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FSH-deficiency in gonadotrope-specific GATA2 knockout mice is associated with a loss of gremlin expression [snRNA-Seq]

ABSTRACT: Mammalian reproduction is dependent on the gonadotropins, follicle-stimulating hormone (FSH) and luteinizing hormone, which are secreted by pituitary gonadotrope cells. The zinc-finger transcription factor, GATA2, was previously implicated in FSH production in male mice, although its mechanisms of action and role in females were not determined. To address these gaps in knowledge, we generated and analyzed gonadotrope-specific Gata2 knockout mice using the Cre-lox system. While conditional knockout (cKO) males exhibited ~50% reductions in serum FSH levels and pituitary FSHβ subunit (Fshb) expression relative to controls, FSH production was apparently normal in cKO females. RNA-seq analysis of purified gonadotropes from control and cKO males revealed a profound decrease in expression of gremlin (Grem1), a bone morphogenetic protein (BMP) antagonist. Grem1 was expressed in gonadotropes, but not other cell lineages, in the adult male mouse pituitary. Gata2, Grem1, and Fshb mRNA levels were significantly higher in pituitaries of wild-type males relative to females but decreased in males treated with estradiol and increased following ovariectomy in control but not cKO females. Recombinant gremlin stimulated Fshb expression in pituitary cultures from wild-type mice. Collectively, the data suggest that GATA2 promotes Grem1 expression in gonadotropes and that the gremlin protein potentiates FSH production. The mechanisms of gremlin action have not yet been established but may involve attenuation of BMP binding to activin type II receptors in gonadotropes, potentiating induction of Fshb transcription by activins or related ligands.

ORGANISM(S): Mus musculus

PROVIDER: GSE190060 | GEO | 2022/07/14

REPOSITORIES: GEO

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Project description:Gonadotropin-releasing hormone (GnRH) is secreted in brief pulses from the hypothalamus. GnRH regulates follicle-stimulating hormone b-subunit (FSHb) gene expression in pituitary gonadotropes in a frequency-sensitive manner that is central to reproductive physiology. The mechanisms underlying the preferential and paradoxical induction of FSHb by low frequency GnRH pulses are incompletely understood. Here, we identify growth differentiation factor 9 (GDF9) as a novel autocrine inducer of FSHb gene expression. GDF9 gene expression was preferentially suppressed by high frequency GnRH pulses due to reduced transcription. Exogenous GDF9 induced FSHb mRNA expression and knockdown or immunoneutralization of GDF9 reduced FSHb gene expression. Treatment with GDF9 stimulated Smad2/3 phosphorylation. The activin receptor-like kinase (ALK) receptor inhibitor SB-505124 antagonized GDF9-induced Smad2/3 phosphorylation and FSHb mRNA induction. Smad2 and Smad3 knockdown studies indicated that the induction of FSHb by GDF9 involves both Smad2 and Smad3. GDF9 and GnRH synergistically induced FSHb mRNA expression and high frequency GnRH pulses suppressed GDF9. We hypothesized that GDF9 contributes to a regulatory loop that tunes the GnRH frequency-response characteristics of the FSHb gene. To test this, we determined the effects of GDF9 knockdown on FSHb induction at different GnRH pulse frequencies using a parallel perifusion system. Reduction of GDF9 shifted the characteristic pattern of GnRH pulse frequency sensitivity. These results identify GDF9 as contributing to an incoherent feed-forward loop, comprised of both intracellular and secreted elementscomponents, that regulates FSHb expression in response to activation of the cell surface GnRH receptor. LbT2 microarray datasets as well as RNA-Seq data (GSE42120) were interrogated to determine the levels of expression of ALK4/5/7. LM-NM-2T2 cells were transfected with either scrambled siRNA or Gas siRNA for 48 h. RNA samples were snap-frozen in dry ice prior to whole-genome expression profiling analysis using MouseWG-6 v2.0 Expression BeadChip (Illumina, San Diego, CA). A total of 6 concentrated conditioned media samples were independently prepared: 3 replicates from control siRNA-treated cells, and 3 replicates from Gas siRNA-treated cells. This submission represents the microarray component of study.

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FSH-deficiency in gonadotrope-specific GATA2 knockout mice is associated with a loss of gremlin expression [snRNA-Seq]

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