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INTRODUCTION In several countries, molecular diagnosis of haemophilia A (HA) and B (HB) is hampered by a lack of resources for DNA analysis. The advent of next-generation sequencing (NGS) has enabled gene analysis at a reasonable cost. AIM Describe a collaboration between Cuban and Spanish researchers to identify candidate variants and investigate the molecular epidemiology of 106 Cuban haemophilia patients using NGS. PATIENTS/METHODS The molecular analysis protocol included well-established LR-PCR procedures to detect F8 inversions, NGS with a 30-gene panel to sequence F8 and F9, and multiplex ligation-dependent probe amplification to identify large structural variants. RESULTS One-hundred and thirty-one candidate variants were identified along F8, F9, and VWF; 72 were unique and 28 (39%) had not been previously recorded. Putative variants were identified in 105/106 patients. Molecular characterization enabled confirmation and reclassification of: 90 HA (85%), 15 HB (14%), and one type 2N VWD (1%). Null variants leading to non-production of FVIII or FIX were common in severe HA (64%), moderate HA (74%), and severe HB (60%), whereas missense variants were frequent in mild HA (57%) and moderate or mild HB (83%). Additional variants in VWF were identified in 16 patients. CONCLUSION This is the first description of the molecular epidemiology of HA and HB in Cuba. Variants identified in index cases will be of value for local implementation of familial studies and prenatal diagnosis using the molecular approaches available in Cuba. The results of this protocolled genetic study improved the accuracy of the clinical diagnosis and will facilitate management of these patients.

Von Willebrand disease (VWD) is the most frequent inherited bleeding disorder caused by quantitative or qualitative defects of von Willebrand factor (VWF). This protein far from simplicity constitutes a very complex molecular model, remaining unravelled yet many aspects of it, even though the VWF gene (VWF) was cloned already in 1985 and the structure of VWF well defined. VWD diagnosis is difficult to achieve in a significant proportion of patients due to both disease heterogeneity and limitations in existing test processes. The cornerstone of diagnosis relies on interpretation of VWF test results, the presence of clinical manifestations of bleeding, especially mucocutaneous, and (in most cases) a positive family history. However, even with a significant bleeding history, a family history may not be positive due to factors of incomplete penetrance and variable expressivity that affect genetic changes. The laboratory diagnosis of VWD can be difficult, as the disease is heterogeneous and an array of assays is required to describe the phenotype. Basic classification of quantitative (type 1 and 3) and qualitative (type 2 variants) VWD requires determination of VWF antigenic (VWF:Ag) levels and assaying of VWF ristocetin cofactor (VWF:RCo) activity. The latter is required for identifying and subtyping VWD, but the assay is poorly standardized. For that reason, novel VWF activity assays have been developed awaiting more extensive comparison data between different methodologies and requiring validation on larger patient series. The qualitative type 2 VWF deficiency can be further divided into four different subtypes (A, B, M and N) using specific assays that measure other activities or the size distribution of VWF multimers. However, frequently, it may be difficult to correctly classify the VWD phenotype, and genetic analysis is through mutation identification may provide a tool to clarify the disorder.

Inherited antithrombin deficiency, the most severe form of thrombophilia, is predominantly caused by variants in SERPINC1. Few causal structural variants have been described, usually detected by multiplex ligation-dependent probe amplification or cytogenetic arrays, which only define the gain or loss and the approximate size and location. This study has done a complete dissection of the structural variants affecting SERPINC1 of 39 unrelated patients with antithrombin deficiency using multiplex ligation-dependent probe amplification, comparative genome hybridization array, long-range PCR, and whole genome nanopore sequencing. Structural variants, in all cases only affecting one allele, were deleterious and caused a severe type I deficiency. Most defects were deletions affecting exons of SERPINC1 (82.1%), but the whole cohort was heterogeneous, as tandem duplications, deletion of introns, or retrotransposon insertions were also detected. Their size was also variable, ranging from 193 bp to 8 Mb, and in 54% of the cases involved neighboring genes. All but two structural variants had repetitive elements and/or microhomologies in their breakpoints, suggesting a common mechanism of formation. This study also suggested regions recurrently involved in structural variants causing antithrombin deficiency and found three structural variants with a founder effect: the insertion of a retrotransposon, duplication of exon 6, and a 20-gene deletion. Finally, nanopore sequencing was determined to be the most appropriate method to identify and characterize all structural variants at nucleotide level, independently of their size or type., Supported by the National Institute for Health Research (NIHR) for the NIHR BioResource project (grant numbers RG65966 and RG94028), by the Instituto de Salud Carlos III grant; Fondo Europeo de Desarrollo Regional (FEDER) grant PI18/00598; and Fundación Séneca 19873/GERM/15. M.E.d.l.M.-B. has a postdoctoral contract from University of Murcia, Murcia, Spain. C.B.-P. has a Río Hortega fellowship. B.d.l.M.-B. has a postdoctoral fellowship from Fundación Séneca. J.C.-G. has a predoctoral fellowship from the Ministry of Universities FPU19/03662.

