TISSUE-SPECIFIC REGULATION BY VITAMIN-D STATUS OF NUCLEAR AND MITOCHONDRIAL GENE-EXPRESSION IN KIDNEY AND INTESTINE

Vitamin D is responsible, through the actions of its metabolite, 1 alpha,25-dihydroxyvitamin D-3 [1 alpha,25-(OH)(2)D-3], for the generation of a wide array of biological responses, particularly in the intestine, kidney, and bone. 1 alpha,25-(OH)(2)D-3 is known to interact with its nuclear receptor to mediate the regulation of gene transcription. Although many genes and gene products have been shown to be regulated by 1 alpha,25-(OH)(2)D-3 (e.g. calbindin-D-28K in the intestine and kidney; collagen, osteocalcin, and osteopontin in bone), their recognition has been largely the result of empirical testing. In this report we have used subtractive hybridization analysis of complementary DNA libraries prepared from messenger RNA (mRNA) isolated from the intestine and kidney of vitamin D-replete or vitamin D-deficient chicks to identify genes for novel proteins whose steady state mRNA levels are regulated by dietary vitamin D status. In the kidney we observed the down-regulated expression of at least seven mitochondrially encoded transcripts and the up-regulated expression of five nuclear encoded genes, two of which are metallothionein and the beta-subunit of aldolase. In the intestine, six mitochondrially encoded transcripts are up-regulated, and seven nuclear encoded transcripts were either up- or down-regulated. Thus, in addition to identifying new nuclear encoded genes whose mRNAs are regulated by vitamin D status, our approach has demonstrated the tissue-specific regulation of mitochondrial gene expression in the intestine and kidney.