Klug Scott Thomas, Ellestad Laura E, Porter Tom E
Department of Animal and Avian Sciences, University of Maryland, College Park, MD 20742, USA.
Department of Poultry Science, University of Georgia, Athens, GA 30602, USA.
Endocrinology. 2025 Jul 8;166(9). doi: 10.1210/endocr/bqaf119.
Numerous studies have implicated glucocorticoids in the regulation of somatotroph differentiation. However, few studies have investigated a requirement for glucocorticoid receptors (GR) in this process. We hypothesized that GR is essential for the normal ontogeny of pituitary growth hormone (GH) during mouse embryonic development. Anterior pituitary cells were isolated from e12.5 to e13.5 mice and e11 chickens and cultured with or without corticosterone (CORT) in the absence or presence of ZK98299, a GR-specific antagonist. CORT induced GH mRNA expression in pituitary cells from both species, and this response was blocked by inclusion of the GR antagonist. Mouse embryos with pituitary-targeted knockout of GR were generated utilizing the cre-LoxP Recombinase system under control of the pituitary-specific alpha-glycoprotein subunit (αGSU) promoter. All cre-positive GR(-/-) embryos died at birth. Therefore, anterior pituitary, brain, heart, liver, and muscle tissues, were collected on embryonic days 17.5/18.5 for RNA isolation and RT-qPCR analysis. Cre mRNA expression was only found in the pituitary, and GR mRNA levels were significantly decreased in the pituitaries of GR(-/-) embryos. GH mRNA was significantly decreased in pituitary-targeted GR(-/-) knockout embryos in comparison to wild-type GR(+/+) embryos. Significant differences in expression of other pituitary hormones in GR(-/-) embryos were not observed, indicating that the effect of pituitary-targeted knockout of GR was restricted to disruption of GH gene expression. To our knowledge, this is the first report that homozygous GR knockout in the anterior pituitary gland in mice suppresses embryonic GH expression, confirming an essential role for GR signaling in the normal ontogeny of somatotrophs.
众多研究表明糖皮质激素参与生长激素细胞分化的调节。然而，很少有研究探讨在此过程中糖皮质激素受体（GR）的必要性。我们推测GR对于小鼠胚胎发育期间垂体生长激素（GH）的正常个体发育至关重要。从胚胎第12.5天至13.5天的小鼠以及胚胎第11天的鸡中分离出垂体前叶细胞，并在存在或不存在GR特异性拮抗剂ZK98299的情况下，用或不用皮质酮（CORT）进行培养。CORT诱导了这两个物种垂体细胞中GH mRNA的表达，并且这种反应被GR拮抗剂的加入所阻断。利用垂体特异性α-糖蛋白亚基（αGSU）启动子控制下的cre-LoxP重组酶系统，生成了垂体靶向敲除GR的小鼠胚胎。所有cre阳性的GR（-/-）胚胎在出生时死亡。因此，在胚胎第17.5/18.5天收集垂体前叶、脑、心脏、肝脏和肌肉组织用于RNA分离和RT-qPCR分析。仅在垂体中发现了Cre mRNA表达，并且GR（-/-）胚胎垂体中的GR mRNA水平显著降低。与野生型GR（+/+）胚胎相比，垂体靶向GR（-/-）敲除胚胎中的GH mRNA显著降低。未观察到GR（-/-）胚胎中其他垂体激素表达的显著差异，表明垂体靶向敲除GR的作用仅限于破坏GH基因表达。据我们所知，这是第一份关于小鼠垂体前叶纯合GR敲除抑制胚胎GH表达的报告，证实了GR信号在生长激素细胞正常个体发育中的重要作用。
