MicroRNA-152 Promotes Slow-Twitch Myofiber Formation via Targeting Uncoupling Protein-3 Gene

SIMPLE SUMMARY: Different pig breeds exhibit evident diversities in pork quality characteristics, which largely resulted from the differences in myofiber type compositions. To explore the decisive role of microRNAs (miRNAs) in myofiber specification, myofiber type compositions, miR-152 expression patterns in various tissues and miR-152 expression level in the longissimus dorsi (LD) muscles from either Rongchang (RC) or large white (LW) pigs were determined. We found that the longissimus dorsi (LD) muscles of the RC pigs have higher proportion of slow-twitch myofibers and more abundant level of miR-152 than those of the LW pigs, which indicated that miR-152 might be involved in myofiber type compositions and myogenesis. Then, the gain- and loss-of-function trials and luciferase activity assays confirmed that miR-152 could promote slow-twitch myofiber formation and skeletal myogenesis via targeting uncoupling protein 3 (UCP3) gene. The knockdown of UCP3 and rescue experiment further verified that UCP3 mediates miR-152 action in slow-twitch myofiber formation. Our findings suggested that miR-152 and its target gene UCP3 might be feasible markers for interposition intended to promoting meat quality in domesticated animals. ABSTRACT: The differences of pork quality characteristics among different pig breeds mainly came from the differences in myofiber type compositions. Growing evidence indicated the key role of miRNAs in myofiber specification. In the present study, we found that miR-152 is more abundant in the slow-twitch myofiber-enriched muscles. However, its role in myofiber type transformation and myogenesis is largely unknown. Overexpression of miR-152 in porcine myotubes promoted the formation of slow-twitch myofibers and myogenesis. While, inhibition of miR-152 expression showed the opposite effect to miR-152 mimics transfection. The luciferase reporter analysis confirmed that miR-152 straightly targets the 3′-untranslated region (3’-UTR) of uncoupling protein 3 (UCP3) to cause its post-transcriptional inhibition in the protein level. The knockdown of UCP3 by siRNA showed the similar effect of miR-152 on myofiber type transition. Furthermore, the rescue experiment in the porcine myotube transfected with miR-152 mimics or/and UCP3 overexpression plasmid with or without the 3’UTR revealed that UCP3 mediates the action of miR-152 in slow-twitch myofiber formation. Taken together, our findings proposed a novel molecular mechanism through which miR-152 epigenetically regulates meat quality via promoting slow-twitch myofiber formation and skeletal myogenesis.