Single-cell sequencing reveals the reproductive variations between primiparous and multiparous Hu ewes

Abstract

In the modern sheep production systems, the reproductive performance of ewes determines the economic profitability of farming. Revealing the genetic mechanisms underlying differences in the litter size is important for the selection and breeding of highly prolific ewes. Hu sheep is a high-quality Chinese sheep breed with high fecundity and it is an ideal model for investigating prolificacy traits. In the current study, animals were divided into two groups according to their delivery rates in three consecutive lambing seasons (namely, the High-reproduction and lowly reproductive groups with ≥ 3 lambs and one lamb per season, respectively). Three ewes were randomly picked from each group and slaughtered within 12 h of estrus, and unilateral ovarian tissues were collected and analyzed by single-cell RNA sequencing. A total of five types of somatic cells were identified and corresponding expression profiles were mapped in the ovaries of each group. Noticeably, the differences in the ovary somatic cell expression profiles between the High-reproduction and lowly reproductivegroups were mainly clustered in the granulosa cells, a cell line that is significantly relevant to female prolificacy. In addition, four granulosa cell subtypes were identified. GeneSwitches revealed that the abundance of the JPH1 expression and the reduction of the LOC101112291 expression could lead to different evolutionary directions of the granulosa cells. The expression levels of FTH1 and FTL in GCs of the Highly reproductive group were significantly higher, which inhibited necroptosis and ferroptosis of mural GCs from decreasing follicular atresia. This study constructed the gene expression atlas of the sheep ovary and revealed related biological characteristics at the cellular and molecular levels. It also provides a theoretical basis for the mechanisms underlying the differences in ovulation numbers, which will be helpful for breeding and molecular genetics-based selection of highly prolific ewes.