Methylation of the vitamin D-dependent CaBP gene (calbindin 9 Kd) does not mediate tissue or vitamin D regulation

The vitamin D-dependent intestinal calcium binding protein gene is predominantly expressed in the intestine. In this report we have examined the possibility that methylation of the gene might play a role in its tissue-specific expression employing genomic Southern analysis. None of the Hpa II and Hha I sites examined by the indicated probes in and around the gene were found to be methylated in the intestine, kidney and liver. No change in the methylation of these sites was detected in response to 1,25-dihydroxy-vitamin D3 administration to vitamin D-deficient rats under conditions which stimulate the expression of the gene. These results indicate that the rat intestinal calcium binding protein gene is not methylated in these tissues, at the indicated sites and, therefore, methylation seems not to be involved in the regulation of this gene's expression.