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Skeletal Muscle Development (skeletal + muscle_development)
Selected AbstractsExpression and alternative splicing of N-RAP during mouse skeletal muscle development,CYTOSKELETON, Issue 12 2008Shajia Lu Abstract N-RAP alternative splicing and protein localization were studied in developing skeletal muscle tissue from pre- and postnatal mice and in fusing primary myotubes in culture. Messages encoding N-RAP-s and N-RAP-c, the predominant isoforms of N-RAP detected in adult skeletal muscle and heart, respectively, were present in a 5:1 ratio in skeletal muscle isolated from E16.5 embryos. N-RAP-s mRNA levels increased three-fold over the first 3 weeks of postnatal development, while N-RAP-c mRNA levels remained low. N-RAP alternative splicing during myotube differentiation in culture was similar to the pattern observed in embryonic and neonatal muscle, with N-RAP-s expression increasing and N-RAP-c mRNA levels remaining low. In both developing skeletal muscle and cultured myotubes, N-RAP protein was primarily associated with developing myofibrillar structures containing ,-actinin, but was not present in mature myofibrils. The results establish that N-RAP-s is the predominant spliced form of N-RAP present throughout skeletal muscle development. Cell Motil. Cytoskeleton 2008. Published 2008 Wiley-Liss, Inc. [source] Analysis of human muscle stem cells reveals a differentiation-resistant progenitor cell population expressing Pax7 capable of self-renewalDEVELOPMENTAL DYNAMICS, Issue 1 2009Bradley Pawlikowski Abstract Studies using mouse models have established a critical role for resident satellite stem cells in skeletal muscle development and regeneration, but little is known about this paradigm in human muscle. Here, using human muscle stem cells, we address their lineage progression, differentiation, migration, and self-renewal. Isolated human satellite cells expressed ,7-integrin and other definitive muscle markers, were highly motile on laminin substrates and could undergo efficient myotube differentiation and myofibrillogenesis. However, only a subpopulation of the myoblasts expressed Pax7 and displayed a variable lineage progression as measured by desmin and MyoD expression. Analysis identified a differentiation-resistant progenitor cell population that was Pax7+/desmin, and capable of self-renewal. This study extends our understanding of the role of Pax7 in regulating human satellite stem cell differentiation and self-renewal. Developmental Dynamics 238:138,149, 2009. © 2008 Wiley-Liss, Inc. [source] From segment to somite: Segmentation to epithelialization analyzed within quantitative frameworksDEVELOPMENTAL DYNAMICS, Issue 6 2007Paul M. Kulesa Abstract One of the most visually striking patterns in the early developing embryo is somite segmentation. Somites form as repeated, periodic structures in pairs along nearly the entire caudal vertebrate axis. The morphological process involves short- and long-range signals that drive cell rearrangements and cell shaping to create discrete, epithelialized segments. Key to developing novel strategies to prevent somite birth defects that involve axial bone and skeletal muscle development is understanding how the molecular choreography is coordinated across multiple spatial scales and in a repeating temporal manner. Mathematical models have emerged as useful tools to integrate spatiotemporal data and simulate model mechanisms to provide unique insights into somite pattern formation. In this short review, we present two quantitative frameworks that address the morphogenesis from segment to somite and discuss recent data of segmentation and epithelialization. Developmental Dynamics 236:1392,1402, 2007. © 2007 Wiley-Liss, Inc. [source] Development-dependent disappearance of caspase-3 in skeletal muscle is post-transcriptionally regulatedJOURNAL OF CELLULAR BIOCHEMISTRY, Issue 1 2002Louis-Bruno Ruest Abstract Caspase-3, a major player in apoptosis, engages apoptosis-activated cells into an irreversible pathway leading to cell death. In this article, we report that caspase-3 protein is absent from rat and mouse adult skeletal muscles, despite the abundant presence of its mRNA. During skeletal muscle development, caspase-3 protein is present in neonatal animals, but its expression gradually decreases, and disappears completely by 1 month