Activating-transcription factor 3 stimulates follicle-stimulating hormone β transcription in vitro, but is dispensable for FSH production in murine gonadotropes in vivo

Follicle-stimulating hormone (FSH), a dimeric glycoprotein produced by pituitary gonadotrope cells, regulates spermatogenesis in males and ovarian follicle growth in females. Hypothalamic gonadotropin-releasing hormone (GnRH) stimulates FSHβ subunit gene (Fshb) transcription, though the underlying mechanisms are poorly understood. To address this gap in knowledge, we examined changes in pituitary gene expression in GnRH-deficient mice (hpg) treated with a regimen of exogenous GnRH that increases pituitary Fshb but not luteinizing hormone β (Lhb) mRNA levels. Activating transcription factor 3 (Atf3) was among the most upregulated genes. ATF3 can heterodimerize with members of the AP-1 family to regulate gene transcription. Co-expression of ATF3 with JunB stimulated murine Fshb, but not Lhb, promoter-reporter activity in homologous LβT2 cells. ATF3 also synergized with a constitutively active activin type I receptor to increase endogenous Fshb expression in these cells. Nevertheless, FSH production was intact in gonadotrope-specific Atf3 knockout mice (cKO) and control littermates. Ovarian follicle development, ovulation, and litter sizes were also equivalent between genotypes. Testis weights and sperm counts did not differ between cKO and control males. Following gonadectomy, increases in LH secretion were enhanced in cKO animals. Though FSH levels did not differ between genotypes, post-gonadectomy increases in pituitary Fshb and gonadotropin α subunit expression were more pronounced in cKO mice. These data indicate that ATF3 can selectively stimulate Fshb transcription in vitro but is not required for FSH production in vivo. 25 samples analyzed. 11 females, 14 males. 5-7 replicates per condition (sex/treatment) *** Submitter declares access to the raw data was lost. ***

促卵泡激素（Follicle-stimulating hormone, FSH）是由垂体促性腺激素细胞分泌的二聚体糖蛋白，可调控雄性的精子发生过程与雌性的卵巢卵泡发育。下丘脑促性腺激素释放激素（Hypothalamic gonadotropin-releasing hormone, GnRH）可刺激FSHβ亚基基因（Fshb）的转录，但其背后的分子机制目前仍不甚明晰。为填补这一研究空白，本研究针对经外源性GnRH处理的GnRH缺陷型小鼠（hpg）的垂体基因表达变化进行了分析，该处理方案可提升垂体中Fshb的mRNA水平，但不会改变黄体生成素β（Lhb）的mRNA水平。激活型转录因子3（Activating transcription factor 3, Atf3）是上调幅度最显著的基因之一。ATF3可与AP-1家族成员形成异二聚体，从而调控基因转录。ATF3与JunB共表达时，可在同源LβT2细胞中激活小鼠Fshb的启动子-报告基因活性，但对Lhb无此调控作用。ATF3还可与组成型激活的激活素I型受体协同作用，提升该细胞中内源性Fshb的表达水平。然而，在促性腺激素细胞特异性Atf3敲除小鼠（cKO）及其同窝对照小鼠中，FSH的合成并未受到影响。两种基因型小鼠的卵巢卵泡发育、排卵情况与产仔数均无显著差异。敲除组与对照组雄性小鼠的睾丸重量与精子计数亦无明显差异。去势手术后，敲除组小鼠的黄体生成素（LH）分泌升高幅度更为显著。尽管两种基因型小鼠的FSH水平并无差异，但去势术后，敲除组小鼠垂体中Fshb与促性腺激素α亚基的表达上调幅度更为显著。上述结果表明，ATF3在体外可选择性激活Fshb的转录，但在体内并非FSH合成所必需。共分析25份样本，其中雌性11只，雄性14只，每个实验条件（性别/处理组）设置5-7次重复。*** 提交者声明原始数据已无法获取 ***