mTOR controls ovarian follicle growth by regulating granulosa cell proliferation

• Published in: PloS one Vol. 6; no. 7; p. e21415
• Main Authors: Yu, James, Yaba, Aylin, Kasiman, Corinna, Thomson, Travis, Johnson, Joshua
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 05.07.2011; Public Library of Science (PLoS)
• Subjects: 17β-Estradiol; Aberration; Adaptor Proteins, Signal Transducing; Analysis; Anaphase; Animals; Apoptosis; Apoptosis - drug effects; Biology; Blotting, Western; Carrier Proteins - metabolism; Cell cycle; Cell Division - drug effects; Cell growth; Cell Line, Transformed; Cell Proliferation; Dose-Response Relationship, Drug; Eggs; Female; Flow Cytometry; Follicles; G1 Phase - drug effects; Gene expression; Granulosa cells; Granulosa Cells - drug effects; Granulosa Cells - metabolism; Growth; Gynecology; Immunosuppressive Agents - pharmacology; Inhibition; Insulin-like growth factors; Kinases; Male; Mammals; Mice; Mice, Inbred C57BL; Obstetrics; Ovarian Follicle - cytology; Ovarian Follicle - growth & development; Ovarian Follicle - metabolism; Ovulation; Phosphorylation; Phosphorylation - drug effects; Preeclampsia; Proteins; Rapamycin; Rats; Regulatory-Associated Protein of mTOR; Ribosomal protein S6 kinase; Ribosomal Protein S6 Kinases, 70-kDa - metabolism; Sex hormones; Sirolimus - pharmacology; TOR protein; TOR Serine-Threonine Kinases - antagonists & inhibitors; TOR Serine-Threonine Kinases - metabolism; Transcription factors; United States > US; Massachusetts; Connecticut
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0021415

We have shown that inhibition of mTOR in granulosa cells and ovarian follicles results in compromised granulosa proliferation and reduced follicle growth. Further analysis here using spontaneously immortalized rat granulosa cells has revealed that mTOR pathway activity is enhanced during M-phase of the cell cycle. mTOR specific phosphorylation of p70S6 kinase and 4E-BP, and expression of Raptor are all enhanced during M-phase. The predominant effect of mTOR inhibition by the specific inhibitor Rapamycin (RAP) was a dose-responsive arrest in the G1 cell cycle stage. The fraction of granulosa cells that continued to divide in the presence of RAP exhibited a dose-dependent increase in aberrant mitotic figures known as anaphase bridges. Strikingly, estradiol consistently decreased the incidence of aberrant mitotic figures. In mice treated with RAP, the mitotic index was reduced compared to controls, and a similar increase in aberrant mitotic events was noted. RAP injected during a superovulation regime resulted in a dose-dependent reduction in the numbers of eggs ovulated. Implications for the real-time regulation of follicle growth and dominance, including the consequences of increased numbers of aneuploid granulosa cells, are discussed.