THE ROLE OF RICTOR IN MTORC2/AKT/FOXO3A/APOPTOTIC PROTEIN SIGNAL AXIS IN REGULATING FOLLICULAR APOPTOSIS IN EARLY-ONSET OVARIAN DYSFUNCTION

Ling Zhou¹, Yan Zhang¹, Yanan Cheng², Li Wang¹, Feifei Feng¹, Xingming Chen^{2, *}

¹Department of Obstetrics and Gynecology, Special Medical Center of the Strategic Support Force, Beijing 100101, China - ²Department of Laboratory, Special Medical Center of the Strategic Support Force, Beijing 100101, China

Objective: To explore the relationship between RICTOR and follicular apoptosis in early-onset ovarian insufficiency (POI) and its possible mechanism.

Methods: We used the Cre-loxP system to construct a Rictor-specific knockout mouse oocyte model. The effects of Rictor knockout were evaluated based on levels of downstream RICTOR/mTORC2 pathway proteins AKT, FOXO3A, BAD, and BAX quantified by immunohistochemical and immunoblot methods. The effects of Rictor knockdown on luteal numbers and follicular cell apoptosis in mice were detected by the TUNEL method. Rictor expression was almost absent in the oocytes of Rictor knockout mice, while it was detected in control mice of the same age. Therefore, Rictor-knockout mouse oocytes were successfully created.

Results: Phosphorylated AKT (p-Akt) and FOXO3A (p-FOXO3A) levels were significantly lower in the oocytes of Rictor knockout mice than in control mice. Levels of apoptotic proteins BAD and BAX were significantly higher in the oocytes of Rictor knockout mice than of control mice (P<0.01). Healthy follicle and corpus luteum numbers were significantly lower in Rictor knockout mice compared to control mice of the same age, while atresia follicle numbers were significantly higher (P<0.05). Apoptotic cell numbers in healthy follicles were significantly higher in Rictor knockout mice than in control mice (P<0.05), consistent with elevated pro-apoptotic BAD and BAX protein levels in Rictor knockout mice.

Conclusion: RICTOR plays a central role in regulating follicular apoptosis via the mTORC2/AKT/FOXO3A/apoptotic protein signal axis in early ovarian development. Rictor gene loss increases mouse follicular cell apoptosis and atresia, leading to POI formation.