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Background: This study focuses on the lncRNA XIST (X inactive-specific transcript), an lncRNA involved in multiple human cancers, and investigates the functional significance of XIST and the molecular mechanisms underlying the epithelial--mesenchymal transition (EMT) in pancreatic cancer (PC). Methods: Clinical specimens from 25 patients as well as 5 human PC cell lines were analyzed for XIST, YAP, and microRNA(miR)-34a by quantitative real-time PCR (qRT-PCR) and immunohistochemistry. To investigate how XIST influences cell proliferation, invasiveness, and apoptosis in PC, we performed the CCK-8 assays, Transwell assays, and flow cytometry. Luciferase reporter assays, qRT-PCR, and Western blot were applied to prove that miR-34a directly binds to XIST. Results: Up-regulation of XIST and Yes associated protein (YAP) and down-regulation of miR-34a were consistently observed in the clinical specimens and PC cell lines. Silencing XIST reduced the expression of YAP and suppressed transforming growth factor (TGF)-[beta]1-induced EMT, while over-expression of XIST increased the expression of YAP and promoted EMT. In addition, inhibition of epidermal growth factor receptor (EGFR) hampered the XIST-promoted EMT. The results from the luciferase reporter assays confirmed that miR-34a directly targets XIST and suggested that XIST regulates cell proliferation, invasiveness, and apoptosis in PC by sponging miR-34a. Conclusions: XIST promotes TGF-[beta]1-induced EMT by regulating the miR-34a-YAP-EGFR axis in PC. Key words: lncRNA XIST, miR-34a, pancreatic cancer, YAP, EGFR. Contexte : Cette étude se concentre sur l'ARNnm long XIST (X inactive-specific transcript), un ARNnm long impliqué dans plusieurs types de cancer chez l'humain, et vise à examiner l'importance fonctionnelle de XIST et les mécanismes moléculaires qui sous-tendent la TEM dans le cancer pancréatique (CP). Méthodes: Des spécimens cliniques prélevés de 25 patients et 5 lignées cellulaires humaines de cancer du pancréas ont été analysées quant à la présence de XIST, YAP, et du micro ARN (miR)-34a par qRT-PCR et immunohistochimie. Afin d'examiner comment XIST influence la prolifération, l'invasion et l'apoptose des cellules de CP, les auteurs ont réalisé un dosage avec le CCK-8, un test sur supports de culture Transwell, et de la cytométrie en flux. Le dosage du rapporteur luciférase, la qRT-PCR et le buvardage de Western ont été réalisés pour confirmer que le miR-34a se lie directement à XIST. Résultats : La régulation à la hausse de XIST et YAP, et la régulation à la baisse du miR-34a étaient systématiquement observées dans les spécimens cliniques et les lignées de CP. Le silençage de XIST réduisait l'expression de YAP et réprimait la TEM induite par le TGF-[beta]1 (Transforming Growth Factor Beta 1), alors que la surexpression de XIST accroissait l'expression de YAP et favorisait la TEM. De plus, l'inhibition du récepteur de l'EGF (EGFR) ralentissait la TEM favorisée par XIST. Le dosage du rapporteur luciférase confirmait que le miR-34a ciblait directement XIST et suggérait que XIST pourrait réguler la prolifération, l'invasion et l'apoptose des cellules de CP en captant le miR-34a. Conclusions: XIST favorise la TEM induite par le TGF-[beta]1 en régulant l'axe miR-34a-YAP-EGFR dans le CP. [Traduit par la Rédaction] Mots-clés: ARNnm long XIST, miR-34a, cancer pancréatique, YAP, EGFR., Introduction As one of the most fatal human malignancies, pancreatic cancer (PC) ranks as the 4th leading cause of cancer-related deaths in the USA (Michaud 2004). Because there is still [...]

