Copy number variation (CNV) is one of structural variation types that shows various numbers of copies in segments of the DNA. This study aimed to identify the association between copy number variation regions (CNVRs) and carcass traits in Hanwoo. We analyzed a total of 571 Hanwoo steers with the four carcass traits (marbling score (MS), backfat thickness (BF), carcass weight (CW), loineye muscle area (LMA)). PennCNV program was used to identify the CNVs and CNVRuler program was used to analyze the association between CNVRs and carcass traits. A total of 1,659 CNVRs were identified in the whole genome of Hanwoo. These 1,659 CNVRs divided into 415 Gain, 1082 Loss and 162 Gain/Loss events. A genome wide association analysis between the CNVRs and the carcass traits was performed using CNVRuler program. The number of significant CNVR at a threshold of p<1×10-4 was 2, 7, 2 and 1 loci for MS, BF, CW and LMA, respectively. We performed gene ontology (GO) analysis for the genes in the significant CNVRs using DAVID. ABCA2 and EDF1 were related to regulation of lipid metabolic process. C8G, TRAF2 and STAB2 were related to immune. CHST11 was related to developmental growth. Our results may provide an important resource for molecular breeding research in Hanwoo.

Since the Bovine sequencing and HapMap projects, there have been millions of genetic variations particularly including single nucleotide polymorphisms (SNPs) available throughout the cattle genome. While cataloguing substantial amounts of SNPs, copy number variation (CNV) has recently become getting great attention as an another form of genetic variation which is extensively distributed across the cattle genome. As it has been well known that CNVs can account for substantial proportions of phenotypic variance in other species including human, CNVs are highly expected to explain genetic variations of diverse economically important traits in cattle. Currently, two main approaches such as hybridization-based microarray and massively parallel sequencing-based method have been successfully applied to detect CNVs throughout the cattle genome. Although there is obvious difference of capabilities to detect genome-wide CNVs at fine scales between different platforms applied, all currently completed investigations exhibited that CNVs are extensively spread throughout the cattle genome as observed in other species. Despite these successes, there are still severe lacks of researches to identify multiple levels of CNVs from diverse cattle or multiple individuals, suggesting that there are a number of CNVs remained undiscovered. Furthermore, there are almost few investigations available to elucidate how each CNV is associated with traits of interest in cattle, so such functional study should be followed along with saturating most of potential CNVs on cattle genome.