von Willebrand disease and quantitative variation in von Willebrand factor

Impact of blood group on survival following critical illness: a single-centre retrospective observational study

Background

Predicting patient outcomes following critical illness is challenging. Recent evidence has suggested that patients with blood group AB are more likely to survive following major cardiac surgery, and this is associated with a reduced number of blood transfusions. However, there are no current data to indicate whether a patient’s blood group affects general intensive care outcomes.

Objective

The objective of this study was to determine if ABO blood group affects survival in intensive care. The primary outcome measure was 90-day mortality with a secondary outcome measure of the percentage of patients receiving a blood transfusion.

Design

Retrospective analysis of electronically collected intensive care data, blood group and transfusion data.

Setting

General intensive care unit (ICU) of a major tertiary hospital with both medical and surgical patients.

Patients

All patients admitted to ICU between 2006 and 2016 who had blood group data available.

Intervention

None.

Measurements and main results

7340 patients were included in the study, blood group AB accounted for 3% (221), A 41% (3008), B 10.6% (775) and O 45.4% (3336). These values are similar to UK averages. Baseline characteristics between the groups were similar. Blood group AB had the greatest survival benefit (blood group AB 90-day survival estimate 76.75, 95% CI 72.89 to 80.61 with the overall estimate 72.07, 95% CI 71.31 to 72.82) (log-rank χ² 16.128, p=0.001). Transfusion requirements were similar in all groups with no significant difference between the percentages of patients transfused (AB 23.1%, A 21.5%, B 18.7%, O 19.9%, Pearson χ² 5.060 p=0.167).

Conclusion

Although this is primarily a hypothesis generating study, intensive care patients with blood group AB appeared to have a higher 90-day survival compared with other blood groups. There was no correlation between blood group and percentage of patients receiving transfusion.

Recombinant factor VIII Fc fusion protein: extended-interval dosing maintains low bleeding rates and correlates with von Willebrand factor levels

BACKGROUND

Routine prophylaxis with replacement factor VIII (FVIII) - the standard of care for severe hemophilia A - often requires frequent intravenous infusions (three or four times weekly). An FVIII molecule with an extended half-life could reduce infusion frequency. The A-LONG study established the safety, efficacy and prolonged pharmacokinetics of recombinant FVIII Fc fusion protein (rFVIIIFc) in previously treated adolescents and adults with severe hemophilia A.

OBJECTIVE

In this post hoc analysis, we investigated the relationship between subjects' prestudy (FVIII) and on-study (rFVIIIFc) regimens.

METHODS

We analyzed two subgroups of subjects: prior prophylaxis and on-study individualized prophylaxis (n = 80), and prior episodic treatment and on-study weekly prophylaxis (n = 16). Subjects' prestudy dosing regimens and bleeding rates were compared with their final rFVIIIFc regimens and annualized bleeding rates (ABRs) in the last 3 months on-study. Dosing regimen simulations based on population pharmacokinetics models for rFVIII and rFVIIIFc were performed.

RESULTS

As compared with their prestudy regimen, 79 of 80 (98.8%) subjects on individualized rFVIIIFc prophylaxis decreased their infusion frequency. Overall ABRs were low, with comparable factor consumption. Longer dosing intervals, including 5-day dosing, were associated with higher baseline von Willebrand factor antigen levels. Simulated dosing regimens predicted a greater proportion of subjects with steady-state FVIII activity trough levels of ≥ 1 IU dL(-1) (1%) with rFVIIIFc than with equivalent rFVIII regimens.

CONCLUSION

These results suggest that patients on rFVIIIFc prophylaxis can reduce their infusion frequency as compared with their prior FVIII regimen while maintaining low bleeding rates, affording more patients trough levels of ≥ 1 IU dL(-1) than with rFVIII products requiring more frequent dosing regimens.

Translational medicine advances in von Willebrand disease

Following the recognition of von Willebrand disease (VWD) in 1926 and the cloning of the gene for von Willebrand factor (VWF) in 1985, significant advances have been made in our fundamental knowledge of both the disease and the protein. Some of this new knowledge has also begun to impact the clinical management of VWD. First, the progressive increase in our understanding of the molecular genetic basis of VWD has resulted in rational applications of molecular testing to complement the current range of phenotypic tests for VWD. These molecular genetic strategies are most effectively directed at the prenatal diagnosis of type 3 VWD and confirmatory testing for types 2B and 2N disease. In contrast, the use of molecular testing to clarify the diagnosis of type 1 VWD is of marginal benefit, at best. In terms of VWD therapies, a new recombinant VWF concentrate has recently completed successful clinical trials and is now awaiting more widespread application. There have even been some preclinical successes with VWF gene transfer although the clinical rationale for this therapeutic strategy needs careful consideration. Much more remains to be learnt about the biology of VWF and further translational advances for the enhancement of VWD care will inevitably be realized.

