产羔数是绵羊育种的重要目标性状。FecB是鉴定出的影响绵羊排卵数和产羔数的第一个主效基因，然而目前FecB基因在卵母细胞和颗粒细胞中影响排卵数的精确调控机制不明晰。因此，围绕FecB基因在卵母细胞和颗粒细胞中如何协同调控绵羊排卵数这一科学问题，本项目以携带FecB三种基因型（++、+B、BB）的地方品种小尾寒羊为试验对象，活体收集并分离同一个卵泡中卵母细胞和颗粒细胞开展单细胞转录组测序，分别筛选卵母细胞和颗粒细胞中受FecB基因突变影响的重要通路，对重要通路中的关键基因从分子、细胞和个体水平进行功能研究，在体外采用过表达和敲除验证相关调控通路。同时，基于转录组数据分析揭示卵母细胞和颗粒细胞的异质性和互作关系，阐释+B型杂合子在排卵数调控中的基因表达偏好性。本项目预期阐明FecB基因影响小尾寒羊排卵数的分子机制，为进一步利用FecB基因构建肉羊高效繁育体系提供理论依据。

The litter size is an important trait of sheep breeding. Fecundity Booroola gene (FecB) is the first identified major gene responsible for high ovulation rate and litter size in sheep. However, the exact regulatory mechanism of FecB influencing the ovulation rate in oocyte and granulosa cells is unclear. Therefore, around this question “how does the FecB gene regulate the ovulation rate in oocyte and granulosa cells respectively”, Small Tail Han sheep (STH，Chinese indigenous breed) with three FecB genotypes (++, +B, BB) were used in this project. After the estrous synchronization, preovulatory follicles were derived from STH sheep with different FecB genotypes independently (wild type (++), heterozygous carriers (+B) and homozygous carriers (BB)) by taking minimally invasive surgery, then oocyte and granulosa cells were separated from the same follicle to be performed single-cell RNA-sequencing. The important pathways involved in the FecB mutation will be screened. The differentially expressed genes and transcript isoforms will be analyzed to screen the key genes involved in the FecB pathway. Functional analysis of key genes will be conducted at molecular, cellular and individual levels, and important regulatory pathways will be validated both in vivo and in vitro by overexpression and knock-out strategy. Based on transcriptome data, the heterogeneity and cross talk between oocyte and granulosa cells will be revealed, and the allele-specific expression profile in +B genotype will be elucidated. These results will reveal the molecular mechanism of FecB affecting prolificacy in STH sheep, and offer a theoretical basis for constructing the efficient breeding system in sheep by the introgression of FecB mutation.