaling through BMPR-IA in limb mesenchyme is essential for distal outgrowth and also influences AP and DV patterning. Author Affiliation: (a) Department of Molecular Genetics, University of Texas M. D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030, USA (b) Institute of Biosciences and Technology, Texas A and M University, Houston, TX 77030, USA (c) Laboratory of Reproductive and Developmental Toxicology, National Institute of Environmental Health Sciences, Research Triangle Park, NC 27709, USA Article History: Received 9 September 2005; Revised 12 February 2006; Accepted 13 March 2006

Mandibular development is regulated by an interplay between a specified branchial arch ectoderm and a plastic mesenchyme. Moreover, signaling from the pharyngeal endoderm has been shown to be important for mandibular morphogenesis. To gain insight into the mechanisms regulating mandibular pattern, it is important to investigate the function of the epithelial-derived signals. Bmp4 is expressed in both distal, mandibular arch ectoderm and pharyngeal endoderm. Here, we show that deletion of Bmp4 in the mandibular ectoderm and to a lesser extent in the pharyngeal endoderm, resulted in severe defects in mandibular development. Furthermore, our data uncovered different Bmp4 thresholds for expression of the Bmp-dependent Msx1 and Msx2 genes in mandibular mesenchyme. We also found thai ectodermal Fgf8 expression was both activated and repressed by Bmp4 in a dosage-dependent fashion indicating a novel Bmp4 function in threshold-specific regulation of Fgf8 transcription. Lastly, we provide evidence that Prx homeobox genes repress expression of an Msx2 transgene, previously shown to be Bmp4-responsive, revealing a mechanism for differential regulation of Msx1 and Msx2 by Bmp signaling. Keywords: Bone morphogenetic protein; Craniofacial morphogenesis

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2004.08.024 Byline: Jennifer Selever (a), Wei Liu (a), Mei-Fang Lu (a), Richard R. Behringer (b), James F. Martin (a) Keywords: Bone morphogenetic protein; Morphogenesis; Patterning Abstract: In the developing limb, Bmp4 is expressed in the apical ectodermal ridge (AER) and underlying mesoderm. Insight into the function of Bmp4 in limb development has been hampered by the early embryonic lethality of Bmp4 null embryos. We directly investigated Bmp4 using a conditional null allele of Bmp4 and the Prx1.sup.cre transgene to inactivate Bmp4 in limb bud mesoderm. The limb bud mesoderm of Prx1.sup.cre ;Bmp4 mutants was defective in production of Bmp4 but still competent to respond to Bmp signaling. Prx1.sup.cre ;Bmp4 mutant embryos had defective digit patterning including hindlimb preaxial polydactyly with posterior digit transformations. The Prx1.sup.cre ;Bmp4 mutants also had postaxial polydactyly with digit five duplications. Bmp4 mutant limbs had delayed induction and maturation of the AER that resulted in expanded Shh signaling. Moreover, the AER persisted longer in the Bmp4 mutant limb buds exposing the forming digits to prolonged Fgf8 signaling. Our data show that Bmp4 in limb mesoderm regulates AER induction and maturation and implicate signaling from the AER in regulation of digit number and identity. Author Affiliation: (a) Alkek Institute of Biosciences and Technology, Texas A&M System Health Science Center, Houston, TX 77030, United States (b) Department of Molecular Genetics, University of Texas M.D. Anderson Cancer Center, Houston, TX 77030, United States Article History: Received 18 June 2004; Accepted 17 August 2004

Results demonstrate that long range signaling by the sonic hedgehog is mediated by a lipophilic modification of the N-terminus with a cholesterol moiety, which aids in the sonic hedgehog's ability to signal over a few hundred microns. The lipophilic modification also modulates the signal by the sonic hedgehog's receptor, Ptc1.

A cooperative interaction between the DNA binding domains of the myocyte enhancer factor-2 (MEF2) and the myogenic basic helix-loop-helix (bHLH) proteins increases muscle gene expression. MEF2 binds to the E box target regions of bHLH. The stimulation of gene expression in fibroblasts requires a transactivation domain in either MEF2 or BHLH. The probable mechanisms of muscle gene activation are discussed.

