I joined François Gros' laboratory as a postdoc at the end of 1971 and continued working with him as a research scientist until 1987, when I became an independent group leader at the Institut ...Pasteur. In the early 1970s, it was the beginning of research in his lab on muscle cell differentiation, as a model eukaryotic system for studying mRNAs and gene regulation. In this article, I recount our work on myogenesis and mention the other research themes in his lab and the people concerned. I remained in close contact with François and pay tribute to him as a major figure in French science and as my personal mentor who provided me with constant support.
The mud loach (Misgurnus anguillicaudatus) is one of the most important aquaculture fishes in Asia. The application of the CRISPR/Cas9 system in the cultivation of loach strains with valuable ...economic traits presents great potential. Myostatin is a candidate factor that can be used for the cultivation of fast-growing loach strains. In this study, the appropriate microinjection dose of the Cas9 protein (600 pg) for genome editing was determined considering both the mutation rate and survival rate of loach embryos. With this microinjection dose of the Cas9 protein, both the exogenous GFP and endogenous myostatin genes were efficiently edited using the CRISPR/Cas9 system. Compared with that in wild-type siblings, the average body weight of the fish in 1-, 2- and 3-month-old myostatin mutant chimeric loaches was significantly increased by 34.9% (P < 0.001), 15.5% (P = 0.024) and 27.8% (P = 0.012), respectively. Mutation of mstn significantly increased the number of muscle fibers and total area of muscle fibers. Also, lipid accumulation was significantly higher in chimeric mutant loach. Additionally, the mRNA levels of myogenesis (myod and myog) and lipogenesis-related genes (scd, fabp1, fabp2 and dgat) were significantly upregulated in chimeric mutants. In particular, the mRNA level of the stearoyl-CoA desaturase gene, whose product catalyses the formation of monounsaturated fatty acids from saturated fatty acids, was increased by 23-fold (P = 0.034) and 736-fold (P < 0.05) in 3 dpf and 1-month-old chimeric loaches, respectively. The gene expression results indicated that the targeted disruption of myostatin activated myogenesis and adipogenesis in loach. Our study is highly valuable for cultivating fast-growing loach strains and understanding the specific role of myostatin in lipogenesis.
•The appropriate microinjection dose of the Cas9 protein for genome editing was determined in loach Misgurnus anguillicaudatus.•Fast-growing loaches were obtained through the targeted mutation of myostatin.•Loss of myostatin activated myogenesis in loach.•Loss of myostatin activated adipogenesis in loach.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Skeletal muscle is the largest tissue in the body and loss of its function or its regenerative properties results in debilitating musculoskeletal disorders. Understanding the mechanisms that drive ...skeletal muscle formation will not only help to unravel the molecular basis of skeletal muscle diseases, but also provide a roadmap for recapitulating skeletal myogenesis
from pluripotent stem cells (PSCs). PSCs have become an important tool for probing developmental questions, while differentiated cell types allow the development of novel therapeutic strategies. In this Review, we provide a comprehensive overview of skeletal myogenesis from the earliest premyogenic progenitor stage to terminally differentiated myofibers, and discuss how this knowledge has been applied to differentiate PSCs into muscle fibers and their progenitors
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Injury to skeletal muscle through trauma, physical activity, or disease initiates a process called muscle regeneration. When injured myofibers undergo necrosis, muscle regeneration gives rise to ...myofibers that have myonuclei in a central position, which contrasts the normal, peripheral position of myonuclei. Myofibers with central myonuclei are called regenerating myofibers and are the hallmark feature of muscle regeneration. An important and underappreciated aspect of muscle regeneration is the maturation of regenerating myofibers into a normal sized myofiber with peripheral myonuclei. Strikingly, very little is known about processes that govern regenerating myofiber maturation after muscle injury. As knowledge of myofiber formation and maturation during embryonic, fetal, and postnatal development has served as a foundation for understanding muscle regeneration, this narrative review discusses similarities and differences in myofiber maturation during muscle development and regeneration. Specifically, we compare and contrast myonuclear positioning, myonuclear accretion, myofiber hypertrophy, and myofiber morphology during muscle development and regeneration. We also discuss regenerating myofibers in the context of different types of myofiber necrosis (complete and segmental) after muscle trauma and injurious contractions. The overall goal of the review is to provide a framework for identifying cellular and molecular processes of myofiber maturation that are unique to muscle regeneration.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Background
Betaglycan, also known as the TGFβ type III receptor (Tgfbr3), is a co‐receptor that modulates TGFβ family signaling. Tgfbr3 is upregulated during C2C12 myoblast differentiation and ...expressed in mouse embryos myocytes.
Results
To investigate tgfbr3 transcriptional regulation during zebrafish embryonic myogenesis, we cloned a 3.2 kb promoter fragment that drives reporter transcription during C2C12 myoblasts differentiation and in the Tg(tgfbr3:mCherry) transgenic zebrafish. We detect tgfbr3 protein and mCherry expression in the adaxial cells concomitantly with the onset of their radial migration to become slow‐twitch muscle fibers in the Tg(tgfbr3:mCherry). Remarkably, this expression displays a measurable antero‐posterior somitic gradient expression.
