Detection of Copy Number Variations in Nelore Beef Cattle with High-Density SNP Genotyping Data

Genome-wide single nucleotide polymorphism (SNP) genotyping platforms have been widely used in studies in diverse areas, ranging from population genetics to applied genetic improvement and breeding. SNP genotyping data generated with these platforms can also be used for detecting and genotyping copy number variations (CNVs). CNVs are defined as a variable copy numbers of DNA segments ranging from 50bp to several megabases (Mbp), in comparison with a reference genome. Several studies have identified an abundance of CNVs in human and domestic animal genomes, where it has been shown that they are involved in phenotypic variability. This initial study reports a high resolution map of CNVs in Nelore beef cattle generated with the PennCNV software. CNVs were called in a dataset from 1709 animals of the Nelore breed genotyped with Illumina BovineHD  BeadChip for a total of 735,242 markers. After non-restrictive quality filtering, a total of 246,290 CNVs were identified on autosomal chromosomes, representing 219,997 and 26,293 gain and loss events, respectively.  CNVs lengths  ranged from 20.02 Kb to 8.37 Mb with an average of 352 Kb and a median of 204.5 Kb. The number of SNPs in each detected CNV varied from 20 to 2,116 with an average of 104 and a median of 63. A total of 138,066 CNVs were present in regions with annotated genes.