Cloning of MHox chicken homolog (gMHox) indicates that the DNA-binding properties and amino acid sequence of the avian gene products are similar to those of murine. The expression pattern indicates that the avian and murine gene products have similar expression sites, with the level of expression high in somatic, splanchnic and limb bud mesoderms. The process of chondrogenesis downregulates the gMHox, though the expression of gMHox is not disturbed in perichondrium and mesenchymal cells. This indicates that the gMHox preserves mesenchymal cell lineages.

Mammalian cardiomyocytes (CMs) undergo polyploidization after birth, accompanied by the loss of CM proliferation and regenerative capacity, although why this occurs is still poorly understood. In this issue of Developmental Cell , Gan et al. show that premature CM polyploidization, through defective RNA splicing, is detrimental to ventricular wall growth. [ABSTRACT FROM AUTHOR]

Although the majority of SUMO substrates are localized in the nucleus, SUMOylation is not limited to nuclear proteins and can be also detected in extra-nuclear proteins. In this review, we will highlight and discuss how SUMOylation in different cellular compartments regulate biological processes. First, we will discuss the key role of SUMOylation of proteins in the extra-nuclear compartment in cardiomyocytes, which is overwhelmingly cardio-protective. On the other hand, SUMOylation of nuclear proteins is generally detrimental to the cardiac function mainly because of the trans-repressive nature of SUMOylation on many transcription factors. We will also discuss the potential role of SUMOylation in epigenetic regulation. In this review, we will propose a new concept that shuttling of SUMO proteases between the nuclear and extra-nuclear compartments without changing their enzymatic activity regulates the extent of SUMOylation in these compartments and determines the response and fate of cardiomyocytes after cardiac insults. Approaches focused specifically to inhibit this shuttling in cardiomyocytes will be necessary to understand the whole picture of SUMOylation and its pathophysiological consequences in the heart, especially after cardiac insults. This article is part of a Special Issue entitled: Genetic and epigenetic control of heart failure - edited by Jun Ren & Megan Yingmei Zhang. [ABSTRACT FROM AUTHOR]

Background and Aims Sedation for GI endoscopy directed by anesthesia professionals (ADS) is used with the intention of improving throughput and patient satisfaction. However, data on its safety are sparse because of the lack of adequately powered, randomized controlled trials comparing it with endoscopist-directed sedation (EDS). This study was intended to determine whether ADS provides a safety advantage when compared with EDS for EGD and colonoscopy. Methods This retrospective, nonrandomized, observational cohort study used the Clinical Outcomes Research Initiative National Endoscopic Database, a network of 84 sites in the United States composed of academic, community, health maintenance organization, military, and Veterans Affairs practices. Serious adverse events (SAEs) were defined as any event requiring administration of cardiopulmonary resuscitation, hospital or emergency department admission, administration of rescue/reversal medication, emergency surgery, procedure termination because of an adverse event, intraprocedural adverse events requiring intervention, or blood transfusion. Results There were 1,388,235 patients in this study that included 880,182 colonoscopy procedures (21% ADS) and 508,053 EGD procedures (23% ADS) between 2002 and 2013. When compared with EDS, the propensity-adjusted SAE risk for patients receiving ADS was similar for colonoscopy (OR, .93; 95% CI, .82-1.06) but higher for EGD (OR, 1.33; 95% CI, 1.18-1.50). Additionally, with further stratification by American Society of Anesthesiologists (ASA) class, the use of ADS was associated with a higher SAE risk for ASA I/II and ASA III subjects undergoing EGD and showed no difference for either group undergoing colonoscopy. The sample size was not sufficient to make a conclusion regarding ASA IV/V patients. Conclusions Within the confines of the SAE definitions used, use of anesthesia professionals does not appear to bring a safety benefit to patients receiving colonoscopy and is associated with an increased SAE risk for ASA I, II, and III patients undergoing EGD. [ABSTRACT FROM AUTHOR]

Summary A fundamental principle governing organ size and function is the fine balance between cell proliferation and cell differentiation. Here, we identify RONIN (THAP11) as a key transcriptional regulator of retinal progenitor cell (RPC) proliferation. RPC-specific loss of Ronin results in a phenotype strikingly similar to that resulting from the G1- to S-phase arrest and photoreceptor degeneration observed in the Cyclin D1 null mutants. However, we determined that, rather than regulating canonical cell-cycle genes, RONIN regulates a cohort of mitochondrial genes including components of the electron transport chain (ETC), which have been recently implicated as direct regulators of the cell cycle. Coincidentally, with premature cell-cycle exit, Ronin mutants exhibited deficient ETC activity, reduced ATP levels, and increased oxidative stress that we ascribe to specific loss of subunits within complexes I, III, and IV. These data implicate RONIN as a positive regulator of mitochondrial gene expression that coordinates mitochondrial activity and cell-cycle progression. [ABSTRACT FROM AUTHOR]

