Vdr, the Vitamin D receptor, is a nuclear receptor that mediates the biological functions of 1α,25-dihydroxyvitamin D3. It is involved in regulating innate and adaptive immune responses, and plays essential roles in multiple biological processes including cell proliferation, barrier function, and immunity [1,2,3]. Genetic models such as gene knockout mice have been valuable in studying Vdr's functions.

In Vdr -/- mice, when combined with a murine model of cardiac steatosis (MHC-DGAT1 Tg), there is an amplification of lipotoxic cardiomyopathy. These double-modified mice show increased myocyte size, heart weight/body weight ratio, natriuretic peptide gene expression, interstitial fibrosis, and up-regulation of related genes, along with significant reduction in ejection fraction and fractional shortening, suggesting Vdr deficiency enhances the pathological phenotype in this cardiomyopathy model [5]. In type II rickets model rats generated by genome editing, including Vdr-knockout (KO), all animals showed rickets symptoms, with only Vdr-KO rats exhibiting abnormal skin formation and alopecia. Functional analysis using an adenovirus vector in human HaCaT-VDR-KO cells demonstrated different nuclear translocation patterns of VDR mutants in response to vitamin D ligands, helping to elucidate VDR functions [4].

In conclusion, Vdr is crucial for multiple biological processes and its deficiency can lead to various pathological conditions. Studies using gene knockout models, such as in cardiomyopathy and rickets models, have significantly contributed to understanding Vdr's role in these disease areas, highlighting its importance in maintaining normal physiological functions and modulating disease severity.