DNA maintenance methylation enzyme Dnmt1 in satellite cells is essential for muscle regeneration

Epigenetic regulation of myogenesis by vitamin C

The micronutrient vitamin C is essential for the maintenance of skeletal muscle health and homeostasis. The pro-myogenic effects of vitamin C have long been attributed to its role as a general antioxidant agent, as well as its role in collagen matrix synthesis and carnitine biosynthesis. Here, we show that vitamin C also functions as an epigenetic compound, facilitating chromatin landscape transitions during myogenesis through its activity as an enzymatic cofactor for histone H3 and DNA demethylation. Utilizing C2C12 myoblast cells to investigate the epigenetic effects of vitamin C on myogenesis, we observe that treatment of cells with vitamin C decreases global H3K9 methylation and increases 5-hmC levels. Furthermore, vitamin C treatment enhances myoblast marker gene expression and myotube formation during differentiation. We identify KDM7A as a histone lysine demethylase markedly upregulated during myogenesis. Accordingly, knockdown of Kdm7a prevents the pro-myogenic effects of vitamin C. Chromatin immunoprecipitation analysis showed that KDM7A occupies the promoter region of the myogenic transcription factor MyoD1 where it facilitates histone demethylation. We also confirm that the methylcytosine dioxygenases TET1 and TET2 are required for myogenic differentiation and that their loss blunts stimulation of myogenesis by vitamin C. In conclusion, our data suggest that an epigenetic mode of action plays a major role in the myogenic effects of vitamin C.

Integrative ATAC-seq and RNA-seq analysis of myogenic differentiation of ovine skeletal muscle satellite cell

Skeletal muscle satellite cells (SMSCs) play an important role in regulating muscle growth and regeneration. Chromatin accessibility allows physical interactions that synergistically regulate gene expression through enhancers, promoters, insulators, and chromatin binding factors. However, the chromatin accessibility altas and its regulatory role in ovine myoblast differentiation is still unclear. Therefore, ATAC-seq and RNA-seq analysis were performed on ovine SMSCs at the proliferation stage (SCG) and differentiation stage (SCD). 17,460 DARs (differential accessibility regions) and 3732 DEGs (differentially expressed genes) were identified. Based on joint analysis of ATAC-seq and RNA-seq, we revealed that PI3K-Akt, TGF-β and other signaling pathways regulated SMSCs differentiation. We identified two novel candidate genes, FZD5 and MAP2K6, which may affect the proliferation and differentiation of SMSCs. Our data identify potential cis regulatory elements of ovine SMSCs. This study can provide a reference for exploring the mechanisms of the differentiation and regeneration of SMSCs in the future.

Fetal programming effect of rumen-protected methionine on primiparous Angus × Simmental offspring's performance and skeletal muscle gene expression

Primiparous Angus × Simmental dams (n = 22) with an average body weight (BW) of 449 ± 32 kg of BW were divided based on two nutritional treatments: control (CTRL) and rumen-protected methionine (RPM). The control group received bermudagrass hay, corn gluten, and soybean hulls pellets supplementation (base diet); whereas the RPM group received the base diet in addition to 0.07% of DM of RPM at a fixed rate during the last trimester of gestation and the first ~80 d of lactation, in which calves (n = 17) were early weaned. Only male calves were included in this study. After weaning, calves born to RPM dams also received RPM from weaning (day 1) to day 100. Blood sampling and skeletal muscle biopsies for subsequent quantitative polymerase chain reaction (PCR) analysis were conducted on days 1, 25, 50, and 100 on calves. Quantitative PCR data were analyzed using GLIMMIX, and blood metabolites concentrations, BW, and body condition score (BCS) were analyzed using the MIXED procedure of SAS. There was no difference in maternal BW and BCS between treatments. Glucose and blood metabolites that served as biomarkers for liver health (e.g., aspartate transaminase, albumin, alkaline phosphatase, and alanine transaminase) were in the normal levels for all calves (P > 0.40). Calves in the RPM group had a greater expression of adipogenic genes (e.g., PPARG, LPL, and CEBPD) at day 100 compared with CTRL (P < 0.01). In addition, DNA methylation (DNMT1) and oxidative stress-related genes (SOD2 and NOS3) in the RPM group were upregulated at day 100 compared with CTRL (P < 0.01). These results may suggest that calves born to primiparous dams exposed to RPM supplementation are more prone to develop greater adipose tissue than CTRL calves. Furthermore, RPM supplementation may improve methylation processes, as shown by the upregulation of DNMT1. The results shown in our study aim at expanding the knowledge on fetal programming and early-life growth and development of beef cattle under supplementation with RPM.

Revelation of genes associated with energy generating metabolic pathways in the fighter type Aseel chicken of India through skeletal muscle transcriptome sequencing

In this study, comparative analysis of skeletal muscle transcriptome was carried out for four biological replicates of Aseel, a fighter type breed and Punjab Brown, a meat type breed of India. The profusely expressed genes in both breeds were related to muscle contraction and motor activity. Differential expression analysis identified 961 up-regulated and 979 down-regulated genes in Aseel at a threshold of log2 fold change ≥ ±2.0 (padj<0.05). Significantly enriched KEGG pathways in Aseel included metabolic pathways and oxidative phosphorylation, with higher expression of genes associated with fatty acid beta-oxidation, formation of ATP by chemiosmotic coupling, response to oxidative stress, and muscle contraction. The highly connected hub genes identified through gene network analysis in the Aseel gamecocks were HNF4A, APOA2, APOB, APOC3, AMBP, and ACOT13, which are primarily associated with energy generating metabolic pathways. The up-regulated genes in Punjab Brown chicken were found to be related to muscle growth and differentiation. There was enrichment of pathways such as focal adhesion, insulin signaling pathway and ECM receptor interaction in these birds. The results presented in this study help to improve our understanding of the molecular mechanisms associated with fighting ability and muscle growth in Aseel and Punjab Brown chicken, respectively.