Summary Expression of Pitx2 on the left side of the embryo patterns left-right (LR) organs including the dorsal mesentery (DM), whose asymmetric cell behavior directs gut looping. Despite the importance of organ laterality, chromatin-level regulation of Pitx2 remains undefined. Here, we show that genes immediately neighboring Pitx2 in chicken and mouse, including a long noncoding RNA ( Pitx2 locus-asymmetric regulated RNA or Playrr ), are expressed on the right side and repressed by Pitx2 . CRISPR/Cas9 genome editing of Playrr, 3D fluorescent in situ hybridization (FISH), and variations of chromatin conformation capture (3C) demonstrate that mutual antagonism between Pitx2 and Playrr is coordinated by asymmetric chromatin interactions dependent on Pitx2 and CTCF. We demonstrate that transcriptional and morphological asymmetries driving gut looping are mirrored by chromatin architectural asymmetries at the Pitx2 locus. We propose a model whereby Pitx2 auto-regulation directs chromatin topology to coordinate LR transcription of this locus essential for LR organogenesis. [ABSTRACT FROM AUTHOR]

The closely related homeobox genes prx-1 and prx-2 are expressed in lateral plate and limb bud mesoderm, but targeted inactivation of these genes failed to demonstrate a limb phenotype. Here we report that mice carrying compound mutations in prx-1 and prx-2 have severe limb deformities. In the forelimb autopod, pre- and postaxial polydactyly were found most commonly, but also syndactyly, oligodactyly, and abnormal digit placement affecting posterior elements were observed. In the hindlimb, preaxial polydactyly with variable expressivity was seen in all cases. Extreme distal digit duplications were seen in both the fore- and hindlimbs. prx-1; prx-2 double-mutant mice also displayed extreme shortening and impaired ossification of the hindlimb zeugopods. Integrity of the forelimb apical ectodermal ridge was abnormal as determined by expression of FGF8 and BMP4. Expression of msx-1 and msx-2, markers for BMP signaling pathways, was absent in regions of the posterior handplates, while expression of Shh and patched was unaffected. The mutant phenotypes were dosage dependent, since prx-1 -/-; prx-2 +/- mice also displayed severe limb abnormalities. These data suggest that prx-1 and prx-2 cooperatively regulate handplate and hindlimb zeugopod morphogenesis through BMP. mediated signaling pathways. Key Words: morphogenesis; limb development; gene targeting; paired homeobox.

Background: The SEDASYS System is an investigational computer-assisted personalized sedation system integrating propofol delivery with patient monitoring to enable endoscopist/nurse teams to safely administer propofol. Objective: To compare the safety and effectiveness of the SEDASYS System to the current standard of care for sedation during routine endoscopic procedures. Design: Nonblinded multicenter randomized comparative study. Setting: Four ambulatory surgery centers, 3 endoscopy centers, and 1 academic center in the United States. Patients: One thousand American Society of Anesthesiologists physical status class I to III adults undergoing routine colonoscopy or EGD. Interventions: Sedation with the SEDASYS System (SED) and sedation with each site''s current standard of care (CSC; benzodiazepine/opioid combination). Main Outcome Measurements: Area under the curve of oxygen desaturation was the primary endpoint. Secondary endpoints included patient satisfaction, clinician satisfaction, level of sedation, and patient recovery time. Results: Four hundred ninety-six patients were randomized to SED and 504 to CSC. Area under the curve of oxygen desaturation was significantly lower for SED (23.6 s·%) than for CSC (88.0 s·%; P = .028). Patients were predominately minimally to moderately sedated in both groups. SED patients were significantly more satisfied than CSC patients (P = .007). Clinician satisfaction was greater with SED than with CSC (P < .001). SED patients recovered faster than CSC patients (P < .001). The incidence of adverse events was 5.8% in the SED group and 8.7% in the CSC group. Limitations: Nonblinded. Conclusions: The SEDASYS System could provide endoscopist/nurse teams a safe and effective on-label means to administer propofol to effect minimal to moderate sedation during routine colonoscopy and EGD. (ClinicalTrials.gov identifier: NCT00452426.) [Copyright &y& Elsevier]

