Insertion of 643bp Retrotransposon Upstream of CDS Is Associated with Backfat of Large White Pigs.

are essential regulators of mammalian fatty acid and lipid metabolism. Although the effects of genetic variations, including single nucleotide polymorphisms (SNPs) in genes on the phenotype of domestic animals have been investigated, there is limited information on the impact of retrotransposon insertion polymorphisms (RIPs). In this study, a combined comparative genome and polymerase chain reaction (PCR) was used to excavate the RIPs in porcine . We also investigated the potential effects of retrotransposon insertion on phenotype and expression patterns. This study identified the two RIPs in genes, namely an ERV in intron 1 of and a combined retrotransposon in intron 2 of , designated as -ERV-RIP and -COM-RIP, respectively. These RIPs exhibited different distribution patterns among Chinese indigenous breeds and Western commercial breeds. Individuals with the -ERV-RIP genotype (+/+ indicated homozygous with insertion) among Large White pigs had significantly higher ( < 0.05) corrected backfat thickness compared to those with the other two genotypes. Similarly, those with the -COM-RIP genotype had significantly higher ( < 0.05) corrected backfat thickness than those with the other two genotypes in Large White pigs. Moreover, in 30-day-old Sujiang piglets, the gene expression in the backfat of those with the -COM-RIP genotype (-/- indicated homozygous without insertion) was significantly greater ( < 0.01) than those with other genotypes. The dual luciferase reporter gene assay demonstrated that the combined retrotransposon insertion significantly reduced the activity of the MYC promoter in both C2C12 and 3T3-L1 cells ( < 0.01). Therefore, the combined retrotransposon insertion could function as a repressor to decrease the expression of , making -COM-RIP a valuable molecular marker for assisted selection of backfat thickness in pig breeding.