<i>GPX8</i> inhibits myogenic differentiation and promotes slow myofiber formation of porcine skeletal muscle satellite cells.

Glutathione peroxidase 8(GPX8) is a key member of the glutathione peroxidase family. Genome-wide association studies (GWAS) have indicated that <i>GPX8</i> is highly associated with growth and carcass traits of pigs. Using porcine skeletal muscle satellite cells, this study explored the effects of <i>GPX8</i> on myogenic differentiation and myofiber type switching through <i>GPX8</i> knockdown and overexpression, combined with analyses involving immunofluorescence staining, qRT-PCR, and Western blotting. The results demonstrated that <i>GPX8</i> knockdown significantly increased the myogenic differentiation index (<i>P</i><0.01) and promoted both mRNA and protein levels of the myogenic marker genes <i>MyHC</i> and <i>MyoG</i> (<i>P</i><0.05). Conversely, <i>GPX8</i> overexpression exhibited the opposite effects. <i>GPX8</i> knockdown significantly reduced the mRNA level of <i>MYH7</i> (<i>P</i><0.01) and protein level of slow-twitch MyHC (slow-MyHC)(<i>P</i><0.05), while suppressing mitochondrial biogenesis. In contrast, <i>GPX8</i> overexpression exhibited opposing results. Integrated multi-omics data from GWAS analyses were employed to identify expression quantitative trait locus (eQTLs) regulating <i>GPX8</i> expression. The effects of candidate SNPs on <i>GPX8</i> promoter activity were further validated using dual-luciferase reporter assays. Five candidate SNPs (rs335618489, rs325233940, rs32989756, rs322106839, and rs701033890) were identified within the <i>GPX8</i> promoter region. Among these, rs335618489-T, rs325233940-G, rs32989756-T, and rs322106839-G significantly upregulated <i>GPX8</i> expression level by altering promoter activity (<i>P</i><0.01), thereby influencing porcine muscle development traits. In summary, this study demonstrates that <i>GPX8</i> inhibits the myogenic differentiation of porcine skeletal muscle satellite cells and promotes the transition from fast-twitch to slow-twitch myofibers. Functional SNPs in the <i>GPX8</i> promoter region influence porcine muscle development by modulating <i>GPX8</i> expression, thereby providing valuable breeding targets for improving pork production.