Integrative multi-omics analysis deciphers the regulatory mechanisms of egg weight traits in chickens

Egg weight is an economically important trait in the chicken, and affects the hatchability and chicks' performance in broiler breeding programs. Our comprehensive analysis of 22,375 chickens revealed that the hens' egg weight was linked to their body weight, egg production and hatchability, with higher egg weight potentially increasing the body weight and delaying the female sexual maturity. Egg weight is a dynamic trait, however, previous studies usually focused on single time point and overlooked the dynamic changes during egg-laying period. We performed both single and longitudinal genome-wide association studies in 2,350 hens, combining selective sweep analysis, to identify genetic variants. Then, we integrated multi-omics data of 40 chickens to determine key genes and metabolites. A multi-omics analysis identified 22 key candidate genes, such as ATF6, CSPG4, SH3GL3, C4, LMX1B, CDC34, and CCDC171, of which four (BSG, CFD, MAP2K2, and POLRMT) were associated with egg weights in the ChickenGTEx database. In particular, the SNP rs315726522 may regulate MAP2K2 and FSHB gene expression by modulating the binding of transcription factors, and the SNP rs738839430 caused amino acid change that affected function of CFD protein. This, in turn, affected gonadotropin expression within the GnRH signaling pathway, which ultimately influenced egg weights. Metabolomic analysis revealed 13 metabolites associated with oxidative stress and metabolism of fatty acids, which potentially influenced reproductive performance through stress reduction and hormonal regulation. This study comprehensively analyzed the effects of egg weight in broiler breeders and enhanced our understanding of the genetic mechanisms underlying egg weight in chickens.