Common Genetic Variants in ABO and CLEC4M Modulate the Pharmacokinetics of Recombinant FVIII in Severe Hemophilia A Patients.

The pharmacokinetic (PK) response of severe hemophilia A (HA) patients to infused factor VIII (FVIII) shows substantial variability. Several environmental and genetic factors are associated with changes in FVIII plasma levels and infused FVIII PK. Based on the hypothesis that factors influencing endogenous FVIII can affect FVIII PK, the contribution of single-nucleotide variants (SNVs) in candidate genes was investigated in 51 severe HA patients. The effects of blood group, F8 variant type, von Willebrand factor antigen and activity levels, age, and weight were also explored. The myPKFiT device was used to estimate individual PK parameters, and SNVs and clinically reportable F8 variants were simultaneously analyzed in an Illumina MiSeq instrument, using the microfluidics-based Fluidigm Access Array system. The contribution of SNVs to FVIII half-life and clearance was addressed by robust regression modeling, taking into account other modulators. In line with previous studies, we provide robust evidence that age, body weight, and blood group, as well as SNVs in ABO and CLEC4M, participate in the variability of FVIII PK in HA patients. Main results: each copy of the rs7853989 (ABO) allele increases FVIII half-life by 1.4 hours (p = 0.0131) and decreases clearance by 0.5 mL/h/kg (p = 5.57E-03), whereas each additional rs868875 (CLEC4M) allele reduces FVIII half-life by 1.1 hours (p = 2.90E-05) and increases clearance by 0.3 mL/h/kg (p = 1.01E-03). These results contribute to advancing efforts to improve FVIII replacement therapies by adjusting to each patient's PK profile based on pharmacogenomic data. This personalized medicine will decrease the burden of treatment and maximize the benefits obtained.

Unraveling the Influence of Common von Willebrand factor variants on von Willebrand Disease Phenotype: An Exploratory Study on the Molecular and Clinical Profile of von Willebrand Disease in Spain Cohort.

The clinical diagnosis of von Willebrand disease (VWD), particularly type 1, can be complex because several genetic and environmental factors affect von Willebrand factor (VWF) plasma levels. An estimated 60% of the phenotypic variation is attributable to hereditary factors, with the ABO blood group locus being the most influential. However, recent studies provide strong evidence that nonsynonymous single nucleotide variants (SNVs) contribute to VWF and factor VIII phenotypic variability in healthy individuals. This study aims to investigate the role of common VWF SNVs on VWD phenotype by analyzing data from 219 unrelated patients included in the "Molecular and Clinical Profile of von Willebrand Disease in Spain project." To that end, generalized linear mixed-effects regression models were fitted, and additive and epistatic analyses, and haplotype studies were performed, considering five VWD-related measures (bleeding score, VWF:Ag, VWF:RCo, factor VIII:C, and VWF:CB). According to these analyses, homozygotes: for p.Thr789Ala(C) would be expected to show 39% higher VWF:Ag levels; p.Thr1381Ala(C), 27% lower VWF:Ag levels; and p.Gln852Arg(C), 52% lower VWF:RCo levels. Homozygotes for both p.Thr789Ala(C) and p.Gln852Arg(T) were predicted to show 185% higher VWF:CB activity, and carriers of two copies of the p.Thr1381Ala(T)/p.Gln852Arg(T) haplotype would present a 100% increase in VWF:RCo activity. These results indicate a substantial effect of common VWF variation on VWD phenotype. Although additional studies are needed to determine the true magnitude of the effects of SNVs on VWF, these findings provide new evidence regarding the contribution of common variants to VWD, which should be taken into account to enhance the accuracy of the diagnosis and classification of this condition. ClinicalTrials.gov identifier: NCT02869074.

Unraveling the effect of silent, intronic and missense mutations on VWF splicing: contribution of next generation sequencing in the study of mRNA.

Large studies in von Willebrand disease patients, including Spanish and Portuguese registries, led to the identification of >250 different mutations. It is a challenge to determine the pathogenic effect of potential splice site mutations on VWF mRNA. This study aimed to elucidate the true effects of 18 mutations on VWF mRNA processing, investigate the contribution of next-generation sequencing to in vivo mRNA study in von Willebrand disease, and compare the findings with in silico prediction. RNA extracted from patient platelets and leukocytes was amplified by RT-PCR and sequenced using Sanger and next generation sequencing techniques. Eight mutations affected VWF splicing: c.1533+1G>A, c.5664+2T>C and c.546G>A (p.=) prompted exon skipping; c.3223-7_3236dup and c.7082-2A>G resulted in activation of cryptic sites; c.3379+1G>A and c.7437G>A) demonstrated both molecular pathogenic mechanisms simultaneously; and the p.Cys370Tyr missense mutation generated two aberrant transcripts. Of note, the complete effect of three mutations was provided by next generation sequencing alone because of low expression of the aberrant transcripts. In the remaining 10 mutations, no effect was elucidated in the experiments. However, the differential findings obtained in platelets and leukocytes provided substantial evidence that four of these would have an effect on VWF levels. In this first report using next generation sequencing technology to unravel the effects of VWF mutations on splicing, the technique yielded valuable information. Our data bring to light the importance of studying the effect of synonymous and missense mutations on VWF splicing to improve the current knowledge of the molecular mechanisms behind von Willebrand disease. clinicaltrials.gov identifier:02869074.

Molecular and clinical profile of von Willebrand disease in Spain (PCM-EVW-ES): comprehensive genetic analysis by next-generation sequencing of 480 patients.

