A novel function of bone morphogenetic protein-15 in the pituitary: selective synthesis and secretion of FSH by gonadotropes.

Bone morphogenetic protein-15 (BMP-15) has been known to be an oocyte-specific factor and regulate granulosa cell functions. Here, we report that BMP-15 is also expressed in the well established gonadotrope cell line, LbetaT2 and mouse pituitary tissue. Interestingly, BMP-15 stimulates FSHbeta subunit transcription in LbetaT2 cells without affecting LHbeta and GnRH receptor transcription. These findings, therefore, suggest a possible autocrine control mechanism selective for FSHbeta synthesis by BMP-15. Moreover, BMP-15 exerts a potent and selective stimulation of FSH, but not LH, secretion by primary pituitary cells. Taken together, we hypothesize that BMP-15 could play a physiological role in the monotropic rise of FSH secretion by the pituitary during the estrous and menstrual cycle. These findings, together with the previous evidence of a negative regulation of FSH receptor expression by BMP-15 in the ovary, may constitute a major role in female fertility.