Genome-wide detection of CNV regions and their potential association with growth and fatness traits in Duroc pigs

Abstract Background: In the process of pig breeding, the average daily gain (ADG), days to 100 kg (AGE), and backfat thickness (BFT) are directly related to growth rate and fatness. However, the genetic mechanisms involved are not well understood. As an essential source of genetic diversity, copy number variation (CNV) that can affect a variety of complex traits and diseases, has gradually been thrust into the limelight. In this study, we reported the genome-wide CNVs of Duroc pigs by SNP genotyping data of 6,627 Duroc pigs. Moreover, we also performed CNV region (CNVR) based association analysis for growth and fatness traits in two Duroc populations.Results: Our study identified a total of 835 nonredundant CNVRs in American and Canadian Duroc pigs, which covered 226.73 Mb (~ 10.00%) of the pig autosomal genome. Among them, we identified 682 CNVRs in the American Duroc pigs and 424 CNVRs in the Canadian Duroc pigs, and 271 CNVRs were detected in both populations. Experimentally, 77.8% of randomly selected CNVRs were validated by quantitative PCR (qPCR). We also identified 24 significant CNVRs for growth and fatness traits though CNVR-based association analysis. Among these, six and three CNVRs in American and Canadian Duroc pigs were found to be associated with both ADG and AGE traits, respectively. Notably, four CNVRs showed both significant in ADG, AGE, and BFT, indicating that these CNVRs may play a pleiotropic role in regulating pig growth and fat deposition. Besides, further bioinformatics analysis determined a subset of potential candidate genes, such as PDGFRB, INSIG1, GPER1, PDGFA, and LPCAT1.Conclusions: The present study provides a necessary supplement to the CNV map of the Duroc genome through a large-scale population genotyping. Also, the CNVR-based association results provide a meaningful way to elucidate the genetic mechanisms of complex traits. The identified CNVRs can be used as molecular markers for genetic improvement in molecular-guided breeding of modern commercial pigs