A novel factor V compound heterozygous mutation associated with thrombosis (Y1961C; FV-Kanazawa, together with 1982_1983del)

BACKGROUND

Factor (F)V is pivotal in both procoagulant and anticoagulant mechanisms. The present report describes a novel F5 mutation in a FV-deficient patient (FV activity, 6 IU/dL; FV antigen, 32 IU/dL) complicated by recurrent deep vein thrombosis. The patient demonstrated activated protein C resistance (APCR) with compound heterozygous mutations consisting of FV-Y1961C (FVKanazawa) and FV-1982_1983del.

OBJECTIVES

To clarify thrombotic mechanisms associated with this FV abnormality.

METHODS AND RESULTS

Levels of FV-1982_1983del were below the detection sensitivity in our expression experiments using human embryonic kidney 293T cells, and analyses were targeted, therefore, on the FV-Y1961C mutation. Activated partial thromboplastin time-based clotting assays demonstrated that FV-Y1961C exhibited APCR and that the reduced activated protein C (APC) susceptibility in FVa-Y1961C resulted in a marked depression of APC-catalyzed inactivation with delayed cleavage at Arg506 and little cleavage at Arg306 with or without protein S. The APC cofactor activity of FV-Y1961C in APC-catalyzed FVIIIa inactivation promoted by Arg336 cleavage in FVIII was impaired. The binding affinity of FVa-Y1961C to phospholipid membranes was reduced in reactions involving APC/protein S-catalyzed inactivation and in prothrombinase activity. Furthermore, the addition of FVa-Y1961C to plasma failed to inhibit tissue factor-induced procoagulant function. These characteristics were similar to those of FV-W1920R (FVNara) and FV-A2086D (FVBesançon).

CONCLUSION

We identified a compound heterozygous FV-Y1961C mutation in the C1 domain representing a novel FV mutation (FVKanazawa) resulting in not only APCR due to impaired FVa susceptibility and FV cofactor activity for APC function but also impaired inhibition of tissue factor-induced procoagulant function. These defects in anticoagulant function associated with FV in FV-Y1961C contributed to a prothrombotic state.

EGFR-TKI-induced Factor V deficiency in a patient with advanced non-small cell lung cancer: The first case report

Osimertinib, a third-generation epidermal growth factor receptor tyrosine kinase inhibitor (EGFR-TKI), is routinely prescribed as first-line therapy for advanced non-small cell lung cancer, regardless of the presence of the T790M resistance mutation. This study reports a rare case of Factor V inhibitor detection during osimertinib therapy in a patient with lung adenocarcinoma. These findings underscore the importance of vigilant monitoring for coagulation abnormalities during EGFR-TKI therapy.

Characterization of zebrafish coagulation cofactors Fviii and Fv mutants and modeling hemophilia A and factor V deficiency

The aim of this study is to characterize zebrafish coagulation cofactors fviii and fv mutant fish and assess if they phenocopy classical hemophilia A and factor V deficiency in humans. The embryos from fviii and fv zebrafish heterozygote mutants generated by ENU mutagenesis were purchased from the ZIRC repository. They were reared to adulthood and genotyped. The heterozygote male and female were crossed to get homozygote, heterozygote, and wild-type fish. Functional kinetic coagulation assays and bleeding assays were performed on normal and mutant adult fish, and venous laser injury assays were performed on the larvae. The DNA from fviii and fv mutants were sequenced to confirm if they have a premature stop codon in exon 19, and in exon 2, respectively, and in both mutants, the amino acid glutamine is replaced with a stop codon. Homozygous and heterozygous 5 days post fertilization (dpf) larvae for fviii and fv deficient mutants exhibited prolonged time to occlusion after venous laser injury compared to wild-type controls. The homozygous and heterozygous fviii adult mutants showed modest bleeding and delayed fibrin formation in the kinetic partial thromboplastin time (kPTT) assay with their plasma. fv homozygous larvae had poor survival beyond 12 dpf. However, heterozygous fv mutants exhibited heavy bleeding and prolonged fibrin formation in the kPTT and kPT assay compared with wild-type siblings. Our characterization showed fviii and fv mutants from ZIRC phenocopied to a considerable extent classical hemophilia A and factor V deficiency in humans, respectively. These models should be useful in studying and developing novel drugs that reverse the phenotype and in generating suppressor mutations to identify novel factors that compensate for these deficiencies.