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2009.12.043 Byline: E.W. Frische, F.J.T. Zwartkruis Keywords: Ras-like GTPases; Rap1; Morphogenesis; Cytoskeleton; Cell adhesion; Polarity; Genetics Abstract: The small Ras-like GTPase Rap1 is an evolutionary conserved protein that originally gained interest because of its capacity to revert the morphological phenotype of Ras-transformed fibroblasts. Rap1 is regulated by a large number of stimuli that include growth factors and cytokines, but also physical force and osmotic stress. Downstream of Rap1, a plethora of effector molecules has been proposed on the basis of biochemical studies. Here, we present an overview of genetic studies on Rap1 in various model organisms and relate the observed phenotypes to in vitro studies. The picture that emerges is one in which Rap1 is a versatile regulator of morphogenesis, by regulating diverse processes that include establishment of cellular polarity, cell-matrix interactions and cell-cell adhesion. Surprisingly, genetic experiments indicate that in the various model organisms, Rap1 uses distinct effector molecules that impinge upon the actin cytoskeleton and adhesion molecules. Author Affiliation: Department of Physiological Chemistry, University Medical Center Utrecht, Centre for Biomedical Genetics and Cancer Genomics Centre, Universiteitsweg 100, 584 CG, Utrecht, The Netherlands Article History: Received 4 September 2009; Revised 28 December 2009; Accepted 30 December 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2009.12.033 Byline: Mita M. Shah (b), Hiroyuki Sakurai (b), Derina E. Sweeney (b)(c), Thomas F. Gallegos (c)(d), Kevin T. Bush (b), Jeffrey D. Esko (c), Sanjay K. Nigam (a)(b)(c) Keywords: Kidney development; Branching morphogenesis; Metanephric mesenchyme; Heparan sulfate Abstract: Heparan sulfate proteoglycans (HSPGs) are central modulators of developmental processes likely through their interaction with growth factors, such as GDNF, members of the FGF and TGF[beta] superfamilies, EGF receptor ligands and HGF. Absence of the biosynthetic enzyme, heparan sulfate 2-O-sulfotransferase (Hs2st) leads to kidney agenesis. Using a novel combination of in vivo and in vitro approaches, we have reanalyzed the defect in morphogenesis of the Hs2st.sup.- .sup./ .sup.- kidney. Utilizing assays that separately model distinct stages of kidney branching morphogenesis, we found that the Hs2st.sup.-/- UB is able to undergo branching and induce mesenchymal-to-epithelial transformation when recombined with control MM, and the isolated Hs2st null UB is able to undergo branching morphogenesis in the presence of exogenous soluble pro-branching growth factors when embedded in an extracellular matrix, indicating that the UB is intrinsically competent. This is in contrast to the prevailing view that the defect underlying the renal agenesis phenotype is due to a primary role for 2-O sulfated HS in UB branching. Unexpectedly, the mutant MM was also fully capable of being induced in recombination experiments with wild-type tissue. Thus, both the mutant UB and mutant MM tissue appear competent in and of themselves, but the combination of mutant tissues fails in vivo and, as we show, in organ culture. We hypothesized a 2OS-dependent defect in the mutual inductive process, which could be on either the UB or MM side, since both progenitor tissues express Hs2st. In light of these observations, we specifically examined the role of the HS 2-O sulfation modification on the morphogenetic capacity of the UB and MM individually. We demonstrate that early UB branching morphogenesis is not primarily modulated by factors that depend on the HS 2-O sulfate modification; however, factors that contribute to MM induction are markedly sensitive to the 2-O sulfation modification. These data suggest that key defect in Hs2st null kidneys is the inability of MM to undergo induction either through a failure of mutual induction or a primary failure of MM morphogenesis. This results in normal UB formation but affects either T-shaped UB formation or iterative branching of the T-shaped UB (possibly two separate stages in collecting system development dependent upon HS). We discuss the possibility that a disruption in the interaction between HS and Wnts (e.g. Wnt 9b) may be an important aspect of the observed phenotype. This appears to be the first example of a defect in the MM preventing advancement of early UB branching past the first bifurcation stage, one of the limiting steps in early kidney development. Author Affiliation: (a) Department of Pediatrics, University of California, San Diego, CA, USA (b) Department of Medicine, University of California, San Diego, CA, USA (c) Department of Cellular and Molecular Medicine, University of California, San Diego, CA, USA (d) Department of Biomedical Sciences, University of California, San Diego, CA, USA Article History: Received 19 May 2009; Revised 18 December 2009; Accepted 23 December 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.cell.2009.11.014 Byline: Ehud Cohen (1), Johan F. Paulsson (2), Pablo Blinder (3), Tal Burstyn-Cohen (4), Deguo Du (2), Gabriela Estepa (1), Anthony Adame (5), Hang M. Pham (5), Martin Holzenberger (6), Jeffery W. Kelly (2), Eliezer Masliah (5), Andrew Dillin (1) Keywords: HUMDISEASE; PROTEINS; SIGNALING Abstract: The insulin/insulin growth factor (IGF) signaling (IIS) pathway is a key regulator of aging of worms, flies, mice, and likely humans. Delayed aging by IIS reduction protects the nematode C. elegans from toxicity associated with the aggregation of the Alzheimer's disease-linked human peptide, A[beta]. We reduced IGF signaling in Alzheimer's model mice and discovered that these animals are protected from Alzheimer's-like disease symptoms, including reduced behavioral impairment, neuroinflammation, and neuronal loss. This protection is correlated with the hyperaggregation of A[beta] leading to tightly packed, ordered plaques, suggesting that one aspect of the protection conferred by reduced IGF signaling is the sequestration of soluble A[beta] oligomers into dense aggregates of lower toxicity. These findings indicate that the IGF signaling-regulated mechanism that protects from A[beta] toxicity is conserved from worms to mammals and point to the modulation of this signaling pathway as a promising strategy for the development of Alzheimer's disease therapy. Author Affiliation: (1) Howard Hughes Medical Institute, Glenn Center for Aging Research, Molecular and Cell Biology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA (2) Department of Chemistry and Molecular and Experimental Medicine and The Skaggs Institute of Chemical Biology, The Scripps Research Institute, 10550 North Torrey Pines Road, La Jolla, CA 92037, USA (3) Department of Physics, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA (4) Molecular Neurobiology Laboratory, The Salk Institute for Biological Studies, 10010 North Torrey Pines Road, La Jolla, CA 92037, USA (5) Department of Neurosciences, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093, USA (6) INSERM and Universite Pierre-et-Marie-Curie, UMRS 938, HA[acute accent]pital Saint-Antoine, 75571 Paris 12, France Article History: Received 6 June 2009; Revised 11 September 2009; Accepted 29 October 2009 Article Note: (miscellaneous) Published: December 10, 2009

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ahj.2009.06.032 Byline: Yi-Da Tang (a), Faisal Hasan (b), Frank J. Giordano (b), Stephen Pfau (b), Henry M. Rinder (c), Stuart D. Katz (b) Abstract: Erythropoietin mitigates myocardial damage and improves ventricular performance after experimental ischemic injury. This study assessed safety and efficacy markers relevant to the biological activity of recombinant human erythropoietin (rHuEpo) in patients with acute myocardial infarction (MI). Author Affiliation: (a) Department of Cardiology Fuwai Hospital Beijing, China (b) Section of Cardiovascular Medicine Yale University School of Medicine, Department of Internal Medicine, New Haven, CT (c) Department of Laboratory Medicine Yale University School of Medicine, New Haven, CT Article History: Received 9 February 2009; Accepted 20 June 2009 Article Note: (footnote) RCT reg #NCT00367991.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2009.08.024 Byline: Gina E. Elsen (a), Louis Y. Choi (b), Victoria E. Prince (a)(b)(c), Robert K. Ho (b)(c) Keywords: Autism; Met; Hgf; Zebrafish; Hindbrain; Cerebellum; Facial motor neuron; Migration; Morphogenesis; Proliferation Abstract: During development, Met signaling regulates a range of cellular processes including growth, differentiation, survival and migration. The Met gene encodes a tyrosine kinase receptor, which is activated by Hgf (hepatocyte growth factor) ligand. Altered regulation of human MET expression has been implicated in autism. In mouse, Met signaling has been shown to regulate cerebellum development. Since abnormalities in cerebellar structure have been reported in some autistic patients, we have used the zebrafish to address the role of Met signaling during cerebellar development and thus further our understanding of the molecular basis of autism. We find that zebrafish met is expressed in the cerebellar primordium, later localizing to the ventricular zone (VZ), with the hgf1 and hgf2 ligand genes expressed in surrounding tissues. Morpholino knockdown of either Met or its Hgf ligands leads to a significant reduction in the size of the cerebellum, primarily as a consequence of reduced proliferation. Met signaling knockdown disrupts specification of VZ-derived cell types, and also reduces granule cell numbers, due to an early effect on cerebellar proliferation and/or as an indirect consequence of loss of signals from VZ-derived cells later in development. These patterning defects preclude analysis of cerebellar neuronal migration, but we have found that Met signaling is necessary for migration of hindbrain facial motor neurons. In summary, we have described roles for Met signaling in coordinating growth and cell type specification within the developing cerebellum, and in migration of hindbrain neurons. These functions may underlie the correlation between altered MET regulation and autism spectrum disorders. Author Affiliation: (a) The Committee on Neurobiology, University of Chicago, 947 East 58th Street, Chicago, IL 60637, USA (b) The Committee on Developmental Biology, University of Chicago, 1027 East 57th Street, Chicago, IL 60637, USA (c) Department of Organismal Biology and Anatomy, University of Chicago, 1027 East 57th Street, Chicago, IL 60637, USA Article History: Received 12 March 2009; Revised 31 July 2009; Accepted 17 August 2009