Deletion of Tfam in Prx1-Cre expressing limb mesenchyme results in spontaneous bone fractures

INTRODUCTION

Osteoblasts require substantial amounts of energy to synthesize the bone matrix and coordinate skeleton mineralization. This study analyzed the effects of mitochondrial dysfunction on bone formation, nano-organization of collagen and apatite, and the resultant mechanical function in mouse limbs.

MATERIALS AND METHODS

Limb mesenchyme-specific Tfam knockout (Tfam^f/f;Prx1-Cre: Tfam-cKO) mice were analyzed morphologically and histologically, and gene expressions in the limb bones were assessed by in situ hybridization, qPCR, and RNA sequencing (RNA-seq). Moreover, we analyzed the mitochondrial function of osteoblasts in Tfam-cKO mice using mitochondrial membrane potential assay and transmission electron microscopy (TEM). We investigated the pathogenesis of spontaneous bone fractures using immunohistochemical analysis, TEM, birefringence analyzer, microbeam X-ray diffractometer and nanoindentation.

RESULTS

Forelimbs in Tfam-cKO mice were significantly shortened from birth, and spontaneous fractures occurred after birth, resulting in severe limb deformities. Histological and RNA-seq analyses showed that bone hypoplasia with a decrease in matrix mineralization was apparent, and the expression of type I collagen and osteocalcin was decreased in osteoblasts of Tfam-cKO mice, although Runx2 expression was unchanged. Decreased type I collagen deposition and mineralization in the matrix of limb bones in Tfam-cKO mice were associated with marked mitochondrial dysfunction. Tfam-cKO mice bone showed a significantly lower Young's modulus and hardness due to poor apatite orientation which is resulted from decreased osteocalcin expression.

CONCLUSION

Mice with limb mesenchyme-specific Tfam deletions exhibited spontaneous limb bone fractures, resulting in severe limb deformities. Bone fragility was caused by poor apatite orientation owing to impaired osteoblast differentiation and maturation.

Reduced dynamic loads due to hip dislocation induce acetabular cartilage degeneration by IL-6 and MMP3 via the STAT3/periostin/NF-κB axis

Developmental dysplasia of the hip (DDH) is characterized by anatomical abnormalities of the hip joint, ranging from mild acetabular dysplasia to hip subluxation and eventually dislocation. The mechanism underlying the cartilage degeneration of the hip joints exposed to reduced dynamic loads due to hip dislocation remains unknown. We established a rodent hip dislocation (disarticulation; DA) model of DDH (DA-DDH rats and mice) by swaddling. Expression levels of periostin (Postn) and catabolic factors, such as interleukin-6 (IL-6) and matrix metalloproteinase 3 (Mmp3), increased and those of chondrogenic markers decreased in the acetabular cartilage of the DA-DDH models. Postn induced IL-6 and Mmp3 expression in chondrocytes through integrin αVβ3, focal adhesion kinase, Src, and nuclear factor-κB (NF-κB) signaling. The microgravity environment created by a random positioning machine induced Postn expression in chondrocytes through signal transducer and activator of transcription 3 (STAT3) signaling. IL-6 stimulated Postn expression via STAT3 signaling. Furthermore, cartilage degeneration was suppressed in the acetabulum of Postn^−/− DA-DDH mice compared with that in the acetabulum of wild type DA-DDH mice. In summary, reduced dynamic loads due to hip dislocation induced acetabular cartilage degeneration via IL-6 and MMP3 through STAT3/periostin/NF-κB signaling in the rodent DA-DDH models.

Uhrf1 governs the proliferation and differentiation of muscle satellite cells

DNA methylation is an essential form of epigenetic regulation responsible for cellular identity. In muscle stem cells, termed satellite cells, DNA methylation patterns are tightly regulated during differentiation. However, it is unclear how these DNA methylation patterns affect the function of satellite cells. We demonstrate that a key epigenetic regulator, ubiquitin like with PHD and RING finger domains 1 (Uhrf1), is activated in proliferating myogenic cells but not expressed in quiescent satellite cells or differentiated myogenic cells in mice. Ablation of Uhrf1 in mouse satellite cells impairs their proliferation and differentiation, leading to failed muscle regeneration. Uhrf1-deficient myogenic cells exhibited aberrant upregulation of transcripts, including Sox9, with the reduction of DNA methylation level of their promoter and enhancer region. These findings show that Uhrf1 is a critical epigenetic regulator of proliferation and differentiation in satellite cells, by controlling cell-type-specific gene expression via maintenance of DNA methylation.

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Uhrf1 is activated in proliferating myogenic cells

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Uhrf1 in satellite cells is required for muscle regeneration

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Ablation of Uhrf1 in satellite cells impairs their proliferation and differentiation

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Uhrf1 controls cell-type-specific transcripts via maintenance of DNA methylation