Foxo1/3 depletion in granulosa cells reveals novel mechanisms controlling follicle growth and death and endocrine regulation of pituitary FSH.

The Foxo transcription factors regulate multiple cellular functions. Foxo1 and Foxo3 are highly expressed in granulosa cells of ovarian follicles. Selective depletion of the Foxo1 and Foxo3 genes in granulosa cells revealed a novel ovarian-pituitary endocrine feedback loop characterized by: 1) undetectable levels of serum FSH but not LH, 2) reduced expression of the pituitary Fshb gene and its transcriptional regulators and 3) ovarian production of a factor(s) that suppresses pituitary cell Fshb. Equally notable and independent of FSH, depletion of Foxo1/3 altered the expression of specific genes associated with follicle growth versus apoptosis by disrupting critical regulatory interactions of Foxo1/3 with the activin and BMP2 pathways, respectively. As a consequence, granulosa cell proliferation and apoptosis were decreased. These data provide the first evidence that Foxo1/3 divergently regulate follicle growth or death by interacting with the activin and BMP pathways in granulosa cells and by modulating pituitary FSH production.

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Liu Z, Castrillon DH, Zhou W, Richards JS