Exosomes are membrane‐bound extracellular vesicles that are produced in the endosomal compartment of most mammalian cell types and then released. Exosomes are effective carriers for the intercellular material transfer of material that can influence a series of physiological and pathological processes in recipient cells. Among loaded cargoes, non‐coding RNAs (ncRNAs) vary for the exosome‐producing cell and its homeostatic state, and characterization of the biogenesis and secretion of exosomal ncRNAs and the functions of these ncRNAs in skeletal muscle myogenesis remain preliminary. In this review, we will describe what is currently known of exosome biogenesis, release and uptake of exosomal ncRNAs, as well as the varied functions of exosomal miRNAs in skeletal muscle myogenesis.

There is growing evidence that non-coding RNAs are emerging as critical regulators of skeletal muscle development. In order to reveal their functional roles and regulatory mechanisms, we constructed a lncRNA–miRNA–mRNA network according to the ceRNA (competitive endogenous RNA) theory, using our high-throughput sequencing data. Subsequently, the network analysis, GO (Gene Ontology) analysis, and KEGG (Kyoto Encyclopedia of Genes and Genomes) pathway analysis were performed for functional annotation and exploration of lncRNA ceRNAs. The results uncovered a scale-free characteristics network which exhibited high functional specificity for bovine skeletal muscle development: co-expression lncRNAs were significantly enriched in muscle development related biological processes and the Wnt signaling pathway. Furthermore, GSEA (Gene Set Enrichment Analysis) indicated that the risk score has a tendency to associate with myogenesis, and differentially expressed RNAs were validated by qPCR, further confirming the credibility of our network. In summary, this study provides insights into lncRNA-mediated ceRNA function and mechanisms in bovine skeletal muscle development and will expand our understanding of lncRNA biology in mammals.

Myogenesis is controlled by a well-established transcriptional hierarchy that coordinates the activities of a set of muscle genes. Recently, roles in myogenesis have been described for non-coding RNAs, including a role of circular RNA (circRNA) to regulate muscle gene expression. However, the functions of circRNA and the underlying mechanism by which circRNAs affect myogenesis remain poorly understood. In this study, we analyzed circRNA high-throughput sequencing results of bovine skeletal muscle samples and constructed a circRNA-miRNA-mRNA network according to the competitive endogenous RNA (ceRNA) theory. The putative circHUWE1-miR-29b-AKT3 network was analyzed and its involvement in myogenesis was confirmed through a series of assays. To assess the potential function of this regulation, bovine myoblasts were infected with overexpression plasmids and small interfering RNAs (siRNAs) that target circHUWE1. Next, cell proliferation, apoptosis, and differentiation were analyzed using Cell Counting Kit-8 (CCK-8), 5-ethynyl-2 0 -deoxyuridine (EdU), flow cytometry, western blotting, and qRT-PCR assays. The results suggest that circHUWE1 facilitates bovine myoblast proliferation and inhibits cell apoptosis and differentiation. Next, bioinformatics, dual-luciferase reporter assay, and AGO2 RNA immunoprecipitation (RIP) approaches were used to verify the interaction between circHUWE1, miR-29b, and AKT3. Subsequently, we identified that circHUWE1 could directly interfere with the ability of miR-29b to relieve AKT3 suppression, which ultimately activates the AKT signaling pathway. These findings suggested a new regulatory pathway for bovine skeletal muscle development, and they also expand our understanding of circRNA functions in mammals.

Exosomes are a subset of nano-sized extracellular vesicles originating from endosomes. Exosomes mediate cell-to-cell communication with their cargos, which includes mRNAs, miRNAs, lncRNAs, and circRNAs. Exosomal RNAs have cell specificity and reflect the conditions of their donor cells. Notably, their detection in biofluids can be used as a diagnostic marker for various diseases. Exosomal RNAs are ideal biomarkers because their surrounding membranes confer stability and they are detectable in almost all biofluids, which helps to reduce trauma and avoid invasive examinations. However, knowledge of exosomal biomarkers remains scarce. The present review summarizes the biogenesis, secretion, and uptake of exosomes, the current researches exploring exosomal mRNAs, miRNAs, lncRNAs, and circRNAs as potential biomarkers for the diagnosis of human diseases, as well as recent techniques of exosome isolation.

RNA m 6 A methylation is a post-transcriptional modification that occurs at the nitrogen-6 position of adenine. This dynamically reversible modification is installed, removed and recognized by methyltransferases, demethylases and readers, respectively. This modification has been found in most eukaryotic mRNA, tRNA, rRNA and other non-coding RNA. Recent studies have revealed important regulatory functions of the m 6 A including effects on gene expression regulation, organism development and cancer development. In this review, we summarize the discovery and features of m 6 A, and briefly introduce the mammalian m 6 A writers, erasers and readers. Finally, we discuss progress in identifying additional functions of m 6 A and the outstanding questions about the regulatory effect of this widespread modification.