Regulation of gene expression by dietary Ca2+ in kidneys of 25-hydroxyvitamin D3-1 alpha-hydroxylase knockout mice.
BACKGROUND
Pseudovitamin D deficiency rickets (PDDR) is an autosomal disease, characterized by undetectable levels of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), rickets and secondary hyperparathyroidism. Mice in which the 25-hydroxyvitamin D3-1 alpha-hydroxylase (1 alpha-OHase) gene was inactivated, presented the same clinical phenotype as patients with PDDR.


METHODS
cDNA Microarray technology was used on kidneys of 1 alpha-OHase knockout mice to study the expression profile of renal genes in this Ca2+-related disorder. Genome wide molecular events that occur during the rescue of these mice by high dietary Ca2+ intake were studied by the use of 15K cDNA microarray chips.


RESULTS
1 alpha-OHase knockout mice fed a normal Ca2+ diet developed severe hypocalcemia, rickets and died with an average life span of 12 +/- 2 weeks. Intriguingly, 1 alpha-OHase-/- mice supplemented with an enriched Ca2+ diet were normocalcemic and not significantly different from wild-type mice. Inactivation of the 1 alpha-OHase gene resulted in a significant regulation of +/- 1000 genes, whereas dietary Ca2+ supplementation of the 1 alpha-OHase-/- mice revealed +/- 2000 controlled genes. Interestingly, 557 transcripts were regulated in both situations implicating the involvement in the dietary Ca2+-mediated rescue mechanism of the 1 alpha-OHase-/- mice. Conspicuous regulated genes encoded for signaling molecules like the PDZ-domain containing protein channel interacting protein, FK binding protein type 4, kinases, and importantly Ca2+ transporting proteins including the Na+-Ca2+ exchanger, calbindin-D28K and the Ca2+ sensor calmodulin.


CONCLUSIONS
Dietary Ca2+ intake normalized disturbances in the Ca2+ homeostasis due to vitamin D deficiency that were accompanied by the regulation of a subset of renal genes, including well-known renal Ca2+ transport protein genes, but also genes not previously identified as playing a role in renal Ca2+ handling.
Hoenderop
Joost G J
JG
Department of Physiology, University Medical Centre Nijmegen, Nijmegen, The Netherlands.
Chon
Helena
H
Gkika
Dimitra
D
Bluyssen
Hans A R
HA
Holstege
Frank C P
FC
St-Arnaud
Rene
R
Braam
Branko
B
Bindels
Rene J M
RJ
D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000235:genetics*; D000818:Animals; D002136:Calcium, Dietary / Q000494:pharmacology*; D015971:Gene Expression Regulation, Enzymologic; D006706:Homeostasis / Q000502:physiology; D007668:Kidney / Q000502:physiology*; D051379:Mice; D018345:Mice, Knockout; D020411:Oligonucleotide Array Sequence Analysis; D010641:Phenotype; D012279:Rickets / Q000401:mortality / Q000503:physiopathology*
D002136:Calcium, Dietary; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase