An atlas of CNV maps in cattle, goat and sheep

Copy number variation(CNV)is the most prevalent type of genetic structural variation that has been recognized as an important source of phenotypic variation in humans,animals and plants.However,the mechanisms underlying the evolution of CNVs and their function in natural or artificial selection remain unknown.Here,we generated CNV region(CNVR)datasets which were diverged or shared among cattle,goat,and sheep,including 886 individuals from 171 diverse populations.Using 9 environmental factors for genome-wide association study(GWAS),we identified a series of candidate CNVRs,including genes relating to immunity,tick resistance,multi-drug resistance,and muscle development.The number of CNVRs shared between species is significantly higher than expected(P<0.00001),and these CNVRs may be more persist than the single nucleotide polymorphisms(SNPs)shared between species.We also identified genomic regions under long-term balancing selection and uncovered the potential diversity of the selected CNVRs close to the important functional genes.This study provides the evidence that balancing selection might be more common in mammals than previously considered,and might play an important role in the daily activities of these ruminant species.

A Hu sheep genome with the first ovine Y chromosome reveal introgression history after sheep domestication

The Y chromosome plays key roles in male fertility and reflects the evolutionary history of paternal lineages.Here,we present a de novo genome assembly of the Hu sheep with the first draft assembly of ovine Y chromosome(o MSY),using nanopore sequencing and Hi-C technologies.The o MSY that we generated spans 10.6 Mb from which 775 Y-SNPs were identified by applying a large panel of whole genome sequences from worldwide sheep and wild Iranian mouflons.Three major paternal lineages(HY1a,HY1b and HY2)were defined across domestic sheep,of which HY2 was newly detected.Surprisingly,HY2 forms a monophyletic clade with the Iranian mouflons and is highly divergent from both HY1a and HY1b.Demographic analysis of Y chromosomes,mitochondrial and nuclear genomes confirmed that HY2 and the maternal counterpart of lineage C represented a distinct wild mouflon population in Iran that diverge from the direct ancestor of domestic sheep,the wild mouflons in Southeastern Anatolia.Our results suggest that wild Iranian mouflons had introgressed into domestic sheep and thereby introduced this Iranian mouflon specific lineage carrying HY2 to both East Asian and Africa sheep populations.

Allele-specific expression and splicing provide insight into the phenotypic differences between thin- and fat-tailed sheep breeds

The sheep(Ovis aries) was one of the first grazing animals to be domesticated approximately 11,000 years ago in the Fertile Crescent(Chessa et al., 2009). Since domestication, a wide variety of sheep breeds with different production traitsand morphological characteristics have been shaped under the influence of natural and artificial selection. According to the fat content in tail, sheep can be mainly classified into two groups: thin-and fat-tailed breeds.