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Background: The asialoglycoprotein receptor (ASGPR) binds with high affinity factor VIII (FVIII) through its N -linked oligosaccharides. However, its contribution to the wide inter-individual variation of infused FVIII pharmacokinetics (PK) in hemophilia A (HA) is unknown., Objective: To investigate the variability in FVIII PK outcomes in relation to genetic variation in the ASGR2, encoding the ASGPR2 subunit., Methods: Thirty-two HA patients with FVIII:C ≤2 IU/dL underwent 66 single-dose FVIII PK studies. PK parameters were evaluated in relation to ASGR2 5' untranslated region (5'UTR) polymorphisms, which were investigated by recombinant and white blood cell reverse transcription-polymerase chain reaction approaches., Results: The 5'UTR polymorphisms determine a frequent and conserved haplotype (HT1) in a regulatory region. The HT1 homozygotes may differ in the amounts of alternatively spliced mRNA transcripts and thus ASGPR2 isoforms. Compared with the other ASGR2 genotypes, the c.-95TT homozygotes ( n  = 9), showed threefold longer Alpha HL (3.60 hours, 95% confidence interval: 1.44-5.76, p  = 0.006), and the c.-95TC heterozygotes ( n  = 17) showed 25% shorter mean residence time (MRT; 18.5 hours, 15.0-22.0, p  = 0.038) and 32% shorter Beta HL (13.5 hours, 10.9-16.0, p  = 0.016). These differences were confirmed in patients ( n  = 27) undergoing PK studies ( n  = 54) with full-length FVIII only. In different linear regression models, the contribution of the ASGR2 genotypes remained significant after adjustment by ABO genotypes and von Willebrand factor (VWF) antigen levels, and explained 14% (MRT), 15 to 18% (Beta HL), and 22% (Alpha HL) of parameter variability., Conclusion: Infused FVIII distribution was modulated by frequent ASGR2 genotypes, independently from and together with ABO and VWF antigen levels, which has potential implications for genetically tailored substitutive treatment in HA., Competing Interests: M. Morfini reports personal fees from Kedrion, grants from Pfizer, personal fees from Novo Nordisk, personal fees from Sobi, personal fees from Bayer, personal fees from Bioverativ, personal fees from Octapharma, personal fees from CSL Behring, outside the submitted work. D. Balestra reports grants and personal fees from Bayer. A. Branchini reports grants and personal fees from Pfizer, grants from Bayer, grants and nonfinancial support from Grifols, outside the submitted work. G. Castaman reports personal fees from Roche, personal fees from Bayer, personal fees from Shire, grants and personal fees from CSL Behring, grants and personal fees from Sobi, personal fees from Uniqure, grants from Pfizer, personal fees from Kedrion, personal fees from Novo Nordisk, personal fees from Werfen, outside the submitted work. F. Bernardi reports grants from Bayer, during the conduct of the study; grants from Pfizer, outside the submitted work. The other authors state that they have no conflict of interest., (Thieme. All rights reserved.)

