Spatiotemporal and single-cell atlases to dissect regional specific cell types of the developing ovary.

Characterization of cellular heterogeneity and molecular diversity greatly enhances our understanding of the ovary differentiation process. However, regional specification remains largely unexplored during ovary development. Here, we combine spatial transcriptomics and single-cell RNA sequencing to build a spatiotemporal developmental atlas of ovaries from the fetal stage through adulthood. We construct the developmental trajectory of female germ cells and identify key genes essential for primordial follicle assembly. Specifically, we characterize the regional heterogeneity of granulosa cell subtypes contributing to the folliculogenesis, and analyze the molecular distinctions between healthy and atretic follicles. Notably, we discover that Onecut2-positive luteal cells exhibit a specific spatial distribution. Furthermore, lineage tracing reveals that these Onecut2-positive luteal cells originate from Foxl2-positive granulosa cells and Cyp17a1-positive theca cells. Collectively, this study provides a comprehensive delineation of ovary development and regional specificity of ovarian cell types.