Thesis (Ph. D.)--University of Iowa, 2009. / Thesis supervisors: Kai Wang, Trudy Burns. Includes bibliographical references (leaves 132-136).

published_or_final_version / Pathology / Master / Master of Medical Sciences

von Willebrand Disease (VWD) is the most common inherited bleeding disorder in humans, resulting from quantitative or qualitative deficiencies of von Willebrand factor (VWF). Type 3 VWD is the rarest and most severe form of the disease. This thesis characterizes the phenotype-genotype correlations of a cohort of Canadian type 3 VWD patients and their family members. Three main findings are highlighted: 1) 50% of families showed evidence of co-dominant inheritance as opposed to recessive, 2) 42% of mutations identified were located in the VWF propeptide region (VWFpp), 3) index cases (IC) with mutations in the VWFpp had a more severe bleeding diatheses than IC with mutations elsewhere. We investigated two of the identified VWFpp mutations (ex4-5del and Cys633Arg) to elucidate their molecular mechanisms using two cellular models. Patient-derived blood outgrowth endothelial cells (BOEC) are ideal for studying the underlying molecular mechanism of VWF mutations as they represent the native vascular endothelium. BOEC were isolated from type 3 VWD IC and family members with the mutations of interest. A heterologous cellular system was also used to study the VWF mutations in vitro. The VWFpp mutations caused impaired VWF secretion, defective multimerization, qualitative and quantitative defects in Weibel-Palade body (WPB) formation, and resulted in VWF retention within the endoplasmic reticulum. We attempted to restore secretion and multimerization by co-transfecting each mutant with the wild-type VWF propeptide (VWFpp), which was unsuccessful. Additionally, we investigated a third mutation, c.8419_8422dupTCCC, which is unique to the Canadian VWD population and is found at a high frequency in a specific geographic population. While we hypothesized that this mutation would disrupt dimerization due to its location in the C-terminal cysteine knot (CK) domain of VWF we did not find this to be true. The results presented within this thesis provide new insight into the genetics and pathobiology of type 3 VWD, the functional contribution of the VWFpp to type 3 VWD and highlight the utility of BOEC as a cellular model for evaluating the pathogenic mechanisms of VWF mutations. / Thesis (Ph.D, Pathology & Molecular Medicine) -- Queen's University, 2013-10-17 21:15:37.685

von Willebrand disease (VWD) is the most common autosomal bleeding disorder. It is divided into type 1, 2 and 3. Type 2 VWD shows qualitative defects in VWF and is further sub-classified into type 2A, 2B, 2M and 2N, each having different functional defects in VWF. Most of the associated mutations are located at the exons in VWF which encode for the affected functional domains. Diagnosis of VWD is currently based on history and phenotypic tests, which can be difficult often times. Therefore, molecular diagnosis of type 2 VWD is an attractive alternative. There are only a few genotypic characterisation studies of type 2 VWD in Chinese. This study aims to provide genetic data of type 2 VWD in Hong Kong. Archive DNA samples of 21non-type 2N type 2 VWD patients (Group 1), 15 type 2N/mild haemophilia A (HA) patients (Group2) and 35 control subjects were recruited. VWF exon 27, 28 and exon 18, 19, 20, 23, 24 were Sanger sequenced in Group 1 and Group 2 subjects, respectively. All seven exons were sequenced in the control subjects. Seven of 21 Group 1 subjects were found to have pathogenic mutation sin exon 28, with 2being novel. Only 1 Group 2 subject was found to be heterozygous for a novel non-synonymous variation at exon 23, the significance of which could not be ascertained. Sixteen benign polymorphisms were detected from exons sequenced in patients and controls. The low pathogenic mutation detection rate may suggest that the pattern of mutation in Chinese is different from other populations. The possibility of misdiagnosis in a proportion of these patients cannot be excluded in view of the known difficulty in patient ascertainment in VWD and the limited phenotypic diagnostic tools available in Hong Kong. Further studies of other exons are indicated to document the mutation spectrum of type 2 VWD in our Chinese population. RNA work and functional studies are required to fully characterise novel sequence variations found. High throughput mutation detection platforms and better phenotypic characterisation will facilitate the introduction of VWD genotyping into routine clinical diagnostics. / published_or_final_version / Pathology / Master / Master of Medical Sciences

