Genome-wide association study and gene ontology for growth and wool characteristics in Zandi sheep

Genome-wide association studies (GWAS) is a major procedure for studying the genetics of complex economically important traits in sheep. The objective of this study was to determine the genomic regions affecting some growth traits and wool characteristics in Zandi sheep. This study is GWAS implementing a medium-density single nucleotide polymorphism (SNP) panel to determine the putative chromosome area affecting some growth and wool traits in a fat-tailed sheep breed, simultaneously. We used a selective genomic approach sampling DNA from animals at the extreme ends using the estimated breeding values derived from a total population size of over 5,000 animals. The examined phenotypic data included the birth weight, weaning weight, 6, 9, and 12-months after birth weight, pre- and post-weaning average daily gain, fiber diameter (micron), prickle factor (%), staple length (mm), kemp (%) and medullated fiber. Genome-wide association analyses were performed based on the mixed linear model. Twenty-three regions, in which four were associated with more than one trait, located on 12 chromosomes were associated with the studied growth and wool traits (P<5×10−6). These genomic regions overlapping with KCNIP4, PPARGC1A, ASAP1, ANK2, WWOX, SYNE1, FBXO5, AKAP6, FABP3, ANGPTL4, ATP6V1B2, PARK2, and KRTAP11-1 genes, were associated with postnatal growth, regulation of metabolic pathways, skeletal muscle differentiation, and bone growth. Gene ontology term enrichment analysis revealed that genes involved in positive regulation of muscle structure, and muscle tissue development were over-represented in the identified candidate genes.