In vitro and ex vivo rescue of a nonsense mutation responsible for severe coagulation factor V deficiency

BACKGROUND

Coagulation factor V (FV) deficiency is a rare bleeding disorder that is usually managed with fresh-frozen plasma. Patients with nonsense mutations may respond to treatment with readthrough agents.

OBJECTIVES

To investigate whether the F5 p.Arg1161Ter mutation, causing severe FV deficiency in several patients, would be amenable to readthrough therapy.

METHODS

F5 mRNA and protein expression were evaluated in a F5 p.Arg1161Ter-homozygous patient. Five readthrough agents with different mechanisms of action, i.e. G418, ELX-02, PTC-124, 2,6-diaminopurine (2,6-DAP), and Amlexanox, were tested in in vitro and ex vivo models of the mutation.

RESULTS

The F5 p.Arg1161Ter-homozygous patient showed residual F5 mRNA and functional platelet FV, indicating detectable levels of natural readthrough. COS-1 cells transfected with the FV-Arg1161Ter cDNA expressed 0.7% FV activity compared to wild-type. Treatment with 0-500 μM G418, ELX-02, and 2,6-DAP dose-dependently increased FV activity up to 7.0-fold, 3.1-fold, and 10.8-fold, respectively, whereas PTC-124 and Amlexanox (alone or in combination) were ineffective. These findings were confirmed by thrombin generation assays in FV-depleted plasma reconstituted with conditioned media of treated cells. All compounds except ELX-02 showed some degree of cytotoxicity. Ex vivo differentiated megakaryocytes of the F5 p.Arg1161Ter-homozygous patient, which were negative at FV immunostaining, turned positive after treatment with all 5 readthrough agents. Notably, they were also able to internalize mutant FV rescued with G418 or 2,6-DAP, which would be required to maintain the crucial platelet FV pool in vivo.

CONCLUSION

These findings provide in vitro and ex vivo proof-of-principle for readthrough-mediated rescue of the F5 p.Arg1161Ter mutation.

Molecular and clinical characterization of two unrelated families with factor V deficiency, including a novel nonsense variant (p.Gln1532*)

BACKGROUND

Factor V (FV) is an essential cofactor in the coagulation cascade. The characterization of novel mutations is advantageous for the clinical management of FV-deficient patients.

METHODS

Coagulation screening and thrombin generation assay were performed with the plate-poor plasma. All 25 exons of the F5 gene were amplified and sequenced. The ClustalX-2.1 software was applied to the multiple sequence alignment. The possible adverse effects of mutations were investigated with online bioinformatics software and protein modeling.

RESULTS

Two unrelated families with FV deficiency were under investigation. Proband A was an 18-year-old youth with recurrent epistaxis. Proband B was a 29-year-old woman who did not present with any bleeding symptoms. Three heterozygous mutations (p.Gln1532*, p.Phe218Ser, and p.Asp2222Gly) were detected. Interestingly, they were compound heterozygotes and both contained the p.Asp2222Gly, a polymorphism. The thrombin generation assay showed that both patients had impaired ability of thrombin generation, and in particular, proband A was more severe. Conservation, pathogenicity and protein modeling studies all indicated that these three mutations could cause deleterious effects on the function and structure of FV.

CONCLUSION

These three mutations are responsible for the FV-deficient in two pedigrees. Moreover, the nonsense variant p.Gln1532* is first reported in the world.

Clinical Characterization and Molecular Analysis of Fourteen Chinese Patients with Factor V Deficiency

INTRODUCTION

 Coagulation factor V (FV) functions as a vital cofactor that performs procoagulant roles in the coagulation system. We investigated 14 unrelated patients whose plasma FV levels were all below the reference range.

METHODS

 FV activity (FV:C) and FV antigen were detected by one-stage clotting and ELISA, respectively. All 25 exons of the F5 gene in patients were amplified by the PCR, and they were sequenced directly. Haplotype analysis was performed with different polymorphisms on F5. Protein modeling was applied to analyze the potential molecular mechanisms.

RESULTS

 Of five patients with higher FV levels (FV:C > 10%), only one had minor bleeding symptoms. In contrast, of the remaining eight patients with lower FV levels (FV:C < 10%), six showed various bleeding manifestations. A total of 10 mutations were detected from 14 patients (6 were novel mutations). Interestingly, the homozygous p.Phe190Ser was found in five pedigrees, and haplotype analysis showed that they shared almost the same haplotype, indicating the common origin rather than a hotspot mutation. In silico analysis preliminarily investigated the potential pathogenic mechanism of the mutation. Modeling analysis showed that all six missense mutations would lead to conformational alterations in the FV protein. Among them, three (p.Gly1715Ser, p.Ser1753Arg, and p.Asp68His) would decrease hydrogen bonds.

