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Von Willebrand disease (VWD) is a bleeding disorder characterized by reduced plasma von Willebrand factor (VWF) levels or functionally abnormal VWF. Low VWF plasma levels in VWD patients are the result of mutations in the VWF gene that lead to decreased synthesis, impaired secretion, increased clearance or a combination thereof. However, expression studies of variants located in the A domains of VWF are limited. We therefore characterized the biosynthesis of VWF mutations, located in the VWF A1-A3 domains, that were found in families diagnosed with VWD. Human Embryonic Kidney 293 (HEK293) cells were transiently transfected with plasmids encoding full-length wild-type VWF or mutant VWF. Six mutations in the A1-A3 domains were expressed. We found that all mutants, except one, showed impaired formation of elongated pseudo-Weibel-Palade bodies (WPB). In addition, two mutations also showed reduced numbers of pseudo-WPB, even in the heterozygous state, and increased endoplasmic reticulum retention, which is in accordance with the impaired regulated secretion seen in patients. Regulated secretion upon stimulation of transfected cells reproduced the in vivo situation, indicating that HEK293 cells expressing VWF variants found in patients with VWD can be used to properly assess defects in regulated secretion., (© 2014 John Wiley & Sons Ltd.)

Elevated plasma levels of interleukin 8 (IL-8) were previously shown to be associated with recurrent venous thrombosis. To assess the risk of venous thrombosis, IL-8 plasma concentrations were measured in patients and control subjects of the Leiden Thrombophilia Study (LETS). This population based case-control study included 474 patients with a first deep-vein thrombosis and 474 age- and sex-matched controls. The risk of venous thrombosis for subjects with elevated IL-8 levels (above 90th percentile of controls) compared with subjects with IL-8 levels below the 90th percentile was increased 1.8-fold (95%CI 1.2-2.8). Adjusted for age and sex, the odds ratio was 1.9 (95%CI 1.3-2.8). IL-8 concentrations were weakly correlated with age, male sex, and concentrations of C-reactive protein, factor VIII coagulation activity and homocysteine, but adjustment for these factors did not substantially affect the association between IL-8 and venous thrombosis. Our results suggest that IL-8 is a risk factor for venous thrombosis.

A mutation in factor XIII (Val34Leu) was reported to protect against venous thromboembolism. We evaluated the effect of Val34Leu on thrombotic risk in 352 factor V Leiden carriers who were first-degree relatives of 132 thrombotic propositi carrying factor V Leiden. The total observation period was 2,594 years in 92 Val34Leu carriers and 7,444 years in 260 non-carriers. The annual incidence of a first episode of venous thromboembolism was 0.31% in Val34Leu carriers and 0.44% in non-carriers [relative risk (RR) for venous thromboembolism: 0.7, 95% CI 0.3-1.5]. Age-specific RR for venous thromboembolism were (for Val34Leu carriers and non-carriers respectively): 1.0 (95% CI 0.3-3.2) in the age group of 15-30 years, 0.4 (95%, CI 0.05-3.0) in the age group of 30-45 years, 0.6 (95% CI 0.1-2.9) in the group aged 45-60 years and 0.5 (95% CI 0.06-4.5) in relatives older than 60 years. In conclusion, the impact of FXIII Val34Leu on the venous thromboembolic risk is modest, suggesting that screening for this mutation in factor V Leiden carriers is not justified.