Von Willebrand Disease (VWD) is the most common bleeding disorder. In addition to known major genes, genetic modifiers, such as ABO blood group, affect quantitative outcome measures for VWD. The data consist of an 854-member Amish pedigree with established linkage of VWD to a locus within the Von Willebrand Factor (VWF) gene on chromosome 12. The DNA sequence of the causative mutation is known. Phenotypic information and genotypic data consisting of VWF mutation status and a genome screen of markers are available for 385 pedigree members. Genetic modifiers of the VWF mutation are investigated using known and new conditional linkage methods that search for modifier genes of a major gene with known mutation. The MCMC-based program LOKI was used to conduct multipoint linkage analysis of VWD outcome measures while controlling for the VWF mutation. Adjustment for the mutation did not eliminate the linkage signal on chromosome 12 in the same location as the VWF mutation. Evidence for QTLs was also found on six other chromosomes. Smod, a score statistic that detects evidence of a genetic modifier conditional on linkage to a major gene, was developed for sib pair data. To limit the modifier gene main effect, Smod was developed so that variance due to the modifier locus is bounded above by the variance of the interaction between major gene and modifier gene. The performance of Smod was compared to other published score statistics. Power to detect linkage to the modifier locus depended on major gene and modifier gene risk allele frequencies, relative contribution of the major gene main effect to the interaction effect, and the upper bound on the modifier gene main effect. The Amish pedigree was broken up into sib pair data and analyzed using Smod and other score statistics. Using these statistics, the strongest evidence for QTLs for VWD was also found on chromosome 12 in the region of the VWF mutation. Combined with the LOKI results, further analysis will help determine if intragenic modification is occurring or if linkage disequilibrium between the mutation and analyzed markers is driving results.

Von Willebrand factor (VWF) promotes platelet adhesion and aggregation at sites of vascular damage. This function is directly related to the multimer size of VWF. The VWF-specific metalloprotease ADAMTS13 decreases VWF multimer size by cleaving at Y1605-M1606 in the VWF A2 domain. This thesis examined the sensitivity of ADAMTS13 cleavage to mutagenesis of the full-length multimerized VWF substrate, and a small VWF A2 domain fragment, VWF115. The ADAMTS13 cleavage site at Y1605-M1606 was mutated with the most severe loss of cleavage observed in Y1605A/M1606A. In addition, 4 single nucleotide polymorphisms were examined, with D1472H, Q1571H, P1601T proteins all showing increased resistance to cleavage. In contrast, G1643S has enhanced cleavage in the full-length VWF substrate but shows cleavage resistance in VWF115. Three von Willebrand disease mutations were also examined. In patients, R1597W has enhanced ADAMTS13 cleavage and a loss of high molecular weight multimers, while R1205H has enhanced protein clearance resulting in very low VWF levels and Y1584C patients have moderately low VWF levels. R1597W has enhanced cleavage of full-length VWF, while a slight cleavage increase is observed in VWF115 for Y1584C, and no change is seen with R1205H. The VWF mutations R1597W, Y1605A/M1606A, R1205H and Y1584C were further examined in the VWF knockout mouse using recombinant VWF protein infusion and hydrodynamic delivery of VWF cDNA to determine the effects these mutations produce on VWF antigen levels, multimer structure, secretion, clearance and function in a thrombotic injury model. All four mutations had different pathogenic mechanisms. R1597W showed accelerated clearance with loss of multimer structure, and greatly increased time to thrombotic occlusion. Y1605A/M1606A showed accelerated clearance with normal or supranormal multimer structure, a loss of thrombotic occlusion but increased platelet accumulation. Y1584C showed no change in protein clearance, with decreased VWF antigen level, reduced multimer structure, and reduced thrombotic potential. R1205H demonstrated a synthetic defect in vitro and in vivo increased clearance with a decrease in VWF antigen levels and normal multimer structure and a variable thrombotic potential. These results validate the use of the genetically-modified VWF knockout mouse model for evaluating the pathogenic mechanisms of putative VWF mutations. / Thesis (Ph.D, Pathology & Molecular Medicine) -- Queen's University, 2010-07-28 10:24:40.654

