Identification of miR-320d as a Negative Regulator of Proliferation and Fatty Acid Synthesis via Targeting SCD in...

Excessive tail fat deposition in sheep limits feed conversion efficiency and carcass quality, making the genetic improvement of this trait a priority. This study aimed to elucidate the molecular mechanisms regulating ovine fat metabolism. We analyzed the tissue specific expression of two candidate microRNAs, miR-320d and miR-151b, alongside their target genes SCD and ACACA, across tissues from fat-tailed and thin-tailed sheep using quantitative real-time PCR. The regulatory function of the tail fat specific miR-320d was further validated in vitro using isolated ovine tail preadipocytes. Results indicated that miR-320d and miR-151b are specifically highly expressed in tail and subcutaneous adipose tissues, respectively, and correlate negatively with their target genes. Dual-luciferase reporter assays confirmed that miR-320d directly targets the 3'UTR of SCD and suppresses its transcription. Overexpression of miR-320d significantly inhibited the proliferation of tail preadipocytes and downregulated downstream genes in the fatty acid metabolism pathway, including ACACA, ELOVL6, ELOVL5, and FASN. In conclusion, miR-320d exerts a negative regulatory effect on sheep tail fat deposition by suppressing preadipocyte proliferation and fatty acid synthesis, while miR-151b emerges as a potential candidate for subcutaneous fat regulation.