A novel lncRNA promotes myogenesis of bovine skeletal muscle satellite cells via PFN1-RhoA/Rac1

Metabolic differences in MSTN and FGF5 dual-gene edited sheep muscle cells during myogenesis

Dynamic metabolic reprogramming occurs at different stages of myogenesis and contributes to the fate determination of skeletal muscle satellite cells (MuSCs). Accumulating evidence suggests that mutations in myostatin (MSTN) have a vital role in regulating muscle energy metabolism. Here, we explored the metabolic reprogramming in MuSCs and myotube cells in MSTN and FGF5 dual-gene edited sheep models prepared previously, and also focused on the metabolic alterations during myogenic differentiation of MuSCs. Our study revealed that the pathways of nucleotide metabolism, pantothenate and CoA biosynthesis were weakened, while the unsaturated fatty acids biosynthesis were strengthened during myogenic differentiation of sheep MuSCs. The MSTN and FGF5 dual-gene editing mainly inhibited nucleotide metabolism and biosynthesis of unsaturated fatty acids in sheep MuSCs, reduced the number of lipid droplets in per satellite cell, and promoted the pentose phosphate pathway, and the interconversion of pentose and glucuronate. The MSTN and FGF5 dual-gene editing also resulted in the inhibition of nucleotide metabolism and TCA cycle pathway in differentiated myotube cells. The differential metabolites we identified can be characterized as biomarkers of different cellular states, and providing a new reference for MSTN and FGF5 dual-gene editing in regulation of muscle development. It may also provide a reference for the development of muscle regeneration drugs targeting biomarkers.

Role of Actin-Binding Proteins in Skeletal Myogenesis

Maintenance of skeletal muscle quantity and quality is essential to ensure various vital functions of the body. Muscle homeostasis is regulated by multiple cytoskeletal proteins and myogenic transcriptional programs responding to endogenous and exogenous signals influencing cell structure and function. Since actin is an essential component in cytoskeleton dynamics, actin-binding proteins (ABPs) have been recognized as crucial players in skeletal muscle health and diseases. Hence, dysregulation of ABPs leads to muscle atrophy characterized by loss of mass, strength, quality, and capacity for regeneration. This comprehensive review summarizes the recent studies that have unveiled the role of ABPs in actin cytoskeletal dynamics, with a particular focus on skeletal myogenesis and diseases. This provides insight into the molecular mechanisms that regulate skeletal myogenesis via ABPs as well as research avenues to identify potential therapeutic targets. Moreover, this review explores the implications of non-coding RNAs (ncRNAs) targeting ABPs in skeletal myogenesis and disorders based on recent achievements in ncRNA research. The studies presented here will enhance our understanding of the functional significance of ABPs and mechanotransduction-derived myogenic regulatory mechanisms. Furthermore, revealing how ncRNAs regulate ABPs will allow diverse therapeutic approaches for skeletal muscle disorders to be developed.

Cellular pathogenesis of Duchenne muscular dystrophy: progressive myofibre degeneration, chronic inflammation, reactive myofibrosis and satellite cell dysfunction

Duchenne muscular dystrophy is a highly progressive muscle wasting disease of early childhood and characterized by complex pathophysiological and histopathological changes in the voluntary contractile system, including myonecrosis, chronic inflammation, fat substitution and reactive myofibrosis. The continued loss of functional myofibres and replacement with non-contractile cells, as well as extensive tissue scarring and decline in tissue elasticity, leads to severe skeletal muscle weakness. In addition, dystrophic muscles exhibit a greatly diminished regenerative capacity to counteract the ongoing process of fibre degeneration. In normal muscle tissues, an abundant stem cell pool consisting of satellite cells that are localized between the sarcolemma and basal lamina, provides a rich source for the production of activated myogenic progenitor cells that are involved in efficient myofibre repair and tissue regeneration. Interestingly, the self-renewal of satellite cells for maintaining an essential pool of stem cells in matured skeletal muscles is increased in dystrophin-deficient fibres. However, satellite cell hyperplasia does not result in efficient recovery of dystrophic muscles due to impaired asymmetric cell divisions. The lack of expression of the full-length dystrophin isoform Dp427-M, which is due to primary defects in the DMD gene,  appears to affect key regulators of satellite cell polarity causing a reduced differentiation of myogenic progenitors, which are essential for myofibre regeneration. This review outlines the complexity of dystrophinopathy and describes the importance of the pathophysiological role of satellite cell dysfunction. A brief discussion of the bioanalytical usefulness of single cell proteomics for future studies of satellite cell biology is provided.

