Identification and Genetic Analysis of a Factor IX Gene Intron 3 Mutation in a Hemophilia B Pedigree in China

Genetic analysis of a hemophilia B family with a novel F9 gene mutation: A STROBE-compliant article

At present, there are no effective methods for the treatment of hemophilia B, and it has high mortality and disability. Therefore, it is very important for the carriers to carry out genetic counseling and make prenatal diagnosis. In this study, we made gene and prenatal diagnoses in a family with a novel F9 gene mutation, and report a novel F9 gene mutation.All exon sequences and flanking sequences of F9 gene were analyzed by Sanger sequencing in the proband; and then according to the F9 gene mutation in the proband, the F9 gene sequencing was performed on the family members. Based on the above results, the pathogenic mutation in F9 gene was finally identified, which was used for prenatal diagnosis.Sanger sequencing revealed c.1232G>C [p.Ser411Thr] mutation in F9 gene in the proband. c.1232G>C heterozygous mutation was also found in the proband's mother and grandmother, but male family members without hemophilia B had no this mutation. The analyses of amniotic fluid samples indicated positive sex-determining region on Y chromosome (SRY), and no c.1232G>C [p.Ser411Thr] mutation in F9 gene.We identified a pathogenic mutation in F9 gene in the family, made a prenatal diagnosis for the female carrier and reported a novel F9 gene mutation.

Hemophilia B: molecular pathogenesis and mutation analysis

Hemophilia B is an X-chromosome-linked inherited bleeding disorder primarily affecting males, but those carrier females with reduced factor IX activity (FIX:C) levels may also experience some bleeding. Genetic analysis has been undertaken for hemophilia B since the mid-1980s, through linkage analysis to track inheritance of an affected allele, and to enable determination of the familial mutation. Mutation analysis using PCR and Sanger sequencing along with dosage analysis for detection of large deletions/duplications enables mutation detection in > 97% of patients with hemophilia B. The risk of the development of inhibitory antibodies, which are reported in ~ 2% of patients with hemophilia B, can be predicted, especially in patients with large deletions, and these individuals are also at risk of anaphylaxis, and nephrotic syndrome if they receive immune tolerance induction. Inhibitors also occur in patients with nonsense mutations, occasionally in patients with small insertions/deletions or splice mutations, and rarely in patients with missense mutations (p.Gln237Lys and p.Gln241His). Hemophilia B results from several different mechanisms, and those associated with hemophilia B Leyden, ribosome readthrough of nonsense mutations and apparently 'silent' changes that do not alter amino acid coding are explored. Large databases of genetic variants in healthy individuals and patients with a range of disorders, including hemophilia B, are yielding useful information on sequence variant frequency to help establish possible variant pathogenicity, and a growing range of algorithms are available to help predict pathogenicity for previously unreported variants.