61 results found
Agarwala R, Millar CM, Campbell JP, 2020, Haemostatic disorders in pregnancy, Bja Education, Vol: 20, Pages: 150-157, ISSN: 2058-5349
Bury L, Megy K, Stephens JC, et al., 2019, Next-generation sequencing for the diagnosis of MYH9-RD: Predicting pathogenic variants, HUMAN MUTATION, Vol: 41, Pages: 277-290, ISSN: 1059-7794
Shovlin C, Millar C, Droege F, et al., 2019, Safety of direct oral anticoagulants in patients with hereditary hemorrhagic telangiectasia, Orphanet Journal of Rare Diseases, Vol: 14, ISSN: 1750-1172
Background: Hereditary haemorrhagic telangiectasia (HHT) is a rare vascular dysplasia resulting in visceral arteriovenous malformations and smaller mucocutaneous telangiectasia. Most patients experience recurrent nosebleeds and become anaemic without iron supplementation. However, thousands may require anticoagulation for conditions such as venous thromboembolismand/or atrial fibrillation. Over decades,tolerance data has been publishedfor almost 200HHT-affected usersof warfarinand heparins, but there are no publisheddata forthe newer direct oralanticoagulants(DOACs)in HHT. Methods: To provide such data, aretrospective audit was conducted across the eight HHT centres of the European Reference Network for Rare Vascular Disorders (VASCERN),in Denmark, France, Germany, Italy, Netherlands and UK. Results: Although HHT Centreshad not specifically recommended the use of DOACs, 32treatment episodes had been initiated by other cliniciansin 28patients reviewed at the centres, at median age 65years(range 30-84). Indications were for atrial fibrillation (16 treatment episodes) and venous thromboembolism (16 episodes).The 32 treatment episodes used Apixaban (n=15), Rivaroxaban (n=14), and Dabigatran (n=3). HHT nosebleeds increased in severity in 24/32 treatment episodes (75%), leading to treatment discontinuation in 11 (34.4%). Treatment discontinuation was required for 4/15(26.7%) Apixabanepisodes and 7/14 (50%)Rivaroxaban episodes.By a 4 point scale of increasing severity,there was a trend for Rivaroxaban to be associated with a greaterbleeding riskboth including and excluding patients who had used more than one agent (age-adjusted coefficients 0.61 (95% confidence intervals 0.11, 1.20) and 0.74 (95% confidence intervals 0.12, 1.36) respectively. Associationswere maintained after adjustment for genderand treatment indication. Extreme haemorrhagic responses, worse thananything
van Oorschot R, Marneth AE, Bergevoet SM, et al., 2019, Inherited missense variants that affect GFI1B function do not necessarily cause bleeding diatheses, HAEMATOLOGICA, Vol: 104, Pages: E260-E264, ISSN: 0390-6078
Wei W, Tuna S, Keogh MJ, et al., 2019, Germline selection shapes human mitochondrial DNA diversity, Science, Vol: 364, ISSN: 0036-8075
INTRODUCTIONOnly 2.4% of the 16.5-kb mitochondrial DNA (mtDNA) genome shows homoplasmic variation at >1% frequency in humans. Migration patterns have contributed to geographic differences in the frequency of common genetic variants, but population genetic evidence indicates that selection shapes the evolving mtDNA phylogeny. The mechanism and timing of this process are not clear.Unlike the nuclear genome, mtDNA is maternally transmitted and there are many copies in each cell. Initially, a new genetic variant affects only a proportion of the mtDNA (heteroplasmy). During female germ cell development, a reduction in the amount of mtDNA per cell causes a “genetic bottleneck,” which leads to rapid segregation of mtDNA molecules and different levels of heteroplasmy between siblings. Although heteroplasmy is primarily governed by random genetic drift, there is evidence of selection occurring during this process in animals. Yet it has been difficult to demonstrate this convincingly in humans.RATIONALETo determine whether there is selection for or against heteroplasmic mtDNA variants during transmission, we studied 12,975 whole-genome sequences, including 1526 mother–offspring pairs of which 45.1% had heteroplasmy affecting >1% of mtDNA molecules. Harnessing both the mtDNA and nuclear genome