A single-cell atlas of bovine skeletal muscle reveals mechanisms regulating intramuscular adipogenesis and fibrogenesis

BACKGROUND

Intramuscular fat (IMF) and intramuscular connective tissue (IMC) are often seen in human myopathies and are central to beef quality. The mechanisms regulating their accumulation remain poorly understood. Here, we explored the possibility of using beef cattle as a novel model for mechanistic studies of intramuscular adipogenesis and fibrogenesis.

METHODS

Skeletal muscle single-cell RNAseq was performed on three cattle breeds, including Wagyu (high IMF), Brahman (abundant IMC but scarce IMF), and Wagyu/Brahman cross. Sophisticated bioinformatics analyses, including clustering analysis, gene set enrichment analyses, gene regulatory network construction, RNA velocity, pseudotime analysis, and cell-cell communication analysis, were performed to elucidate heterogeneities and differentiation processes of individual cell types and differences between cattle breeds. Experiments were conducted to validate the function and specificity of identified key regulatory and marker genes. Integrated analysis with multiple published human and non-human primate datasets was performed to identify common mechanisms.

RESULTS

A total of 32 708 cells and 21 clusters were identified, including fibro/adipogenic progenitor (FAP) and other resident and infiltrating cell types. We identified an endomysial adipogenic FAP subpopulation enriched for COL4A1 and CFD (log2FC = 3.19 and 1.92, respectively; P < 0.0001) and a perimysial fibrogenic FAP subpopulation enriched for COL1A1 and POSTN (log2FC = 1.83 and 0.87, respectively; P < 0.0001), both of which were likely derived from an unspecified subpopulation. Further analysis revealed more progressed adipogenic programming of Wagyu FAPs and more advanced fibrogenic programming of Brahman FAPs. Mechanistically, NAB2 drives CFD expression, which in turn promotes adipogenesis. CFD expression in FAPs of young cattle before the onset of intramuscular adipogenesis was predictive of IMF contents in adulthood (R2  = 0.885, P < 0.01). Similar adipogenic and fibrogenic FAPs were identified in humans and monkeys. In aged humans with metabolic syndrome and progressed Duchenne muscular dystrophy (DMD) patients, increased CFD expression was observed (P < 0.05 and P < 0.0001, respectively), which was positively correlated with adipogenic marker expression, including ADIPOQ (R2  = 0.303, P < 0.01; and R2  = 0.348, P < 0.01, respectively). The specificity of Postn/POSTN as a fibrogenic FAP marker was validated using a lineage-tracing mouse line. POSTN expression was elevated in Brahman FAPs (P < 0.0001) and DMD patients (P < 0.01) but not in aged humans. Strong interactions between vascular cells and FAPs were also identified.

CONCLUSIONS

Our study demonstrates the feasibility of beef cattle as a model for studying IMF and IMC. We illustrate the FAP programming during intramuscular adipogenesis and fibrogenesis and reveal the reliability of CFD as a predictor and biomarker of IMF accumulation in cattle and humans.

Bta-miR-206 and a Novel lncRNA-lncA2B1 Promote Myogenesis of Skeletal Muscle Satellite Cells via Common Binding Protein HNRNPA2B1

Skeletal muscle satellite cells (MuSCs) can proliferate, differentiate, and self-renew, and can also participate in muscle formation and muscle injury repair. Long noncoding RNAs (lncRNAs) can play an important role with the RNA binding protein and microRNAs (miRNAs) to regulate the myogenesis of bovine MuSCs, however, its molecular mechanism is still being explored. In this study, differentially expressed 301 lncRNAs were identified during the myogenic differentiation of cells based on an in vitro model of induced differentiation of bovine MuSCs using RNA sequencing (RNA-seq). Based on the ability of miR-206 to regulate myogenic cell differentiation, a new kind of lncRNA-lncA2B1 without protein-coding ability was found, which is expressed in the nucleus and cytoplasm. Subsequently, lncA2B1 inhibited cell proliferation by downregulating the expression of the proliferation marker Pax7 and promoted myogenic differentiation by upregulating the expression of the differentiation marker MyHC, whose regulatory function is closely related to miR-206. By RNA pulldown/LC-MS experiments, heterogeneous ribonucleoprotein A2/B1 (HNRNPA2B1), and DExH-Box Helicase 9 (DHX9) were identified as common binding proteins of lncA2B1 and miR-206. Overexpression of lncA2B1 and miR-206 significantly upregulated the expression level of HNRNPA2B1. Downregulation of HNRNPA2B1 expression significantly decreased the expression level of the differentiation marker MyHC, which indicates that miR-206 and lncA2B1 regulate myogenic differentiation of bovine MuSCs by acting on HNRNPA2B1. This study screened and identified a novel lncRNA-lncA2B1, which functions with miR-206 to regulate myogenesis via the common binding proteins HNRNPA2B1. The results of this study provide a new way to explore the molecular mechanisms by which lncRNAs and miRNAs regulate muscle growth and development.

