Exonic point mutations in NADH-cytochrome B5 reductase genes of homozygotes for hereditary methemoglobinemia, types I and III: putative mechanisms of tissue-dependent enzyme deficiency.
We analyzed the NADH-cytochrome b5 reductase gene of hereditary methemoglobinemia type I and type III, by using PCR-related techniques. The mutation in type I is a guanine-to-adenine substitution in codon 57 of exon 3 of the NADH-cytochrome b5 reductase gene, and the sense of this codon is changed from arginine to glutamine. In type III the mutation is a thymine-to-cytosine transition in codon 148 of exon 5, causing leucine-to-proline replacement in type III. The former mutation abolishes the MspI recognition site. Homozygosity for the former mutation in a patient with type I was confirmed by restriction analysis of PCR-amplified fragments and by dot blot hybridization of amplified products with allele-specific oligonucleotide probes. The latter mutation generates a recognition site for MspI. Amplification of exon 5 by PCR followed by digestion with MspI revealed homozygosity for this mutation in patients with type-III. Putative mechanisms of tissue-dependent enzyme defects in hereditary methemoglobinemia are discussed.
Katsube
T
T
Research Laboratory for Genetic Information, Kyushu University, Fukuoka, Japan.
Sakamoto
N
N
Kobayashi
Y
Y
Seki
R
R
Hirano
M
M
Tanishima
K
K
Tomoda
A
A
Takazakura
E
E
Yubisui
T
T
Takeshita
M
M
D000328:Adult; D001483:Base Sequence; D002874:Chromosome Mapping; D003579:Cytochrome Reductases / Q000172:deficiency* / Q000235:genetics; D042966:Cytochrome-B(5) Reductase; D019003:Deoxyribonuclease HpaII; D015252:Deoxyribonucleases, Type II Site-Specific; D005091:Exons; D006720:Homozygote; D006801:Humans; D007438:Introns; D008297:Male; D008708:Methemoglobinemia / Q000235:genetics*; D008969:Molecular Sequence Data; D009154:Mutation; D016133:Polymerase Chain Reaction; D011487:Protein Conformation
D003579:Cytochrome Reductases; D042966:Cytochrome-B(5) Reductase; D019003:Deoxyribonuclease HpaII; D015252:Deoxyribonucleases, Type II Site-Specific