miR-425-5p Promotes Proliferation of Bovine Mammary Epithelial Cells by Targeting TOB2

In recent years, heat stress (HS) affects livestock production and growth as ambient temperatures increase, and heat stimulation poses a great challenge to the livestock industry. Mammary epithelial cells have synthetic, secretory and lactogenic functions that are related to milk production and milk composition. It is well known that some microRNAs are involved in cellular value-addition by regulating the expression of target mRNAs and thus MiR-425-5p is one of the miRNAs that are closely associated with value-addition in dairy mammary epithelial cells (bMECs). In this study, heat stress significantly down-regulated the expression of endogenous miRNA-425-5p. In addition, miRNA-425-5p upregulation significantly promoted the value-added of bovine mammary epithelial cells. To investigate the regulatory mechanism of miRNA-425-5p in bovine mammary epithelial cell value-addition, TOB2 was predicted as a new potential miRNA-425-5p target gene using TargetScan. Further studies revealed that TOB2 gene overexpression significantly reversed the value-adding effect of miRNA-425-5p on BMEC cells. These results suggest that miRNA-425-5p promotes BMEC value-addition by targeting TOB2. The results of this study provide a reliable reference to address the reduction of milk production in dairy cows under heat stress conditions at the molecular level.