Diss. (sammanfattning) Stockholm : Karol. inst., 2003. / Härtill 6 uppsatser.

von Willebrand factor (VWF) protein acts in the intrinsic coagulation pathway by stabilizing FVIII from proteolytic clearance and at the site of injury, by promoting the adhesion and aggregation of platelets to the exposed subendothelial wall. von Willebrand disease (VWD) results from quantitative and qualitative deficiencies in VWF protein. The variability expressivity in phenotype presentations is in partly caused by the action of modifier genes. Zebrafish has been used as hemostasis animal model. However, it has not been used to evaluate VWD. Here, we report the development of a heterozygote VWF mutant zebrafish using the genome editing CRISPR/Cas9 system to screen for modifier genes involved in VWD. We designed CRISPR oligonucleotides and inserted them into pT7-gRNa plasmid. We then prepared VWF gRNA along with the endonuclease Cas9 RNA from Cas9 plasmid. We injected these two RNAs into 1-4 cell-stage zebrafish embryos and induced a mutation in VWF exon 29 of the zebrafish with a mutagenesis rate of 16.6% (3/18 adult fish). Also, we observed a germline transmission with an efficiency rate of 5.5% (1/18 adult fish). We obtained a deletion in exon 29 which should result in truncated VWF protein.

A doença de von Willebrand (DvW) é uma coagulopatia hereditária, causada por defeitos qualitativos ou quantitativos do fator de von Willebrand. O tratamento e a prevenção das intercorrências da DvW são bastante dispendiosos e, em geral, se baseiam na administração de concentrado de Fator VIII/FvW (CFVIII/FvW) e/ou da Desmopressina (DDAVP). Em muitas situações, o DDAVP é um tratamento eficaz que não expõe os pacientes aos riscos de contaminação viral e apresenta custo inferior quando comparado ao CFVIII/FvW. No entanto, a dificuldade de diagnóstico e classificação da DvW, bem como o baixo número de pacientes que se submetem ao teste para avaliação da resposta ao DDAVP, restringem a indicação do DDAVP como alternativa terapêutica para esses pacientes. O objetivo deste estudo foi avaliar retrospectivamente a indicação, o uso e o custo dos medicamentos no tratamento de pacientes com DvW com DDAVP e CFVIII/FvW no Hemocentro de Belo Horizonte no período entre 2011 a 2013. Este estudo incluiu 124 (24,22%) pacientes com DvW atendidos no hemocentro. Em 18 pacientes (14,52%) o diagnóstico de DvW não pode ser confirmado. Doze pacientes (9,68%) não puderam ser classificados e 73 foram classificados como tipo 1, 19 como tipo 2 e 2 pacientes como tipo 3. Oitenta e um pacientes fizeram o teste de DDAVP, sendo que 87,65% foram considerados responsivos. Nos pacientes tipo 1, a taxa de resposta ao DDAVP foi de 92%. Quase 32% dos pacientes tipo 1 não realizaram o teste. No período avaliado, foram utilizadas 3.794mcg de DDAVP (R$13.165,18) e 1.582.250 UI de CFVIII/FvW (R$1.075.930,00). Vinte por cento dos pacientes responsivos ao DDAVP utilizaram CFVIII/FvW em indicações onde o DDAVP poderia ter sido considerado (69.200UI de CFVIII/FvW versus 131 ampolas de DDAVP). Nos pacientes potencialmente responsivos ao DDAVP 108.700UI de CFVIII/FvW (R$73.916,00) poderiam ter sido substituídas por 247 ampolas de DDAVP (R$3.428,36). A escolha do DDAVP nessas situações poderia representar uma economia de 95,7% do valor gasto no tratamento do grupo de 27 pacientes responsivos e potencialmente responsivos ao DDAVP