Conclusions
tgfbr3 is transcriptionally regulated during somitic muscle development in zebrafish with an antero‐posterior gradient expression that preferentially marks the adaxial cells and their descendants.
Key Findings
Tgfbr3 is transcriptionally regulated in zebrafish muscle.
Tgfbr3 is specifically expressed in adaxial cells and slow twitch somitic muscle.
Tgfbr3 is expressed in an antero‐posterior somitic gradient.
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FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
Cysteine, the rate-controlling amino acid in cellular glutathione synthesis is imported as cystine, by the cystine/glutamate antiporter, xCT, and subsequently reduced to cysteine. As glutathione ...redox is important in muscle regeneration in aging, we hypothesized that xCT exerts upstream control over skeletal muscle glutathione redox, metabolism and regeneration. Bioinformatic analyses of publicly available datasets revealed that expression levels of xCT and GSH-related genes are inversely correlated with myogenic differentiation genes. Muscle satellite cells (MuSCs) isolated from Slc7a11sut/sut mice, which harbour a mutation in the Slc7a11 gene encoding xCT, required media supplementation with 2-mercaptoethanol to support cell proliferation but not myotube differentiation, despite persistently lower GSH. Slc7a11sut/sut primary myotubes were larger compared to WT myotubes, and also exhibited higher glucose uptake and cellular oxidative capacities. Immunostaining of myogenic markers (Pax7, MyoD, and myogenin) in cardiotoxin-damaged tibialis anterior muscle fibres revealed greater MuSC activation and commitment to differentiation in Slc7a11sut/sut muscle compared to WT mice, culminating in larger myofiber cross-sectional areas at 21 days post-injury. Slc7a11sut/sut mice subjected to a 5-week exercise training protocol demonstrated enhanced insulin tolerance compared to WT mice, but blunted muscle mitochondrial biogenesis and respiration in response to exercise training. Our results demonstrate that the absence of xCT inhibits cell proliferation but promotes myotube differentiation by regulating cellular metabolism and glutathione redox. Altogether, these results support the notion that myogenesis is a redox-regulated process and may help inform novel therapeutic approaches for muscle wasting and dysfunction in aging and disease.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Understanding how skeletal muscle fiber proportions are regulated is vital to understanding muscle function. Oxidative and glycolytic skeletal muscle fibers differ in their contractile ability, ...mitochondrial activity, and metabolic properties. Fiber-type proportions vary in normal physiology and disease states, although the underlying mechanisms are unclear. In human skeletal muscle, we observed that markers of oxidative fibers and mitochondria correlated positively with expression levels of PPARGC1A and CDK4 and negatively with expression levels of CDKN2A, a locus significantly associated with type 2 diabetes. Mice expressing a constitutively active Cdk4 that cannot bind its inhibitor p16.sup.INK4a, a product of the CDKN2A locus, were protected from obesity and diabetes. Their muscles exhibited increased oxidative fibers, improved mitochondrial properties, and enhanced glucose uptake. In contrast, loss of Cdk4 or skeletal muscle-specific deletion of Cdk4's target, E2F3, depleted oxidative myofibers, deteriorated mitochondrial function, and reduced exercise capacity, while increasing diabetes susceptibility. E2F3 activated the mitochondrial sensor PPARGC1A in a Cdk4- dependent manner. CDK4, E2F3, and PPARGC1A levels correlated positively with exercise and fitness and negatively with adiposity, insulin resistance, and lipid accumulation in human and rodent muscle. All together, these findings provide mechanistic insight into regulation of skeletal muscle fiberspecification that is of relevance to metabolic and muscular diseases.
Long noncoding RNAs (lncRNAs) have been reported to play diverse roles in biologic and pathologic processes, including myogenesis. We found that lncRNA AK017368 is highly expressed in skeletal muscle ...cells. Functional analyses showed that overexpression of AK017368 promoted proliferation and restrained differentiation of myoblasts; whereas inhibition of AK017368 had completely opposite effects in vitro. In mice, knockdown of AK017368 promoted muscle hypertrophy in vivo. RNA molecules of AK017368 acted mechanistically as competing endogenous RNAs to target micro‐RNA (miR)‐30c, which was supported by the results of bioinformatics analyses and dual‐luciferase reporter assays. It has been shown that lncRNA AK017368 competes with trinucleotide repeat containing‐6A (Tnrc6a)for miR‐30c. Tnrc6a was previously reported to promote proliferation and inhibit differentiation of myoblast cells, whereas miR‐30c targets the 3'‐UTR of Tnrc6a mRNA to weaken its function. Taken together, lncRNA AK017368 promotes proliferation and inhibits differentiation of myoblast cells by attenuating function of miR‐30c.—Liang, T., Zhou, B., Shi, L., Wang, H., Chu, Q., Xu, F., Li, Y., Chen, R., Shen, C., Schinckel, A. P. lncRNA AK017368 promotes proliferation and suppresses differentiation of myoblasts in skeletal muscle devel‐opment by attenuating the function of miR‐30c. FASEB J. 32,377‐389 (2018). www.fasebj.org
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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