CONCLUSION

 This is the largest genetic analysis of a single cohort of FV deficiency in Chinese. The study demonstrated that FV levels tended to be correlated with the probability of hemorrhage. The identification of a large number of unique FV-deficient pedigrees highlighted the screening for mutations in F5.

Hemophilia A and factor V deficiency in a girl with Turner syndrome: a case report

BACKGROUND

Hemophilia is an X-linked, recessive inherited disease caused by a defect or deficiency of one of the coagulation factors (VIII or IX). It is considered a rare disease in females. One of the reasons that hemophilia affects females is Turner syndrome. Hemophilia with Turner syndrome is a very rare case, but the combination of Turner syndrome, hemophilia, and factor V deficiency is an isolated case that has never been recorded in the medical literature.

CASE PRESENTATION

In our case, a 5-year-old Syrian girl presented with hemorrhage of gum, epistaxis, and short stature. The lab tests showed: prolonged activated partial thromboplastin time and prothrombin time with deficiency of factor V (1%) and factor VIII (1%). We diagnosed hemophilia A with factor V deficiency. In addition to short stature, the patient was noted to have spaced nipples and winged neck. We performed karyotyping that showed deletion of one X chromosome (45X0), Turner syndrome. There is no family history of hemophilia or any other genetic disease.

CONCLUSIONS

In females affected with hemophilia, karyotyping should be performed. It is very important not to exclude the possibility of a combination of deficiency of more than one clotting factor, and to note that deficiency of more than one factor does not necessarily increase the severity of bleeding compared with deficiency of a single factor.

Clinical Phenotype and Genetic Analysis of Twins With Congenital Coagulation Factor V Deficiency

OBJECTIVE

The aim was to investigate the clinical characteristics and molecular pathogenic mechanism of twins with congenital factor V (FV) deficiency.

METHODS

We comprehensively analyzed the clinical manifestations and laboratory test results of a set of twins and their parents and performed point mutation analysis with direct high-throughput exon sequencing.

RESULTS

The prothrombin time and activated partial thromboplastin time were prolonged for both probands, and the FV activity levels were 13.0% and 9.8%. Next-generation sequencing showed that the affected individuals harbored a paternal c.5113A>C (p.S1705R) and a maternal c.4949C>T (p.A1650V) heterozygous variants in the FV gene, which conformed to an autosomal recessive inheritance pattern. This is the first report of these point mutations. The older boy also had a congenital patent foramen ovale.

CONCLUSION

In this set of twins, missense mutations of the FV gene were related to congenital FV deficiency but unrelated to the patent foramen ovale observed in the older boy.

Hereditary factor V deficiency from heterozygous mutations with a novel variant p.Pro798Leufs∗13 in the F5 gene

To explore the causative mutation for autosomal recessive inheritance factor V (FV) deficiency in a Chinese family. Relative coagulation indexes and the FV antigen were tested by the one-stage clotting method and ELISA, respectively. At the same time, the calibrated automated thrombogram (CAT) was used to analyze the mutant protein function. All 25 exons, flanking sequences, 5' and 3' untranslated regions of the F5 were amplified by PCR and sequenced directly, while each suspected variant was verified by reverse sequencing. The possible impact of the mutant was analyzed by the corresponding bioinformatics software. The phenotypic tests showed that the proband's FV activity has decreased to 24%, whereas the FV antigen has also reduced to 28%. The genetic analysis revealed that she was a compound heterozygote for a frameshift variant from small deletion in the exon 13 (c.2390_2390delC, p.Pro798Leufs∗13) and a missense mutation in the exon 25 (c.6665A>G, p.Asp2222Gly). Meanwhile, the online bioinformatics software indicated that the frameshift variant was disease-causing. The pathogenic variant p.Pro798Leufs∗13 and the benign variant p.Asp2222Gly largely account for the decrease of the FV deficiency in this Chinese family, of which the pathogenic variant is firstly reported in the world.