e 10,6% do valor total gasto para todo o tratamento dos pacientes no período do estudo. Estudos mais complexos de farmacoeconomia serão necessários para avaliar a magnitude da economia gerada com esse uso. O presente estudo mostrou que o DDAVP é uma alternativa terapêutica de menor custo, cuja indicação e utilização podem ser ampliadas no tratamento dos pacientes com DvW. Dessa maneira, a implementação de estratégias visando melhorar o diagnóstico, a classificação da doença, o acesso à testagem quanto à resposta ao DDAVP, bem como a conscientização dos profissionais de saúde e pacientes, quanto ao custo e segurança do DDAVP podem contribuir para o uso racional dos recursos destinados a essa parcela da população. / Von Willebrand disease (VWD) is a hereditary coagulopathy caused by qualitative or quantitative defects on von Willebrand factor. The treatment and the prevention of VWD complications is quite expensive and is generally based on the administration of vWF:FVIII Concentrates and/or Desmopressin (DDAVP). In many situations, DDAVP is an effective treatment that does not expose patients to viral contamination risks and presents a lower cost when compared to vWF:FVIII concentrates. However, the difficulty of diagnosis and classification of VWD, as well as the low number of patients tested to their responsiveness to DDAVP, restrict the use of DDAVP as an alternative treatment for these patients. The aim of this study was to evaluate retrospectively the clinical indications, the use and the cost of treatment of VWD patients with DDAVP and vWF:FVIII concentrates in the Blood Center of Belo Horizonte between 2011 and 2013. This study enrolled 124 (24.22%) VWD patients attended at the Blood Center.For18 (14.52%) patients, the diagnosis of VWD could not be confirmed. Twelve patients (9.68%) could not be classified and 73patients were classified as type 1, 19 as type 2 and 2 as type 3. Eighty-one patients were tested for DDAVP response and 87.65% (n=71) were considered responsive for the treatment. For type 1 VWD patients, the response rate to DDAVP was 92%. Almost 32% of type 1 VWD patients were not tested. In the period evaluated, 3,794mcg of DDAVP (R$ 13,165.18) and 1,582,250 IU of vWF:FVIII concentrates (R$ 1,075,930.00) were used. Between the cases with clinical indication of DDAVP use, 20% patients used vWF:FVIII concentrates (69.200UI of vWF:FVIII versus 131ampoules of DDAVP). In patients with good responsive to DDAVP, 108,700 IU of vWF:FVIII concentrates used (R$ 73,916.00) could be replaced by 247 ampoules of DDAVP (R$ 3,428.36). The choice of DDAVP in these situations could represent an economy of 95.7% of the value spent on the treatment of the 27 responsive and potentially responsive patients to DDAVP and 10.6% of the total value spent for the entire treatment of patients in the study period. More detailed studies of pharmacoeconomics are necessary to assess the magnitude of the economy generated by the use of DDAVP. This study demonstrated that DDAVP is a lower cost therapeutic alternative whose indication and use can be enhanced in the treatment of VWD patients. In this context, adoption of strategies to improve the differential diagnosis, expand the DDAVP responsiveness test, and aware health professionals and patients about the costs and safety use of DDAVP, could contribute to the rational use of resources designated to treatment of VWD.

