Analysis of glucocorticoid signalling by gene targeting

Area of Science:

• Molecular Biology
• Endocrinology
• Genetics

Background:

• Glucocorticoids regulate physiological processes primarily through the glucocorticoid receptor (GR).
• GR mediates gene expression via DNA-binding (dimer activation) and protein-protein interactions (monomer repression).
• Understanding the distinct roles of these mechanisms is crucial for deciphering glucocorticoid action.

Purpose of the Study:

• To investigate the molecular mechanisms underlying glucocorticoid effects.
• To differentiate GR functions regulated by DNA-binding versus protein-protein interactions.
• To generate and analyze mouse models with specific GR mutations.

Main Methods:

• Gene targeting to disrupt the GR gene in mice.
• Generation of GR(dim) mice with a point mutation in the GR dimerization domain using Cre/loxP system.
• Analysis of physiological and molecular phenotypes in mutant mice.

Main Results:

• Complete GR gene disruption leads to embryonic lethality with severe lung defects and HPA-axis dysregulation.
• GR(dim) mice are viable but exhibit impaired gluconeogenesis, defective erythroid progenitor renewal, and altered pituitary POMC/ACTH expression.
• Histological abnormalities were absent in the lungs and adrenals of GR(dim) mice.

Conclusions:

• GR dimerization domain mutations dissociate DNA-binding-dependent and -independent functions.
• DNA-binding-independent GR functions are critical for lung development and adrenal function.
• GR(dim) mice provide a valuable model for dissecting GR-mediated physiological effects.