of age, when there is still abundant caspase-3 mRNA. This discordance between caspase-3 message and protein expression is unique to skeletal muscle, as in all other analyzed tissues the protein presence correlates with the presence of the mRNA. The only circumstance in which caspase-3 protein appears in adults is in regenerating muscles; once regeneration is complete, however, it again becomes undetectable in repaired muscles. We conclude that caspase-3 protein in skeletal muscle is uniquely regulated at the post-transcriptional level, unseen in other tissues such as brain, heart, lung, kidney, thymus, spleen, liver, or testis. The post-transcriptional regulation of caspase-3 might serve as a fail-safe mechanism to avoid accidental cell death. J. Cell. Biochem. 86: 21,28, 2002. © 2002 Wiley-Liss, Inc. [source] Clenbuterol increases muscle fiber size and GATA-2 protein in rat skeletal muscle in uteroMOLECULAR REPRODUCTION & DEVELOPMENT, Issue 5 2008Diane Downie Abstract Certain ,2 -adrenoceptor agonists, such as clenbuterol, are known to elicit a muscle-specific anabolism or hypertrophy in both normal and catabolic muscle in a wide variety of species. However, the underlying mechanism(s) of the ,2 -agonist-induced anabolism remains unclear. This study aimed to determine the effects of clenbuterol administration in utero on skeletal muscle and to examine the underlying molecular mechanisms. Pregnant rats were fed clenbuterol (2 mg/kg diet) from Day 4 of gestation (4 dg) until weanling and fetal samples were taken from 13.5, 15.5, 17.5, and 19.5 dg and from 1d neonatal pups. Muscles were analyzed for total DNA, RNA and protein and sections examined morphologically for changes in muscle development. Western and immunohistochemical analyses were performed to identify changes in known myogenic signaling proteins. Clenbuterol increased the size of both fast and slow fibers in utero which was associated with a decreased DNA:protein ratio (28%) and an increased RNA:DNA ratio (36%). Additionally, drug treatment in utero induced a decrease in the fast:slow fiber ratio (38%). These myogenic changes were correlated with an increase in the GATA-2 hypertrophic transcription factor at both 17.5 dg (by 250%) and 19.5 dg (by 40%) in fetuses from clenbuterol treated dams. In addition, drug treatment resulted in increased membrane association of PKC-µ at 17.5 dg (325%) and increased PKC-, cytosolic abundance (40%) and PKC-, membrane abundance at 19.5 dg (250%). These results are the first demonstration that ,2 -agonists such as clenbuterol may act through upregulating the GATA-2 transcription factor and implicate certain PKC isoforms in the drug-induced regulation of skeletal muscle development. Mol. Reprod. Dev. 75: 785,794, 2008. © 2007 Wiley-Liss, Inc. [source] Identification of serine 205 as a site of phosphorylation on Pax3 in proliferating but not differentiating primary myoblastsPROTEIN SCIENCE, Issue 11 2008Patrick J. Miller Abstract Pax3, a member of the paired class homeodomain family of transcription factors, is essential for early skeletal muscle development. Previously, others and we have shown that the stability of Pax3 is regulated on a post-translational level. Evidence in the literature and from our laboratory suggests that phosphorylation, a common form of regulation, may play a role. However, at present, the sites of Pax3 phosphorylation are not known. We demonstrate here the first evidence that Pax3 exists as a phosphoprotein in proliferating mouse primary myoblasts. Using an in vitro kinase assay, deletion, and point mutant analysis, we conclusively identify Ser205 as a site of phosphorylation. The phosphorylation of Ser205 on endogenously expressed Pax3 was confirmed in vivo using antibodies specific for phosphorylation at Ser205. Finally, we demonstrate for the first time that the phosphorylation status of endogenous Pax3 changes rapidly upon the induction of myogenic differentiation. The presence of phosphorylation in a region of Pax3 important for mediating protein,protein interactions, and the fact that phosphorylation is lost upon induction of differentiation, allow for speculation on the biological relevance of phosphorylation. [source] AMP-activated protein kinase signalling pathways are down regulated and skeletal muscle development impaired in fetuses of obese, over-nourished sheepTHE JOURNAL OF PHYSIOLOGY, Issue 