A sequence variation in the 3'-untranslated region of the prothrombin (PT) gene (20210 G-->A) was recently claimed to be associated with elevated plasma prothrombin levels and an increased risk for venous and arterial thrombosis. We examined the prevalence of the 20210 A allele in the prothrombin gene in 400 healthy controls and in 263 patients with proven premature atherosclerotic disease. In addition, we measured prothrombin, prothrombin fragment 1 + 2, thrombin-antithrombin (TAT) complex and D-dimer levels in plasma from carrier and non-carrier patients. The frequency of the variant allele was 1% in the control subjects and 2.7% in the patient group, yielding a relative risk (RR) for the 20210 A allele of 2.7 (95% CI 0.8-9.4). All heterozygotes in the patient group were found to have had a myocardial infarction (MI), yielding a RR for MI of 4.2 (95% CI 1.2-14.6). Plasma prothrombin levels in carriers (126+/-10) were higher than in non-carriers (103+/-1, P=0.02). The levels of TAT complexes (16+/-9 v 6+/-1 microg/ml, P=0.02) as well as of prothrombin fragment 1 + 2 (1.5+/-0.3 v 1.0+/-0.1 nmol/l, P=0.02) were also elevated in carriers of the mutation. Our findings suggest that the 20210 G-->A mutation in the prothrombin gene is a genetic risk factor for MI. In addition, our data provide evidence for an association of the mutation with excessive thrombin generation, which may contribute to the understanding of its role in venous and arterial disease.

It has been proposed that iron accumulation may contribute to atherogenesis by increasing free radical formation and oxidative stress. Epidemiological studies in which the association of iron status with atherosclerosis was assessed raised conflicting results. To test whether genetic haemochromatosis is associated with increased atherosclerosis, we determined the prevalence of two mutations in the HFE gene related to haemochromatosis (845G-->A; Cys282Tyr. and 187 C-->G, His63Asp) in 265 consecutive patients with premature (<50 years of age) angiographically-proven atherosclerotic disease (coronary and/or peripheral), and in 272 healthy controls. PCR amplification followed by RsaI (Cys282Tyr analysis) and BclI (His63Asp analysis) restriction digestion was employed to define the genotypes. The mutant Cys282Tyr allele had a frequency of 0.07 among controls and 0.04 among patients (carrier frequency of 14.0% and 8.3%, respectively). The frequency of the His63Asp mutant allele was 0.14 (28.6% of carriers) in controls and 0.11 (22.2% of carriers) in patients. Five of 265 patients (1.1%) and 9/272 controls (3.3%) were compound heterozygotes. In conclusion, a lower prevalence of the Cys 282Tyr mutation and a similar frequency of the His63Asp mutation was observed in patients with atherosclerotic disease in comparison with normal controls. These findings do not support an association between haemochromatosis and atherogenesis.

Factor V (FV) deficiency (parahaemophilia) is an autosomal recessive bleeding disorder with an incidence of 1:10(6). We have studied a young girl with very mild bleeding symptoms and undetectable levels of plasma factor V antigen and activity (<0.3% and <1.6% of normal, respectively). Both parents showed plasma levels of factor V activity of about 50% of normal. Sequence analysis of the 5'- and 3'-untranslated, coding and adjacent regions of the factor V gene revealed the presence of a 4 bp deletion in exon 13. Subsequent screening of members of the family for the mutation showed that both parents were heterozygous for the mutation, that one healthy sister carried only normal alleles, and that the patient was homozygous for the mutated allele. The mutation introduced a frameshift and a novel premature stop codon in codon 1303, and would predict the synthesis of a truncated factor V molecule that lacks part of the B domain and the complete light chain. However, no factor V heavy chain could be detected in the plasma of the patient. Furthermore, factor V activity could not be detected in the patients' platelets. This is the first reported mutation in the factor V gene that predicts a type I quantitative factor V deficiency. Surprisingly, the patient, who is homozygous for the mutation, so far has only a very mild bleeding tendency.

Resistance to the anticoagulant effect of activated protein C (APC resistance), a frequent abnormality in patients with a history of venous thrombosis, is known to be due, in the large majority of cases, to the presence of an abnormal factor V: the factor V Leiden. It is reasonable to surmise that screening for this abnormality should be performed with a clotting method for APC resistance, before submitting the patients with abnormal results to DNA analysis. The present study was performed on 216 individuals enrolled at the Bologna centre, of which 189 were unrelated patients with a history of juvenile venous thromboembolism and 27 were relatives with or without thrombosis. APC resistance was first measured in Bologna by a standard commercial method and then, in Leiden, by an in-house method: DNA analysis was performed in those cases in which at least one of the clotting methods was abnormal. The data obtained confirm the good performance and the optimal positive predictive value for the Leiden mutation (100%) of the Leiden in-house clotting method. Performance of the commercial method was less satisfactory but markedly improved by expressing the data in relation to the values simultaneously obtained with a normal plasma pool. Even with optimal data expression, however, the positive predictive value of the commercial method, versus DNA analysis, did not exceed 88%. It is concluded that further standardization of the commercial method here evaluated is necessary before it can be widely adopted for the screening of APC resistance and prediction of the presence of factor V Leiden.

