Arterial calcifications and increased expression of vitamin D receptor targets in mice lacking TIF1alpha

Calcification of arteries is a major risk factor for cardiovascular mortality in humans. Using genetic approaches, we demonstrate here that the transcriptional intermediary factor 1α (TIF1α), recently shown to function as a tumor suppressor in murine hepatocytes, also participates in a molecular cascade that prevents calcifications in arterioles and medium-sized arteries. We further provide genetic evidence that this function of TIF1α is not exerted in hepatocytes. The sites of ectopic calcifications in mutant mice lacking TIF1α resemble those seen in mice carrying an activating mutation of the calcium sensor receptor ( Casr ) gene and, in TIF1 α-deficient kidneys, Casr expression is increased together with that of many other vitamin D receptor (VDR) direct target genes, namely Car2 , Cyp24a1 , Trpv5 , Trpv6 , Calb1 , S100g , Pthlh , and Spp1 . Thus, our data indicate that TIF1α represses the VDR pathway in kidney and suggest that an up-regulation of Casr expression in this organ could account for ectopic calcifications generated upon TIF1 α deficiency. Interestingly, the calcifying arteriopathy of TIF1 α-null mutant mice shares features with the human age-related Mönckeberg's disease and, overall, the TIF1 α-null mutant pathological phenotype supports the hypothesis that aging is promoted by increased activity of the vitamin D signaling pathway.