sequences, we then determined whether the nuclear genetic background influenced mtDNA heteroplasmy, validating our findings in another 40,325 individuals.RESULTSPreviously unknown mtDNA variants were less likely to be inherited than known variants, in which the level of heteroplasmy tended to increase on transmission. Variants in the ribosomal RNA genes were less likely to be transmitted, whereas variants in the noncoding displacement (D)–loop were more likely to be transmitted. MtDNA variants predicted to affect the protein sequence tended to have lower heteroplasmy levels than synonymous variants. In 12,975 individuals, we identified a correlation between
Ito Y, Carss KJ, Duarte ST, et al., 2018, De Novo truncating mutations in WASF1 cause intellectual disability with seizures, American Journal of Human Genetics, Vol: 103, Pages: 144-153, ISSN: 0002-9297
Next-generation sequencing has been invaluable in the elucidation of the genetic etiology of many subtypes of intellectual disability in recent years. Here, using exome sequencing and whole-genome sequencing, we identified three de novo truncating mutations in WAS protein family member 1 (WASF1) in five unrelated individuals with moderate to profound intellectual disability with autistic features and seizures. WASF1, also known as WAVE1, is part of the WAVE complex and acts as a mediator between Rac-GTPase and actin to induce actin polymerization. The three mutations connected by Matchmaker Exchange were c.1516C>T (p.Arg506Ter), which occurs in three unrelated individuals, c.1558C>T (p.Gln520Ter), and c.1482delinsGCCAGG (p.Ile494MetfsTer23). All three variants are predicted to partially or fully disrupt the C-terminal actin-binding WCA domain. Functional studies using fibroblast cells from two affected individuals with the c.1516C>T mutation showed a truncated WASF1 and a defect in actin remodeling. This study provides evidence that de novo heterozygous mutations in WASF1 cause a rare form of intellectual disability.
Lane DA, Lynch CJ, Millar C, et al., 2017, A common mechanism by which type 2A von Willebrand Disease mutations enhance ADAMTS13 proteolysis revealed with a von Willebrand Factor A2 domain FRET construct, PLoS ONE, Vol: 12, ISSN: 1932-6203
Rheological forces in the blood trigger the unfolding of von Willebrand factor (VWF) and its A2 domain, exposing the scissile bond for proteolysis by ADAMTS13. Under quiescent conditions, the scissile bond is hidden by the folded structure due to the stabilisation provided by the structural specialisations of the VWF A2 domain, a vicinal disulphide bond, a calcium binding site and a N1574-glycan.The reduced circulating high MW multimers of VWF in patients with type 2A von Willebrand disease (VWD) may be associated with mutations within the VWF A2 domain and this is attributed to enhanced ADAMTS13 proteolysis. We investigated 11 VWF A2 domain variants identified in patients with type 2A VWD. In recombinant full-length VWF, enhanced ADAMTS13 proteolysis was detected for all of the expressed variants in the presence of urea-induced denaturation. A subset of the FLVWF variants displayed enhanced proteolysis in the absence of urea. The mechanism of enhancement was investigated using a novel VWF A2 domain FRET construct. In the absence of induced unfolding, 7/8 of the expressed mutants exhibited a disrupted domain fold, causing spatial separation of the N- and C- termini. Three of the type 2A mutants were not secreted when studied within the VWF A2 domain FRET construct. Urea denaturation revealed for all 8 secreted mutants reduced unfolding cooperativity and stability of the VWF A2 domain. As folding stability was progressively disrupted, proteolysis by ADAMTS13 increased. Due to the range of folding stabilities and wide distribution of VWF A2 domain mutations studied, we conclude that these mutations disrupt regulated folding of the VWF A2 domain. They enhance unfolding by inducing separation of N- and C-termini, thereby promoting a more open conformation that reveals its binding sites for ADAMTS13 and the scissile bond.
