A single-cell atlas of the single versus multiple parous Hu Sheep ovary

In the modern sheep production system, the reproductive performance of ewes determines the economic profitability of farming. The mechanism of difference in litter size is important for the selection and breeding of high-fecundity ewes. Hu sheep is a high-quality sheep breed with high fecundity in China and is ideal for investigating high reproductive traits. In the current study, the sheep with lambing number ≥3 in three consecutive lambing records were assigned to the HLS group, and lambing number = 1 as the LLS group selected from the same farm with three consecutive lambing. Three randomly picked ewes were slaughtered within 12 h of estrus, and unilateral ovarian tissue was collected and analyzed by single-cell RNA sequencing in each group. A total of five types of somatic cells were identified, and corresponding expression profiles were mapped in the ovaries of the Hu sheep. Additionally, the results of the difference in ovary somatic cell expression profiles between HLS and LLS present that the differences between multiples vs. singleton Hu sheep were mainly clustered in the GCs. In addition, 4 granulosa cell subtypes were identified. GeneSwitches results revealed the opening of JPH1 expression and the closure of LOC101112291 , which leads to different evolutionary directions of the granular cells. The expression levels of FTH1 and FTL in GCs of Hu sheep in the HLS group were significantly higher, which inhibited necroptosis and ferroptosis of mural– GCs from decreasing follicular atresia. This study constructed the cellular atlas of the ovary and revealed related biological characteristics at the cellular molecular level. It provides a theoretical basis for the mechanisms underlying the differences in ovulation numbers, which contributes to breeding high-fertility sheep and molecular genetics-based selection.