Clinical, genetic, and enzymatic characterization of P450 oxidoreductase deficiency in four patients.
BACKGROUND
P450 oxidoreductase (POR) deficiency causes disordered steroidogenesis; severe mutations cause genital ambiguity in both sexes plus the Antley-Bixler skeletal malformation syndrome, whereas mild mutations can cause adult infertility.


OBJECTIVE
We describe four patients with POR deficiency and identify and characterize the activities of their mutations. A 46,XY male with micropenis and two 46,XX female infants with genital ambiguity presented with skeletal malformations, and a 46,XX adolescent presented with primary amenorrhea, elevated 17alpha-hydroxyprogesterone, and low sex steroids.


METHODS
The coding regions of the POR gene were sequenced, and the identified mutations were recreated in human POR cDNA expression vectors lacking 27 N-terminal residues. POR and human P450c17 were expressed in bacteria. POR activity was measured by four assays: reduction of cytochrome c, oxidation of reduced nicotinamide adenine dinucleotide phosphate, and support of the 17alpha-hydroxylase and 17,20 lyase activities of P450c17.


RESULTS
All four patients were compound heterozygotes for POR mutations, including five novel mutations: L577R, N185K, delE217, and frameshift mutations 1363delC and 697-698insGAAC. N185K and delE217 lacked measurable activity in the assays based on P450c17 but retained partial activity in the assays based on cytochrome c. As assessed by V(max)/Km, L577R supported 46% of 17alpha-hydroxylase activity but only 27% of 17,20 lyase activity. Computational modeling of these novel mutants revealed the structural basis for their reduced or absent activities.


CONCLUSIONS
These patients illustrate the broad clinical spectrum of POR deficiency, including amenorrhea and infertility as the sole manifestation. POR assays based on P450c17 correlate well with hormonal and clinical phenotypes.
Sahakitrungruang
Taninee
T
Department of Pediatrics, University of California San Francisco, San Francisco, California 94143, USA.
Huang
Ningwu
N
Tee
Meng Kian
MK
Agrawal
Vishal
V
Russell
William E
WE
Crock
Patricia
P
Murphy
Nuala
N
Migeon
Claude J
CJ
Miller
Walter L
WL
D000293:Adolescent; D000328:Adult; D001842:Bone and Bones / Q000002:abnormalities; D002384:Catalysis; D045304:Cytochromes c / Q000235:genetics; D004247:DNA / Q000235:genetics; D012734:Disorders of Sex Development / Q000235:genetics / Q000473:pathology; D004926:Escherichia coli / Q000235:genetics; D005260:Female; D005822:Genetic Vectors; D005835:Genitalia / Q000002:abnormalities; D006728:Hormones / Q000097:blood; D006801:Humans; D007231:Infant, Newborn; D007246:Infertility / Q000235:genetics; D008297:Male; D009154:Mutation; D009249:NADP / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000172:deficiency* / Q000235:genetics*; D011247:Pregnancy; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics; D013577:Syndrome
D006728:Hormones; D009249:NADP; D045304:Cytochromes c; D004247:DNA; D013254:Steroid 17-alpha-Hydroxylase; D009251:NADPH-Ferrihemoprotein Reductase