Exploration of non-coding RNAs related to intramuscular fat deposition Xinjiang Brown cattle and Angus × Wagyu cattle

Non-coding RNAs (ncRNAs) serve as crucial regulatory elements in the process of adipogenesis in animals; however, the specific roles and interrelationships of ncRNAs in bovine fat deposition remain poorly understood. This study aims to investigate the differentially expressed ncRNAs in the longissimus dorsi muscle of Xinjiang Brown cattle (XB) and Angus $\times$ Wagyu cattle (AW), to elucidate the regulatory mechanisms underlying lipidogenesis that may involve ncRNAs. Four Xinjiang Brown cattle and four Angus $\times$ Wagyu cattle were selected, ensuring they are subjected to identical feeding conditions, in order to evaluate the intermuscular fat (IMF) of longissimus dorsi muscles. The fat content of muscle tissue was quantified using the Soxhlet extraction method, revealing that the fat levels in the AW group were significantly elevated compared to those in the XB group. Taking muscle samples for paraffin sectioning and observing their morphology, it was found that the fat richness of the AW group was significantly higher than that of the XB group. Utilizing high-throughput RNA sequencing technology, we conducted an extensive transcriptomic analysis of longissimus dorsi muscles of XB and AW to identify significant ncRNAs implicated in fat metabolism and adipogenesis. The miRNA analysis yielded between 109,343,831 117,258,570 clean reads, whereas the lncRNA and circRNA analyses produced between 81,607,756 102,917,174 clean reads. Subsequent analysis revealed the identification of 53 differentially expressed miRNAs, 176 differentially expressed lncRNAs, and 234 differentially expressed circRNAs. KEGG enrichment analysis revealed that the target genes of differentially expressed miRNAs, lncRNAs, and circRNAs are significantly enriched in 2, 17, and 22 distinct pathways, respectively. The pathways associated with the differential enrichment of miRNA target genes involve processes such as phosphorylation and protein modification. Concurrently, the pathways linked to the varying enrichment of lncRNA target genes encompass G protein-coupled receptor signaling, regulation of cell death and apoptosis, activities related to GTPase activation, and functions governing nucleotide triphosphatases, among others. The circRNA exhibiting differential expression are significantly enriched in a variety of biological processes, including signal transduction, nucleic acid synthesis, cellular architecture, GTPase activation, and phosphatase activities, among others. The analysis of the ncRNA interaction network suggests that AGBL1, THRB, and S100A13 may play pivotal roles in the formation and adipogenic differentiation of adipocytes. In conclusion, we conducted a comprehensive analysis and discussion of the complete transcriptome of intermuscular fat tissue from the longissimus dorsi muscles in Xinjiang Brown cattle and Angus $\times$ Wagyu cattle. This study provides a theoretical foundation for enhancing our understanding of the molecular mechanisms underlying fat metabolism and deposition in beef cattle.