Von Willebrand disease: an update in the Aland islands

In the past decades von Willebrand disease (vWD) has, in several respects, fallen into the shadow of classical haemophilia due to all problems that have faced those dealing with congenital bleeding disorders, not least regarding blood-borne diseases. The time has come to revisit and refocus on vWD, probably the most common bleeding disorder. Accordingly, a number of Nordic physicians and scientists working in this field organized a meeting on the ferry boat from Stockholm to Mariehamn, in the Aland islands, the home of the index families with this disease, as described by Erik von Willebrand in 1926. The objective of the meeting was to make a comprehensive survey of vWD as seen from the situation in the Nordic countries. In order to achieve all goals some scientists of note from countries outside the Nordic area were invited as well. This paper gives a summary of the symposium, mainly based on the separate papers published in this issue.

von Willebrand disease: clinical and laboratory lessons learned from the large von Willebrand disease studies

During the past 25 years, our knowledge concerning the pathogenesis, diagnostic strategies, and treatment of von Willebrand disease (VWD) has increased significantly. Following the immunological differentiation of factor VIII (FVIII) and von Willebrand factor (VWF) in the 1970s and the cloning of the FVIII and VWF genes in the mid-1980s, substantial progress has been made in our understanding of this, the most common inherited bleeding disorder. We now recognize that VWD represents a range of genetic diseases all with the clinical endpoint of increased mucocutaneous bleeding. The molecular pathology of Type 2 and 3 VWD is now comprehensively documented and involves rare sequence variants at the VWF locus. In contrast, the genetic causation of Type 1 disease remains incompletely defined and in many cases appears to involve genetic determinants in addition to or instead of VWF. The diagnostic triad of a personal history of excessive mucocutaneous bleeding, laboratory tests for VWF that are consistent with VWD, and a family history of the condition remain the keystone to VWD identification. In the laboratory, measurement of VWF antigen and function continue to be the most important diagnostic studies, and while our understanding of the molecular genetic pathology of VWD has advanced considerably in the past decade, genetic testing as a component of diagnosis is limited to certain distinct subtypes of the disorder. Treatment of VWD has been relatively unchanged for the past decade and continues to involve either stimulation of the release of intrinsic VWF with desmopressin or the infusion of VWF concentrates.

Laboratory testing for von Willebrand disease: toward a mechanism-based classification

The heterogeneity of von Willebrand disease reflects the varied roles of von Willebrand factor in coagulation. Significant challenges remain in the detection, classification, and determination of bleeding risk in disorders related to von Willebrand factor. A clearer understanding of the specific disease mechanisms is essential to the development of improved methods for prognosis and management in this and other conditions with abnormalities of the von Willebrand factor system.

How I treat von Willebrand disease

Recent multicenter studies have clarified the molecular basis underlying the different von Willebrand disease (VWD) types, all of which are caused by the deficiency and/or abnormality of von Willebrand factor (VWF). These studies have suggested a unifying pathophysiologic concept. The diagnosis of VWD, remains difficult because its clinical and laboratory phenotype is very heterogeneous and may overlap with normal subjects. Stringent criteria are therefore required for a clinically useful diagnosis. In this paper, we delineate a practical approach to the diagnosis and treatment of VWD. Our approach is based on the critical importance of a standardized bleeding history that has been condensed into a final bleeding score and a few widely available laboratory tests, such as VWF ristocetin cofactor activity, VWF antigen and factor VIII. This approach would help identify those subjects who will probably benefit from a diagnosis of VWD. The next step involves performing a trial infusion with desmopressin in all patients who fail to exhibit an enhanced responsiveness to ristocetin. On the basis of these results and through a series of illustrative examples, the clinician will be able to select the best approach for the optimal management of VWD, according to the patient's characteristics and clinical circumstances.

