Non-Inversion Factor VIII Mutations in 80 Hemophilia A Families Including 24 with Alloimmune Responses

Abstract

SummaryHeteroduplex screening identified 74 small mutations in the factor VIII genes of 72 families with hemophilia A. In addition, patients from 3 families with high titer inhibitors had partial gene deletions and 5 unrelated families that were negative for heteroduplex formation had a mutation on direct sequencing. The latter had mild hemophilia A with an inhibitor, and sequencing their exon 23 fragments found a transition predicting a recurrent Arg2150 to His. Of 69 distinct mutations (including the 3 partial gene deletions), 47 are novel. Of small mutations, 51 were missense (one possibly a normal variant and two that could also alter splicing) at 39 sites, 13 were small deletions or insertions (3 inframe and one a normal variant in an intron), 13 were nonsense at 12 sites and 2 altered intron splice junctions. In 24 families, at least one affected member had evidence for an alloimmune response to factor VIII; of these, 11 were associated with missense mutations. In 14 families, de novo origin was demonstrated.

Identification of 31 novel mutations in the F8 gene in Spanish hemophilia A patients: structural analysis of 20 missense mutations suggests new intermolecular binding sites

“…4,70 It is conceivable that a bulkier side chain at position 494 would impair these FVIIIa-FX interactions, thus compromising substrate recognition. Moderate bleeding has also been reported for mutant p.Gly494Ser, 68 also in line with the proposed involvement of this loop in FX activation. We note that a discrepancy between antigen and FVIII activity levels for the latter mutant (23% and 4%, respectively) suggests its involvement in intermolecular interactions.…”

“…16,17 Finally, and also in line with the hypothetical role of this region as a FX-interactive site, more dramatic loop rearrangements due to in-frame deletion of Pro66 or the Arg65/ Pro66 pair lead to moderately severe and severe HA, respectively. 68 Considering the predicted distance from the phospholipid membrane ( Figure 1B), we speculate that this loop interacts with EGF2 and/or serine protease domains of substrate FX.…”

Case Report: Development of Factor VIII Inhibitor in a Patient with an Uncommon de novo Mutation in the Factor VIII Gene

“…This patient was reported to have severe hemophilia A without development of an inhibitor [7, 19]. The same paper also reported on a patient with a c.5816C>T missense mutation resulting in substitution of valine for alanine at position 1939; however, this mutation was thought to be nonpathogenic, as the patient also had a C>T substitution resulting in substitution of a stop codon for arginine at codon 1941, a mutation that was described in another patient with severe hemophilia A with inhibitor formation [19]. …”

Factor VIII genetic mutations and protein alterations in hemophilia A: A review

“…In mild to moderately severe hemophilia A missense mutations within the exons coding for the three A domains or the two C domains account for most of the mutations detected (Kemball-Cook and Tuddenham, 1998; Liu et al, 1998Liu et al, , 2000Liu et al, , 2002. The CpG site is one of the hotspots in hemophilia A, with arginine (CGC,CGG, CGT) being the most frequently affected as the cells DNA repair mechanism does not regard thymidine formed by deamination of methycytosion residues, as abnormal.…”

“…The CpG site is one of the hotspots in hemophilia A, with arginine (CGC,CGG, CGT) being the most frequently affected as the cells DNA repair mechanism does not regard thymidine formed by deamination of methycytosion residues, as abnormal. For example, codon with three different amino acid changes are the arginine codon 531in exon 11 , codon 1781 in exon 16 (Faridi et al, 2011) and codon 2150 in exon 23 (Liu et al, 2002;Cutler et al, 2002;Habart et al, 2002;Fernandez-Lopez et al, 2005), which has been reported 61 times (Table 1), since arginine is involved in 25% of all missense mutations found so far and play a crucial role in protein function. Ahmed et al (2005) carried out mutation studies in inversion negative hemophilia A patients by the high performance liquid chromatography (dHPLC) method and found 11 missense mutations, and some other mutations (Ahmed et al, 2005), whereas Jayandharan et al (2005) detected 101 mutations by using multiplex polymerase chain reactions (PCRs) and the Cap analysis gene expression (CAGE) technique, of which 21 were missense mutations (Jayandharan., 2005).…”