Westbury SK, Canault M, Greene D, et al., 2017, Expanded repertoire of RASGRP2 variants responsible for platelet dysfunction and severe bleeding, Blood, Vol: 130, Pages: 1026-1030, ISSN: 1528-0020
Heritable platelet function disorders (PFDs) are genetically heterogeneous and poorly characterised. Pathogenic variants in RASGRP2, which encodes calcium and diacylglycerol-regulated guanine exchange factor I (CalDAG-GEFI), have been reported previously in three pedigrees with bleeding and reduced platelet aggregation responses. To better define the phenotype associated with pathogenic RASGRP2 variants, we compared high-throughput sequencing and phenotype data from 2,042 cases in pedigrees with unexplained bleeding or platelet disorders to data from 5,422 controls. Eleven cases harboured 11 different, previously unreported RASGRP2 variants that were biallelic and likely pathogenic. The variants included five high-impact variants predicted to prevent CalDAG-GEFI expression and six missense variants affecting the CalDAG-GEFI CDC25 domain, which mediates Rap1 activation during platelet inside-out αIIbβ3 signalling. Cases with biallelic RASGRP2 variants had abnormal mucocutaneous, surgical and dental bleeding from childhood, requiring at least one blood or platelet transfusion in 78% of cases. Platelets displayed reduced aggregation in response to ADP and epinephrine, but variable aggregation defects with other agonists. There were no other consistent clinical or laboratory features. These data enable definition of human CalDAG-GEFI deficiency as a non-syndromic, recessive PFD associated with a moderate or severe bleeding phenotype and complex defects in platelet aggregation.
Millar CM, Laffan MA, 2017, Corrigendum: Drug therapy in anticoagulation: which drug for which patient?, Clinical Medicine, Vol: 17, Pages: 347-349, ISSN: 1470-2118
Millar CM, Laffan MA, 2017, Drug therapy in anticoagulation: which drug for which patient?, CLINICAL MEDICINE, Vol: 17, Pages: 233-244, ISSN: 1470-2118
Four non-vitamin K oral anticoagulants (NOACs) are now licensed and available in the UK, offering unprecedented choices in anticoagulant therapy for clinicians and patients. NOACs have many clear benefits over warfarin, the most striking being the reduction in intracranial haemorrhage. However, a number of uncertainties remain: their efficacy in certain situations, utility of drug assays, significance of drug interactions and management of bleeding. In the absence of any direct comparative trials, it is not clear that any of the NOACs is significantly better than the others in any of the licensed indications. The differential activities, pharmacokinetics, metabolism, excretion and side effects of the agents should be considered when selecting the most appropriate anticoagulant. In this article, we discuss how, with careful selection for the relevant indication, NOACs can simplify therapy while improving outcomes. We aim to provide clinicians with the information needed to select the most suitable anticoagulant drug for an individual patient in a given situation.
Batty P, Austin SK, Khair K, et al., 2017, Treatment burden, haemostatic strategies and real world inhibitor screening practice in non-severe haemophilia A, British Journal of Haematology, Vol: 176, Pages: 796-804, ISSN: 1365-2141
Inhibitor formation in non-severe haemophilia A is a life-long risk and associated with morbidity and mortality. There is a paucity of data to understand real-world inhibitor screening practice. We evaluated the treatment burden, haemostatic strategies, F8 genotyping and inhibitor screening practices in non-severe haemophilia A in seven London haemophilia centres. In the 2-year study period, 44% (377/853) patients received at least one haemostatic treatment. Seventy-nine percent of those treated (296/377) received factor VIII (FVIII) concentrate. F8 genotype was known in 88% (331/377) of individuals. Eighteen per cent (58/331) had ‘high-risk’ F8 genotypes. In patients with ‘standard-risk’ F8 genotypes treated on-demand with FVIII concentrate, 51·3% episodes (243/474) were screened within 1 year. However, poor screening compliance was observed after ‘high-risk’ treatment episodes. In patients with ‘standard-risk’ F8 genotypes, 12·3% (28/227) of treatment episodes were screened in the subsequent 6 weeks after surgery or a bleed requiring ≥5 exposure days. Similarly, in the context of ‘high-risk’ F8 genotypes after any FVIII exposure, only 13·6% (12/88) of episodes were screened within 6 weeks. Further study is required to assess optimal practice of inhibitor screening in non-severe haemophilia A to inform subsequent clinical decisions and provide more robust prevalence data to further understand the underlying immunological mechanism.