Selection on cis-regulatory variation at B4galnt2 and its influence on von Willebrand factor in house mice

The RIIIS/J inbred mouse strain is a model for type 1 von Willebrand disease (VWD), a common human bleeding disorder. Low von Willebrand factor (VWF) levels in RIIIS/J are due to a regulatory mutation, Mvwf1, which directs a tissue-specific switch in expression of a glycosyltransferase, B4GALNT2, from intestine to blood vessel. We recently found that Mvwf1 lies on a founder allele common among laboratory mouse strains. To investigate the evolutionary forces operating at B4galnt2, we conducted a survey of DNA sequence polymorphism and microsatellite variation spanning the B4galnt2 gene region in natural Mus musculus domesticus populations. Two divergent haplotypes segregate in these natural populations, one of which corresponds to the RIIIS/J sequence. Different local populations display dramatic differences in the frequency of these haplotypes, and reduced microsatellite variability near B4galnt2 within the RIIIS/J haplotype is consistent with the recent action of natural selection. The level and pattern of DNA sequence polymorphism in the 5′ flanking region of the gene significantly deviates from the neutral expectation and suggests that variation in B4galnt2 expression may be under balancing selection and/or arose from a recently introgressed allele that subsequently increased in frequency due to natural selection. However, coalescent simulations indicate that the heterogeneity in divergence between haplotypes is greater than expected under an introgression model. Analysis of a population where the RIIIS/J haplotype is in high frequency reveals an association between this haplotype, the B4galnt2 tissue-specific switch, and a significant decrease in plasma VWF levels. Given these observations, we propose that low VWF levels may represent a fitness cost that is offset by a yet unknown benefit of the B4galnt2 tissue-specific switch. Similar mechanisms may account for the variability in VWF levels and high prevalence of VWD in other mammals, including humans.

Genetic linkage and association analysis in type 1 von Willebrand disease: results from the Canadian type 1 VWD study

BACKGROUND

von Willebrand disease (VWD) is the most common bleeding disorder known in humans, with type 1 VWD representing the majority of cases. Unlike the other variant forms of VWD, type 1 disease represents a complex genetic trait, influenced by both genetic and environmental factors.

AIM

To evaluate the contribution of the von Willebrand factor (VWF) and ABO blood group loci to the type 1 VWD phenotype, and to assess the potential for locus heterogeneity in this condition, we have performed genetic linkage and association studies on a large, unselected type 1 VWD population.

METHOD

We initially collected samples from 194 Canadian type 1 VWD families for analysis. After the exclusion of families found to have either type 2 or type 3 VWD, and pedigrees with samples from single generations, linkage and association analysis was performed on 155 type 1 VWD families.

RESULTS AND CONCLUSION

The linkage study has shown a low heterogeneity LOD score of 2.13 with the proportion of families linked to the VWF gene estimated to be 0.41. Linkage was not detected to the ABO locus in this type 1 VWD population. In the family-based association test, significant association was found between the type 1 VWD phenotype, the quantitative traits, VWF:Ag, VWF:RCo, and FVIII:C and the ABO 'O' and 'A' alleles and the VWF codon 1584 variant. There was also weak association with the -1185 promoter polymorphism and VWF:Ag, VWF:RCo, and FVIII:C plasma levels. These studies provide further evidence to support the role for genetic loci other than VWF and ABO in the pathogenesis of type 1 VWD.

The discriminant power of bleeding history for the diagnosis of type 1 von Willebrand disease: an international, multicenter study

OBJECTIVE

The aim of this study was the validation of the criteria defining a significant mucocutaneous-bleeding history in type 1 von Willebrand disease (VWD).

SUBJECTS AND METHODS

To avoid selection bias, 42 obligatory carriers (OC) of type 1 VWD were identified from a panel of 42 families with type 1 VWD enrolled by 10 expert centers. OC were identified by the presence of an offspring and another first degree relative with type 1 VWD (affected subjects, AFF). A standardized questionnaire was administered to evaluate hemorrhagic symptoms at the time of first examination, using a bleeding score ranging from 0 (no symptom) to 3 (hospitalization, replacement therapy, blood transfusion). Sensitivity, specificity, diagnostic likelihood ratios, positive and negative predictive values for the diagnosis of type 1 VWD were calculated from the data collected in OC and in 215 controls.

RESULTS

Having at least three hemorrhagic symptoms or a bleeding score of 3 in males and 5 in females was very specific (98.6%) for the bleeding history of type 1 VWD, although less sensitive (69.1%). None of the misclassified OC had life-threatening bleeding episodes after diagnosis.

CONCLUSIONS

We suggest that the use of a standardized questionnaire and bleeding score may be useful for the identification of subjects requiring laboratory evaluation for VWD.

