Study of the copy number variation on the sex chromosome in some Iranian sheep breeds

Copy number variation (CNVs) is one of the most important structural variations in the genome which play an important role in the genetic variance of economic traits. In this study, CNVs and copy number variation regions (CNVRs) on the sex chromosome were investigated in three native Iranian sheep breeds, including fat-tailed Baluchi and Lori-Bakhtiari breeds and thin-tailed Zel breed. 50K genotyped samples were obtained and CNVs were identified for each individual using PennCNV software. After identifying CNVs in each individual, the quality control of CNVs was performed with different filters, and CNVRs were identified by using the overlapping regions of CNVs using CNVRuler software. In total, 37, 11 and 4 CNVs of gain events were identified on the X chromosome of Baluchi, Zel and Lori-Bakhtiari sheep, respectively. The minimum, maximum and average length of identified CNVs were 94477, 1293154 and 447694 bp in Baluchi breed, 271819, 906644 and 674854 bp in Zel breed and 99705, 306525 and 167913 bp in Lori Bakhtiari breed, respectively. After merging the CNVs, 30, 10 and 4 CNVRs were identified in these three breeds, respectively, all of which were of the gain events. The analysis of genes in CNVR regions showed that some of these genes (VEGF, VAM21, TRPC5, NDUFA1, APLN and TNMD) were related to fat metabolism. Annotations of genes for molecular function were significantly enriched in the pathway of arylsulfatase activity, which plays a role in reproduction. Further studies on these CNV regions can help identify genes affecting fat metabolism in sheep.