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.

Identification of qualitative variants of von Willebrand disease (VWD) can be a diagnostic challenge because of discrepant results obtained in the multiple laboratory tests available for its appropriate classification. We report two cases of infrequent inherited variants of VWD with unclear preliminary results with the test panel available at the time of first consultation and that were finally diagnosed as a VWD type 2A/IID with a c.8318 G C, p.Cys2773Ser mutation and a VWD type 2M with c.4225 T G, p.Val1409Phe mutation, respectively. The description of these two cases highlights that despite the limited diagnostic panel for the evaluation of von Willebrand Factor (VWF) functionality, the multimeric analysis and genetic family studies were fundamental tools to achieve the final diagnosis.

Allele-level HLA compatibility in cord blood transplantation, together with noninherited maternal antigen or NIMA matching, have been associated with better transplant outcomes. The aim of this work is to develop a cost-efficient high-resolution HLA typing strategy based on next-generation sequencing to improve the quality of the Barcelona Cord Blood Bank's inventory, and to investigate the impact of high-resolution HLA typing and NIMA determination on the preferential selection of cord blood for transplantation. In this line, the developed strategy was validated and the HLA-A, -B, -C, -DRB1, and -DQB1 genes of 5000 cord blood units and 2500 of their associated maternal samples were typed. Subsequently, three study groups of 2012 units each were monitored for up to 2 years: (1) units with high-resolution and maternal HLA typing, (2) units with high-resolution but not maternal typing, and (3) units typed at low-resolution for class I and only high-resolution for HLA-DRB1. Despite a trend toward a greater selection of units with high-resolution typing, no significant impact of these variables was observed. These results highlight the need for evidence-based and globally accepted criteria for cord blood selection, together with the necessity to improve the accessibility of clinicians to donor registry's data.

Introduction Type 2N von Willebrand disease (VWD) is characterized by a decreased affinity of von Willebrand factor (VWF) for factor VIII (FVIII). Abnormal binding of FVIII to VWF (VWF:FVIIIB), results in low FVIII plasma levels, which can lead to a misdiagnosis of mild haemophilia A. Accurate diagnosis of type 2N VWD is essential for appropriate genetic counselling and therapy. This disease can be distinguished from haemophilia A by in vitro assays (measurement VWF:FVIIIB activity) and/or genetic analysis. Aim To identify the current challenges in the diagnosis and treatment of this type of VWD and provide an in-depth description of the phenotypes and mutations identified. Results Twenty-eight patients had at least one type 2N mutation, and 13 of these had a type 2N mutation combined with other variations. Three type 2N mutations were detected: p.Arg816Trp, p.Arg854Gln, and p.Arg763Ser. Two of these are the most frequently described mutations worldwide. This mutational spectrum differs from the broad spectrum seen in neighbouring France, where at least eight distinct 2N mutations have been found. In the PCM-EVW-ES cohort, 11 asymptomatic type 2N carriers with borderline FVIII plasma levels would probably have been excluded if the evaluation had been based on clinical and laboratory data only. Likewise, three patients with a severe phenotype would have been classified as homozygous for a 2N mutation if only the phenotype study had been performed. Conclusion The high detection yield and affordability of next-generation sequencing support the use of this technology as a first-line diagnostic tool in this setting.

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.

Diagnosis of von Willebrand disease (VWD) depends on personal and family history of bleeding and confirmatory laboratory testing. Currently available phenotypic tests for VWD contain potential sources for error that may distort results. Despite an exponential growth of information about the von Willebrand factor gene (VWF), the role of molecular diagnosis in VWD is still controversial. Due to the complexity and high cost of conventional molecular analyses, some investigators have recommended limiting this approach to distinguish suspected type 2N VWD from hemophilia A, type 2B from platelet-type VWD, and the exploration of type 3 VWD. New genetic methodologies and approaches are becoming available, but there is still some reluctance for their implementation in VWD diagnosis. This article discusses the pros and cons of molecular testing in VWD considering the experience obtained through the multicenter project “Molecular and Clinical Profile of VWD in Spain (PCM-EVW-ES).”