Oral contraceptives and DDAVP nasal spray: patterns of use in managing vWD-associated menorrhagia: a single-institution study

The purpose of this study was to examine patterns of use for oral contraceptive and desmopressin acetate nasal spray, both used in managing menorrhagia in adolescents with von Willebrand disease (vWD). Hospital records of adolescents with documented vWD and menorrhagia were reviewed retrospectively. Subjects with vWD type 1 (n = 36) administered either oral contraceptives (OC) or intranasal desmopressin acetate (DDAVP) and followed from 6 months to 4 years were selected for inclusion. Treatment outcomes were examined with respect to effectiveness and safety. Assessing menstrual blood loss using PBAC scores from pretreatment and treatment periods determined effectiveness. Safety was evaluated by monitoring reported adverse events. No significant differences were identified in treatment effectiveness for controlling menorrhagia in vWD adolescents in the OC and intranasal DDAVP group comparisons: 86% versus 77% (P > 0.05), respectively. When combining both treatment groups, the majority of vWD adolescents, 81% (P > 0.05), experienced alleviation of menorrhagia symptoms. Treatment failures were attributed to either the inability of a regimen to control bleeding or to adverse events, including severe headaches and flushing with DDAVP. Safety outcomes were not significantly greater in vWD patients with menorrhagia when OC were compared with intranasal DDAVP. Both medical approaches, OC and DDAVP nasal spray, used in managing menorrhagia in adolescents with documented type I vWD were well tolerated and showed equivalent effectiveness, and no serious adverse events were reported.

Guidelines for the diagnosis and management of von Willebrand disease in Italy

von Willebrand disease (vWD) is a bleeding disorder caused by quantitative (type 1 and 3) or qualitative (type 2) defects of von Willebrand factor (vWF). The molecular basis of type 2 and 3 vWD are now known and those of type 1 vWD are being understood. Phenotypic diagnosis is based on the measurements of plasma and platelet vWF, of the ability of vWF to interact with platelet receptors and the analysis of the multimeric structure of vWF. Due to the heterogeneity of vWF defects and the variables that interfere with vWF levels, a correct diagnosis of types and subtypes may sometimes be difficult but is very important for therapy. The aim of treatment is to correct the dual defects of haemostasis, i.e. abnormal intrinsic coagulation expressed by low levels of factor VIII (FVIII) and abnormal platelet adhesion. Desmopressin is the treatment of choice in patients with type 1 vWD, who account for approximately 70% of cases, because it corrects FVIII-vWF levels and the prolonged bleeding time (BT) in the majority of these patients. In type 3 and in severe forms of type 1 and 2 vWD patients, desmopressin is not effective and it is necessary to resort to plasma concentrates containing FVIII and vWF. Treated with virucidal methods, these concentrates are effective and safe, but they cannot always correct BT defect. Platelet concentrates or desmopressin can be used as adjunctive treatments when poor correction of BT after plasma concentrate treatment is associated with continued bleeding.

von Willebrand disease: still an intriguing disorder in the era of molecular medicine

von Willebrand disease (vWD) is a single-locus disorder resulting from a deficiency of von Willebrand factor (vWF): a multimeric multifunctional protein involved in platelet adhesion and platelet-to-platelet cohesion in high shear stress vessels, and in protecting from proteolysis and directing circulating factor VIII (FVIII) to the site of injury. vWD is the most frequent bleeding disorder, with an estimated prevalence in the general population of 1%. Almost all these cases are represented by a partial quantitative deficiency of von Willebrand factor (vWF) (type 1 vWD). Type 1 is transmitted as an autosomal dominant trait with an extremely variable penetrance and expressivity. A consensus figure for the prevalence of cases with significant bleeding symptoms, requiring some form of treatment, is approximately 100 cases million-1. Among these cases, more than 70-80% are represented by type 1 and respond to deamino-D-arginine vasopressin (DDAVP; desmopressin) administration. The remaining cases are represented by type 2 vWD (qualitative), some of which require substitutive treatment. Only 3-5 cases million-1 result from a total deficiency of vWF in plasma and platelets because of the recessive inheritance of two defective alleles. These cases may have severe bleeding episodes and may require frequent substitutive treatment. The molecular basis of type 2 (missense mutation in the functional domains of the vWF subunit) and type 3 (nonsense or large deletions) is quite well understood. On the contrary the molecular basis for most type 1 cases remains largely unknown, and many genetic factors (e.g. ABO blood group) and environmental or circumstantial factors (e.g. age, stress, drugs, pregnancy, and inflammation) are superimposed on to the genetic background determined by the vWF gene to produce a continuous spectrum from normality to mild type 1 cases. It is extremely difficult to make a clear distinction between mild type 1 cases and normal people because of the wide 'normal' range of laboratory measurements (e.g. length of bleeding time, and levels of vWF and FVIII) and of bleeding symptoms. Molecular testing is useless in this situation, and only good history-taking and repeated laboratory testing of vWF-related measurements in the propositus and his/her family members can help in clinical diagnosis, albeit imprecisely. This difficult task is the main focus of this review which is aimed at alerting the physician toward a balanced approach that should take into consideration both the risk of over- and under-diagnosis of this frequent disorder and the unavoidable production of a number of false positive and false negative cases.

