Two factor IX mutations in the family of an isolated haemophilia B patient : direct carrier diagnosis by amplification mismatch detection (AMD)

• Rapid identification of gene defects allows definite carrier and prenatal diagnosis in virtually every family with haemophilia B. We report a study of the family of an isolated patient. Analysis of all the essential regions of the patient's factor IX gene (promoter, exons, transcript processing signals) revealed two mutations: one C----T transition at residue 17762 and another at residue 30890. The former created a translation stop at codon 116, and the latter caused substitution of His 257 by Tyr. The translation stop is an obvious detrimental mutation, while the His 257----Tyr substitution has uncertain functional consequences. From analysis of other family members, it was found that the first mutation had occurred at grandpaternal gametogenesis, in keeping with the negative family history, while the second was of more remote origin and did not reduce the maternal grandfather's factor IX coagulant and antigen level. This neutral mutation (His 257----Tyr) pinpoints a poorly conserved amino acid in factor IX and related serine proteases. Its coexistence with a detrimental mutation stresses the need to examine all essential regions of a gene before attempting to interpret the functional consequences of its sequence changes.

Ämnesord

MEDICIN OCH HÄLSOVETENSKAP  -- Klinisk medicin -- Hematologi (hsv//swe)

MEDICAL AND HEALTH SCIENCES  -- Clinical Medicine -- Hematology (hsv//eng)

Nyckelord

Antigens

Base Sequence

Child, Preschool

Codon

Exons

Factor IX

Hemophilia B

Heterozygote Detection

Humans

Male

Molecular Sequence Data

Mutation

Nucleic Acid Amplification Techniques

Pedigree

Polymerase Chain Reaction

Case Reports

Journal Article

Research Support, Non-U.S. Gov't

Publikations- och innehållstyp

art (ämneskategori)

ref (ämneskategori)