Activated factor VII-anti-thrombin (FVIIa-AT) complex is a potential biomarker of pro-thrombotic diathesis reflecting FVIIa-tissue factor (TF) interaction and has been associated with mortality in patients with coronary artery disease (CAD). Previous data indicated plasma lipids as predictors of FVIIa-AT variability, and plasma lipoproteins as potential stimulators of the coagulation cascade. Our aim was to evaluate the relationships between FVIIa-AT plasma concentration and a broad apolipoprotein profile (including ApoA-I, ApoB, ApoC-III and ApoE). Within the framework of the observational Verona Heart Study, we selected 666 subjects (131 CAD-free and 535 CAD, 75.4% males, mean age: 61.1 ± 10.9 years) not taking anticoagulant drugs and for whom plasma samples were available for both FVIIa-AT assay and a complete lipid profile. Plasma concentration of FVIIa-AT levels significantly and directly correlated with total and high-density lipoprotein cholesterol, triglycerides, ApoA-I, ApoC-III and ApoE levels. ApoC-III showed the strongest correlation ( R  = 0.235, p  = 7.7 × 10 -10 ), confirmed in all the sub-group analyses (males/females and CAD/CAD-free). Only ApoC-III remained associated with FVIIa-AT plasma concentration, even after adjustment for sex, age, CAD diagnosis, body mass index, renal function, smoking status, lipid-lowering therapies and FVIIa levels. The APOC3 gene locus-tagging polymorphism rs964184, previously linked with cardiovascular risk and plasma lipids by genome-wide association studies, was associated with both ApoC-III and FVIIa-AT plasma concentration. Our results indicate a strong association between ApoC-III and FVIIa-AT levels, thereby suggesting that an increased ApoC-III concentration may identify subjects with a pro-thrombotic diathesis characterized by an enhanced TF-FVIIa interaction and activity., Competing Interests: N. Martinelli reports having received a payment from Diagnostica Stago, Asnieres, France, for management and conduct of the study. B. Woodhams reports having been a consultant for Diagnostica Stago via Haemacon Ltd. The other authors state that they have no conflict of interest., (Georg Thieme Verlag KG Stuttgart · New York.)

Data with border-line statistical significance, copiously generated in genome-wide association studies of coronary artery disease (CAD), could include functionally relevant associations. We propose an integrated genomic and transcriptomic approach for unravelling new potential genetic signatures of atherosclerosis. Fifteen among 91 single nucleotide polymorphisms (SNPs) were first selected for association in a sex- and age-adjusted model by examining 510 patients with CAD and myocardial infarction and 388 subjects with normal coronary arteries (CAD-free) in the replication stages of a genome-wide association study. We investigated the expression of 71 genes proximal to the 15 tag-SNPs by two subsequent steps of microarray-based mRNA profiling, the former in vascular smooth muscle cell populations, isolated from non-atherosclerotic and atherosclerotic human carotid portions, and the latter in whole carotid specimens. BCL3 and PVRL2, contiguously located on chromosome 19, and ABCA1, extensively investigated before, were found to be differentially expressed. BCL3 and PVRL2 SNPs were genotyped within a second population of CAD patients (n=442) and compared with CAD-free subjects (n=393). The carriership of the BCL3 rs2965169 G allele was more represented among CAD patients and remained independently associated with CAD after adjustment for all the traditional cardiovascular risk factors (odds ratio=1.70 with 95% confidence interval 1.07-2.71), while the BCL3 rs8100239 A allele correlated with metabolic abnormalities. The up-regulation of BCL3 mRNA levels in atherosclerotic tissue samples was consistent with BCL3 protein expression, which was detected by immunostaining in the intima-media of atherosclerotic specimens, but not within non-atherosclerotic ones. Our integrated approach suggests a role for BCL3 in cardiovascular diseases.

Coagulation factor V (FV) deficiency is characterised by variable bleeding phenotypes and heterogeneous mutations. To add new insights into the FV genotype-phenotype relationship, we characterised the R1698W change in the A3 domain, at the poorly investigated interface with the A2 domain. The FV R1698W mutation was responsible for a markedly reduced expression level (10% of FV-WT) and specific activity in thrombin generation (0.39). Interestingly, the FVa1698W showed rapid activity decay upon activation due to increased dissociation rate between the heavy and light chains. The importance of the size and charge of the residue at position 1698 was investigated by three additional recombinant mutants, FVR1698A, FVR1698Q, and FVR1698E. FVR1698A and FVR1698Q expression (30 and 45% of FV-WT), specific activity (both 0.57) and stability were all reduced. Noticeably, FVR1698E showed normal activity and stability despite poor expression (10% of FV-WT). These data indicate the essential role of R1698 for normal biosynthetic process and support local flexibility for positively or negatively charged residues to produce stable and functional A3-A2 domain interactions. Their experimental alteration produces a gradient of FV defects, which help to interpret the wide spectrum of phenotypes in FV-deficient patients.