Smith K, Starke R, Dufton N, et al., 2017, Von Willebrand Factor modulates blood vessel formation and function via Angiopoietin-2, 2nd Joint Meeting of the European-Society-for-Microcirculation (ESM) and European-Vascular-Biology-Organisation (EVBO), Publisher: KARGER, Pages: 38-38, ISSN: 1018-1172
Simeoni I, Stephens JC, Hu F, et al., 2016, A high-throughput sequencing test for diagnosing inherited bleeding, thrombotic, and platelet disorders, Blood, Vol: 127, Pages: 2791-2803, ISSN: 0006-4971
Inherited bleeding, thrombotic and platelet disorders (BPDs) are diseases affecting approximately 300 individuals per million births. With the exception of haemophilia and von Willebrand disease patients, a molecular analysis for patients with a BPD is often unavailable. Many specialised tests are usually required to reach a putative diagnosis and they are typically performed in a step-wise manner to control costs. This approach causes delays and a conclusive molecular diagnosis is often never reached which can compromise treatment and impede rapid identification of affected relatives. To address this unmet diagnostic need, we designed a high-throughput sequencing (HTS) platform targeting 63 genes relevant for BPDs. The platform can call single nucleotide variants (SNVs), short insertions/deletions (indels) and large copy number variants (CNVs), though not inversions, which are subjected to automated filtering for diagnostic prioritization, resulting in an average of 5.34 candidate variants per individual. We sequenced 159 and 137 samples respectively from cases with and without previously known causal variants. Among the latter group, 61 cases had clinical and laboratory phenotypes indicative of a particular molecular etiology while the remainder had ana priorihighly uncertain etiology. All previously detected variants were recapitulated and, when the etiology was suspected but unknown or uncertain, a molecular diagnosis was reached in 56 of 61 and only eight of 76 cases, respectively. The latter category highlights the need for further research into novel causes of BPDs. The ThromboGenomics platform thus provides an affordable DNA-based test to diagnose patients suspected of having a known inherited BPD.
Stritt S, Nurden P, Turro E, et al., 2016, A gain-of-function variant in DIAPH1 causes dominant macrothrombocytopenia and hearing loss, Blood, Vol: 127, Pages: 2903-2914, ISSN: 0006-4971
Macrothrombocytopenia (MTP) is a heterogeneous group of disorders characterized by enlarged and reduced numbers of circulating platelets, sometimes resulting in abnormal bleeding. In most MTP, this phenotype arises because of altered regulation of platelet formation from megakaryocytes (MKs). We report the identification of DIAPH1, which encodes the Rho-effector diaphanous-related formin 1 (DIAPH1), as a candidate gene for MTP using exome sequencing, ontological phenotyping, and similarity regression. We describe 2 unrelated pedigrees with MTP and sensorineural hearing loss that segregate with a DIAPH1 R1213* variant predicting partial truncation of the DIAPH1 diaphanous autoregulatory domain. The R1213* variant was linked to reduced proplatelet formation from cultured MKs, cell clustering, and abnormal cortical filamentous actin. Similarly, in platelets, there was increased filamentous actin and stable microtubules, indicating constitutive activation of DIAPH1. Overexpression of DIAPH1 R1213* in cells reproduced the cytoskeletal alterations found in platelets. Our description of a novel disorder of platelet formation and hearing loss extends the repertoire of DIAPH1-related disease and provides new insight into the autoregulation of DIAPH1 activity.
