[Screening and identification of key miRNAs in post-transcriptional regulation of CART in the bovine hypothalamus].

This study aimed to explore the roles of microRNAs (miRNAs) in the post-transcriptional regulation of cocaine- and amphetamine-regulated transcript (CART) peptide in the bovine hypothalamus and to screen key regulatory miRNAs. Targetscan was used to predict the potential miRNAs binding to <i>CART</i> 3' untranslated regions (3'UTR). Bioinformatics analysis predicted 7 miRNA binding sites in the bovine <i>CART</i> 3'UTR, which were bta-miR-377, bta-miR-331-3p, bta-miR-491, bta-miR-493, bta-miR-758, bta-miR-877, and bta-miR-381, respectively. Reverse transcription-PCR (RT-PCR) was carried out to determine the endogenous expression of <i>CART</i> and target miRNAs in the bovine hypothalamus. All the 7 target miRNAs and <i>CART</i> were endogenously expressed in the bovine hypothalamus. The dual-luciferase reporter gene assay was employed to detect the targeted binding relationship between <i>CART</i> 3'UTR and target miRNAs obtained from bioinformatics analysis. The dual-luciferase reporter gene assay confirmed that the 3'UTR of <i>CART</i> had a targeted binding relationship with the 7 target miRNAs. Cell experiments were conducted to examine the effects of target miRNAs on the messenger RNA (mRNA) and protein levels of exogenous CART and screen for key regulatory miRNAs. The results of cell experiments showed that the 7 miRNAs downregulated the mRNA level of <i>CART</i>, with bta-miR-491 demonstrating the strongest downregulating effect. Bta-miR-377, bta-miR-331-3p, bta-miR-491, bta-miR-493, and bta-miR-381 downregulated the protein level of CART, with bta-miR-381 exerting the strongest downregulating effect. Animal experiments were conducted to explore the effects of key regulatory miRNAs on the mRNA and protein levels of CART in the hypothalamus and the CART concentration in the serum. The results from animal experiments showed that miR-491 and miR-381 regulated the endogenous expression of CART in the hypothalamus and the concentration in the serum by binding to the <i>CART</i> 3'UTR. These results suggest that miR-491 and miR-381 are the main miRNAs regulating CART expression in the bovine hypothalamus, which can affect serum CART concentration by modulating endogenous CART expression.