The influence of supplemental protein during gestation on maternal hormones and fetal growth was determined in composite beef heifers. At AI, 118 heifers were stratified by BW within each composite genotype (BeefX = 1/2 Senepol, 1/4 Brahman, 1/8 Charolais, 1/8 Red Angus and CBX = 1/2 Senepol, 1/4 Brahman, 1/4 Charolais) into 4 treatment groups: high high (HH = 1.4 kg CP/d for first and second trimesters of gestation), high low (HL = 1.4 kg of CP/d for first trimester and 0.4 kg of CP/d for second trimester), low high (lowH = 0.4 kg CP/d for first trimester and 1.4 kg of CP/d and for second trimester), or low low (LL = 0.4 kg CP/d for first and second trimesters). Maternal plasma IGF-I and -II, total IGFBP, and leptin concentrations were determined at 14 d before AI and at d 28, 82, 179, and 271 post-AI (mean gestation length 286 d), and leptin concentrations were also determined at calving. Increased dietary protein increased maternal plasma IGF-I (P < 0.001 on d 28, 82, and 179), IGF-II (P = 0.01 on d 82; P = 0.04 on d 271), and total IGFBP (P = 0.002 on d 82; P = 0.005 on d 179; P = 0.03 on d 271). Maternal plasma IGF-I at d 271 was negatively associated with calf crown-rump length at birth (P = 0.003). BeefX had greater birth weight calves (P = 0.01), greater IGF-II (P < 0.001), increased ratios of IGF-I:total IGFBP (P = 0.008) and IGF-II:total IGFBP (P < 0.001), and reduced total IGFBP compared with CBX (P = 0.02). Increased dietary protein during second trimester increased maternal plasma leptin at calving (P = 0.005). Maternal plasma leptin near term was positively associated with heifer BCS (P = 0.02) and with calf birth weight (P = 0.04), and at calving was positively associated with heifer age at AI (P = 0.02). These findings suggest that maternal dietary protein, age, and genotype influence plasma concentrations of metabolic hormones and fetal growth in Bos indicus-influenced heifers. Key words: cattle, crude protein, fetal growth, gestation, insulin-like growth factor, leptin

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2008.06.003 Byline: Vanessa Ribes (a), Fanny Stutzmann (a), Laurent Bianchetti (a), Francois Guillemot (b), Pascal Dolle (a), Isabelle Le Roux (a) Keywords: Neurogenin2; Promoter analysis; Spinal cord; RA; Shh; FGF Abstract: A central issue during embryonic development is to define how different signals cooperate in generating unique cell types. To address this issue, we focused on the function and the regulation of the proneural gene Neurogenin2 (Neurog2) during early mouse spinal neurogenesis. We showed that Neurog2 is first expressed in cells within the neural plate anterior to the node from the 5 somite-stage. The analysis of Neurog2 mutants established a role for this gene in triggering neural differentiation during spinal cord elongation. We identified a 798 base pair enhancer element (Neurog2-798) upstream of the Neurog2 coding sequence that directs the early caudal expression of Neurog2. Embryo culture experiments showed that Retinoic Acid (RA), Sonic hedgehog (Shh) and Fibroblast Growth Factor signals act in concert on this enhancer to control the spatial and temporal induction of Neurog2. We further demonstrated by transgenesis that two RA response elements and a Gli binding site within the Neurog2-798 element are absolutely required for its activity, strongly suggesting that the regulation of Neurog2 early expression by RA and Shh signals is direct. Our data thus support a model where signal integration at the level of a single enhancer constitutes a key mechanism to control the onset of neurogenesis. Author Affiliation: (a) Institut de Genetique et de Biologie Moleculaire et Cellulaire, Inserm U 596, CNRS UMR 7104, Universite Louis Pasteur, 1 rue Laurent Fries, Illkirch, BP 10142 F-67400, France (b) Division of Molecular Neurobiology, National Institute for Medical Research (NIMR), the Ridgeway Mill Hill, London NW7 1AA, UK Article History: Received 18 January 2008; Revised 15 May 2008; Accepted 3 June 2008

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ahj.2007.12.031 Byline: Robert C. Kaplan (a), Aileen P. McGinn (a), Michael N. Pollak (b), Lewis Kuller (c), Howard D. Strickler (a), Thomas E. Rohan (a), Anne R. Cappola (d), XiaoNan Xue (a), Bruce M. Psaty (e) Abstract: Low levels of insulinlike growth factor 1 (IGF-I) may influence the development of age-related cardiovascular diseases including congestive heart failure (CHF). Insulinlike growth factor binding protein 1 (IGFBP-1), which increases during catabolic states and inhibits anabolic IGF-I effects, is increased in patients with CHF and has been associated prospectively with increased mortality among older adults and survivors of myocardial infarction. We investigated the association between fasting plasma levels of IGF-I, IGFBP-1, IGFBP-3, and insulin and risk of incident CHF in the prospective Cardiovascular Health Study. Author Affiliation: (a) Department of Epidemiology and Population Health, Albert Einstein College of Medicine, Bronx, NY (b) Cancer Prevention Research Unit, Departments of Medicine and Oncology, Lady Davis Research Institute of Jewish General Hospital and McGill University, Montreal, Quebec, Canada (c) Department of Medicine and Epidemiology, Cardiovascular Health Research Unit, University of Pittsburgh, Pittsburgh, PA (d) Division of Endocrinology, Diabetes, and Metabolism, Department of Medicine, University of Pennsylvania School of Medicine, Philadelphia, PA (e) Departments of Epidemiology, Medicine and Health Services, University of Washington, Seattle, WA Article History: Received 3 August 2007; Accepted 26 December 2007 Article Note: (footnote) This study was supported by contracts N01-HC-35129, N01-HC-45133, N01-HC-75150, N01-HC-85079 through N01-HC-85086, N01 HC-15103, N01 HC-55222, and U01 HL080295 from the National Heart, Lung, and Blood Institute (NHLBI), with additional contribution from the National Institute of Neurological Disorders and Stroke, and grant 1R01HL083760-01 from the NHLBI (to Dr Kaplan). The funders had no role in data analysis or the preparation of this manuscript.

