Bone morphogenetic protein 2 inhibits FSH responsiveness in hen granulosa cells

Abstract

Prior to follicle selection into the preovulatory hierarchy, hen granulosa cells from prehierarchal follicles remain undifferentiated, as defined in part by the virtual absence of LHR mRNA expression and inability to produce progesterone. It has previously been proposed that prior to follicle selection, granulosa cells are actively maintained in an undifferentiated state by epidermal growth factor receptor ligands (EGFRL) signaling via the MAP kinase/extracellular regulated kinase pathway. Moreover, there is recent evidence that EGFRL/MAP kinase signaling modulates FSH receptor (FSHR) transcription, in part, via inhibitor of differentiation/DNA-binding (ID) proteins. In the present studies with undifferentiated granulosa, recombinant human (rh) bone morphogenetic protein 2 (BMP2) induced the phosphorylation of SMAD1/5/8, and blocked transforming growth factor b and FSH-induced FSHR expression and progesterone production. Significantly, BMP2 rapidly induced mRNAs encoding betacellulin and EGF, plus ID proteins (ID1, ID3, and ID4). Alternatively, the bioactivity of BMPs can be modulated by one or more BMP antagonists, including noggin (NOG). NOG mRNA is expressed by both hen granulosa and theca tissues from prehierarchal follicles. Pretreatment of cultured granulosa with rh NOG reversed both the stimulatory effects of BMP2 on ID1, ID3, and ID4 expression and the inhibitory effects of BMP2 on FSHR mRNA levels and progesterone production. Collectively, these data provide evidence that prior to follicle selection, BMP2 signaling contributes toward maintaining granulosa cells in an undifferentiated state. The actions of BMP2 are, at least in part, mediated indirectly via enhanced EGFRL expression and ERBB receptor-mediated MAP kinase signaling, and can be modulated by the autocrine/paracrine production of NOG.

Bone morphogenetic protein 6 promotes FSH receptor and anti-Müllerian hormone mRNA expression in granulosa cells from hen prehierarchal follicles

“…Western blot analysis for STAR, phospho-SMAD, and total SMAD proteins was conducted essentially as described previously (Haugen & Johnson 2010). Briefly, cells were homogenized in a protein lysis buffer (RIPA, Santa Cruz Biotechnology, Santa Cruz, CA, USA) containing a cocktail of enzyme (including phosphatase) inhibitors (Sigma-Aldrich).…”

“…A previous report has identified mRNA expression for both BMP type I (BMPR1A and BMPR1B) and type II (BMPR2) membrane receptors in hen granulosa cells (Onagbesan et al 2003). In turn, BMP-activated receptor complexes signal via SMAD1/ 5/8 (Haugen & Johnson 2010). By comparison, mammalian AMH signals via a BMP type I receptor (including ACVR1B (ACTR1A)/ACVR1 (ALK2) and BMPR1B/ALK6) that complexes with an AMH-specific type II receptor (Visser 2003).…”

“…We recently reported that BMP2 contributes to maintaining hen granulosa cells from prehierarchal follicles in an undifferentiated state by suppressing TGFb-induced FSHR expression (Haugen & Johnson 2010). Based upon published reports, there is general consensus that BMP6 represents an important local regulator of follicle development, both before and after gonadotropin responsiveness.…”

The Molecular Genetics of Ovarian Differentiation in the Avian Model

“…In the adult chicken ovary, BMP signaling is involved in maintenance of follicles in an undifferentiated state prior to follicle selection [Haugen and Johnson, 2010], yet BMP signaling may also play a role in the developing chicken ovary. Recent expression analysis in chicken embryos has shown that various TGF-␤ family signaling molecules and effector proteins are upregulated in ZW gonads during and after sexual differentiation, including several BMPs (BMP2, 3, 4 and 7) [Carré et al, 2011].…”

Effect of epidermal growth factor on follicle-stimulating hormone-induced proliferation of granulosa cells from chicken prehierarchical follicles

“…Circulating levels of FSH and its receptor (FSHR) expressions on granulosa cells play a decisive role in avian follicular selection. In the avian ovary, prior to follicle selection, the granulosa cells from prehierarchical follicles remain undifferentiated, as defined by high FSHR mRNA expression, as well as the low expression of luteinizing hormone receptor (LHR) mRNA (Haugen and Johnson, 2010).…”