This is a case of a 36-year-old Spanish-speaking Hispanic man who was brought to a busy suburban New Jersey emergency department (ED) by family members for altered mental status. By report, patient was noted by family to be "not acting normal" at home, when he went into his bathroom and locked the door. A brief time thereafter, he emerged smelling of bleach and with confused speech. The family surmised that he tried to commit suicide by drinking bleach and emergently brought the patient to the ED. [ABSTRACT FROM AUTHOR]

Background: Demand for colonoscopy and EGD procedures is increasing. Impediments to performing these examinations persist. Patients perceive these procedures as unpleasant and painful. The use of suboptimal sedatives results in inefficiency in endoscopy practices. Improving sedation methods utilizing precise control of preferred sedatives may increase patient satisfaction and practice efficiency. Objective: Our purpose was to demonstrate the feasibility of computer-assisted personalized sedation (CAPS) for facilitating the precise administration of propofol by endoscopist/nurse teams, achieving minimal to moderate sedation in subjects undergoing routine endoscopies. Design: Open label, single-center studies. Setting: Endoscopy clinics in Charlottesville, Virginia, and Gent, Belgium. Subjects: Twenty-four adults per center; 12 colonoscopies, 12 EGDs. Interventions: Propofol sedation with CAPS by endoscopist/registered nurse care teams. Main Outcome Measurements: Sedation level measured by modified observer''s assessment of alertness/sedation (MOAA/S), recovery time measured from endoscope removal until Aldrete ≥ 12, dosage of propofol, oxygen saturation, and safety assessments. Results: Subjects responded to mild tactile and verbal stimuli MOAA/S = 5, 4, 3, or 2) 99% of the time. Mean propofol doses in the United States and Belgium were 65.4 and 72.1 mg, respectively. Mean recovery times were 29 and 10 seconds, respectively. Oxygen desaturation occurred in only 6% of subjects. No device-related adverse events occurred. Limitation: Open-label design. Conclusions: Using CAPS, the endoscopist/nurse teams precisely controlled the administration of propofol achieving minimal to moderate sedation in subjects undergoing colonoscopy and EGD procedures. Mean propofol dosage was low and post-procedure recovery times were rapid. The device performed well when operated by the endoscopist/nurse team, with no device-related adverse events. [Copyright &y& Elsevier]

In response to retinal damage, the Müller glial cells (MGs) of the zebrafish retina have the ability to undergo a cellular reprogramming event in which they enter the cell cycle and divide asymmetrically, thereby producing multipotent retinal progenitors capable of regenerating lost retinal neurons. However, mammalian MGs do not exhibit such a proliferative and regenerative ability. Here, we identify Hippo pathway-mediated repression of the transcription cofactor YAP as a core regulatory mechanism that normally blocks mammalian MG proliferation and cellular reprogramming. MG-specific deletion of Hippo pathway components Lats1 and Lats2 , as well as transgenic expression of a Hippo non-responsive form of YAP (YAP5SA), resulted in dramatic Cyclin D1 upregulation, loss of adult MG identity, and attainment of a highly proliferative, progenitor-like cellular state. Our results reveal that mammalian MGs may have latent regenerative capacity that can be stimulated by repressing Hippo signaling. • Hippo represses YAP activity in Müller glial cells of the damaged mammalian retina • Genetic bypass of Hippo signaling causes spontaneous Müller glial proliferation • Single-cell transcriptomic analysis of reprogrammed Müller glia • Hippo prevents Müller glial reprogramming to a proliferative, progenitor-like state Rueda et al. identify the Hippo pathway as an endogenous molecular mechanism normally preventing mammalian Müller glial reprogramming to a proliferative, progenitor-like state. [ABSTRACT FROM AUTHOR]