Elevated factor VIII (FVIII) levels are a recognized risk factor for venous thrombosis. Recently, family studies suggested that the G allele of the 3951C/G (D1241E) FVIII polymorphism is associated to lower FVIII activity. We investigated in case-control studies both biological effects (FVIII levels and activated protein C sensitivity ratio) and clinical associations (venous thromboembolism) of the D1241E change. Among 145 healthy and 150 thrombotic women, not carriers of known thrombophilic defects, the 1241E allele was associated with 11% reduced (t-test, P<0.05) FVIII levels. The effect on activated protein C sensitivity ratio was not statistically significant. Carriership of the 1241E allele, potentially conferring protection from thrombosis, was found in 22.8% of controls and in 15.3% of cases. In an additional cohort of factor V Leiden carriers (n=283), carriership of the 1241E allele was 25.2% among 143 asymptomatic subjects and 17.1% among 140 thrombotic patients. Our data do not indicate a specific interaction with factor V Leiden. These genotype distributions suggest a mild protective effect from venous thrombosis conferred by 1241E FVIII, masked by other genetic and/or environmental components, and detectable only in very large population studies. Our findings point toward the presence of genetic determinant of coagulation factor levels with a biologically significant role, but with a poor predictive value to estimate thrombotic risk beyond established risk factors.

Activated protein C resistance (APCR) is a major risk factor for venous thromboembolism (VTE). Although the factor V (FV) Leiden mutation accounts for the vast majority of APCR cases, other polymorphisms may contribute to the APCR phenotype. Genetic components of APCR and thrombophilia were investigated by two dinucleotide repeats, characterized in introns 2 and 11 of the FV gene. Only the intron 11 marker was genetically stable and thus suitable for further analysis. Its allelic frequencies were found to differ significantly (P=0.003) between subjects selected for increased APCR in the absence of the FV R506Q mutation (n=70, normalized ratios /=1.31). Genotype differences were also found (P=0.017) between FV R506Q heterozygotes (n=100) who had experienced previous VTE and those (n=100), who were still asymptomatic for VTE. Significance was mostly driven by the relative over-representation of the 12R allele and to a minor extent by the under-representation of the 15R allele among the symptomatic versus the asymptomatic FV Leiden carriers. Two SNPs (4070A/G and 2391A/G) were found to underlie the 12R and 15R alleles respectively, and marked extended haplo-types, previously (HR2) or newly (HT2) identified. Only the FV HR2 differed (P=0.002) in frequency between the two groups of FV R506Q heterozygotes, suggesting that it represents the most relevant FV genetic component of APCR or VTE detectable by this experimental and clinical approach. Our analysis indicates that frequent FV genetic components might contribute to shape the risk for VTE in FV Leiden carriers.

Molecular genetics and biochemical studies were performed in homozygotes for the R2 allele (4070G) in the factor V gene, most of them affected by coronary artery disease. Novel polymorphisms (G642T, 156Ser; T1328C, 385Met/Thr), among which a functional candidate (A6755G, 2194Asp/Gly) located in the C2 domain of FV, were identified in the R2 gene. In chromatographic studies R2 FV appeared qualitatively identical to normal FV. However, a relative increase of the more thrombogenic and more glycosylated FV isoform (FV1) was observed in plasma of 2194Gly homozygotes (mean FV1/FV2 ratio 0.71, 95% CI 0.66-0.77) as compared to R2-free controls (0.37, 95% CI 0.34-0.40). We conclude that carriership of the R2 FV gene is associated with an imbalance between the two functionally different FV isoforms, and propose that genetically determined differential glycosylation of FV could represent a novel mechanism of thrombotic disease.

