Myostatin, a member of the transforming growth factor-β superfamily, is a pivotal regulator of skeletal muscle growth in mammals. Its discovery has sparked significant interest due to its multifaceted roles in various physiological processes and its potential therapeutic implications. This review explores the diverse functions of myostatin in skeletal muscle development, maintenance and pathology. We delve into its regulatory mechanisms, including its interaction with other signalling pathways and its modulation by various factors such as microRNAs and mechanical loading. Furthermore, we discuss the therapeutic strategies aimed at targeting myostatin for the treatment of muscle-related disorders, including cachexia, muscular dystrophy and heart failure. Additionally, we examine the impact of myostatin deficiency on craniofacial morphology and bone development, shedding light on its broader implications beyond muscle biology. Through a comprehensive analysis of the literature, this review underscores the importance of further research into myostatin\'s intricate roles and therapeutic potential in human health and disease.

Skeletal muscle, which is predominantly constituted by multinucleated muscle fibers, plays a pivotal role in sustaining bodily movements and energy metabolism. Myoblasts, which serve as precursor cells for differentiation and fusion into muscle fibers, are of critical importance in the exploration of the functional genes associated with embryonic muscle development. However, the in vitro proliferation of primary myoblasts is inherently constrained. In this study, we achieved a significant breakthrough by successfully establishing a chicken myoblast cell line through the introduction of the exogenous chicken telomerase reverse transcriptase (chTERT) gene, followed by rigorous G418-mediated pressure screening. This newly developed cell line, which was designated as chTERT-myoblasts, closely resembled primary myoblasts in terms of morphology and exhibited remarkable stability in culture for at least 20 generations of population doublings without undergoing malignant transformation. In addition, we conducted an exhaustive analysis that encompassed cellular proliferation, differentiation, and transfection characteristics. Our findings revealed that the chTERT-myoblasts had the ability to proliferate, differentiate, and transfect after multiple rounds of population doublings. This achievement not only furnished a valuable source of homogeneous avian cell material for investigating embryonic muscle development, but also provided valuable insights and methodologies for establishing primary cell lines.

Sestrin2 (Sesn2) has been previously confirmed to be a stress-response molecule. However, the influence of Sesn2 on myogenic differentiation remains elusive. This study was conducted to analyze the role of Sesn2 in the myogenic differentiation of C2C12 myoblasts and related aspects in mdx mice, an animal model of Duchenne muscular dystrophy (DMD). Our results showed that knockdown of Sesn2 reduced the myogenic differentiation capacity of C2C12 myoblasts. Predictive analysis from two databases suggested that miR-182-5p is a potential regulator of Sesn2. Further experimental validation revealed that overexpression of miR-182-5p decreased both the protein and mRNA levels of Sesn2 and inhibited myogenesis of C2C12 myoblasts. These findings suggest that miR-182-5p negatively regulates myogenesis by repressing Sesn2 expression. Extending to an in vivo model of DMD, knockdown of Sesn2 led to decreased Myogenin (Myog) expression and increased Pax7 expression, while its overexpression upregulated Myog levels and enhanced the proportion of slow-switch myofibers. These findings indicate the crucial role of Sesn2 in promoting myogenic differentiation and skeletal muscle regeneration, providing potential therapeutic targets for muscular dystrophy.

Skeletal muscle is a postmitotic tissue composed of contractile myofibers that are oriented and connected to different layers of connective tissue. Nevertheless, adult muscle fibers retain the capacity to regenerate in response to damage, activating the classical muscle stem cell compartment, namely, satellite cells (SCs), which are mitotically quiescent cells until required for growth or repair and are localized between the basal lamina and sarcolemma of myofibers. The transition of SCs from the quiescent state toward activation, commitment, and differentiation involves the genetic and epigenetic adaptation to novel biological functions, entailing dynamic changes in the protein expression profile. Interestingly, some of the activities and signaling regulating proliferation, commitment, differentiation, and survival/apoptosis of satellite cells have been also partially recapitulated in vitro, taking advantage of robust markers, reliable techniques, and reproducible protocols. Over the years, different techniques of muscular cell culture have been designed including primary cultures from embryonic or postnatal muscle, myogenic cell line, and three-dimensional (3D) skeletal muscle construct. Typical two-dimensional (2D) muscle cell culture cannot fully recapitulate the complexity of living muscle tissues, restricting their usefulness for physiological studies. The development of functional 3D culture models represents a valid alternative to overcome the limitations of already available in vitro model, increasing our understanding of the roles played by the various cell types and how they interact. In this chapter, the development of bidimensional and three-dimensional cell cultures have been described, improving the technical aspect of satellite cell isolation, the best culture-based conditions for muscle cell growth and differentiation, and the procedures required to develop a three-dimensional skeletal muscle construct.