Advances in the genetics and treatment of von Willebrand disease

von Willebrand disease (VWD) is a bleeding disorder caused by quantitative (type 1 and 3) or qualitative (type 2) defects of von Willebrand factor (VWF). The mechanisms of most inherited VWD types have been recently elucidated by genetic and molecular diagnosis, but the phenotypic tests based on measurements of plasma and platelet VWF, the ability of VWF to interact with its platelet receptor, and the analysis of the multimeric composition of VWF are always essential to identify patients with different VWD subtypes. The aim of treatment is to correct the dual defects of hemostasis, ie, abnormal coagulation expressed by low levels of factor VIII (FVIII) and abnormal platelet adhesion expressed by prolonged bleeding time (BT). Desmopressin is the treatment of choice in most patients with type 1 and type 2 VWD, who account for 60 to 70% of cases. In type 3 and in some severe forms of type 1 and type 2 VWD, desmopressin is not effective, and it is necessary to resort to plasma concentrates containing FVIII and VWF. Treated with virucidal methods, these concentrates are effective and currently safe, but they do not always correct the BT defect. Platelet concentrates or desmopressin can be used as adjunctive treatments when poor correction of the BT after concentrates is associated with continued bleeding.

Diagnosis and incidence of inherited von Willebrand disease

Von Willebrand disease is the most commonly inherited bleeding disorder, caused by the inheritance of a quantitative or qualitative abnormality of von Willebrand factor. Clinical manifestations of this disorder are diverse, and traditional diagnostic tools vary in sensitivity, specificity, and overall usefulness. However, as more accurate diagnostic testing is developed and implemented, determination of the disease's incidence and prevalence will improve, allowing the identification and treatment of patients who suffer from this disorder.

Congenital von Willebrand disease type I: definition, phenotypes, clinical and laboratory assessment

Von Willebrand disease, with a prevalence of about 1% in the general population, is the most frequent inherited bleeding disorder. Among the major subtypes, type I von Willebrand disease represents by far the more prevalent category (about 70%) and includes cases with a partial deficiency of plasma von Willebrand factor and no evidence of qualitative defects. The clinical expression as well as the laboratory phenotype of the disorder and its penetrance are greatly variable. The diagnosis usually requires the presence of autosomally inherited bleeding history co-segregating with a low von Willebrand factor level. The influence of several genetic and acquired conditions on the level of von Willebrand factor is however, widely appreciated and represents the major obstacle in correctly identifying von Willebrand disease as the cause of a bleeding diathesis in several families. The molecular genetics of the minority of cases showing high penetrance and expressivity of the phenotype are unravelling, but for the large majority of milder cases, the molecular basis is still unknown. We present a practical approach to diagnosis, based on scientific evidence and direct experience. The implications of the diagnosis of von Willebrand disease for the patient's quality of life are also considered.

The influence of smoking on von Willebrand factor is already manifest in healthy adolescent females: the Floren-teen (Florence Teenager) Study

The early onset of atherosclerosis and the involvement of physiological biochemical, and environmental factors in its pathogenesis is well documented. Few data are available on the role of risk factors related to hemostasis in the pathogenesis of atherosclerosis in the young and, in particular, little information is available on adolescent populations. In the Study of Preventive Medicine and Education Program (Floren-teen Study), von Willebrand factor, a risk factor for cardiovascular disorder, was studied, together with classical cardiovascular risk factors, in apparently healthy students from two high schools in Florence. Familial and personal history, physical examination, and cardiovascular risk factors were evaluated in 144 students (aged 17-19 years). Blood was withdrawn to assess von Willebrand factor (ELISA) and lipid parameters. Levels of von Willebrand factor were significantly higher (P<0.044) in smokers than in nonsmokers and were correlated with the number of cigarettes per day in the whole group (P=0.01) and in females (P=0.006). In females a positive correlation was observed between von Willebrand factor and high-density lipoprotein cholesterol (P=0.0365). There was no significant correlation between von Willebrand factor and blood pressure or between von Willebrand factor and physical activity. In conclusion, this study shows an association between levels of von Willebrand factor and smoking habits and is the first show that even a brief period of smoking affects levels of von Willebrand factor in healthy adolescent females independently of other risk factors. These results stress the relevance of extending prevention programs to reduce smoking in high school students.