10 2008Mei J. Zhu Maternal obesity and over-nutrition give rise to both obstetric problems and neonatal morbidity. The objective of this study was to evaluate effects of maternal obesity and over-nutrition on signalling of the AMP-activated protein kinase (AMPK) pathway in fetal skeletal muscle in an obese pregnant sheep model. Non-pregnant ewes were assigned to a control group (Con, fed 100% of NRC nutrient recommendations, n= 7) or obesogenic group (OB, fed 150% of National Research Council (NRC) recommendations, n= 7) diet from 60 days before to 75 days after conception (term 150 days) when fetal semitendinosus skeletal muscle (St) was sampled. OB mothers developed severe obesity accompanied by higher maternal and fetal plasma glucose and insulin levels. In fetal St, activity of phosphoinositide-3 kinase (PI3K) associated with insulin receptor substrate-1 (IRS-1) was attenuated (P < 0.05), in agreement with the increased phophorylation of IRS-1 at serine 1011. Phosphorylation of AMP-activated protein kinase (AMPK) at Thr 172, acetyl-CoA carboxylase at Ser 79, tuberous sclerosis 2 at Thr 1462 and eukaryotic translation initiation factor 4E-binding protein 1 at Thr 37/46 were reduced in OB compared to Con fetal St. No difference in energy status (AMP/ATP ratio) was observed. The expression of protein phosphatase 2C was increased in OB compared to Con fetal St. Plasma tumour necrosis factor , (TNF,) was increased in OB fetuses indicating an increased inflammatory state. Expression of peroxisome proliferator-activated receptor , (PPAR,) was higher in OB St, indicating enhanced adipogenesis. The glutathione: glutathione disulphide ratio was also lower, showing increased oxidative stress in OB fetal St. In summary, we have demonstrated decreased signalling of the AMPK system in skeletal muscle of fetuses of OB mothers, which may play a role in altered muscle development and development of insulin resistance in the offspring. [source] MicroRNA identity and abundance in porcine skeletal muscles determined by deep sequencingANIMAL GENETICS, Issue 2 2010M. Nielsen Summary MicroRNAs (miRNA) are short single-stranded RNA molecules that regulate gene expression post-transcriptionally by binding to complementary sequences in the 3, untranslated region (3, UTR) of target mRNAs. MiRNAs participate in the regulation of myogenesis, and identification of the complete set of miRNAs expressed in muscles is likely to significantly increase our understanding of muscle growth and development. To determine the identity and abundance of miRNA in porcine skeletal muscle, we applied a deep sequencing approach. This allowed us to identify the sequences and relative expression levels of 212 annotated miRNA genes, thereby providing a thorough account of the miRNA transcriptome in porcine muscle tissue. The expression levels displayed a very large range, as reflected by the number of sequence reads, which varied from single counts for rare miRNAs to several million reads for the most abundant miRNAs. Moreover, we identified numerous examples of mature miRNAs that were derived from opposite sides of the same predicted precursor stem-loop structures, and also observed length and sequence heterogeneity at the 5, and 3, ends. Furthermore, KEGG pathway analysis suggested that highly expressed miRNAs are involved in skeletal muscle development and regeneration, signal transduction, cell-cell and cell-extracellular matrix communication and neural development and function. [source] Identification and characterization of microRNAs from porcine skeletal muscleANIMAL GENETICS, Issue 2 2010S. S. Xie Summary MicroRNAs (miRNAs) are a class of non-coding RNAs that negatively regulate gene expression at the post-transcriptional level. There is increasing evidence to suggest that miRNAs participate in muscle development in mice and humans; however, few studies have focused on miRNAs in porcine muscle tissue. Here, we experimentally detected and identified conserved and unique miRNAs from porcine skeletal muscle. Fifty-seven distinct miRNAs were identified, of which 39 have not been reported earlier in the pig. Of these, two miRNAs appear to be novel and pig-specific. Surprisingly, these two differ only by a single nucleotide. A part of their primary transcript was cloned and confirmed by sequencing analysis. Alignment of the two sequences using ClustalW showed