Global Long Noncoding RNA Expression Profiling of MSTN and FGF5 Double-Knockout Sheep Reveals the Key Gatekeepers of Skeletal Muscle Development

Improving livestock and poultry growth rates and increasing meat production are urgently needed worldwide. Previously, we produced a myostatin (MSTN) and fibroblast growth factor 5 (FGF5) double-knockout (MF^-/-) sheep by CRISPR Cas9 system to improve meat production, and also wool production. Both MF^-/- sheep and the F1 generation (MF^+/-) sheep showed an obvious "double-muscle" phenotype. In this study, we identified the expression profiles of long noncoding RNAs (lncRNAs) in wild-type and MF^+/- sheep, then screened out the key candidate lncRNAs that can regulate myogenic differentiation and skeletal muscle development. These key candidate lncRNAs can serve as critical gatekeepers for muscle contraction, calcium ion transport and skeletal muscle cell differentiation, apoptosis, autophagy, and skeletal muscle inflammation, further revealing that lncRNAs play crucial roles in regulating muscle phenotype in MF^+/- sheep. In conclusion, our newly identified lncRNAs may emerge as novel molecules for muscle development or muscle disease and provide a new reference for MSTN-mediated regulation of skeletal muscle development.

Identification of key genes in bovine muscle development by co-expression analysis

Background

Skeletal muscle is not only an important tissue involved in exercise and metabolism, but also an important part of livestock and poultry meat products. Its growth and development determines the output and quality of meat to a certain extent, and has an important impact on the economic benefits of animal husbandry. Skeletal muscle development is a complex regulatory network process, and its molecular mechanism needs to be further studied.

Method

We used a weighted co-expression network (WGCNA) and single gene set enrichment analysis (GSEA) to study the RNA-seq data set of bovine tissue differential expression analysis, and the core genes and functional enrichment pathways closely related to muscle tissue development were screened. Finally, the accuracy of the analysis results was verified by tissue expression profile detection and bovine skeletal muscle satellite cell differentiation model in vitro (BSMSCs).

Results

In this study, Atp2a1, Tmod4, Lmod3, Ryr1 and Mybpc2 were identified as marker genes in muscle tissue, which are mainly involved in glycolysis/gluconeogenesis, AMPK pathway and insulin pathway. The assay results showed that these five genes were highly expressed in muscle tissue and positively correlated with the differentiation of bovine BSMSCs.

Conclusions

In this study, several muscle tissue characteristic genes were excavated, which may play an important role in muscle development and provide new insights for bovine molecular genetic breeding.

PFN1 Inhibits Myogenesis of Bovine Myoblast Cells via Cdc42-PAK/JNK

Myoblast differentiation is essential for the formation of skeletal muscle myofibers. Profilin1 (Pfn1) has been identified as an actin-associated protein, and has been shown to be critically important to cellular function. Our previous study found that PFN1 may inhibit the differentiation of bovine skeletal muscle satellite cells, but the underlying mechanism is not known. Here, we confirmed that PFN1 negatively regulated the myogenic differentiation of bovine skeletal muscle satellite cells. Immunoprecipitation assay combined with mass spectrometry showed that Cdc42 was a binding protein of PFN1. Cdc42 could be activated by PFN1 and could inhibit the myogenic differentiation like PFN1. Mechanistically, activated Cdc42 increased the phosphorylation level of p2l-activated kinase (PAK), which further activated the phosphorylation activity of c-Jun N-terminal kinase (JNK), whereas PAK and JNK are inhibitors of myogenic differentiation. Taken together, our results reveal that PFN1 is a repressor of bovine myogenic differentiation, and provide the regulatory mechanism.

