A splicing mutation in the cytochrome b5 gene from a patient with congenital methemoglobinemia and pseudohermaphrodism

Hum Genet. 1994 May;93(5):568-70. doi: 10.1007/BF00202825.


We have analyzed reticulocyte and leukocyte mRNAs isolated from a patient with congenital methemoglobinemia and pseudohermaphrodism. The cytochrome b5 cDNA sequences were amplified using specific oligonucleotide primers and the polymerase chain reaction (PCR). DNA sequencing indicated that there was a 16-bp deletion in the cDNA leading to a new, in-frame stop signal and resulting in a truncated protein of 45 amino acids. Genomic DNA was analyzed, and the molecular lesion was shown to be an AG-->GG alteration in the 3' splicing junction of intron 1. The splice site alteration leads to the usage of the nearest AG as an alternative splice site, resulting in a 16-bp deletion in the mRNA. All of the studies on reticulocyte mRNA and genomic DNA indicated that the patient was homozygous for the lesion.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Cytochromes b5 / genetics*
  • DNA Primers / chemistry
  • DNA, Recombinant*
  • Disorders of Sex Development / enzymology*
  • Disorders of Sex Development / genetics
  • Gene Deletion
  • Humans
  • Leukocytes / metabolism
  • Male
  • Methemoglobinemia / congenital*
  • Methemoglobinemia / enzymology*
  • Molecular Sequence Data
  • Mutation*
  • Polymerase Chain Reaction
  • RNA, Messenger / metabolism
  • Reticulocytes / metabolism


  • DNA Primers
  • DNA, Recombinant
  • RNA, Messenger
  • Cytochromes b5