SummaryThe diagnosis of von Willebrand disease (VWD), the most common inherited bleeding disorder, is characterised by a variable bleeding tendency and heterogeneous laboratory phenotype. The sequencing of the entire VWF coding region has not yet become a routine practice in diagnostic laboratories owing to its high costs. Nevertheless, nextgeneration sequencing (NGS) has emerged as an alternative to overcome this limitation. We aimed to determine the correlation of genotype and phenotype in 92 Portuguese individuals from 60 unrelated families with VWD; therefore, we directly sequenced VWF. We compared the classical Sanger sequencing approach and NGS to assess the value-added effect on the analysis of the mutation distribution in different types of VWD. Sixty-two different VWF mutations were identified, 27 of which had not been previously described. NGS detected 26 additional mutations, contributing to a broad overview of the mutant alleles present in each VWD type. Twenty-nine probands (48.3 %) had two or more mutations; in addition, mutations with pleiotropic effects were detected, and NGS allowed an appropriate classification for seven of them. Furthermore, the differential diagnosis between VWD 2B and platelet type VWD (n = 1), Bernard–Soulier syndrome and VWD 2B (n = 1), and mild haemophilia A and VWD 2N (n = 2) was possible. NGS provided an efficient laboratory workflow for analysing VWF. These findings in our cohort of Portuguese patients support the proposal that improving VWD diagnosis strategies will enhance clinical and laboratory approaches, allowing to establish the most appropriate treatment for each patient.

In families at risk from monogenic diseases affected offspring, it is fundamental the development of a suitable Double Factor Preimplantation Genetic Testing (DF-PGT) method for both single-gene analysis and chromosome complement screening. Aneuploidy is not only a major issue in advanced-maternal-age patients and balanced translocation carriers, but also the aneuploidy rate is extremely high in patients undergoing in vitro fertilization (IVF), even in young donors. To adequate NGS technology to the DF-PGT strategy four different whole genome amplification systems (Sureplex, MALBAC, and two multiple displacement amplification systems-MDA) were tested using TruSight One panel on cell lines and blastocyst trophectoderm biopsies-TE. Embryo cytogenetic status was analyzed by Nexus software. Sureplex and MALBAC DNA products were considered not suitable for PGT diagnosis due to inconsistent and poor results on Trusight one (TSO) panel. Results obtained with both MDA based methods (GEH-MDA and RG-MDA) were appropriate for direct mutation detection by TSO NGS platform. Nevertheless, RG-MDA amplification products showed better coverage and lower ADO rates than GEH-MDA. The present work also demonstrates that the same TSO sequencing data is suitable not only for the direct mutation detection, but also for the indirect mutation detection by linkage analysis of informative SNPs. The present work also demonstrates that Nexus software is competent for the detection of CNV by using with TSO sequencing data from RG-MDA products, allowing for the whole cytogenetic characterization of the embryos. In conclusion, successfully development of an innovative and promising DF-PGT strategy using TSO-NGS technology in TE biopsies, performed in-house in a single laboratory experience, has been done in the present work. Additional studies should be performed before it could be used as a diagnostic alternative in order to validate this approach for the detection of chromosomal aneuploidies.

