Expression of the mouse glucocorticoid receptor and its role during development.

Genes encoding enzymes involved in gluconeogenesis are activated in liver shortly after birth by the synergistic effect of glucagon and glucocorticoids. This induction is achieved by the synergistic action of hormone responsive and liver-specific enhancer elements. In the case of glucocorticoids, this enhancer is composed of a glucocorticoid-response element (GRE) and a number of cell-specific hepatocyte nuclear factor 3 (HNF-3) binding sites. The GRE binds the ligand-activated glucocorticoid receptor (GR) which is ubiquitously expressed and the HNF-3 element binds a cell-specific protein factor. To further understand the role of cell-specific glucocorticoid signalling in the perinatal period and earlier during development we have studied the expression of the mouse GR gene. The gene has been cloned and fully characterized. Expression of the gene is controlled by at least three promoters, one of which is only active in T-lymphocytes. Expression of GR mRNA has been detected back to day 9.5 of mouse development. The role of GR during mouse development has been further analysed by disruption of the GR gene in vivo by homologous recombination in mouse embryonic stem cells.