Glucocorticoid-induced changes in gene expression in embryonic anterior pituitary cells

Abstract

Within the anterior pituitary gland, glucocorticoids such as corticosterone (CORT) provide negative feedback to inhibit adrenocorticotropic hormone secretion and act to regulate production of other hormones including growth hormone (GH). The ontogeny of GH production during chicken embryonic and rat fetal development is controlled by glucocorticoids. The present study was conducted to characterize effects of glucocorticoids on gene expression within embryonic pituitary cells and to identify genes that are rapidly and directly regulated by glucocorticoids. Chicken embryonic pituitary cells were cultured with CORT for 1.5, 3, 6, 12, and 24 h in the absence and presence of cycloheximide (CHX) to inhibit protein synthesis. RNA was analyzed with custom microarrays containing 14,053 chicken cDNAs, and results for selected genes were confirmed by quantitative reverse transcription real-time PCR (qRT-PCR). Levels of GH mRNA were maximally induced by 6 h of CORT treatment, and this response was blocked by CHX. Expression of 396 genes was affected by CORT, and of these, mRNA levels for 46 genes were induced or repressed within 6 h. Pathway analysis of genes regulated by CORT in the absence of CHX revealed networks of genes associated with endocrine system development and cellular development. Eleven genes that were induced within 6 h in the absence and presence of CHX were identified, and eight were confirmed by qRT-PCR. The expression profiles and canonical pathways defined in this study will be useful for future analyses of glucocorticoid action and regulation of pituitary function.

Pre‐ and Postnatal Effects of Corticosterone on Fitness‐Related Traits and the Timing of Endogenous Corticosterone Production in a Songbird

“…Corticosterone deposited in the egg may have elicited its effect on brood‐day 11 body mass through its influence on growth hormone production, increased nestling begging, or both. Corticosterone treatment increases the production of pituitary growth hormone secreting cells in chicken ( Gallus gallus ) embryos (Porter, ) and positively affects production of growth hormone mRNAs in cultured embryonic pituitary cells (Jenkins et al., ). Although there has been considerable debate about the role, whether positive or negative, of glucocorticoids in regulating growth hormone production, Vakili and Cattini () argue that glucocorticoids clearly play a positive role in the development of growth hormone‐producing cells and growth hormone gene expression in the anterior pituitary.…”

Transcriptional profiling and pathway analysis reveal differences in pituitary gland function, morphology, and vascularization in chickens genetically selected for high or low body weight

“…This design necessitated the use of 32 microarray slides (one per individual pituitary gland). Labeling with Cy3 and Cy5, microarray hybridization, and image scanning were performed at the University of Maryland Biotechnology Institute’s Microarray Core Facility as previously described [68, 69].…”

“…Data from the microarray analysis were processed, normalized, and trimmed as described earlier [28, 68, 69] using software that is part of the TM4 suite of microarray data analysis applications [74] freely available from The Institute for Genomic Research (TIGR, Rockville, MD). During image processing, cDNA spots that were flagged due to lack of detection, detection below background, pixel intensity saturation, or malformation were rejected from further processing and normalization and removed from the dataset.…”

Glucocorticoid action in the anterior pituitary gland: Insights from corticotroph physiology

“…Inhibitors of transcription and translation block many aspects of early glucocorticoid inhibition although this has not been verified or tested in all cases. Although a wide array of glucocorticoid induced proteins have been reported in pituitary cells ranging from calcium binding proteins [ 38 , 39 ], small GTPases [ 40 ], protein kinases [ 41 , 42 ] and ion channel subunits [ 24 , 43 , 44 ], bone-fide glucocorticoid induced proteins essential for early glucocorticoid inhibition remain largely elusive.…”