An approach that uses a multicanonical Monte Carlo method to search for rare growth factors on random matrices, while solving linear systems using Gaussian elimination, is presented.

Puberty unmasks or accelerates progressive kidney diseases, including diabetes mellitus (DM), perhaps through effects of sex steroids. To test the hypothesis that rising androgen levels at puberty permit diabetic kidney damage, we studied four groups of male rats with and without streptozocin-induced DM: adult onset (A), adult onset after castration (AC), juvenile onset (J), and juvenile onset with testosterone treatment (JT). Profibrotic markers were measured after 6 wk with blood glucose levels 300-450 mg/dl. JT permitted increased expression of mRNA for two isoforms of transforming growth factor-[beta] and connective tissue growth factor compared with J animals with DM; prior castration did not provide protection in adult-onset DM. JT also permitted greater tubular staining for or-smooth muscle actin and fibroblast-specific protein, two markers of cell damage and potential epithelial mesenchymal transition. Once again, castration was not protective for these effects of DM in the AC group. These data indicate that puberty permits detrimental effects in the tubulointerstitium in the diabetic kidney, an effect mimicked by testosterone treatment of juvenile animals and partially blunted by castration of adults, hut damage does not correlate with testosterone levels, suggesting a less direct mechanism. connective tissue growth factor; transforming growth factor-[beta]; epithelial mesenchymal transition; glomerulus; castration doi:10.1152/ajprenal.00482.2006.

High ambient glucose activates intracellular signaling pathways to induce the expression of extracellular matrix and cytokines such as connective tissue growth factor (CTGF). Cell responses to CTGF in already glucose-stressed cells may act to transform the mesangial cell phenotype leading to the development of glomerulosclerosis. We analyzed cell signaling downstream of CTGF in high glucose-stressed mesangial cells to model signaling in the diabetic milieu. The addition of CTGF to primary human mesangial cells activates cell migration which is associated with a PKC-[zeta]-GSK313 signaling axis. In high ambient glucose basal PKC-[zeta] and GSK3[beta] phosphorylation levels are selectively increased and CTGF-stimulated PKC-[zeta] and GSK3[beta] phosphorylation was impaired. These effects were not induced by osmotic changes. CTGF-driven profibrotic cell signaling as determined by p42/44 MAPK and Akt phosphorylation was unaffected by high glucose. Nonresponsiveness of the PKC-[zeta]-GSK3[beta] signaling axis suppressed effective remodeling of the microtubule network necessary to support cell migration. However, interestingly the cells remain plastic: modulation of glucose-induced PKC-[beta] activity in human mesangial cells reversed some of the pathological effects of glucose damage in these cells. We show that inhibition of PKC-[beta] with LY379196 and PKC-[beta] siRNA reduced basal PKC-[zeta] and GSK3[beta] phosphorylation in human mesangial cells exposed to high glucose. CTGF stimulation under these conditions again resulted in PKC-[zeta] phosphorylation and human mesangial cell migration. Regulation of PKC-[zeta] by PKC-[beta] in this instance may establish PKC-[zeta] as a target for constraining the progression of mesangial cell dysfunction in the pathogenesis of diabetic nephropathy. GSK3[beta]; PKC-[zeta]; migration; diabetic nephropathy doi:10.1152/ajprenal.00342.2006.

Real-time nucleic acid amplification methods can be extremely useful for the identification and quantitation of nucleic acid analytes, but are more difficult to adapt to protein or other analytes. To facilitate the development of real-time rolling circle amplification (RCA) for protein targets, we have developed a novel type of conformation-switching aptamer that can be circularized upon interaction with its protein target, the platelet-derived growth factor (PDGF). Using the structure-switching aptamer, real-time RCA can be used to specifically quantitate PDGF down to the low-nanomolar range (limit of detection, 0.4 nM), even against a background of cellular lysate. The aptamer can also be adapted to RCA on surfaces, although quantitation proved to be more difficult. One of the great advantages of the method described herein is that it can be immediately adapted to almost any aptamer and does not require two or more affinity reagents as do sandwich or proximity assays.

To link to full-text access for this article, visit this link: http://dx.doi.org/10.1016/j.ydbio.2006.08.048 Byline: Francois Lapraz (a), Eric Rottinger (a), Veronique Duboc (a), Ryan Range (a), Louise Duloquin (a), Katherine Walton (b), Shu-Yu Wu (b), Cynthia Bradham (b), Mariano A. Loza (c), Taku Hibino (c), Karen Wilson (d), Albert Poustka (e), Dave McClay (b), Lynne Angerer (f), Christian Gache (a), Thierry Lepage (a) Keywords: Receptor tyrosine kinase; Signaling; TGF-[beta]; Sea urchin; Genome; Deuterostome; FGFR; Nodal; TGF-[beta] receptors; Smad Abstract: The Receptor Tyrosine kinase (RTK) and TGF-[beta] signaling pathways play essential roles during development in many organisms and regulate a plethora of cellular responses. From the genome sequence of Strongylocentrotus purpuratus, we have made an inventory of the genes encoding receptor tyrosine kinases and their ligands, and of the genes encoding cytokines of the TGF-[beta] superfamily and their downstream components. The sea urchin genome contains at least 20 genes coding for canonical receptor tyrosine kinases. Seventeen of the nineteen vertebrate RTK families are represented in the sea urchin. Fourteen of these RTK among which ALK, CCK4/PTK7, DDR, EGFR, EPH, LMR, MET/RON, MUSK, RET, ROR, ROS, RYK, TIE and TRK are present as single copy genes while pairs of related genes are present for VEGFR, FGFR and INSR. Similarly, nearly all the subfamilies of TGF-[beta] ligands identified in vertebrates are present in the sea urchin genome including the BMP, ADMP, GDF, Activin, Myostatin, Nodal and Lefty, as well as the TGF-[beta] sensu stricto that had not been characterized in invertebrates so far. Expression analysis indicates that the early expression of nodal, BMP2/4 and lefty is restricted to the oral ectoderm reflecting their role in providing positional information along the oral-aboral axis of the embryo. The coincidence between the emergence of TGF-[beta]-related factors such as Nodal and Lefty and the emergence of the deuterostome lineage strongly suggests that the ancestral function of Nodal could have been related to the secondary opening of the mouth which characterizes this clade, a hypothesis supported by functional data in the extant species. The sea urchin genome contains 6 genes encoding TGF-[beta] receptors and 4 genes encoding prototypical Smad proteins. Furthermore, most of the transcriptional activators and repressors shown to interact with Smads in vertebrates have orthologues in echinoderms. Finally, the sea urchin genome contains an almost complete repertoire of genes encoding extracellular modulators of BMP signaling including Chordin, Noggin, Sclerotin, SFRP, Gremlin, DAN and Twisted gastrulation. Taken together, these findings indicate that the sea urchin complement of genes of the RTK and TGF-[beta] signaling pathways is qualitatively very similar to the repertoire present in vertebrates, and that these genes are part of the common genetool kit for intercellular signaling of deuterostomes. Author Affiliation: (a) UMR 7009 CNRS, Universite Pierre et Marie Curie-Paris 6, Observatoire Oceanologique, 06230 Villefranche-sur-Mer, France (b) Developmental, Molecular, and Cellular Biology Group, Duke University, Durham, NC, USA (c) Sunnybrook and Women's Research Institute and Department of Medical Biophysics, University of Toronto. 2075 Bayview Ave., Toronto, Ontario, Canada M4N 3M5 (d) Kristineberg Marine Research Station 45034 Fiskebackskil, Sweden (e) Evolution and Development Group Max-Planck Institut fuer Molekulare Genetik Ihnestrasse 7314195, Berlin (f) National Institute for Dental and Craniofacial Research, National Institutes of Health, Bethesda, MD 20892, USA Article History: Received 25 May 2006; Revised 16 August 2006; Accepted 16 August 2006