Escobar MA, Auerswald G, Austin S, et al., 2016, Experience of a new high-purity factor X concentrate in subjects with hereditary factor X deficiency undergoing surgery, Haemophilia, Vol: 22, Pages: 713-720, ISSN: 1351-8216
Introduction: Maintaining haemostasis in surgery is challenging for hereditary rare bleeding disorders in which multi-coagulation-factor concentrates are the only therapeutic option. Hereditary factor X (FX) deficiency affects 1:500 000 to 1:1 000 000 individuals, and no specific replacement FX concentrate has been available. A high-purity, plasma-derived FX concentrate (pdFX) has been developed for patients with hereditary FX deficiency.Aim: Our objective was to assess the safety and efficacy of pdFX in subjects with FX deficiency undergoing surgery.Methods: Subjects with hereditary mild-to-severe FX deficiency (basal plasma FX activity [FX:C] <20 IU/dL) undergoing surgery received pdFX preoperatively to raise FX:C to 70 90 IU/dL and postoperatively to maintain levels >50 IU/dL until the subject was no longer at risk of bleeding due to surgery. Efficacy of pdFX was assessed by blood loss during surgery, requirement for blood transfusion, postoperative bleeding from the surgical or other sites, and changes in haemoglobin levels. Safety was assessed by adverse events (AEs), development of inhibitors, and clinically significant changes in laboratory parameters.Results: Five subjects (aged 14-59 years) underwent 7 surgical procedures (4 major and 3 minor). Treatment duration was 1-15 days. For each procedure, pdFX treatment was assessed as “excellent” in preventing bleeding and achieving haemostasis. No blood transfusions were required, no AEs related to pdFX were observed, and no clinically significant trends were found in any laboratory parameters.Conclusion: These data demonstrate that pdFX is safe and effective as replacement therapy in 5 subjects with mild-to-severe FX deficiency undergoing surgery on 7 occasions.
Turro E, Greene D, Wijgaerts A, et al., 2016, A dominant gain-of-function mutation in universal tyrosine kinase SRC causes thrombocytopenia, myelofibrosis, bleeding, and bone pathologies, Science Translational Medicine, Vol: 8, ISSN: 1946-6234
The Src family kinase (SFK) member SRC is a major target in drug development because it is activated in many human cancers, yet deleterious SRC germline mutations have not been reported. We used genome sequencing and Human Phenotype Ontology patient coding to identify a gain-of-function mutation in SRC causing thrombocytopenia, myelofibrosis, bleeding, and bone pathologies in nine cases. Modeling of the E527K substitution predicts loss of SRC’s self-inhibitory capacity, which we confirmed with in vitro studies showing increased SRC kinase activity and enhanced Tyr419 phosphorylation in COS-7 cells overexpressing E527K SRC. The active form of SRC predominates in patients’ platelets, resulting in enhanced overall tyrosine phosphorylation. Patients with myelofibrosis have hypercellular bone marrow with trilineage dysplasia, and their stem cells grown in vitro form more myeloid and megakaryocyte (MK) colonies than control cells. These MKs generate platelets that are dysmorphic, low in number, highly variable in size, and have a paucity of α-granules. Overactive SRC in patient-derived MKs causes a reduction in proplatelet formation, which can be rescued by SRC kinase inhibition. Stem cells transduced with lentiviral E527K SRC form MKs with a similar defect and enhanced tyrosine phosphorylation levels. Patient-derived and E527K-transduced MKs show Y419 SRC–positive stained podosomes that induce altered actin organization. Expression of mutated src in zebrafish recapitulates patients’ blood and bone phenotypes. Similar studies of platelets and MKs may reveal the mechanism underlying the severe bleeding frequently observed in cancer patients treated with next-generation SFK inhibitors.
