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Six novel and three recurrent mutations in nine Austrian patients with hemophilia B
J Walter1, I Pabinger-Fasching, H H Watzke
1Department of Medicine I, University of Vienna, Austria.
Insights
This study identifies genetic defects in the factor IX (FIX) gene causing hemophilia B in nine patients. Researchers discovered novel mutations and deletions, advancing understanding of this rare bleeding disorder.
Area of Science:
- Genetics
- Hematology
- Molecular Biology
Background:
- Hemophilia B is a rare bleeding disorder caused by deficiency in coagulation factor IX (FIX).
- Understanding the molecular basis of FIX deficiency is crucial for diagnosis and potential therapeutic strategies.
Purpose of the Study:
- To identify the specific genetic mutations responsible for factor IX deficiency in nine patients with hemophilia B.
- To characterize the nature and location of these mutations within the FIX gene.
Main Methods:
- DNA was extracted from nine patients diagnosed with hemophilia B.
- Polymerase chain reaction (PCR) was used for enzymatic amplification of all FIX gene exons and exon-intron junctions.
- Direct sequencing was performed to identify genetic variations.
Main Results:
- Genetic defects in the FIX gene were identified in all nine patients.
- Mutations included one small deletion, one point deletion, and seven point mutations (six missense, one nonsense).
- Novel mutations were identified in patients Vienna I, VII (deletions), and Vienna II, VI, VIII (missense).
Conclusions:
- The study successfully identified the causative genetic mutations for hemophilia B in the studied cohort.
- The findings contribute to the understanding of the genetic heterogeneity of hemophilia B and identify novel mutations.
- This molecular characterization aids in the diagnosis and genetic counseling for hemophilia B patients.
Abstract:
In this report we describe the molecular basis of the factor IX (FIX) deficiency in nine patients with severe (n = 6), moderate (n = 1) or mild (n = 2) hemophilia B. The following genetic defects were identified by enzymatic amplification with the polymerase chain reaction (PCR) and subsequent direct sequencing of all exons and exon-intron-junctions: patient B.B. (FIX "Vienna I"): deletion of nucleotides 6343 to 6362; patient M.H. and W.J. (FIX "Vienna II"): nucleotide 17704 (C to G), Gln 97 to Glu; patient L.K. (FIX "Vienna III"): nucleotide 17761 (C to T), Arg 116 to stop; patient U.A. (FIX "Vienna IV"): nucleotide 10415 (C to G), Pro 55 to Ala; patient H.G. (FIX "Vienna V"): nucleotide 6488 (C to T), Thr 38 to Ile; patient H.M. (FIX "Vienna VI"): nucleotide 31276 (G to C), Trp 385 to Cys; patient L.C. (FIX "Vienna VII"): deletion of nucleotide 6700; patient S.F. (FIX "Vienna VIII"): nucleotide 10392 (A to T), Asp 47 to Val. The causative mutation was detected in the FIX gene in each of the nine patients with hemophilia B. There was one small deletion, one point deletion and seven point mutations. The latter include six missense mutations and one nonsense mutation. The mutations in Vienna III, IV and V have already been described in previous studies. The two deletions, Vienna I and Vienna VII have not been reported previously. The genetic defects observed in Vienna II, VI and VIII are novel missense mutations which result in amino acid changes at residues 97, 47 and 385, respectively.