Genome-wide association study reveals candidate genes for body size and reproductive traits in Hu sheep

Larger body size and enhanced reproductive performance are correlated with increased profitability for sheep farmers. Hu sheep have smaller statures compared to other meat sheep breeds, necessitating improvement. The molecular mechanisms underlying the high fecundity of Hu sheep remain unclear. Body size and reproductive traits are economically important traits in Hu sheep production, necessitating further research.

We conducted direct measurements of the body size traits, including body weight, body height and length, chest circumference and cannon bone circumference, for 558 Hu sheep. Additionally, we statistically recorded their reproductive traits, specifically litter size and teat number. Candidate genes for these traits were identified using a mixed linear model in a genome-wide association study (GWAS). The significant threshold for single nucleotide polymorphism was determined using a 1,000 permutation test. Subsequently, functional annotations were conducted on the candidate genes.

We identified CHST3 as a key candidate gene affecting the body size, along with SCMH1 and BAZ2B as key candidate genes influencing reproductive traits in Hu sheep. CHST3 affected multiple body size traits and was highly expressed in the muscle tissues of Hu sheep. The SCMH1 and BAZ2B were significantly annotated by GWAS and selection signature, and they were highly expressed in the reproductive system of Hu sheep. Furthermore, through a phenome-wide association study in humans, we found that these key candidate genes were significantly associated with similar traits in human population.

This represents the initial evidence linking these genes to body size and fecundity in Hu sheep. These findings provide genetic markers for selective breeding, and contribute to the selection process for high-quality breeding sheep.