High Mutational Heterogeneity, and New Mutations in the Human Coagulation Factor V Gene. Future Perspectives for Factor V Deficiency Using Recombinant and Advanced Therapies

Factor V is an essential clotting factor that plays a key role in the blood coagulation cascade on account of its procoagulant and anticoagulant activity. Eighty percent of circulating factor V is produced in the liver and the remaining 20% originates in the α-granules of platelets. In humans, the factor V gene is about 80 kb in size; it is located on chromosome 1q24.2, and its cDNA is 6914 bp in length. Furthermore, nearly 190 mutations have been reported in the gene. Factor V deficiency is an autosomal recessive coagulation disorder associated with mutations in the factor V gene. This hereditary coagulation disorder is clinically characterized by a heterogeneous spectrum of hemorrhagic manifestations ranging from mucosal or soft-tissue bleeds to potentially fatal hemorrhages. Current treatment of this condition consists in the administration of fresh frozen plasma and platelet concentrates. This article describes the cases of two patients with severe factor V deficiency, and of their parents. A high level of mutational heterogeneity of factor V gene was identified, nonsense mutations, frameshift mutations, missense changes, synonymous sequence variants and intronic changes. These findings prompted the identification of a new mutation in the human factor V gene, designated as Jaén-1, which is capable of altering the procoagulant function of factor V. In addition, an update is provided on the prospects for the treatment of factor V deficiency on the basis of yet-to-be-developed recombinant products or advanced gene and cell therapies that could potentially correct this hereditary disorder.

[Clinical and genetic analyses of hereditary factor Ⅴ deficiency cases]

Objective: To analyze the clinical phenotype and molecular pathogenesis of nine patients with hereditary factor Ⅴ (FⅤ) deficiency. Methods: Nine patients with hereditary FⅤ deficiency who were admitted to the Institute of Hematology and Blood Diseases Hospital from April 1999 to September 2019 were analyzed. The activated partial thromboplastin time, prothrombin time, and FⅤ procoagulant activity (FⅤ∶C) were measured for phenotypic diagnosis. High-throughput sequencing was employed for the F5 gene mutation screening, Sanger sequencing was adopted to confirm candidate variants and parental carrying status, Swiss-model was used for three-dimensional structure analysis, and ClustalX v.2.1 was used for homologous analysis. Results: The FⅤ∶C of the nine patients ranged from 0.1 to 10.6. Among them, eight had a hemorrhage history, with kin/mucosal bleeding as the most common symptom (three cases, 37.5%) , whereas one case had no bleeding symptom. There were five homozygotes and four compound heterozygotes. A total of 12 pathogenic or likely pathogenic mutations were detected, of which c.6100C>A/p.Pro2034Thr, c.6575T>C/p.Phe2192Ser, c.1600_1601delinsTG/p. Gln534*, c.4713C>A/p.Tyr1571*, and c.952+5G>C were reported for the first time. Conclusion: The newly discovered gene mutations enriched the F5 gene mutation spectrum associated with hereditary FⅤ deficiency. High-throughput sequencing could be an effective method to detect F5 gene mutations.

[Analysis of a pedigree with inherited factor V deficiency caused by compound heterozygous mutation]

Objective: To explore the molecular pathogenesis of a family with hereditary factor Ⅴ (FⅤ) deficiency. Methods: All the exons, flanking sequences, 5' and 3' untranslated regions of the F5 of the proband, and the corresponding mutation sites of the family members were analyzed via direct DNA sequencing. The CAT measurement was used to detect the amount of thrombin produced. The ClustalX software was used to analyze the conservation of mutation sites. The online bioinformatics software, Mutation Taster, PolyPhen-2, PROVEAN, LRT, and SIFT were applied to predict the effects of mutation sites on protein function. The Swiss-PdbViewer software was used to analyze the changes in the protein model and intermolecular force before and after amino acid variation. Results: The proband had a heterozygous missense mutation c.1258G>T (p.Gly392Cys) in exon 8 of the F5, and a heterozygous deletion mutation c.4797delG (p.Glu1572Lys fsX19) in exon 14, which results in a frameshift and produces a truncated protein. Her grandfather and father had p.Gly392Cys heterozygous variation, whereas her maternal grandmother, mother, little aunt, and cousin all had p.Glu1572LysfsX19 heterozygous variation. The ratio of proband's thrombin generation delay to peak time was significantly increased. Conservation analysis results showed that p.Gly392 was located in a conserved region among the 10 homologous species. Five online bioinformatics software predicted that p.Gly392Cys was pathogenic, and Mutation Taster also predicted p.Glu1572Lys fsX19 as a pathogenic variant. Protein model analysis showed that the replacement of Gly392 by Cys392 can lead to the extension of the original hydrogen bond and the formation of a new steric hindrance, which affected the stability of the protein structure. Conclusion: The c.1258G>T heterozygous missense mutation in exon 8 and the c.4797delG heterozygous deletion mutation in exon 14 of the F5 may be responsible for the decrease of FⅤ levels in this family.