Essentials The Royal disease (RD) is a form of hemophilia B predicted to be caused by a splicing mutation. We generated an iPSC-based model of the disease allowing mechanistic studies at the RNA level. F9 mRNA analysis in iPSC-derived hepatocyte-like cells showed the predicted abnormal splicing. Mutated F9 mRNA level was very low but we also found traces of wild type transcripts. SummaryBackground The royal disease is a form of hemophilia B (HB) that affected many descendants of Queen Victoria in the 19th and 20th centuries. It was found to be caused by the mutation F9 c.278-3A>G. Objective To generate a physiological cell model of the disease and to study F9 expression at the RNA level. Methods Using fibroblasts from skin biopsies of a previously identified hemophilic patient bearing the F9 c.278-3A>G mutation and his mother, we generated induced pluripotent stem cells (iPSCs). Both the patient's and mother's iPSCs were differentiated into hepatocyte-like cells (HLCs) and their F9 mRNA was analyzed using next-generation sequencing (NGS). Results and Conclusion We demonstrated the previously predicted aberrant splicing of the F9 transcript as a result of an intronic nucleotide substitution leading to a frameshift and the generation of a premature termination codon (PTC). The F9 mRNA level in the patient's HLCs was significantly reduced compared with that of his mother, suggesting that mutated transcripts undergo nonsense-mediated decay (NMD), a cellular mechanism that degrades PTC-containing mRNAs. We also detected small proportions of correctly spliced transcripts in the patient's HLCs, which, combined with genetic variability in splicing and NMD machineries, could partially explain some clinical variability among affected members of the European royal families who had lifespans above the average. This work allowed the demonstration of the pathologic consequences of an intronic mutation in the F9 gene and represents the first bona fide cellular model of HB allowing the study of rare mutations at the RNA level.

SummaryThe diagnosis of von Willebrand disease (VWD) remains difficult in a significant proportion of patients. A Spanish multicentre study investigated a cohort of 556 patients from 330 families who were analysed centrally. VWD was confirmed in 480. Next generation sequencing (NGS) of the whole coding VWF was carried out in all recruited patients, compared with the phenotype, and a final diagnosis established. A total of 238 different VWF mutations were found, 154 were not included in the Leiden Open Variation Database (LOVD). Of the patients, 463 were found to have VWF mutation/s. A good phenotypic/ genotypic association was estimated in 96.5 % of the patients. One hundred seventy-four patients had two or more mutations. Occasionally a predominant phenotype masked the presence of a second abnormality. One hundred sixteen patients presented with mutations that had previously been associated with increased von Willebrand factor (VWF) clearance. RIPA unavailability, central phenotypic results disagreement and difficult distinction between severe type 1 and type 3 VWD prevented a clear diagnosis in 70 patients. The NGS study facilitated an appropriate classification in 63 of them. The remaining seven patients presented with a VWF novel mutation pending further investigation. In five patients with a type 3 and two with a type 2A or 2B phenotype with no mutation, an acquired von Willebrand syndrome (AVWS) was suspected/confirmed. These data seem to support NGS as a first line efficient and faster paradigm in VWD diagnosis.Supplementary Material to this article is available online at www.thrombosis-online.com.

The correct diagnosis and classification of von Willebrand disease (VWD) is difficult because of the variability of its clinical expression and limitations of laboratory methods. However, correctly diagnosing VWD is important for therapy and genetic counselling. A survey related to the referred VWD patients in Spain revealed local diagnostic problems in at least one third of the cases of VWD. Consequently, a Spanish multicenter study was carried out in which a cohort of 556 patients from 330 families was analyzed centrally. VWD was confirmed in 480 patients. Next generation sequencing (NGS) of the whole coding von Willebrand factor gene ( VWF ) was carried out in all recruited patients, compared with the phenotype, and a final diagnosis was established. A total of 238 different VWF mutations were found: 154 were not included in the Leiden Open Variation Database (LOVD). Of the patients, 467 were found to have a VWF mutation/s. A good phenotype/genotype association was estimated in 94.6% of the cases. One hundred and eighty patients had two or more mutations. Occasionally a predominant phenotype masked the presence of a second abnormality. One hundred and sixteen patients presented with mutations that had previously been associated with an increased VWF clearance. Ristocetin induced platelet agglutination (RIPA) unavailability, central phenotypic results disagreement and difficult distinction between severe type 1 and type 3 VWD prevented a clear diagnosis in 74 patients. A local/central disagreement over diagnosis occurred in 42.3% of the whole cohort. The NGS study facilitated an appropriate classification in 60 of them. Based on these results, a proposal for a change in the VWD diagnostic paradigm, suggesting the inclusion of the analysis of VWF at the initial diagnostic process, has been made. An extension of this project to include 400 new VWD patients has begun. A diagnostic strategy has been developed, and a Spanish consensus guideline for optimal treatment of VWD was developed in Spain. Desmopressin (DDAVP) is the treatment of choice in responsive VWD patients. VWF concentrates (VWF/FVIII) are used in individuals unresponsive to DDAVP, when DDAVP is contraindicated, or in VWD types 2B and 3, and for long term management needs (e.g., post major surgery).