Summary Cellular heterogeneity within the mammalian brain poses a challenge toward understanding its complex functions. Within the olfactory bulb, odor information is processed by subtypes of inhibitory interneurons whose heterogeneity and functionality are influenced by ongoing adult neurogenesis. To investigate this cellular heterogeneity and better understand adult-born neuron development, we utilized single-cell RNA sequencing and computational modeling to reveal diverse and transcriptionally distinct neuronal and nonneuronal cell types. We also analyzed molecular changes during adult-born interneuron maturation and uncovered developmental programs within their gene expression profiles. Finally, we identified that distinct neuronal subtypes are differentially affected by sensory experience. Together, these data provide a transcriptome-based foundation for investigating subtype-specific neuronal function in the olfactory bulb (OB), charting the molecular profiles that arise during the maturation and integration of adult-born neurons and how they dynamically change in an activity-dependent manner. Graphical Abstract Highlights • Single-cell sequencing reveals cellular heterogeneity in the mouse olfactory bulb • Differential gene expression uncovers selective markers for cell types • Pseudotemporal ordering of adult-born neurons reveals developmentally governed genes • Olfactory experience changes the cellular composition of olfactory bulb circuits Using single-cell sequencing, Tepe et al. describe cellular heterogeneity in the mouse olfactory bulb, uncover markers for each cell type, and reveal differentially regulated genes in adult-born neurons. These findings provide a framework for studying cell-type-specific functions and circuit integration in the mammalian brain. [ABSTRACT FROM AUTHOR]

Ischemic heart disease is one of the leading causes of mortality. Myocardial infarction causes loss of cardiomyocytes in the injury area accompanied by formation of a fibrotic scar. This initiates a cascade of events including further loss of myocyte, increased fibrosis, and pathological cardiac hypertrophy, eventually leading to the heart failure. Cardiomyocytes in mammals have limited regenerative potential due to post mitotic nature of cardiomyocytes. Recently, multiple studies have provided substantial insights in to the molecular pathways governing this block in adult cardiomyocyte proliferation, and successfully employed that understanding to achieve cardiac regeneration. These strategies include directly reprograming the cardiomyocytes or manipulating the cardiac interstitium to repair the injured heart. In this review, we discuss the recent advances made in the field in the past two years. [ABSTRACT FROM AUTHOR]

Abstract: Our previous studies have demonstrated the essential roles of the transcription factor Sox9 in the commitment of mesenchymal cells to a chondrogenic cell lineage and in overt chondrogenesis during limb bud development. However, it remains unknown if Sox9 induces chondrogenesis in mesenchyme ectopically in vivo as a master regulator of chondrogenesis. In this study, we first generated mutant mice in which Sox9 was misexpressed in the limb bud mesenchyme. The mutant mouse embryos exhibited polydactyly in limb buds in association with ectopic expression of Sox5 and Sox6 although markers for the different axes of limb bud development showed a normal pattern of expression. Misexpression of Sox9 stimulated cell proliferation in limb bud mesenchyme, suggesting that Sox9 has a role in recruiting mesenchymal cells to mesenchymal condensation. Second, despite the facts that misexpression of Sonic hedgehog (Shh) induces polydactyly in a number of mutant mice and Shh-null mutants have severely defective cartilage elements in limb buds, misexpression of Sox9 did not restore limb bud phenotypes in Shh-null mutants. Rather, there was no expression of Sox9 in digit I of Hoxa13Hd mutant embryos, and Sox9 partially rescued hypodactyly in Hoxa13Hd mutant embryos. These results provide evidence that Sox9 induces ectopic chondrogenesis in mesenchymal cells and strongly suggest that its expression may be regulated by Hox genes during limb bud development. [Copyright &y& Elsevier]

Background The molecular mechanisms underlying the early development of atrial fibrillation (AF) remain poorly understood. Emerging evidence suggests that abnormal epigenetic modulation via microRNAs (miRNAs) might be involved in the pathogenesis of paroxysmal AF (pAF). Objective To identify key molecular changes associated with pAF, we conducted state-of-the-art transcriptomic studies to identify the abnormal miRNA-mRNA interactions potentially driving AF development. Methods High-quality total RNA including miRNA was isolated from atrial biopsies of age-matched and sex-matched pAF patients and control patients in sinus rhythm (SR; n = 4 per group) and used for RNA-sequencing and miRNA microarray. Results were analyzed bioinformatically and validated using quantitative real-time (qRT)-PCR and 3'UTR luciferase reporter assays. Results 113 genes and 49 miRNAs were differentially expressed (DE) in pAF versus SR patients. Gene ontology analysis revealed that most of the DE genes were involved in the "gonadotropin releasing hormone receptor pathway" and "p53 pathway". Of these DE genes, bioinformatic analyses identified 23 pairs of putative miRNA-mRNA interactions that were altered in pAF (involving 15 miRNAs and 17 mRNAs). Using qRT-PCR and 3'UTR luciferase reporter assays, the interaction between upregulation of miR-199a-5p and downregulation of FKBP5 was confirmed in samples from pAF patients. Conclusion Our combined transcriptomic analysis and miRNA microarray study of atrial samples from pAF patients revealed novel pathways and miRNA-mRNA regulations that may be relevant in the development of pAF. Future studies are required to investigate the potential involvement of the gonadotropin releasing hormone receptor and p53 pathways in AF pathogenesis. [ABSTRACT FROM AUTHOR]

