Functional Analysis of VDR Gene Mutation R343H in a Child with Vitamin D-Resistant Rickets with Alopecia

This study investigated a novel R343H mutation in the VDR gene in a family with hereditary vitamin D-resistant rickets (HVDRR) and alopecia. The proband and his sister showed typical HVDRR symptoms and alopecia, which responded to high doses of active vitamin D3, except for the alopecia. The R343H mutation, located in the RXR-binding domain of VDR, did not affect the expression, conformation, nuclear localization, or heterodimerization with RXR of the VDR protein. However, it impaired the CYP24A1 promoter activity in the presence of 1,25 (OH)2 vitamin D3, likely due to disrupted interaction between specific molecular groups. This impairment in transactivation activity explained the HVDRR features with alopecia.