Pseudo-homozygous APC resistance, the condition resulting from compound heterozygosity for FV R506Q (FV Leiden) and quantitative FV deficiency, provides a natural model to study the interaction between procoagulant and anticoagulant defects. This paper reports a complete FV characterization of a pseudo-homozygous APC resistant thrombotic patient. The expression of the patient's non-Leiden gene was found to be severely impaired both at the mRNA and protein levels. In particular, only FV Leiden molecules were detected in the patient's plasma by immunoblotting, which accounts for the observed marked APC resistance. Analysis of the FV cDNA obtained by reverse transcription of platelet RNA revealed that the mRNA of the non-Leiden gene was extremely reduced in amount. A PAC clone containing the whole FV gene was used to design primers for a complete FV exon scanning. A 2-bp insertion at nucleotide 3706 in the large exon 13 of the non-Leiden gene, predicting a frame-shift and premature termination of protein synthesis, was identified as responsible for the FV defect. Failure to find any case of pseudo-homozygous APC resistance in a large sample (6,804) of blood donors suggests that this condition is extremely rare among normal controls and that its detection is favoured by the thrombotic risk that it may confer.

Two novel polymorphisms were identified in the factor V gene by direct sequencing of intronic areas. One of them, located in intron 9, is the marker closest to the Leiden mutation ever described, whereas the other, in intron 16, displays a rare allele invariantly associated to the mutation. Allele-specific amplification protocols were designed to perform extensive screenings for both polymorphic sites. The new markers were used in combination with six previously described polymorphisms to define specific factor V gene haplotypes. Haplotype investigations in 506Q homozygous thrombotic patients and normal controls showed the presence of a single haplotype underlying the factor V Leiden mutation in Mediterranean populations (among which Greek Cypriots, where the R506Q mutation is particularly frequent) and Indians. When traced in the absence of the Leiden mutation, the background haplotype was found to be present and roughly as frequent as the mutation itself in these populations. These findings indicate a single mutational event, that probably occurred outside Europe, as the cause of the Leiden mutation and provide a powerful tool to investigate its evolutionary history.

305 patients with juvenile thromboembolic episodes were screened for the presence of heparin cofactor II deficiency. The heterozygous deletion of two bases was found in the exon 5 of the heparin cofactor II gene in two unrelated patients, very likely due to a founder effect. This molecular lesion, causing a frameshift and elongated translation, affects the core of the molecule and should cause the complete unfolding of the protein, which is in accordance with the observed type I deficiency. The corresponding region of antithrombin III gene is affected by a cluster of frameshift mutations suggesting that heparin cofactor II and antithrombin III could share similar mutational patterns. The heparin cofactor II gene alteration was associated with, in one patient, the factor V Leiden mutation and, in the other, type I protein C deficiency. The tracing of the single defects in several family members indicated that the mutations became clinically manifest only when present in the doubly heterozygous condition. This study provides two examples, based on molecular findings, of the interplay of risk factors which is potentially useful to define a role for heparin cofactor II deficiency in inherited thrombophilia.

Three novel polymorphisms were found in the repeated region of the large exon 13 of factor V gene, one giving rise to a codon dimorphism (Ser1240) and two causing aminoacid substitutions (His1299Arg, Leu1257Ile). An increasing frequency of the Arg1299 (R2 allele) correlated with a decreasing mean plasma factor V activity in the groups of subjects under study, which included 26 unrelated subjects with partial factor V deficiency. Family studies supported the co-inheritance both of low factor V activity and of R2 allele. The reduction of factor V activity associated with the R2 allele was not clinically symptomatic even in the homozygous condition and was characterized by a parallel reduction of antigen in plasma, in which abnormal molecules were not detected. Data suggest that the R2 allele represents a marker in linkage with an unknown defect rather than a functional polymorphism. These studies provide the first evidence of a genetic component in determining factor V levels in plasma and of a genetic linkage between the factor V gene and factor V deficiency. They also define specific haplotypes which are associated with factor V deficiency or with APC resistance (Arg506Gln) and are valuable tools for the study of factor V defects.