OBJECTIVES. The objectives of this study were to assess whether (1) in-hospital growth velocity is predictive of neurodevelopmental and growth outcomes at 18 to 22 months' corrected age among extremely low birth weight (ELBW) infants and (2) in-hospital growth velocity contributes to these outcomes after controlling for confounding demographic and clinical variables. METHODS. Infants 501 to 1000 g birth weight from a multicenter cohort study were divided into quartiles of in-hospital growth velocity rates. Variables considered for the logistic-regression models included gender, race, gestational age, small for gestational age, mother's education, severe intraventricular hemorrhage, periventricular leukomalacia, age at regaining birth weight, necrotizing enterocolitis, late-onset infection, bronchopulmonary dysplasia, postnatal steroid therapy for pulmonary disease, and center. RESULTS. Of the 600 discharged infants, 495 (83%) were evaluated at 18 to 22 months' corrected age. As the rate of weight gain increased between quartile 1 and quartile 4, from 12.0 to 21.2 g/kg per day, the incidence of cerebral palsy, Bayley II Mental Developmental Index (MDI) <70 and Psychomotor Developmental Index (PDI) <70, abnormal neurologic examination, neurodevelopmental impairment, and need for rehospitalization fell significantly. Similar findings were observed as the rate of head circumference growth increased. The in-hospital rate of growth was associated with the likelihood of anthropometric measurements at 18 months' corrected age below the 10th percentile values of the Centers for Disease Control and Prevention 2000 growth curve. Logistic-regression analyses, controlling for potential demographic or clinical cofounders, and adjusted for center, identified a significant relationship between growth velocity and the likelihood of cerebral palsy, MDI and PDI scores of <70, and neurodevelopmenta] impairment. CONCLUSIONS. These analyses suggest that growth velocity during an ELBW infant's NICU hospitalization exerts a significant, and possibly independent, effect on neurodevelopmental and growth outcomes at 18 to 22 months' corrected age. Key Words extremely low birth weight infant, growth, neurodevelopmental outcome Abbreviations ELBW--extremely low birth weight MDI--Mental Developmental Index PDI--Psychomotor Developmental Index PMA--postmenstrual age CP--cerebral palsy NDI--neurodevelopmental impairment SGA--small for gestational age NEC--necrotizing enterocolitis IVH--intraventricular hemorrhage PVL--periventricular leukomalacia BPD--bronchopulmonary dysplasia OR--odds ratio CI--confidence interval, POSTNATAL GROWTH FAILURE is the norm for extremely low birth weight (ELBW) infants, especially the sickest infants. (1-4) The NICHD Growth Observational Study (1) demonstrated that, although the rate of […]

This study describes a systematic comparison of the preparation, sensitivity, and response of direct label and sandwich fluoroimmunoassay protein arrays for parallel detection of cytokines and growth factors. Five model analytes were examined, IL-1[beta], TNF-[alpha], VEGF, MIP-1[beta], and TGF- [beta]1, as well as four different array printing slides. Each slide was printed with four identical anti-cytokine arrays, two arrays employed for direct labeling and two for sandwich assays. All five target cytokines assayed using the sandwich format significantly outperformed the corresponding direct label assays in terms of background-subtracted fluorescent intensity, although the extent varied for different cytokines, growth factors, and slides examined. Binding of target protein by immobilized capture antibody was examined by Biacore surface plasmon resonance with and without labeling of the target protein. A major explanation for the superior performance of the sandwich assay protocol was the dilution of the labeled target cytokine in the size exclusion gel filtration column during labeling procedure. Other possible explanations included that binding of the detection antibody-induced signal amplification, and labeling of target cytokine reduced efficiency of cytokine binding to immobilized capture antibody.

Economic weights are obtained for feed intake using a growth model and an economic model. The underlying concept of the growth model is the linear plateau model. Parameters of this model are the marginal ratio (MR) of extra fat and extra protein deposition with increasing feed intake (FI) and the maximum protein deposition ([Pd.sub.max]). The optimum feed intake (F[I.sub.0]) is defined as the minimum feed intake that meets energy requirements for [Pd.sub.max]. The effect of varying FI and MR on performance traits was determined. An increase in FI results in a larger increase in growth rate with lower MR. For a given MR, feed conversion ratio is lowest when FI equals F[I.sub.0]. Lean meat percentage (LMP) is largest for a low MR in combination with a low FI. The decrease in LMP with higher FI is largest when FI exceeds F[I.sub.0]. Economic weights for FI, MR and [Pd.sub.max] depend on FI in relation to F[I.sub.0]. Economic weights for FI are positive when FI is less than F[I.sub.0] and negative when FI is larger than F[I.sub.0]. The MR has only then a negative economic weight, when FI is below F[I.sub.0]. Economic weights of FI and MR have a larger magnitude with lower MR and lower FI. In contrast, economic weights for growth rate and FI derived from the economic model only change in magnitude and not in sign with different levels of these traits. The economic model always puts a negative economic weight on FI since it expresses profit due to a decrease in FI with constant growth rate and LMP. This holds the risk of continuous decrease in FI in pig breeding programs. In contrast, the use of growth models for genetic improvement allows direct selection for an optimum feed intake which maximizes feed efficiency in combination with maximum lean meat growth. It is concluded that recording procedures have to be adapted to collect the data necessary to implement growth models in practical pig breeding applications. Key Words: Breeding, Economic Evaluation, Feed Intake, Growth Models, Pigs