[Identification of a novel variant of F5 gene in a consanguineous pedigree affected with inherited coagulation factor V deficiency]

OBJECTIVE

To explore the genetic basis for a consanguineous pedigree affected with inherited coagulation factor V deficiency.

METHODS

Genomic DNA was extracted from peripheral blood samples from the pedigree and subjected to next generation sequencing for screening variants of the F5 gene. Suspected pathogenic variant was verified by using Sanger sequencing. Pathogenicity of the variant was evaluated according to ACMG guidelines.

RESULTS

A homozygous frameshifting variant, c.4096delC (p.Leu1366Phefs*3), was identified in the F5 gene in the proband, which was confirmed to be derived from her consanguineous parents. This variant was absent in all databases including 10 000 in-house Chinese exome sequences. Based on the ACMG guidelines, the c.4096delC was predicted to be a pathogenic variant.

CONCLUSION

A novel pathogenic variant has been identified in the F5 gene in a consanguineous pedigree with inherited coagulation factor V deficiency, which has enriched the spectrum of F5 gene variants.

[Clinical phenotype and variantal analysis of a pedigree affected with hereditary coagulation factor V deficiency]

OBJECTIVE

To explore the molecular basis for a pedigree affected with coagulation factor V (FV) deficiency.

METHODS

Clinical data of the patient and his family members was analyzed. Targeted capture and next-generation sequencing (NGS) and Sanger sequencing were carried out to detect potential variant of the FV gene.

RESULTS

The patient presented with jaundice and prolonged prothrombin time (PT) and activated partial thromboplastic time (APTT). V factor activity measured only 0.1% of the normal level, though the patient had no sign of bleeding. A paternal heterozygous variant c.653T>C (p.F218S) and a maternal heterozygous variant c.3642_3643del (p.P1215Rfs*175) were identified in the FV gene of the patient. His elder brother was a heterozygous carrier of the c.653T>C (p.F218S) variant. c.653T>C(p.F218S) was a known pathogenic variant, while the c.3642_3643del (p.P1215Rfs*175) variant was unreported previously.

CONCLUSION

Mutations of the FV gene probably underlie the hereditary coagulation factor V deficiency in this patient. NGS combined with Sanger sequencing has detected potential variant with efficiency and provided a reliable basis for clinical and prenatal diagnosis for this family.

Congenital factor V deficiency from compound heterozygous mutations with a novel variant c.2426del (p.Pro809Hisfs*2) in the F5 gene: A case report

INTRODUCTION

Congenital factor V deficiency (FVD) is a rare bleeding disorder characterized by low or undetectable plasma factor V (FV) levels leading to mild to severe bleeding symptoms. Currently, more than 100 mutations have been reported in F5. We herein report a patient with FVD from mutations in the F5 gene.

PATIENT CONCERNS

A 52-year-old man with prolonged prothrombin time and activated partial thromboplastin time corrected by mixing test on preoperative screening. His past medical or family history was not remarkable.

DIAGNOSIS

Factor assays revealed a markedly reduced FV activity at 7%. Other factors were not decreased. DNA sequencing analysis to detect F5 gene mutations showed the patient was compound heterozygous for c.286G>C (p.Asp96His) and c.2426del (p.Pro809Hisfs*2). Asp96His was previously described missense mutation and Pro809Hisfs*2 was a novel deleterious mutation.

INTERVENTIONS

Fresh-frozen plasma was administered to supplement FV before surgery.

OUTCOMES

Subsequent factor assays revealed temporarily increased FV activity at 33%.

CONCLUSION

As was the case in our patient, genotype-phenotype correlations are poor in FVD, and molecular genetic test is necessary to confirm the diagnosis.

[Phenotypic and genetic analysis of a pedigree affected with hereditary FV deficiency due to a novel deletional variant of F5 gene]

OBJECTIVE

To analyze the phenotype and F5 gene variant in a pedigree affected with hereditary coagulation factor V (FV) deficiency.

METHODS

All of the exons, flanking sequences, and 5' and 3' untranslated regions of the F5 gene were subjected to PCR and direct sequencing. Suspected variant sites were confirmed by clone sequencing. Influence of the variants was predicted by using software including ClustalX and Mutation Taster.

