Expression profiles and their influence on intramuscular fat in yaks at two developmental stages role of RNA sequencing.

MicroRNAs (miRNAs) are a class of non-coding RNAs (ncRNAs) that negatively regulate gene expression at the post-transcriptional level. Intramuscular fat (IMF) deposition in livestock is crucial for meat quality, affecting the meat's taste and tenderness. However, there has been little research on the miRNA transcriptome of yak in relation to intramuscular fat deposition in yak. In this study, RNA sequencing in the longissimus dorsi (LD) muscle samples was conducted to uncover the miRNAs expression profiles of yak at two ages: 3 months (calf) and 3 years (adult). A total of 1030 known miRNAs and 279 novel miRNAs were identified, of which 40 differentially expressed miRNAs (DE-miRNAs) were screened. We then obtained target genes of 40 DE-miRNAs and established enrichment analyses using Gene Ontology (GO) and the Kyoto Encyclopedia of Genes Genomes (KEGG). We found target genes were involved in four significantly enriched pathways, and the MAPK signaling pathways were the key pathways. Moreover, we constructed a miRNA-mRNA regulatory network to visualize the functions of miRNAs related to IMF deposition in the yak. miR-122, miR-375, and miR-378 may play a key role in IMF deposition in the yak, and RORC, STAT3, ACACA, FTO, and FOXO1 were the core target genes. We randomly selected six miRNAs from DE-miRNAs to validate the sequencing results using RT-qPCR. This study revealed miRNAs expression profiles in yak IMF development between calf and adult and provided a miRNA database for further studies on the molecular mechanisms of IMF deposition in the yak.