Seventy-three crossbred steers (initial BW = 170.5 [+ or -] 5.5 kg) from The Ohio State University (Exp. 1) and 216 crossbred steers (initial BW 135.4 [+ or -] 4.4 kg) from the University of Illinois (Exp. 2) were used to determine the effect of source of energy and rate of growth on performance, carcass characteristics, and glucose and insulin profiles on early-weaned steers. Effects of the diets used in Exp. 1 and 2 on ruminal pH and VFA concentrations were quantified using ruminally fistulated steers (Exp. 3). Cattle were weaned at an average age of 119 d in all experiments and were allotted by age, BW, and breed to one of four diets: high-concentrate, fed ad libitum (ALCONC), high-concentrate fed to achieve a gain of either 1.2 kg/d (1.2CONC) or 0.8 kg/d (0.8CONC), or high-fiber, fed ad libitum (ALFIBER). At 218 d of age, all steers were placed on the ALCONC diet until slaughter. Steers were implanted with Compudose at the initiation of all experiments and with Revalor-S when they were estimated to be 100 d from slaughter. When steers in Exp. 1 averaged 181 and 279 d of age, serum samples were collected to determine glucose and insulin concentrations. Steers were slaughtered when a fat thickness of 1.27 cm was reached (Exp. 1) or after 273 d on feed (Exp. 2). In Exp. 1, days in the feedlot (P < 0.01) and age at slaughter (P < 0.01) were lowest for ALCONC and ALFIBER steers, and greatest for 0.8CONC steers. Overall, ADG was greatest for ALCONC and lowest for 0.8CONC steers; feed efficiency was lowest (P < 0.01) for ALFIBER steers. Final BW did not differ (P > 0.57) among treatments. At 181 and 218 d of age, serum insulin was increased (P < 0.10) and intramuscular fat percentage was greatest (P < 0.07), respectively, for ALCONC steers. In Exp. 2, overall ADG (P < 0.06) and final BW (P < 0.04) were greatest for ALCONC and lowest for 1.2CONC and 0.8CONC steers. Overall feed efficiency was greatest for 0.8CONC and lowest for ALFIBER (P < 0.01). Growing phase diet did not affect marbling score at 218 d of age or at slaughter (P > 0.81). In Exp. 3, differences in ruminal pH after feeding may have been a consequence of increasing acetate (ALFIBER), propionate (ALCONC), or a combination of VFA (0.8CONC and 1.2CONC), respectively (diet x time after feeding, P < 0.10). Controlling growth by limit-feeding a high-concentrate diet for only 100 d does not extend the growth curve of early-weaned steers or enhance intramuscular fat deposition at slaughter compared to ad libitum intake of a high-concentrate or high-fiber diet. Key Words: Beef Cattle, Carcass Composition, Early Weaning, Feedlots, Insulin

We have identified, cultured, characterized, and propagated adult pluripotent stem cells (PSC) from a subset of human peripheral blood monocytes. These cells, which in appearance resemble fibroblasts, expand in the presence of macrophage colony-stimulating factor and display monocytic and hematopoietic stem cell markers including CD14, CD34, and CD45. We have induced these cells to differentiate into mature macrophages by lipopolysaccharide, T lymphocytes by IL-2, epithelial cells by epidermal growth factor, endothelial cells by vascular endothelial cell growth factor, neuronal cells by nerve growth factor, and liver cells by hepatocyte growth factor. The pluripotent nature of individual PSC was further confirmed by a clonal analysis. The ability to store, expand, and differentiate these PSC from autologous peripheral blood should make them valuable candidates for transplantation therapy.

Living PC12 cells, a model cell type for studying neuronal function, were imaged using the negative feedback mode of a scanning electrochemical microscope (SECM). Six biocompatible redox mediators were successfully identified from a large pool of candidates and were then used for imaging PC12 cells before and after exposure to nerve growth factor (NGF). When exposed to NGF, cells differentiate into a neuron phenotype by growing narrow neurites (1-2 [micro]m wide) that can extend > 100 [micro]m from the cell proper. We demonstrate that carbon fiber electrodes with reduced tip diameters can be used for imaging both the cell proper and these neurites. Regions of decreased current, possibly resulting from raised features not identifiable by light microscopy, are clearly evident in the SECM images. Changes in the morphology of undifferentiated PC12 cells could be detected in real time with the SECM. After exposure to hypotonic and hypertonic solutions, reversible changes in cell height of

Results suggest that growth inhibition due to short-chain linear saturated fatty acids can not be ascribed merely to decreased membrane bilayer thickness in mycoplasmas but can be assigned to the induction of an inappropriate distribution of short-chain saturated fatty acids.

TSG101 was discovered in a screen for tumor susceptibility genes and has since been shown to have a multiplicity of biological effects. However, the basis for TSG101's ability to regulate cell growth has not been elucidated. We report here that the TSG101 protein binds to the cyclin/cyclin-dependent kinase (CDK) inhibitor (CKI) [p21.sup.Cip1/WAF1] and increases stability of the p21 protein in HEK293F cells and differentiating primary keratinocytes, suppressing differentiation in a p21-dependent manner. In proliferating keratinocytes where the p21 protein is relatively stable, TSG101 does not affect the stability or expression of p21 but shows p21-dependent recruitment to cyclin/CDK complexes, inhibits cyclin/CDK activity, and causes strong growth suppression to a much greater extent in p21+/+ than in p21-/- cells. Conversely, suppression of endogenous TSG101 expression by an antisense TSG101 cDNA causes doubling of the fraction of keratinocytes in the S phase of the cell cycle as occurs during p21 deficiency. Our results indicate that TSG101 has a direct role in the control of growth and differentiation in primary epithelial cells, and that p21 is an important mediator of these TSG101 functions.

