1,25-Dihydroxyvitamin D3 Controls a Cohort of Vitamin D Receptor Target Genes in the Proximal Intestine That Is Enriched for Calcium Regulating Components (RNA-seq)

1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) plays an integral role in calcium homeostasis in higher organisms through its actions in the intestine, kidney and skeleton. Interestingly, while several intestinal genes are known to play a contributory role in calcium homeostasis, the entire caste of key components remains to be identified. To examine this issue, Cyp27b1 null mice on either a normal or a high calcium/phosphate-containing rescue diet were treated with either vehicle or 1,25(OH)2D3 and evaluated 6h later. RNA samples from duodena were then subjected to RNA-seq analysis and the data analyzed bioinformatically. 1,25(OH)2D3 altered expression of large collections of genes raised under either dietary condition. 45 genes were found common to both 1,25(OH)2D3-treated groups, and were comprised of genes previously linked to intestinal calcium uptake including S100g, Trpv6, Atp2b1 and Cldn2 as well as others. An additional distinct network of 56 genes was regulated exclusively by diet. This study revealed a global network of genes in the intestine that both represent direct targets of vitamin D action in mice and are involved in calcium absorption. Male Cyp27b1-/- mice weaned at 3 wk of age were divided into 2 groups of 12 mice each. One group was fed a highly purified vitamin D-deficient diet containing 0.47% Ca, 0.3% P and vitamins A, E, and K (normal diet) while the other was fed the same diet containing 20% lactose, 2% Ca, 1.25% P (rescue diet). At 8 weeks of age, 8 mice per group were administered 1,25(OH)2D3 (2 ng/g body weight (bw)) or vehicle by intraperitoneal injection. Mice were euthanized at 6 h and duodena were collected for RNA-seq analysis. Six samples per experimental group were prepared.