Comparison of granulosa cells from WT and Inha KO mice following gonadotropin stimulation

Inhibin knockout (Inha-/-) female mice develop sex cord-stromal ovarian cancer with complete penetrance and previous studies demonstrate that the pituitary gonadotropins [follicle stimulating hormone (FSH) and luteinizing hormone (LH)] are influential modifiers of granulosa cell tumor development and progression in inhibin-deficient females. Recent studies have demonstrated that Inha-/- ovarian follicles develop precociously to the early antral stage in prepubertal mice without any increase in serum FSH and these studies suggested that in the absence of inhibins, granulosa cells differentiate abnormally, and thus at sexual maturity may undergo an abnormal response to gonadotropin signaling. To test this hypothesis, we stimulated immature WT and Inha-/- female mice prior to gross tumor formation with gonadotropin analogs, and subsequently examined post-gonadotropin induced ovarian follicle development, as well as preovulatory and hCG-induced gene expression changes in granulosa cells. We find that at three weeks of age, inhibin-deficient ovaries do not show further antral development nor undergo cumulus expansion. Widespread alterations in the transcriptome of gonadotropin-treated Inha-/- granulosa cells suggest that gonadotropins initiate an improper program of cell differentiation in Inha-/- cells. Overall, our experiments reveal that inhibins are essential for the normal gonadotropin-dependent response of granulosa cells.

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Nagaraja AK, Middlebrook BS, Rajanahally S, Myers M, Li Q, Matzuk MM, Pangas SA