We show that a signal from the germ line represses growth in the nematode Caenorhabditis elegans. Laser-microbeam ablation of cells that give rise to the germ line causes adults to become giant. Ablation of these cells in self-sterile mutant worms also causes gigantism, suggesting that the germ line represses growth because it is the source of a growth-antagonizing signal rather than because of a sink of resources required for reproduction. The C. elegans germ line also emits a signal that represses longevity. This longevity-repressing signal requires the activity of DAF-16, a forkhead/winged-helix transcription factor, but we find that that the growth-repressing signal does not. The growth-repressing signal also does not require the activity of DBL-1, a transforming growth factor [beta]-related protein that promotes growth in worms. By ablating the germ-line precursors of other species of free-living nematodes, we also found that both the growth-repressing and longevity-repressing signals are evolutionarily variable. Some species have both signals; others have just one or the other. We suggest that variation in germ-line signaling contributes to body size and life-history diversity in the nematodes.

Inhibitory Smads (I-Smads) repress signaling by cytokines of the transforming growth factor-[beta] (TGF-[beta]) superfamily. I-Smads have conserved carboxy-terminal Mad homology 2 (MH2) domains, whereas the amino acid sequences of their amino-terminal regions (N domains) are highly divergent from those of other Smads. Of the two different I-Smads in mammals, Smad7 inhibited signaling by both TGF-[beta] and bone morphogenetic proteins (BMPs), whereas Smad6 was less effective in inhibiting TGF-[beta] signaling. Analyses using deletion mutants and chimeras of Smad6 and Smad7 revealed that the MH2 domains were responsible for the inhibition of both TGF-[beta] and BMP signaling by I-Smads, but the isolated MH2 domains of Smad6 and Smad7 were less potent than the full-length Smad7 in inhibiting TGF-[beta] signaling. The N domains of I-Smads determined the subcellular localization of these molecules. Chimeras containing the N domain of Smad7 interacted with the TGF-[beta] type I receptor (T[beta]R-I) more efficiently, and were more potent in repressing TGF-[beta] signaling, than those containing the N domain of Smad6. The isolated N domain of Smad7 physically interacted with the MH2 domain of Smad7, and enhanced the inhibitory activity of the latter through facilitating interaction with TGF-[beta] receptors. The N domain of Smad7 thus plays an important role in the specific inhibition of TGF-[beta] signaling.

This article examines the affects of the rhythm of maturation on the duration and intensity of height growth during puberty among both girls and boys, using longitudinal clinical follow-ups. Results found that late maturers were taller than early ones during puberty, but final height depending on age of onset did not differ in either sex.

This article examines sex differences in growth spurts among teenage Japanese boys and girls. Regression analysis included age at takeoff, height at takeoff, velocity takeoff, peak height takeoff, age at peak height takeoff and height at peak height takeoff.

Research has been conducted on Myxococcus xanthus. Results indicate that this bacteria can sporulate in two ways and these sporulation pathways differ in certain respects.

Research has been conducted on the DL-pipecolic acid that promotes Sinorhizobium meliloti cell growth restoration. The results of the chromatographic analysis of intracellular solutes are described.

Research has been conducted on the N-myc and c-myc of cellular oncogenes family. The replacement of the endogenous c-myc coding sequences with N-myc coding sequences in mice has been examined.

Research has been conducted on the insulin-like growth factor-binding proteins. Results include molecular characterization of circulating human IGFBP-4 fragments that have been formed in vivo.

Research has been conducted on the bZIP proto-oncoprotein c-Fos. Results indicate that the C-terminal domain of the human c-Fos is intrinsically disordered.

Research has been conducted on the growth rate-independent rrn P1 promoter mutants. The ability of these mutants to respond to the changes in rrn gene dosage has been tested.

Research has been conducted on the Halobacillus halophilus motility. The involvement of chloride in flagella synthesis in H. halophilus is discussed.

This study was conducted to determine whether an antimicrobially induced (ASP-250) increase in serum IGF-I was the result of differences in feed intake. Serum IGF-I concentrations were measured in crossbred pigs that were fed a control diet or a diet supplemented with ASP-250 either for ad libitum consumption or limited to 85% of the control pigs' consumption. The pigs that consumed either diet ad libitum, control or ASP-250, consumed similar quantities of feed. The ASP-250 ad libitum-intake pigs had serum IGF-I concentrations that were greater (P < .01) than those of their ad libitum-intake control littermates. Similarly, the ASP-250 limit-fed pigs had serum IGFI concentrations that were greater (P < .01) than those of the controls. Although the serum IGF-I concentrations of pigs fed the ASP-250-supplemented diet for ad libitum intake were greater than the serum IGF-I concentrations of the pigs limit-fed the ASP-250-supplemented diet, the differences were not significant (P < .08). The ASP-250-fed pigs had higher serum IGF binding protein (BP)-3 concentrations than did their control littermates (P < .003). A time course of antimicrobially induced alterations in serum IGF-I concentrations revealed that the effect of increased serum IGF-I levels in ASP-250-supplemented pigs (P < .02) was observed within 4 d and was maintained throughout the 4-wk study. These findings show that feed intake is not responsible for the increase in serum IGF-I observed with ASP-250 supplementation. Additionally, the antimicrobially induced increase in serum IGF-I concentrations occurs within a few days after initiation of the treatment. Key Words: Insulin-Like Growth Factor, Pigs, Antibiotics

Research was conducted to illustrate how the nuclear translocation of p42 and p44 mitogen-activated protein kinases (MAPK) can be triggered via the activation of the p42/p44 MAPK pathway. Nuclear accumulation was observed to be facilitated by the use of the chimera Raf-1:ER to directly activate the pathway. The neosynthesis of short-lived proteins are required for the nuclear accumulation of p42/p44 MAPK.

Hypoxia induces a group of physiologically important genes such as erythropoietin and vascular endothelial growth factor. These genes are transcriptionally upregulated by hypoxia-inducible factor 1 (HIF-1), a global regulator that belongs to the basic helix-loop-helix PAS family. Although HIF-1 is a heterodimer composed of [Alpha] and [Beta] subunits, its activity is primarily determined by hypoxiainduced stabilization of HIF-1[Alpha], which is otherwise rapidly degraded in oxygenated cells. We report the identification of an oxygen-dependent degradation (ODD) domain within HIF-1[Alpha] that controls its degradation by the ubiquitin-proteasome pathway. The ODD domain consists of [approximately equal to]200 amino acid residues, located in the central region of HIF-1[Alpha]. Because portions of the domain independently confer degradation of HIF-1[Alpha], deletion of this entire region is required to give rise to a stable HIF-1[Alpha], capable of heterodimerization, DNA-binding, and transactivation in the absence of hypoxic signaling. Conversely, the ODD domain alone confers oxygen-dependent instability when fused to a stable protein, Gal4. Hence, the ODD domain plays a pivotal role for regulating HIF-1 activity and thereby may provide a means of controlling gene expression by changes in oxygen tension.