The molecular basis of von Willebrand disease

von Willebrand disease (VWD) is a clinically heterogeneous bleeding disorder that reflects a wide array of defects. Quantitative subtypes of the disorder, including types 1 and 3 VWD, result in bleeding due to reduced levels of circulating von Willebrand factor (VWF) protein. Qualitative subtypes, defined as type 2 VWD, act through altered VWF function. A range of molecular defects are responsible for many of these subtypes, including missense, nonsense, splicing, insertion, and deletion mutations, resulting in either dominant or recessive inheritance. While many mutations correspond to selected variants, the basis for variation in expression and the imperfect correlations between genotype and phenotype remain to be understood.

Mvwf, a dominant modifier of murine von Willebrand factor, results from altered lineage-specific expression of a glycosyltransferase

We have identified altered lineage-specific expression of an N-acetylgalactosaminyltransferase gene, Galgt2, as the gain-of-function mechanism responsible for the action of the Mvwf locus, a major modifier of plasma von Willebrand factor (VWF) level in RIIIS/J mice. A switch of Galgt2 gene expression from intestinal epithelial cell-specific to a pattern restricted to the vascular endothelial cell bed leads to aberrant posttranslational modification and rapid clearance of VWF from plasma. Transgenic expression of Galgt2 directed to vascular endothelial cells reproduces the low VWF phenotype, confirming this switch in lineage-specific gene expression as the likely molecular mechanism for Mvwf. These findings identify alterations in glycosyltransferase function as a potential general mechanism for the genetic modification of plasma protein levels.

Comparative mapping of distal murine chromosome 11 and human 17q21.3 in a region containing a modifying locus for murine plasma von Willebrand factor level

Type 1 von Willebrand disease (VWD) is a common inherited disorder characterized by mild to moderate bleeding and reduced levels of von Willebrand factor (VWF). An animal model for human type 1 VWD, the RIIIS/J mouse strain, exhibits a prolonged bleeding time and reduced plasma VWF levels. We have previously mapped the defect in RIIIS/J to distal mouse Chr 11, distinct from the Vwf locus on Chr 6. This locus, Mvwf, was localized to an approximately 0.5-cM interval, tightly linked to Gip, distal to Ngfr, and proximal to Hoxb. We have now used these genetic markers to construct a contig of yeast and bacterial artificial chromosomes and bacteriophage P1 clones spanning the approximately 300-kb Mvwf nonrecombinant interval. In a comparative mapping approach, mouse homologues of mapped human expressed sequence tags (ESTs) were localized relative to the candidate interval. Twenty-one sequence-tagged sites and ESTs from the corresponding human syntenic region 17q21.3 were ordered using the high-resolution Stanford TNG3 radiation hybrid panel. Based on the resulting radiation hybrid map and our mouse genetic and physical maps, the order of human and mouse genes in a >0.7-cM region appears to be conserved. Six genes localized to the Mvwf nonrecombinant interval by comparative mapping included orthologs of GNGT2, ATP6N1, and a nuclear domain protein. Seven other genes or ESTs were excluded from the candidate interval, including orthologs of PHB, PDK2, a speckle-type protein, and a UDP-galactose transporter. Using exon trapping, 10 additional putative expressed sequences were identified within the Mvwf nonrecombinant interval, including a previously cloned murine glycosyltransferase as well as exons showing sequence similarity to genes for Caenorhabditis elegans and Saccharomyces cerevisiae predicted proteins, an Arabidopsis thaliana ubiquitin-conjugating enzyme, and a Gallus gallus mRNA zipcode-binding protein. Further characterization of these putative genes could identify the dominant mutation responsible for low plasma VWF levels in RIIIS/J mice. These data may also aid in the localization of other disease loci mapped to this region, including the gene for tricho-dento-osseous syndrome and a murine locus for susceptibility to ozone-induced acute lung injury.