A long-PCR-based technique was developed to investigate a possible deletion in the protein S gene, PROS1, in a family with type I protein S (PS) deficiency (pedigree PS62). Long-PCR across introns produced an unexpected 2kb PCR product between exon VII and XII not seen in control individuals, in addition to the expected 2.5 kb exon VII-VIII product. This result suggested that a deletion had occurred between exons VII and XII in the PS-deficient family members. All were heterozygous for the deletion, Sequencing of the cloned 2 kb fragment gave the precise location of the breakpoints within introns 7 and 11. Significant similarity existed in both introns to repetitive sequences, e.g. Alu and Mer12, but no significant similarity was evident between the two introns themselves. The technique of long-PCR is simple and more informative than Southern blotting in detecting and characterizing large intragenic deletions.

The molecular characterization of mutations in haemophilia A patients in this study was carried out by PCR-SSCP, Southern blotting, and reverse transcribed-PCR. A multiplex PCR in which four to eight exons were co-amplified was developed to reduce the time needed for screening the coding region of the factor VIII gene. PCR-SSCP was used to screen for small molecular defects, and reverse transcriptase PCR combined with Southern blotting was used to screen DNA for the inversions that occur frequently in intron 22 of the factor VIII gene. A group of 35 haemophilia A patients was analysed by these methods and 31 mutations were detected. In one patient two mutations were identified. The cases of mild and moderate haemophilia A showed changes in single nucleotides which predicted amino acid changes. The patients affected by severe haemophilia A showed two types of mutations. First, deletions or insertions that result in a frameshift in the coding DNA sequence were observed. Second, inversions were found which result in a disruption of the gene. With the screening strategies used we succeeded in elucidating an abnormality in the factor VIII gene in 30/35 haemophilia A patients.

In three affected members of a family with type I 'platelet discordant' von Willebrand's disease displaying desmopressin-induced thrombocytopenia, we have detected in exon 28 of the von Willebrand factor gene a heterozygous G(4121)-->A transition, which predicts an Arg611-->His substitution. The mutated allele was absent in 50 normal individuals. An unrelated patient with a similar phenotype was also found to be heterozygous for this mutation. The mutation is located in the A1 domain of von Willebrand factor, where most type 2B von Willebrand's disease mutations are found. Mutations in this domain result in von Willebrand factor multimers with enhanced affinity for platelet glycoprotein Ib, and this may explain the association of Arg611-->His with the moderate thrombocytopenia observed after desmopressin infusion.

The von Willebrand factor gene contains a highly polymorphic variable number tandem repeat sequence (VNTR) in intron 40. We observed the spontaneous mutation to a new length allele. Sequence analysis revealed that the change in length corresponds to one tetranucleotide repeat unit. This observation emphasizes the risk of errors in family studies and prenatal diagnosis due to VNTR instability.

We describe a patient with a lifelong bleeding disorder previously classified as von Willebrand's disease (vWD) type I. The factor VIII (FVIII) level in this patient was disproportionately low and we showed that this was due to a decreased factor VIII binding capacity of her vWF. To characterize the molecular defect in this type of vWD, a cDNA-dependent polymerase chain reaction (PCR) amplification was performed using platelet RNA as a template. Direct sequencing of the amplified fragment, which encodes for the FVIII-binding domain, showed a single nucleotide change in exon 20 at codon 854, resulting in the substitution of CAG glutamine (Gln) for CGG arginine (Arg). At the level of the cDNA only the mutated sequence was found, whereas at genomic DNA level the patient was heterozygous for this mutation. This patient is therefore a compound heterozygote for a point mutation resulting in a FVIII-binding defect and a vWF allele with low transcript levels.