Millar C, 2016, Does subclassification of Von Willebrand disease help?, Haemophilia, Vol: 22, Pages: 9-9, ISSN: 1351-8216
Millar C, 2015, Why and how do we classify von Willebrand disease?, Haemophilia, Vol: 21, Pages: 407-410, ISSN: 1365-2516
Escobar M, Auerswald G, Austin S, et al., 2015, Experience of FACTOR X, a New High Purity Factor X Concentrate in Subjects with Factor X Deficiency Undergoing Surgery, HAEMOPHILIA, Vol: 21, Pages: E262-E262, ISSN: 1351-8216
Westbury SK, Turro E, Greene D, et al., 2015, Human phenotype ontology annotation and cluster analysis to unravel genetic defects in 707 cases with unexplained bleeding and platelet disorders, Genome Medicine, Vol: 7, ISSN: 1756-994X
BackgroundHeritable bleeding and platelet disorders (BPD) are heterogeneous and frequently have an unknown genetic basis. The BRIDGE-BPD study aims to discover new causal genes for BPD by high throughput sequencing using cluster analyses based on improved and standardised deep, multi-system phenotyping of cases.MethodsWe report a new approach in which the clinical and laboratory characteristics of BPD cases are annotated with adapted Human Phenotype Ontology (HPO) terms. Cluster analyses are then used to characterise groups of cases with similar HPO terms and variants in the same genes.ResultsWe show that 60% of index cases with heritable BPD enrolled at 10 European or US centres were annotated with HPO terms indicating abnormalities in organ systems other than blood or blood-forming tissues, particularly the nervous system. Cases within pedigrees clustered closely together on the bases of their HPO-coded phenotypes, as did cases sharing several clinically suspected syndromic disorders. Cases subsequently found to harbour variants in ACTN1 also clustered closely, even though diagnosis of this recently described disorder was not possible using only the clinical and laboratory data available to the enrolling clinician.ConclusionsThese findings validate our novel HPO-based phenotype clustering methodology for known BPD, thus providing a new discovery tool for BPD of unknown genetic basis. This approach will also be relevant for other rare diseases with significant genetic heterogeneity.
Mathias M, Yee TT, Dhaif F, et al., 2015, Rare platelet disorder treatment and antibody screening: a North London network audit, 55th Annual Scientific Meeting of the British-Society-for-Haematology, Publisher: WILEY-BLACKWELL, Pages: 50-50, ISSN: 0007-1048
Laffan MA, Lester W, O'Donnell JS, et al., 2014, The diagnosis and management of von Willebrand disease: a United Kingdom Haemophilia Centre Doctors Organization guideline approved by the British Committee for Standards in Haematology, BRITISH JOURNAL OF HAEMATOLOGY, Vol: 167, Pages: 453-465, ISSN: 0007-1048
Escobar M, Millar C, Austin S, et al., 2014, Safety and efficacy of a new high purity factor X concentrate in subjects with factor X deficiency undergoing surgery, HAEMOPHILIA, Vol: 20, Pages: 23-23, ISSN: 1351-8216
Batty P, Rangarajan S, Austin S, et al., 2014, Uptake and timing of inhibitor screening in non-severe hemophilia A: results of a pan-London evaluation, HAEMOPHILIA, Vol: 20, Pages: 48-48, ISSN: 1351-8216
Norton M, Mitchell WB, Alvarez MT, et al., 2014, Safety of a new high purity factor X concentrate in the management of hereditary factor X deficiency, HAEMOPHILIA, Vol: 20, Pages: 53-53, ISSN: 1351-8216
Yu Y, Millar CM, 2014, Measurement of factor IX activity in plasma-derived and recombinant concentrates: insights from thrombin generation and activation-based assays, JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Vol: 12, Pages: 62-70, ISSN: 1538-7933
Starke RD, Paschalaki K, Millar CM, et al., 2014, Von Willebrand factor (VWF) regulates angiogenesis through angiopoietin-2 (Ang-2)-dependent and independent pathways, ANGIOGENESIS, Vol: 17, Pages: 290-290, ISSN: 0969-6970
Mannucci PM, Kempton C, Millar C, et al., 2013, Pharmacokinetics and safety of a novel recombinant human von Willebrand factor manufactured with a plasma-free method: a prospective clinical trial, BLOOD, Vol: 122, Pages: 648-657, ISSN: 0006-4971
Lentaigne CE, Sodhi V, Usman N, et al., 2013, Haemostatic management of pregnant women with platelet function disorders: utility of PFA-100, JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Vol: 11, Pages: 1152-1152, ISSN: 1538-7933
Mangles SE, Paschalaki KE, Starke RD, et al., 2013, Increased fibrinolysis on blood outgrowth endothelial cells (BOEC) from chronic thromboembolic pulmonary hypertension (CTEPH) patients, JOURNAL OF THROMBOSIS AND HAEMOSTASIS, Vol: 11, Pages: 920-921, ISSN: 1538-7933
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