Vermicomposts have a reputation for being superior to other kinds of compost. Researchers at the Soil Ecology Laboratory at the Ohio State University studied the effects of worm castings on the growth and germination of petunias, marigolds, poinsettia and other flowering plants. The researchers discovered that compared to other composts, vermicomposts had very low concentrations of ammonium-nitrogen and high concentrations of nitrate-nitrogen. The microbial activity of both kinds of composting are different. Vermicomposting is processed through mesophilic bacteria and fungi while composting is characterized by thermophilic bacteria.

The insulin-like growth factors (IGF) are evolutionarily ancient growth factors present in all vertebrates. The central importance of IGF for normal development and growth has been illustrated by the severe growth-retarded phenotype exhibited by IGF-I, IGF-II or IGF-I receptor 'knockout' mice. Although we know much about the gross effects of IGF on the overall size of the fetus and the clinical manifestations that result from fetal and neonatal deficiency of IGF (i.e., severe growth retardation leads to dwarfism), very little is known about the in vivo actions of IGF during embryogenesis at the cellular and molecular levels. Most research on the developmental role of IGF has relied on rodent models, and attempts to elucidate the molecular and cellular basis of IGF actions have been hampered by the inaccessibility of the mammalian fetus enclosed in the uterus. During the past decade, there has been growing support for the concept that the IGF have been highly conserved in all vertebrates. Both IGF-I and IGF-II are present in fish, and their structures are highly conserved. Human and fish IGF-I are equally potent in mammalian and fish bioassay systems. Insulin-like growth factor mRNA is found in all life stages of fish, ranging from unfertilized egg to adult. The temporal and spatial expression patterns of fish IGF-I seem to be similar to those in mammals. Nutritional status and growth hormone both have a profound effect on IGF-I expression in fish, as they do in mammals. These features suggest that the IGF system is highly conserved between teleost fish and mammals. Because fish embryos develop externally, they provide excellent animal models for understanding the regulatory roles of IGF, IGF receptor and IGF-binding proteins in vertebrate embryonic development. Current research on the developmental and nutritional roles of IGF in fish will undoubtedly contribute to knowledge of the basic physiology of vertebrates in general. KEY WORDS: insulin-like growth factors; embryogenesis; nutrition; gene expression; fish

Insulin-like growth factor-I and -II are important multifunctional polypeptides that interact with membrane-bound receptors as well as soluble binding proteins. The biological actions of these hormones are multifaceted and dependent to a large extent on binding protein interactions. Some unique differences in insulin-like growth factor physiology and biochemistry are evident between mammalian and avian species. These include amino acid compositional and significant receptor differences as well as binding protein status. The biological response to both growth factors is different in birds. A greater proportion of the insulin-like growth factors exists in plasma as free peptide compared with the situation in mammals. This review is a brief summary of our knowledge of insulin-like growth factor physiology in domestic fowl. KEY WORDS: chickens; turkeys; metabolism; hormone

The Saccharomyces cerevisiae genes TOR1 and TOR2 encode phosphatidylinositol kinase homologs. TOR2 has two essential functions. One function overlaps with TOR1 and mediates protein synthesis and cell cycle progression. The second essential function of TOR2 is unique to TOR2 and mediates the cell-cycle-dependent organization of the actin cytoskeleton. We have isolated temperature-sensitive mutants that are defective for either one or both of the two TOR2 functions. The three classes of mutants were as follows. Class A mutants, lacking only the TOR2-unique function, are defective in actin cytoskeleton organization and arrest within two to three generations as small-budded cells in the G2/M phase of the cell cycle. Class B mutants, lacking only the TOR-shared function, and class C mutants, lacking both functions, exhibit a rapid loss of protein synthesis and a GI arrest within one generation. To define further the two functions of TOR2, we isolated multicopy suppressors that rescue the class A or B mutants. Overexpression of MSS4, PKC1, PLC1, RH02, ROM2, or SUR1 suppressed the growth defect of a class A mutant. Surprisingly, overexpression of PLC1 and MSS4 also suppressed the growth defect of a class B mutant. These genes encode proteins that are involved in phosphoinositide metabolism and signaling. Thus, the two functions (readouts) of TOR2 appear to involve two related signaling pathways controlling cell growth.

Chondrogenesis during embryonic skeletal development involves the condensation of mesenchymal cells followed by their differentiation into chondrocytes. We describe herein a previously unrecognized regulator of mammalian chondrogenesis encoded by a murine growth factor-inducible immediate-early gene, cyr61. The Cyr61 protein is a secreted, heparin-binding protein (379 amino acids with 38 conserved cysteines) that promotes cell adhesion, migration, and proliferation. The expression pattern of the cyr61 gene during embryogenesis is tissue specific and temporally regulated. Most notably, cyr61 is transiently expressed in mesenchymal cells of both mesodermal and neuroectodermal origins undergoing chondrogenesis, suggesting that Cyr61 may play a role in the development of the embryonic skeleton. In this communication, we demonstrate that the Cyr61 protein promotes chondrogenesis in micromass cultures of limb bud mesenchymal cells in vitro and is likely to play a similar role in vivo based on the following observations: (1) Cyr61 is present in the embryonic limb mesenchyme during chondrogenesis in vivo and in vitro; (2) purified recombinant Cyr61 protein added exogenously to micromass cultures promotes chondrogenesis as judged by precocious expression of type II collagen, increased [3SS]sulfate incorporation, and larger Alcian blue-staining cartilage nodules; (3) Cyr61 enhances cell-cell aggregation, an initial step in chondrogenesis, and promotes chondrogenic differentiation in cultures plated at subthreshold cell densities that are otherwise unable to support differentiation; and (4) neutralization of the endogenous Cyr61 with specific antibodies inhibits chondrogenesis. Taken together, these results identify Cyr61 as a novel player in chondrogenesis that contributes to the development of the mammalian embryonic skeleton. Key Words: micromass culture; mouse embryo; connective tissue growth factor; Nov; type II collagen.