Summary: A critical aspect of gut morphogenesis is initiation of a leftward tilt, and failure to do so leads to gut malrotation and volvulus. The direction of tilt is specified by asymmetric cell behaviors within the dorsal mesentery (DM), which suspends the gut tube, and is downstream of Pitx2, the key transcription factor responsible for the transfer of left-right (L-R) information from early gastrulation to morphogenesis. Although Pitx2 is a master regulator of L-R organ development, its cellular targets that drive asymmetric morphogenesis are not known. Using laser microdissection and targeted gene misexpression in the chicken DM, we show that Pitx2-specific effectors mediate Wnt signaling to activate the formin Daam2, a key Wnt effector and itself a Pitx2 target, linking actin dynamics to cadherin-based junctions to ultimately generate asymmetric cell behaviors. Our work highlights how integration of two conserved cascades may be the ultimate force through which Pitx2 sculpts L-R organs. [Copyright &y& Elsevier]

Summary: MicroRNAs (miRNAs) are small, noncoding RNAs that regulate gene expression posttranscriptionally. We investigated the hypothesis that bone morphogenetic protein (Bmp) signaling regulates miRNAs in cardiac progenitor cells. Bmp2 and Bmp4 regulate OFT myocardial differentiation via regulation of the miRNA-17-92 cluster. In Bmp mutant embryos, myocardial differentiation was delayed, and multiple miRNAs encoded by miRNA-17-92 were reduced. We uncovered functional miRNA-17-92 seed sequences within the 3′ UTR of cardiac progenitor genes such as Isl1 and Tbx1. In both Bmp and miRNA-17-92 mutant embryos, Isl1 and Tbx1 expression failed to be correctly downregulated. Transfection experiments indicated that miRNA-17 and miRNA-20a directly repressed Isl1 and Tbx1. Genetic interaction studies uncovered a synergistic interaction between miRNA-17-92 cluster and Bmp4, providing direct in vivo evidence for the Bmp-miRNA-17-92 regulatory pathway. Our findings indicate that Bmp signaling directly regulates a miRNA-mediated effector mechanism that downregulates cardiac progenitor genes and enhances myocardial differentiation. [ABSTRACT FROM AUTHOR]

To understand the role of microRNAs (miRNAs) in pituitary development, a group of pituitary-specific miRNAs were identified, and Dicer1 was then conditionally knocked out using the Pitx2-Cre mouse, resulting in the loss of mature miRNAs in the anterior pituitary. The Pitx2-Cre/Dicer1 mutant mice demonstrate growth retardation, and the pituitaries are hypoplastic with an abnormal branching of the anterior lobe, revealing a role for microRNAs in pituitary development. Growth hormone, prolactin, and thyroid-stimulating hormone β-subunit expression were decreased in the Dicer1 mutant mouse, whereas proopiomelanocortin and luteinizing hormone β-subunit expression were normal in the mutant pituitary. Further analyses revealed decreased Pit-1 and increased Lef-1 expression in the mutant mouse pituitary, consistent with the repression of the Pit-1 promoter by Lef-1. Lef-1 directly targets and represses the Pit-1 promoter. miRNA-26b (miR-26b) was identified as targeting Lef-1 expression, and miR-26b represses Lef-1 in pituitary and non-pituitary cell lines. Furthermore, miR-26b up-regulates Pit-1 and growth hormone expression by attenuating Lef-1 expression in GH3 cells. This study demonstrates that microRNAs are critical for anterior pituitary development and that miR-26b regulates Pit-1 expression by inhibiting Lef-1 expression and may promote Pit-1 lineage differentiation during pituitary development. [ABSTRACT FROM AUTHOR]

