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Molecular genetic analysis of glucocorticoid signalling in development
W Schmid1, T J Cole, J A Blendy
1Division Molecular Biology of the Cell I, German Cancer Research Center, Heidelberg.
Summary
Glucocorticoid receptor null mutation impairs lung development and adrenal gland function in mice. This genetic defect disrupts the hypothalamic-pituitary-adrenal (HPA) axis, leading to altered hormone levels and perinatal mortality.
Area of Science:
- Endocrinology
- Developmental Biology
- Genetics
Background:
- The glucocorticoid receptor (GR) plays a crucial role in regulating the hypothalamic-pituitary-adrenal (HPA) axis and mediating the effects of glucocorticoids.
- Understanding the precise functions of GR in development and physiological regulation is essential for comprehending endocrine disorders.
Purpose of the Study:
- To investigate the physiological consequences of a complete loss-of-function mutation in the glucocorticoid receptor.
- To elucidate the role of GR in lung development, adrenal gland morphology, and HPA axis regulation.
Main Methods:
- Generation of a null mutation in the glucocorticoid receptor gene using homologous recombination in mice.
- Phenotypic analysis of homozygous and heterozygous mutant mice, including assessment of lung development, adrenal gland size and histology, and hormone levels (corticosterone, ACTH).
- Evaluation of liver gluconeogenetic enzyme activity and survival rates.
Main Results:
- Homozygous mutant mice exhibited impaired lung development, adrenal cortex hypertrophy, and reduced adrenal medulla size.
- Phenylethanolamine N-methyltransferase (PNMT) was undetectable in mutant adrenals, and serum corticosterone and ACTH levels were significantly elevated.
- Heterozygous animals also showed increased corticosterone and ACTH, indicating GR's dose-dependent role in HPA axis feedback.
- Reduced liver gluconeogenetic enzymes and high perinatal mortality in homozygous mutants.
Conclusions:
- A null mutation of the glucocorticoid receptor leads to severe developmental defects and HPA axis dysregulation due to impaired feedback.
- GR is critical for normal lung development, adrenal gland homeostasis, and the regulation of corticosterone and ACTH secretion.
- These findings highlight the essential role of glucocorticoid signaling in mammalian development and survival.