Characterization of Ovarian Cell Types and Molecular Signatures in Mauremys reevesii Using Single-Cell Sequencing.

The ovary orchestrates female reproduction, where cellular composition and intercellular communication dictate reproductive cycles. Despite advances in chelonian reproductive biology, the cellular composition and regulatory mechanisms of the ovary remain unclear, thereby restricting insights into reproductive ecology and conservation strategies. Here, we performed single-cell RNA sequencing (scRNA-seq) to systematically characterize the molecular signatures of ovarian cell types in the Chinese pond turtle (Mauremys reevesii). By integrating differential gene expression analysis and functional enrichment, we constructed a high-resolution ovarian cell atlas and identified major cell populations, including granulosa cells and oocytes. Specifically, we identified Wnt family member 4 (WNT4) and Wnt family member 6 (WNT6) as specific markers for granulosa cells and Ubiquitin C-terminal hydrolase L1 (UCHL1) for oocytes. Furthermore, the specific expression of these granulosa cell markers was validated using dual-color in situ hybridization. Collectively, this study elucidates the ovarian biology of M. reevesii at the cellular and molecular levels, providing a vital theoretical foundation for understanding chelonian reproductive ecology and offering important insights into reproductive ecology in turtles.