An atlas of expression quantitative trait loci of microRNAs in longissimus muscle of eight-way crossbred pigs

MicroRNAs(miRNAs)are key regulators of myocyte development and traits,yet insight into the genetic basis of variation in miRNA expression is still limited.Here,we present a systematic analysis of expression quantitative trait loci(eQTL)for miRNA profiling in longissimus muscle of pigs from an eight-breed crossed heterogeneous population.By integrating the whole-genome sequencing and miRNAomics data,we map 54 cis-and 292 trans-e QTLs at high resolution that are associated with the expression of 54 and 92miRNAs,respectively.Twenty-three trans-acting loci are identified to affect the expression of nine myomi Rs(known muscle-specific miRNAs).MiRNAs in mammalian conserved miRNA clusters are found to be subjected to regulation by shared cis-e QTLs,while the expression of mature miRNA-5p/-3p counterparts is more likely to be regulated by different cis-e QTLs.Fine mapping and bioinformatics analyses pinpoint the peak cis-e SNP of mi R-4331-5p,rs344650810,which is located in its seed region,as a causal variant for the changes in expression and function of this miRNA.Additionally,rs344650810 is significantly(P<0.01)correlated with the density and percentage of type I muscle fibers.Altogether,this study provides a comprehensive atlas of miRNA-e QTLs in porcine skeletal muscle and new insights into regulatory mechanisms of miRNA expression.