Summary: We have investigated the structural basis by which the counterclockwise direction of the amniote gut is established. The chirality of midgut looping is determined by left-right asymmetries in the cellular architecture of the dorsal mesentery, the structure that connects the primitive gut tube to the body wall. The mesenchymal cells of the dorsal mesentery are more condensed on the left side than on the right and, additionally, the overlying epithelium on the left side exhibits a columnar morphology, in contrast to a cuboidal morphology on the right. These properties are instructed by a set of transcription factors: Pitx2 and Isl1 specifically expressed on the left side, and Tbx18 expressed on the right, regulated downstream of the secreted protein Nodal which is present exclusively on the left side. The resultant differences in cellular organization cause the mesentery to assume a trapezoidal shape, tilting the primitive gut tube leftward. [Copyright &y& Elsevier]

Complement regulatory proteins prevent excessive complement system activation and deposition, which can lead to host tissue damage, including fetal loss during pregnancy. To further understand the regulation of complement during development, we examined the expression of the complement protein, C3, and the active subunit of carboxypeptidase N (CPN1), the complement anaphylatoxin regulator. RNA and protein analyses indicated that CPN1 expression occurred as early as 8.5 days post coitus (dpc) and continued through birth. At 10.5 and 13.5 dpc, in situ hybridization revealed CPN1 RNA in erythroid progenitor cells. At 16.5 dpc, expression of CPN1 was also detected in hepatocytes. In comparison to CPN1, C3 RNA expression occurred later (after 13.5 dpc). Moreover, C3 expression was limited to the liver erythroid progenitor cells at 16.5 dpc. These results demonstrated that mouse embryos contain RNA and protein for both C3 and CPN1, and CPN1 expression precedes that of C3 by several days. [Copyright &y& Elsevier]

Summary Specialized adult somatic cells, such as cardiomyocytes (CMs), are highly differentiated with poor renewal capacity, an integral reason underlying organ failure in disease and aging. Among the least renewable cells in the human body, CMs renew approximately 1% annually. Consistent with poor CM turnover, heart failure is the leading cause of death. Here, we show that an active version of the Hippo pathway effector YAP, termed YAP5SA, partially reprograms adult mouse CMs to a more fetal and proliferative state. One week after induction, 19% of CMs that enter S-phase do so twice, CM number increases by 40%, and YAP5SA lineage CMs couple to pre-existing CMs. Genomic studies showed that YAP5SA increases chromatin accessibility and expression of fetal genes, partially reprogramming long-lived somatic cells in vivo to a primitive, fetal-like, and proliferative state. Graphical Abstract Highlights • Creation of a mouse conditionally expressing active YAP called YAP5SA • YAP5SA in adult cardiomyocytes (CMs) induces a more primitive transcriptional state • YAP5SA activates developmental enhancers • YAP5SA expression in CMs causes CM hyperplasia and overall heart hypercellularity As highly differentiated cells, cardiomyocytes have poor renewal capacity, a contributing factor to heart failure in aging and disease. Monroe et al. created a mouse conditionally overexpressing active YAP (YAP5SA) and show that YAP5SA expression induces adult cardiomyocytes to adopt a more proliferative state with fetal-like chromatin and transcriptional landscapes. [ABSTRACT FROM AUTHOR]

Summary During development, progenitors progress through transition states. The cardiac epicardium contains progenitors of essential non-cardiomyocytes. The Hippo pathway, a kinase cascade that inhibits the Yap transcriptional co-factor, controls organ size in developing hearts. Here, we investigated Hippo kinases Lats1 and Lats2 in epicardial diversification. Epicardial-specific deletion of Lats1/2 was embryonic lethal, and mutant embryos had defective coronary vasculature remodeling. Single-cell RNA sequencing revealed that Lats1/2 mutant cells failed to activate fibroblast differentiation but remained in an intermediate cell state with both epicardial and fibroblast characteristics. Lats1/2 mutant cells displayed an arrested developmental trajectory with persistence of epicardial markers and expanded expression of Yap targets Dhrs3, an inhibitor of retinoic acid synthesis, and Dpp4, a protease that modulates extracellular matrix (ECM) composition. Genetic and pharmacologic manipulation revealed that Yap inhibits fibroblast differentiation, prolonging a subepicardial-like cell state, and promotes expression of matricellular factors, such as Dpp4, that define ECM characteristics. [ABSTRACT FROM AUTHOR]