Inbreeding can lead to the accumulation of homozygous single nucleotide polymorphisms (SNPs) in the genome, which can significantly affect gene expression and phenotype. In this study, we examined the impact of homozygous SNPs resulting from inbreeding on alternative polyadenylation (APA) site selection and the underlying genetic mechanisms using inbred Luchuan pigs. Genome resequencing revealed that inbreeding results in a high accumulation of homozygous SNPs within the pig genome. 3\' mRNA-seq on leg muscle, submandibular lymph node, and liver tissues was performed to identify differences in APA events between inbred and outbred Luchuan pigs. We revealed different tissue-specific APA usage caused by inbreeding, which were associated with differentially biological process. Furthermore, we explored the role of polyadenylation signal (PAS) SNPs in APA regulation under inbreeding and identified key genes such as PUM1, SCARF1, RIPOR2, C1D, and LRRK2 that are involved in biological processes regulation. This study provides resources and sheds light on the impact of genomic homozygosity on APA regulation, offering insights into genetic characteristics and biological processes associated with inbreeding.

A physiological concentration of magnesium (Mg) is essential for optimal skeletal muscle function. Indeed, Mg plays a crucial role during the differentiation process (myogenesis), in muscle fiber composition, muscle contraction and performance. This narrative review describes in detail the relevance of Mg in skeletal muscle, highlighting the importance of adequate Mg intake to ensure optimal skeletal muscle cell function and performance in individuals of all ages.

Breast muscle growth rate and intramuscular fat (IMF) content show apparent differences between fast-growing broilers and slow-growing indigenous chickens. However, the underlying genetic basis of these phenotypic characteristics remains elusive. In this study, we investigate the dynamic alterations of three-dimensional genome architecture and chromatin accessibility in breast muscle across four key developmental stages from embryo to starter chick in Arbor Acres (AA) broilers and Yufen (YF) indigenous chickens. The limited breed-specifically up-regulated genes (Bup-DEGs) are embedded in breed-specific A compartment, while a majority of the Bup-DEGs involving myogenesis and adipogenesis are regulated by the breed-specific TAD reprogramming. Chromatin loops allow distal accessible regions to interact with myogenic genes, and those loops share an extremely low similarity between chicken with different growth rate. Moreover, AA-specific loop interactions promote the expression of 40 Bup-DEGs, such as IGF1, which contributes to myofiber hypertrophy. YF-specific loop interactions or distal accessible regions lead to increased expression of 5 Bup-DEGs, including PIGO, PEMT, DHCR7, TMEM38B, and DHDH, which contribute to IMF deposition. These results help elucidate the regulation of breast muscle growth and IMF deposition in chickens.

Anatomically connected bones and muscles determine movement of the body. Forces exerted on muscles are then turned to bones to promote osteogenesis. The crosstalk between muscle and bone has been identified as mechanotransduction previously. In addition to the mechanical features, bones and muscles are also secretory organs which interact closely with one another through producing myokines and osteokines. Moreover, besides the mechanical features, other factors, such as nutrition metabolism, physiological rhythm, age, etc., also affect bone-muscle crosstalk. What\'s more, osteogenesis and myogenesis within motor system occur almost in parallel. Pathologically, defective muscles are always detected in bone associated diseases and induce the osteopenia, inflammation and abnormal bone metabolism, etc., through biomechanical or biochemical coupling. Hence, we summarize the study findings of bone-muscle crosstalk and propose potential strategies to improve the skeletal or muscular symptoms of certain diseases. Altogether, functional improvement of bones or muscles is beneficial to each other within motor system.

Skeletal muscle is a complex organ essential for locomotion, posture, and metabolic health. This review explores our current knowledge of Mustn1, particularly in the development and function of skeletal muscle. Mustn1 expression originates from Pax7-positive satellite cells in skeletal muscle, peaks during around the third postnatal month, and is crucial for muscle fiber differentiation, fusion, growth, and regeneration. Clinically, Mustn1 expression is potentially linked to muscle-wasting conditions such as muscular dystrophies. Studies have illustrated that Mustn1 responds dynamically to injury and exercise. Notably, ablation of Mustn1 in skeletal muscle affects a broad spectrum of physiological aspects, including glucose metabolism, grip strength, gait, peak contractile strength, and myofiber composition. This review summarizes our current knowledge of Mustn1\'s role in skeletal muscle and proposes future research directions, with a goal of elucidating the molecular function of this regulatory gene.

Rhabdomyosarcoma (RMS) is a pediatric tumor that resembles undifferentiated muscle cells; yet the extent to which cell state heterogeneity is shared with human development has not been described. Using single-cell/nucleus RNA sequencing from patient tumors, patient-derived xenografts, primary in vitro cultures, and cell lines, we identify four dominant muscle-lineage cell states: progenitor, proliferative, differentiated, and ground cells. We stratify these RMS cells/nuclei along the continuum of human muscle development and show that they share expression patterns with fetal/embryonal myogenic precursors rather than postnatal satellite cells. Fusion-negative RMS (FN-RMS) have a discrete stem cell hierarchy that recapitulates fetal muscle development and contain therapy-resistant FN-RMS progenitors that share transcriptomic similarity with bipotent skeletal mesenchymal cells. Fusion-positive RMS have tumor-acquired cells states, including a neuronal cell state, that are not found in myogenic development. This work identifies previously underappreciated cell state heterogeneity including unique treatment-resistant and tumor-acquired cell states that differ across RMS subtypes.