Profiling of factor VIII mutations in Korean haemophilia A

Mutation detection and inhibitor risk in Iranian patients with Hemophilia A: Six novel mutations

This investigation facilitates a better understanding of inhibitor development, the critical treatment morbidity in HA patients. Furthermore, six novel mutations are reported, which would expand the mutation spectrum of the F8 gene.

Restoration of FVIII expression by targeted gene insertion in the FVIII locus in hemophilia A patient-derived iPSCs

Target-specific genome editing, using engineered nucleases zinc finger nuclease (ZFN), transcription activator-like effector nuclease (TALEN), and type II clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9), is considered a promising approach to correct disease-causing mutations in various human diseases. In particular, hemophilia A can be considered an ideal target for gene modification via engineered nucleases because it is a monogenic disease caused by a mutation in coagulation factor VIII (FVIII), and a mild restoration of FVIII levels in plasma can prevent disease symptoms in patients with severe hemophilia A. In this study, we describe a universal genome correction strategy to restore FVIII expression in induced pluripotent stem cells (iPSCs) derived from a patient with hemophilia A by the human elongation factor 1 alpha (EF1α)-mediated normal FVIII gene expression in the FVIII locus of the patient. We used the CRISPR/Cas9-mediated homology-directed repair (HDR) system to insert the B-domain deleted from the FVIII gene with the human EF1α promoter. After gene targeting, the FVIII gene was correctly inserted into iPSC lines at a high frequency (81.81%), and these cell lines retained pluripotency after knock-in and neomycin resistance cassette removal. More importantly, we confirmed that endothelial cells from the gene-corrected iPSCs could generate functionally active FVIII protein from the inserted FVIII gene. This is the first demonstration that the FVIII locus is a suitable site for integration of the normal FVIII gene and can restore FVIII expression by the EF1α promoter in endothelial cells differentiated from the hemophilia A patient-derived gene-corrected iPSCs.

A strategy to restore the expression of the gene encoding blood clotting factor VIII (FVIII) offers new hope to patients with hemophilia A. Hemophilia A is a rare bleeding disorder caused by a variety of mutations in the FVIII gene which affect the function of FVIII protein. At present, the main treatment option relies on the injection of expensive clotting-factor concentrates to restore functional levels of the FVIII. Dong-Wook Kim and colleagues at Yonsei University in Seoul, South Korea, have used genome editing techniques to insert a corrected version of the FVIII gene into stem cells derived from a patient with severe hemophilia A. When these cells differentiated into the cells lining blood vessels they were able to produce and secrete active FVIII protein. This approach offers the attractive possibility of correcting all hemophilia-causing FVIII mutations.

Genotyping of Intron Inversions and Point Mutations in Exon 14 of the FVIII Gene in Iranian Azeri Turkish Families with Hemophilia A

Hemophilia A (HA) is an inherited X-linked bleeding disorder caused by a variety of mutations that are distributed throughout the large FVIII gene (F8). The most common mutations in studied populations with severe HA are introns 22 and 1 inversions, gross exon deletions and point mutations in exon 14. The aim of this study was to define the frequency of these common mutations in Iranian population of Azeri Turkish in North West of Iran. Fifty patients with severe HA and forty-three female potential carriers were genotyped by inverse shifting polymerase chain reaction (IS-PCR), long-range PCR, multiplex PCR, and sequencing methods for the detection of Intron 22 and 1 inversions, gross exon deletions, and exon 14 point mutations, respectively. F8 intron 22 inversion was detected in 22 (44 %) out of 50 patients. Moreover, we detected one intron 1 inversion (2 %), and one point mutation in exon 14 (2 %). In this population, 52 % of the patients with hemophilia A did not show to carry a mutation in the analyzed regions by three mentioned methods. F8 intron 22 inversion was the major causative mutation in nearly 50 % of severe HA cases in an Azerbaijani Turkish population, which is similar to the incidence of other populations. IS-PCR is a robust, rapid, efficient, and cost-effective method for the genetic analysis of patients with severe HA and for HA carrier detection, especially in developing countries.

Human coagulation factor VIII domain-specific recombinant polypeptide expression

Background

Hemophilia A is caused by heterogeneous mutations in F8. Coagulation factor VIII (FVIII), the product of F8, is composed of multiple domains designated A1-A2-B-A3-C1-C2. FVIII is known to interact with diverse proteins, and this characteristic may be important for hemostasis. However, little is known about domain-specific functions or their specific binding partners.

Methods

To determine F8 domain-specific functions during blood coagulation, the FVIII domains A1, A2, A3, and C were cloned from Hep3B hepatocytes. Domain-specific recombinant polypeptides were glutathione S-transferase (GST)- or polyhistidine (His)-tagged, over-expressed in bacteria, and purified by specific affinity chromatography.

Results

Recombinant polypeptides of predicted sizes were obtained. The GST-tagged A2 polypeptide interacted with coagulation factor IX, which is known to bind the A2 domain of activated FVIII.

Conclusion

Recombinant, domain-specific polypeptides are useful tools to study the domain-specific functions of FVIII during the coagulation process, and they may be used for production of domain-specific antibodies.

Most factor VIII B domain missense mutations are unlikely to be causative mutations for severe hemophilia A: implications for genotyping

BACKGROUND & OBJECTIVE

 The factor VIII (FVIII) B domain shares very little amino acid homology with other known proteins and is not directly necessary for procoagulant activity. Despite this, missense mutations within the B domain have been reported in patients with hemophilia A. Given that the B domain is dispensable for secretion and function of FVIII, we hypothesized that these mutations should not be causative of hemophilia A in these patients.

METHODS

 Plasmid vectors containing B domain missense mutations that were reported to be associated with moderate/severe hemophilia A (T751S, D826E, V993L, H1047Y, T1353A, N1441K, L1462P, E1579D, A1591S, P1641L and S1669L) were analyzed for their effect on synthesis and secretion compared with FVIII wild-type (WT) following transient transfection into COS-1 and CHO cells in vitro. Further, H1047Y, N1441K and E1579D mutants were expressed in vivo in a hemophilia A mouse model by hydrodynamic tail-vein injection.

RESULTS

 FVIII activity and antigen levels for all mutants expressed into the conditioned media of COS-1 and CHO cells were similar to FVIII WT. Also, plasma expression of these mutants was similar to FVIII WT in hemophilia A mice. An in vivo tail clip bleeding assay also demonstrated that blood loss from hemophilia A mice expressing FVIII WT, H1047Y, N1441K and E1579D was similar.

CONCLUSIONS

 We conclude that most missense mutations within the FVIII B domain would be unlikely to lead to severe hemophilia A and that the majority of such missense mutations represent polymorphisms or non-pathologic mutations.

Identification of a shared F8 mutation in the Korean patients with acquired hemophilia A

Although uncommon, acquired hemophilia A (HA) is associated with a high rate of mortality due to severe bleeding. In spite of many hypotheses regarding the cause of acquired HA, there is as yet no established theory. In this study, we investigated the possibility that mutation(s) in the F8 gene may be correlated with the development of inhibitory autoantibodies. Direct sequencing analysis was performed on all 26 exons of the F8 gene of 2 patients exhibiting acquired HA. Both patients were found to share a common point mutation (c.8899G>A) in the 3'-untranslated region (3'-UTR) of exon 26. This is the first report on the genotyping of F8 in the context of acquired HA.