Abstract
Investigating the key genes and mutations regulating year-round estrus can enhance the reproductive performance of sheep, thereby boosting sheep industry efficiency. In this study, we employed genomic research methods to analyze whole-genome resequencing data from 392 sheep, including six year-round estrus breeds and ten seasonal estrus breeds. Here we show the Melanocortin 4 receptor (MC4R) gene as a significant player in the regulation of year-round estrus in sheep. Specifically, I173M (g.59480440G > C, P.Ile173Met), demonstrating potential relevance to sheep estrus, was identified in MC4R. The mutation frequency of this variant was higher in year-round estrus breeds than in seasonal estrus breeds, suggesting it could be a crucial functional mutation affecting sheep estrus. Transcriptome sequencing analysis indicated that genes differentially expressed after transfection with the M173 receptor were enriched in pathways related to reproduction such as GnRH signaling pathway and Ovarian steroidogenesis. Subsequent functional exploration revealed that the I173M mutation enhanced cAMP and MAPK/ERK signal transduction activation, increased receptor constitutive activity, and significantly improved receptor function. Consequently, we posit that MC4R is involved in regulating year-round estrus and the I173M mutation in the MC4R gene identified as a pivotal functional mutation influencing year-round estrus in sheep.