Molecular diagnosis of patients with von Willebrand disease is pending in most populations due to the complexity and high cost of conventional molecular analyses. The need for molecular and clinical characterization of von Willebrand disease in Spain prompted the creation of a multicenter project (PCM-EVW-ES) that resulted in the largest prospective cohort study of patients with all types of von Willebrand disease. Molecular analysis of relevant regions of the VWF, including intronic and promoter regions, was achieved in the 556 individuals recruited via the development of a simple, innovative, relatively low-cost protocol based on microfluidic technology and next-generation sequencing. A total of 704 variants (237 different) were identified along VWF, 155 of which had not been previously recorded in the international mutation database. The potential pathogenic effect of these variants was assessed by in silico analysis. Furthermore, four short tandem repeats were analyzed in order to evaluate the ancestral origin of recurrent mutations. The outcome of genetic analysis allowed for the reclassification of 110 patients, identification of 37 asymptomatic carriers (important for genetic counseling) and re-inclusion of 43 patients previously excluded by phenotyping results. In total, 480 patients were definitively diagnosed. Candidate mutations were identified in all patients except 13 type 1 von Willebrand disease, yielding a high genotype-phenotype correlation. Our data reinforce the capital importance and usefulness of genetics in von Willebrand disease diagnostics. The progressive implementation of molecular study as the first-line test for routine diagnosis of this condition will lead to increasingly more personalized and effective care for this patient population.

Rapid molecular diagnosis of von Willebrand disease by direct sequencing. Detection of 12 novel putative mutations in VWF gene.

Molecular diagnosis of von Willebrand Disease (VWD) is particularly complex. The autosomal von Willebrand factor gene (VWF) is large and highly polymorphic, and there is a highly homologous (>96%) partial pseudogene in chromosome 22. Because of these difficulties, application of molecular study of VWD to the clinical routine has been considerably delayed. Recent advances in sequencing technology and bioinformatics could convert direct sequencing of the complete VWF into a routine diagnostic tool for VWD, which is especially desirable in types 1 and 3. This study describes a highly optimized procedure in which all the coding and intronic flanking regions of VWF are amplified under identical thermocycling parameters in a ready-to-use PCR plate format. The entire sequencing procedure, from blood extraction to mutation identification, can be done within 24 hours, resulting in a simple, versatile, cost-effective strategy with little hands-on time requirements. To validate the method, we performed full-length VWF sequencing of 21 index cases including seven of each VWD type. A total of 30 VWF genetic variations were identified. Twelve of these sequence variations are new, including four missense, one nonsense, one insertion, the first insertion-deletion described in VWF, and 5 potential splice site mutations. To our knowledge, this is the fastest and most efficient protocol designed to date for complete sequencing of the VWF coding region in the molecular diagnosis of VWD.

A versatile strategy for preimplantation genetic diagnosis of haemophilia A based on F8-gene sequencing.

Preimplantation genetic diagnosis (PGD) of hemophilia A (HA) and other X-linked diseases through sex selection implies that male embryos will be systematically discarded, even though 50% are unaffected. The objective of the present work was to develop a PGD protocol for direct mutation identification that could be applied to first polar bodies (1PBs) in several HA clinical cases. Single buccal cells from controls and patients, and 1PBs were subjected to primer extension preamplification (PEP) PCR followed by amplification of F8 gene coding and intronic flanking regions, and direct sequencing. Moreover, multiplex fluorescent amplification of four short tandem repeats was adapted to a single cell preamplification in order to rule out contamination and allele drop-out, and for confirmatory indirect diagnosis. A couple at risk of HA transmission, with a familial mutation characterized as a 41-bp duplication in exon 14 of the F8 gene, was selected for the first clinical study. After optimizing the protocol, the complete F8 gene coding sequence was obtained from single cells to demonstrate the sensitivity of our methodology although in any clinical case only the relevant region, not the whole gene, must be amplified. The woman enrolled in the first clinical case has completed the first in-vitro fertilization cycle, and seven oocytes were analyzed with concordant results by both linkage analysis and direct sequencing method. Only one oocyte, among those diagnosed as mutation free, developed to embryo at day 3. It was transferred but pregnancy was not achieved. This PGD procedure enables non-affected and noncarrier embryo selection in families with any point or small-range mutation in the F8 gene, without the need for further custom-made modifications.

Von Willebrand gene tracking by single-tube automated fluorescent analysis of four short tandem repeat polymorphisms.

Molecular diagnosis of von Willebrand disease (VWD) has been hampered by the large size and complex genomic characteristics of the gene involved. For this reason, indirect methods using intragenic polymorphic markers described along the von Willebrand factor (VWF) gene are valuable tools for gene monitoring and linkage analysis. Several studies have demonstrated the four commonly utilized short tandem repeats (STRs), three located in intron 40 and one in the promoter region of the VWF gene, to be highly informative for this task. Our objective was t o develop a rapid, automated method to simultaneously analyze these four STRs for VWF gene tracking. Amplification of the four loci is achieved in a single multiplex fluorescent PCR which is then analyzed in the same run by capillary electrophoresis. Data processing with GeneScan and Genotyper software has simplified management and tabulation of the resulting haplotypes. Analysis of the VWF gene in DNA from 102 individuals (204 chromosomes) revealed that the three STRs within intron 40 showed significant linkage disequilibrium against each other but not against the VWP locus. Moreover, the combination of the four markers offers a high heterozygosity rate (>99%) that improves tracing VWF gene inheritance. In conclusion, the automated fluorescent capillary electrophoresis method presented here is an extremely rapid, simple and highly informative technique for association studies between VWD and the VWF gene in addition to genetic counseling and prenatal diagnosis by precise linkage analysis in VWD-affected families.

Factor VII activado recombinante en la hemorragia masiva / Factor VII activated recombinant in massive hemorrhage

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