that the precursor sequences were almost identical, but the flanking sequences were different, indicating that these two novel miRNAs may represent rapidly evolving miRNAs in the pig genome. The expression patterns of eight miRNAs were characterized by real-time polymerase chain reaction of eight pig tissue samples. The ssc-let-7e and ssc-miR-181b miRNAs were expressed in all tissues analysed. The ssc-let-7c, ssc-miR-125b, ssc-miR-new1 and ssc-miR-new2 miRNAs were expressed in several tissues, while ssc-miR-122 and ssc-miR-206 were specifically expressed in the liver and muscle respectively. Our results add to existing data on porcine miRNAs and are useful for investigating the biological functions of miRNAs in porcine skeletal muscle development. [source] Effects of maternal hyperthermia on myogenesis-related factors in developing upper limb,BIRTH DEFECTS RESEARCH, Issue 3 2009Jin Lee Abstract BACKGROUND: Maternal hyperthermia is one causative factor in various congenital anomalies in experimental animals and humans. In the present study, we assessed the effects of high temperature on limb myogenesis in mice. METHODS: Pregnant mice, C57BL/6 strain, were exposed to hyperthermia (43°C, 5 minutes) on embryonic day (ED) 8. Fetuses on ED 11, 13, 15, and 17 and neonates on postnatal day (PD) 1 were collected. To characterize the effects of hyperthermia on myogenesis-related factors Pax3, MyoD, myogenin, and myosin heavy chain (MyHC) during skeletal muscle development, we performed RT-PCR, western blotting, immunohistochemistry, and transmission electron microscopy. RESULTS: Pax3 gene expression was still detected on ED 13 in hyperthermia-exposed fetuses. The expression of MyoD protein was down-regulated in fetuses exposed to hyperthermia. In contrast, myogenin and MyHC protein expression were up-regulated on PD 1 and ED 17, respectively, in the group exposed to hyperthermia. Immunohistochemical analysis confirmed the findings from western blot analysis. Compared with control neonates, a TEM study revealed immature muscle fibers in PD 1 hyperthermia neonates. Thus, our studies showed that maternal hyperthermia induced delayed expression of Pax3 and inhibited expression of MyoD proteins, which are known to play important roles in migration of myogenic progenitor cells, and in myoblast proliferation. In addition, maternal hyperthermia also delayed the expression of myogenin protein for the formation of myotubes, and MyHC protein, which is one of the final muscle differentiation factors. CONCLUSION: Our data suggest that maternal hyperthermia delays limb myogenesis in part by disregulating the expression of key myogenesis-related factors. Birth Defects Research (Part A), 2009. © 2009 Wiley-Liss, Inc. [source] Inward relocation of exogenous phosphatidylserine triggered by IGF-1 in non-apoptotic C2C12 cells is concentration dependentCELL BIOCHEMISTRY AND FUNCTION, Issue 6 2005Cyril Rauch Abstract The plasma membrane is composed of two leaflets that are asymmetric with regard to their phospholipid composition with phosphatidylserine (PS) predominantly located within the inner leaflet whereas other phospholipids such as phosphatidylcholine (PC) are preferentially located in the outer leaflet. An intimate relationship between cellular physiology and the composition of the plasma membrane has been demonstrated, with for example apoptosis requiring PS exposure for macrophage recognition. In skeletal muscle development, differentiation also requires PS exposure in myoblasts to create cell,cell contact areas allowing the formation of multinucleate myotubes. Although it is clearly established that membrane composition/asymmetry plays an important role in cellular physiology, the role of cytokines in regulating this asymmetry is still unclear. When incubated with myoblasts, insulin-like growth factor I (IGF-1) has been shown to promote proliferation versus differentiation in a concentration dependent manner and therefore, may be a potential candidate regulating cell membrane asymmetry. We show, in non-apoptotic C2C12 cells, that relocation of an exogenous PS analogue, from the outer into the inner leaflet, is accelerated by IGF-1 in a concentration-dependent manner and that maintenance of membrane asymmetry triggered by IGF-1 is however independent of the PI3K inhibitor wortmannin. Copyright © 2005 John Wiley & Sons, Ltd. [source] | ||||||||||