Evidence for frequent gene conversion in the steroid 21-hydroxylase P-450(C21) gene: implications for steroid 21-hydroxylase deficiency.
Oligonucleotide probes specific for the deleterious mutations harbored in the P-450(C21)A pseudogene and oligonucleotide probes specific for the corresponding sequences in the B gene were prepared to examine the molecular lesions in the P-450(C21) gene of P-450(C21)-deficient patients. Using these gene-specific probes, we performed Southern blot analyses of genomic DNAs from 11 patients and eight normal individuals. At least one allele of the B gene (the 3.7-kb TaqI fragment) in a patient was inactivated by mutations caused by recombination with the A gene. The A genes in normal individuals and patients seemed to be replaced frequently (i.e., 10/19 individuals) in their 3' portions by B gene sequences. All of these alterations occurred without changing the characteristic length (3.2 kb) of the TaqI fragment of the A gene, a result strongly suggesting that frequent gene conversions and/or intragenic recombinations have happened in the P-450(C21) genes. Densitometric analysis of the autoradiograms from hybridization experiments revealed extensive variation (from one to five copies) in the copy number of the A gene (the 3.2-kb TaqI fragment) whereas that of the B gene (the 3.7-kb TaqI fragment) was relatively constant at two or three copies.
Higashi
Y
Y
Department of Biochemistry, Cancer Institute, Tokyo, Japan.
Tanae
A
A
Inoue
H
H
Fujii-Kuriyama
Y
Y
D000312:Adrenal Hyperplasia, Congenital; D004247:DNA / Q000235:genetics; D004262:DNA Restriction Enzymes; D005260:Female; D005785:Gene Conversion; D006801:Humans; D008297:Male; D009154:Mutation; D009693:Nucleic Acid Hybridization; D009841:Oligonucleotides; D011544:Pseudogenes; D011995:Recombination, Genetic; D013255:Steroid 21-Hydroxylase / Q000235:genetics*; D013250:Steroid Hydroxylases / Q000235:genetics*
D009841:Oligonucleotides; D004247:DNA; D013250:Steroid Hydroxylases; D013255:Steroid 21-Hydroxylase; D004262:DNA Restriction Enzymes