La Malaltia de von Willebrand (VWD) és la coagulopatia congènita més freqüent a la població general. Consisteix en una diàtesi hemorràgica causada per una deficiència qualitativa i/o quantitativa del factor de von Willebrand (VWF) que es transmet amb caràcter autosòmic dominant o, menys freqüentment, recessiu. El VWF és una glicoproteïna adhesiva present en plaquetes, cèl•lules endotelials i megacariòcits que té diferents funcions donat que participa en l’hemostàsia primària i col•labora al mateix temps en la secundària. És un mediador de l’adhesió de les plaquetes al subendotel•li en el lloc de la lesió vascular i transporta al FVIII, al que protegeix de la degradació proteolítica prematura. El gen del VWF (VWF) s’extén unes 178 kilobases en el genoma i conté un total de 52 exons, sent un dels gens més grans i complexos descrits en humans. Addicionalment existeixen una sèrie de factors que dificulten de manera considerable la caracterització molecular de la VWD i que han fet que la seqüenciació directa no s’hagi considerat el mètode de referència per al seu diagnòstic. En primer lloc, el VWF és un gen altament polimòrfic i, fins al moment, s’hi han descrit 102 SNPs (Build 132) en regió codificant, el que pot dificultar la identificació de les mutacions i, en segon lloc, existeix un pseudogèn parcial al cromosoma 22 d’aproximadament 30 kb molt homòleg (>96%) als exons 23-34 del VWF. Amb l’objectiu de facilitar l’anàlisi genètic de la VWD, s’ha dissenyat un procediment simplificat basat en la seqüenciació completa del gen, que s’ha utilitzat per identificar la mutació en un total de 40 famílies i demostra la seva validesa com a mètode rutinari de diagnòstic molecular. Amb l’aplicació d’aquest mètode s’han identificat un total de 58 mutacions (41 diferents), 19 de las quals no s’havien descrit prèviament a la literatura. Entre els diferents tipus de mutació responsables de la VWD, aquelles que modifiquen la regió codificant del gen tenen un clar efecte deleteri, però les conseqüències de les mutacions que afecten potencialment l’splicing (PSSM) són menys evidents. Amb l’objectiu d’estudiar l’efecte d’aquestes mutacions s’ha desenvolupat un mètode per a la seqüenciació completa del cDNA del VWF en leucòcits i plaquetes que ens ha permès revelar l’efecte de diverses PSSM. L’aparició de les plataformes de seqüenciació de nova generació (NGS), que són fins 200 vegades més ràpides i econòmiques que la seqüenciació tradicional, ha plantejat nous reptes en el diagnòstic molecular de les malalties hereditàries. Per això s’ha desenvolupat una nova estratègia d’amplificació del gen en un total de 14 PCRs llargues i hem adaptat el procediment desenvolupat prèviament per a la seqüenciació completa del VWF a les noves plataformes de NGS. Aquestes estratègies permetran l’anàlisi simultània d’un gran nombre de mostres de pacients i familiars de manera més ràpida i econòmica que per seqüenciació tradicional. Amb l’objectiu de recopilar tota la informació generada a partir del diagnòstic molecular dels pacients amb VWD i fer-la accessible, hem dissenyat un nou apartat dins d’Hemobase (registre de mutacions per a les Hemofílies A i B) dedicat a la VWD (www.vwf.hemobase.com). Aquesta pàgina d’accés lliure per Internet, conté un registre de les mutacions identificades en pacients amb VWD després de la seqüenciació directa del VWF. El registre permet realitzar cerques, relacionar qualsevol mutació amb la base de dades internacional i accedir directament a les publicacions corresponents. Es pretén que l’estudi molecular dels pacients permeti una millor comprensió dels mecanismes implicats en la fisiopatologia de la malaltia i ofereixi una visió més àmplia de l’epidemiologia molecular a la nostra població. / Von Willebrand Disease (VWD) is the most frequent congenital coagulopathy in the general population. It has been proved to be particularly complex due to a series of factors that make difficult the molecular diagnostic of the disease: the von Willebrand Factor gene (VWF) is large and complex; it is very polymorphic; there is a partial pseudogene in chromosome 22 highly homologous (>96%) to a region of the VWF; and the existence of other genes implied in the disease cannot be discarded. All this set of difficulties causes that the molecular study of the VWD remains confined to basic investigation and the application to the clinical routine has been considerably delayed. With the aim to facilitate the genetic study of the VWD, we designed and optimized a procedure for direct sequencing of the VWF, that allowed us to study 40 families identifying 58 mutations (41 different), 19 of which were new. Among the different types of mutation that cause VWD, those affecting the coding region have frequently a clear deleterious effect; however, the consequences of the potential splice site mutations (PSSM) are less predictable. A method for the complete sequencing of the VWF cDNA in leukocytes and platelets has been developed allowing the elucidation of the effect of several PSSM studied. Next Generation Sequencing (NGS) platforms are faster and cheaper that the traditional sequencing. In order to take advantage of this new technology, we have developed an optimized strategy for the amplification of the VWF by LR-PCRs and we have tailored the previously developed short PCR procedure. The objective is to achieve high performance in the molecular characterization of VWD patients and relatives and to establish the basis for a large-scale molecular study approach. Finally, a database of the mutations identified, responsible for the pathology (www.vwf.hemobase.com), has been established in order to correlate molecular and clinical parameters. The development of suitable tools for the molecular diagnosis of VWD will significantly facilitate the clinical diagnosis and will guide the clinician towards the better therapeutic option.