Inactivating mutations in the 25-hydroxyvitamin D3 1alpha-hydroxylase gene in patients with pseudovitamin D-deficiency rickets.
BACKGROUND
Pseudovitamin D-deficiency rickets is characterized by the early onset of rickets with hypocalcemia and is thought to be caused by a deficit in renal 25-hydroxyvitamin D3 1alpha-hydroxylase, the key enzyme for the synthesis of 1alpha,25-dihydroxyvitamin D3.


METHODS
We cloned human 25-hydroxyvitamin D3 1alpha-hydroxylase complementary DNA (cDNA) using a mouse 1alpha-hydroxylase cDNA fragment as a probe. Its genomic structure was determined, and its chromosomal location was mapped by fluorescence in situ hybridization. We then identified mutations in the 1alpha-hydroxylase gene in four unrelated patients with pseudovitamin D-deficiency rickets by DNA-sequence analysis. Both the normal and the mutant 1alpha-hydroxylase proteins were expressed in COS-1 cells and were assayed for 1alpha-hydroxylase activity.


RESULTS
The gene for 25-hydroxyvitamin D3 1alpha-hydroxylase was mapped to chromosome 12q13.3, which had previously been reported to be the locus for pseudovitamin D-deficiency rickets by linkage analysis. Four different homozygous missense mutations were detected in this gene in the four patients with pseudovitamin D-deficiency rickets. The unaffected parents and one sibling tested were heterozygous for the mutations. Functional analysis of the mutant 1alpha-hydroxylase protein revealed that all four mutations abolished 1alpha-hydroxylase activity.


CONCLUSIONS
Inactivating mutations in the 25-hydroxyvitamin D3 1alpha-hydroxylase gene are a cause of pseudovitamin D-deficiency rickets.
Kitanaka
S
S
Institute of Molecular and Cellular Biosciences, University of Tokyo, Japan.
Takeyama
K
K
Murayama
A
A
Sato
T
T
Okumura
K
K
Nogami
M
M
Hasegawa
Y
Y
Niimi
H
H
Yanagisawa
J
J
Tanaka
T
T
Kato
S
S
D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase / Q000235:genetics* / Q000378:metabolism; D001483:Base Sequence; D002874:Chromosome Mapping; D002881:Chromosomes, Human, Pair 12; D003001:Cloning, Molecular; D004252:DNA Mutational Analysis; D018076:DNA, Complementary / Q000235:genetics; D005260:Female; D006801:Humans; D008297:Male; D009154:Mutation; D010375:Pedigree; D012279:Rickets / Q000201:enzymology / Q000235:genetics*; D017422:Sequence Analysis, DNA; D014808:Vitamin D Deficiency
D018076:DNA, Complementary; D015090:25-Hydroxyvitamin D3 1-alpha-Hydroxylase