Congenital adrenal hyperplasia caused by mutant P450 oxidoreductase and human androgen synthesis: analytical study.
BACKGROUND
Congenital adrenal hyperplasia with apparent combined P450C17 and P450C21 deficiency is associated with accumulation of steroid metabolites, indicating impaired activity of 17alpha-hydroxylase and 21-hydroxylase. However, no mutations have been reported in the CYP17 and CYP21 genes, which encode these P450 enzymes. Affected girls are born with ambiguous genitalia, but their circulating androgens are low, and virilisation does not progress. We aimed to investigate the underlying molecular basis of congenital adrenal hyperplasia with apparent combined P450C17 and P450C21 deficiency in affected children.


METHODS
We did sequence analysis of the human gene encoding P450 oxidoreductase, an enzyme that is important in electron transfer from NADPH to P450C17 and P450C21. We studied two unrelated families with a total of three affected children and 100 healthy controls. Wild-type and mutant P450 oxidoreductase proteins were bacterially expressed, purified, and assayed for cytochrome c reductase activity.


RESULTS
We identified four mutations encoding single aminoacid changes in P450 oxidoreductase. All patients were compound heterozygotes, whereas their parents and an unaffected sibling harboured a mutation in only one allele. By contrast, no mutations were noted in the controls. Bacterial expression of recombinant mutant proteins revealed deficient or reduced enzyme activity.


CONCLUSIONS
Molecular pathogenesis of this form of congenital adrenal hyperplasia is caused by mutations in the gene encoding P450 oxidoreductase. Deficiency of this enzyme could suggest an alternative pathway in human androgen synthesis, present only in fetal life, which explains the combination of antenatal androgen excess and postnatal androgen deficiency.
Arlt
Wiebke
W
Division of Medical Sciences, Institute of Biomedical Research, Medical School, Birmingham B15 2TT, UK. w.arlt@bham.ac.uk
Walker
Elizabeth A
EA
Draper
Nicole
N
Ivison
Hannah E
HE
Ride
Jon P
JP
Hammer
Fabian
F
Chalder
Susan M
SM
Borucka-Mankiewicz
Maria
M
Hauffa
Berthold P
BP
Malunowicz
Ewa M
EM
Stewart
Paul M
PM
Shackleton
Cedric H L
CH
D000293:Adolescent; D000312:Adrenal Hyperplasia, Congenital / Q000235:genetics* / Q000378:metabolism; D019943:Amino Acid Substitution; D000728:Androgens / Q000096:biosynthesis*; D002675:Child, Preschool; D003577:Cytochrome P-450 Enzyme System / Q000737:chemistry / Q000235:genetics*; D005260:Female; D006801:Humans; D008297:Male; D009154:Mutation
D000728:Androgens; D003577:Cytochrome P-450 Enzyme System