The aim of this study was to elucidate the effect of FAM13A on the differentiation of goat intramuscular precursor adipocytes and its mechanism of action. Here, we cloned the CDS region 2094 bp of the goat FAM13A gene, encoding a total of 697 amino acid residues. Functionally, overexpression of FAM13A inhibited the differentiation of goat intramuscular adipocytes with a concomitant reduction in lipid droplets, whereas interference with FAM13A expression promoted the differentiation of goat intramuscular adipocytes. To further investigate the mechanism of FAM13A inhibiting adipocyte differentiation, 104 differentially expressed genes were screened by RNA-seq, including 95 up-regulated genes and 9 down-regulated genes. KEGG analysis found that the RIG-I receptor signaling pathway, NOD receptor signaling pathway and toll-like receptor signaling pathway may affect adipogenesis. We selected the RIG-I receptor signaling pathway enriched with more differential genes as a potential adipocyte differentiation signaling pathway for verification. Convincingly, the RIG-I like receptor signaling pathway inhibitor (HY-P1934A) blocked this pathway to save the phenotype observed in intramuscular adipocyte with FAM13A overexpression. Finally, the upstream miRNA of FAM13A was predicted, and the targeted inhibition of miR-21-5p on the expression of FAM13A gene was confirmed. In this study, it was found that FAM13A inhibited the differentiation of goat intramuscular adipocytes through the RIG-I receptor signaling pathway, and the upstream miRNA of FAM13A (miR-21-5p) promoted the differentiation of goat intramuscular adipocytes. This work extends the genetic regulatory network of IMF deposits and provides theoretical support for improving human health and meat quality from the perspective of IMF deposits.

Intramuscular fat (IMF) is a crucial indicator of meat quality. Recent studies increasingly suggest that methionine (Met) plays a role in fat accumulation. However, the mechanism by which Met affects the proliferation and differentiation of intramuscular adipocytes remains unclear. In this study, goat intramuscular adipocytes were cultured in basal complete medium supplemented with Met at 0, 50, 100, 200, 400, and 800 μM. This study demonstrates a quadratic relationship between the level of Met supplementation and cellular proliferation and differentiation, with an optimal effect observed at 100 μM Met. The results of RNA-seq analysis demonstrated that supplementation with Met led to the downregulation of genes involved in lipid metabolism, including the genes PER2, PRKG1, and SLC5A5. Furthermore, we found that overexpression of SLC5A5 inhibits adipogenic differentiation in goat intramuscular adipocytes, while Met supplementation reversed this inhibitory effect. In addition, silencing SLC5A5 significantly promoted adipogenic differentiation, whilst Met supplementation further enhanced this promotion effect. In conclusion, this study indicates that Met supplementation of basal complete medium benefits adipogenic differentiation of goat intramuscular adipocytes, likely by inhibiting the expression of SLC5A5. This research provides a foundation for improving goat meat quality.