Physiological insights from the vitamin D receptor knockout mouse

Area of Science:

• Endocrinology
• Molecular Biology
• Dermatology

Background:

• Vitamin D was identified as a key antirachitic factor nearly a century ago.
• Research has focused on its mechanism of action and target tissues.
• Studies in human VDR mutations and animal models have elucidated its role in calcium and skeletal homeostasis.

Purpose of the Study:

• To investigate the molecular mechanisms underlying vitamin D's action.
• To understand the specific roles of the vitamin D receptor (VDR) in various physiological processes.
• To differentiate the functions of the liganded and unliganded VDR.

Main Methods:

• Utilizing mouse models with VDR ablation.
• Analyzing genetic data from human kindreds with VDR mutations.
• Employing dietary and transgenic rescue strategies in VDR-ablated mice.

Main Results:

• VDR is essential for intestinal calcium absorption, preventing severe skeletal defects and hyperparathyroidism.
• Intestine-specific VDR ablation leads to significant skeletal pathology.
• VDR plays a role in hair follicle regeneration and cutaneous homeostasis, independent of 1,25-dihydroxyvitamin D.

Conclusions:

• The liganded VDR primarily regulates intestinal calcium absorption and skeletal integrity.
• The unliganded VDR is critical for maintaining skin homeostasis and hair follicle cycling.
• VDR signaling is vital for both systemic mineral balance and cutaneous health.