Assessing the Role of Ancestral Fragments and Selection Signatures by Whole-Genome Scanning in Dehong Humped Cattle at the China-Myanmar Border

Dehong humped cattle are precious livestock resources of Yunnan Province, China; they have typical zebu traits. Here, we investigated their genetic characteristics using whole-genome resequencing data of Dehong humped animals (n = 18). When comparing our data with the publicly-available data, we found that Dehong humped cattle have high nucleotide diversity. Based on clustering models in a population structure analysis, Dehong humped cattle had a mutual genome ancestor with Chinese and Indian indicine cattle. While using the RFMix method, it is speculated that the body sizes of Dehong humped cattle were influenced by the Chinese indicine segments and that the immune systems of Dehong humped cattle were affected by additional ancestral segments (Indian indicine). Furthermore, we explored the position selection regions harboring genes in the Dehong humped cattle, which were related to heat tolerance (FILIP1L, ABHD6) and immune responses (GZMM, PRKCZ, STOML2, LRBA, PIK3CD). Notably, missense mutations were detected in the candidate gene ABHD6 (c.870C>A p.Asp290Glu; c.987C>A p.Ser329Arg). The missense mutations may have implications for Dehong humped cattle adaptation to hot environments. This study provides valuable genomic resource data at the genome-wide level and paves the way for future genetic breeding work in the Dehong humped cattle.

An Emerging Role for Epigenetics in Cerebral Palsy

Cerebral palsy is a set of common, severe, motor disabilities categorized by a static, nondegenerative encephalopathy arising in the developing brain and associated with deficits in movement, posture, and activity. Spastic CP, which is the most common type, involves high muscle tone and is associated with altered muscle function including poor muscle growth and contracture, increased extracellular matrix deposition, microanatomic disruption, musculoskeletal deformities, weakness, and difficult movement control. These muscle-related manifestations of CP are major causes of progressive debilitation and frequently require intensive surgical and therapeutic intervention to control. Current clinical approaches involve sophisticated consideration of biomechanics, radiologic assessments, and movement analyses, but outcomes remain difficult to predict. There is a need for more precise and personalized approaches involving omics technologies, data science, and advanced analytics. An improved understanding of muscle involvement in spastic CP is needed. Unfortunately, the fundamental mechanisms and molecular pathways contributing to altered muscle function in spastic CP are only partially understood. In this review, we outline evidence supporting the emerging hypothesis that epigenetic phenomena play significant roles in musculoskeletal manifestations of CP.

A novel lncRNA promotes myogenesis of bovine skeletal muscle satellite cells via PFN1-RhoA/Rac1

Myogenesis, the process of skeletal muscle formation, is a highly coordinated multistep biological process. Accumulating evidence suggests that long non-coding RNAs (lncRNAs) are emerging as a gatekeeper in myogenesis. Up to now, most studies on muscle development-related lncRNAs are mainly focussed on humans and mice. In this study, a novel muscle highly expressed lncRNA, named lnc23, localized in nucleus, was found differentially expressed in different stages of embryonic development and myogenic differentiation. The knockdown and over-expression experiments showed that lnc23 positively regulated the myogenic differentiation of bovine skeletal muscle satellite cells. Then, TMT 10-plex labelling quantitative proteomics was performed to screen the potentially regulatory proteins of lnc23. Results indicated that lnc23 was involved in the key processes of myogenic differentiation such as cell fusion, further demonstrated that down-regulation of lnc23 may inhibit myogenic differentiation by reducing signal transduction and cell fusion among cells. Furthermore, RNA pulldown/LC-MS and RIP experiment illustrated that PFN1 was a binding protein of lnc23. Further, we also found that lnc23 positively regulated the protein expression of RhoA and Rac1, and PFN1 may negatively regulate myogenic differentiation and the expression of its interacting proteins RhoA and Rac1. Hence, we support that lnc23 may reduce the inhibiting effect of PFN1 on RhoA and Rac1 by binding to PFN1, thereby promoting myogenic differentiation. In short, the novel identified lnc23 promotes myogenesis of bovine skeletal muscle satellite cells via PFN1-RhoA/Rac1.