RESULTS

The prothrombin time (PT) and activated partial thromboplastin time (APTT) of the proband were prolonged to 20.3 s and 59.2 s, respectively, while FV activity (FV:C) and FV antigen (FV:Ag) were reduced by 13% and 17%, respectively. The FV:C and FV:Ag of his father, sister and daughter were decreased to 35%, 37%, 29% and 42%, 46%, 35%, respectively. The proband was found to carry a heterozygous c.2851delT variant in exon 13 of the F5 gene, which caused a frameshift and resulted in a truncated protein (p.Ser923LeufsX8). In addition, a heterozygous c.1538G to A (p.Arg485Lys) variant was found in exon 10. The father, sister and daughter of the proband all carried the p.Ser923LeufsX8 variant, while his mother and son carried the heterozygous p.Arg485Lys polymorphism. His younger brother and wife were of the wild type. Bioinformatic analysis showed that p.Ser923 was highly conserved across various species. Mutation Taster scored 1.00 for the p.Ser923LeufsX8 variant, and the result has predicted a corresponding disease.

CONCLUSION

A heterozygous deletional mutation c.2851delT in exon 13 of the F5 gene and a heterozygous c.1538G to A polymorphism harbored by the proband may be associated with the decreased FV level in this pedigree.

Inherited disorders of the fibrinolytic pathway

Deficiencies or excessive activation of the  fibrinolytic system can result in severe, lifelong bleeding disorders. The most severe clinical phenotype is caused by α2-Antiplasmin (α2-AP) deficiency which results in excess fibrinolysis due to the inability to inhibit plasmin. Another bleeding disorder due to a defect in the fibrinolytic pathway results from Plasminogen activator inhibitor-1 (PAI-1) deficiency causing enhanced fibrinolysis due to the decreased inhibition of plasminogen activators resulting in increased conversion of plasminogen to plasmin. Both these disorders are rare and have an autosomal recessive pattern of inheritance. They can remain undetected as routine coagulation and platelet function tests are normal. A unique gain-of-function defect in fibrinolysis causes the Quebec platelet disorder (QPD) which is characterized by profibrinolytic platelets containing increased urokinase-type plasminogen activator (uPA) in the α-granules. A high index of suspicion based on clinical phenotype along with the availability of specialized hemostasis testing is required for timely and accurate diagnosis. Antifibrinolytic agents, such as tranexamic acid or ε-aminocaproic acid, are the mainstays of treatment which inhibit fibrinolysis by preventing the binding of plasminogen to fibrin and thereby stabilizing the fibrin clot. The purpose of this review is to summarize the pathogenesis, clinical phenotype, approaches to diagnosis and treatment for these three major disorders of fibrinolysis.

[Phenotypic and mutational analysis of a pedigree affected with hereditary coagulation factor Ⅴ deficiency]

OBJECTIVE

To explore the molecular pathogenesis for a pedigree affected with coagulation factor Ⅴ (FⅤ) deficiency.

METHODS

Prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen (FIB), coagulation factor Ⅱ activity (FⅡ: C), FⅤ activity (FⅤ: C), coagulation factor Ⅶ activity (FⅦ: C), and coagulation factor Ⅹ activity (FⅩ: C) were determined with a STAGO automatic coagulometer. FⅤ antigen (FⅤ: Ag) was detected with enzyme linked immunosorbent assay (ELISA). All exons and their flanking regions, and 5' and 3' untranslated regions of the F5 gene were analyzed by direct sequencing. Suspected mutation was verified by reverse sequencing as well as testing of family members. ClustalX software was used to analyze the conservative property of the mutation sites. PROVEAN and MutationTaster online software was used to predict the effect of the mutation on the protein function. Swiss-pdbViewer was used to analyze the protein model and interaction of amino acids.

RESULTS

The PT and APTT of the proband were slightly prolonged to 15.2 s and 41.8 s, respectively. And the FⅤ: C and FⅤ: Ag measured 55% and 62%, respectively. The FⅤ: C and FⅤ: Ag of his father and son were decreased to various extent (60%, 65% and 31%, 40%, respectively). A c.911G>A heterozygous mutation (Gly276Glu) was detected in exon 6 of the proband, for which her father and son were heterozygotes. The same mutation was not found in her mother, brother and husband. Conservation analysis showed that the Gly276 is highly conserved across various species. By bioinformatic analysis, the PROVEAN (scored -6.214) indicated Gly276Glu was harmful, and MutationTaster (scored 0.976) suggested that it is pathogenic. Model analysis suggested there are two hydrogen bonds between Gly276 and Ile298 in the wild type protein. When Gly276 was replaced by Glu276, the original hydrogen bond did not change, but the side chain of Glu was extended, which added steric hindrance with the surrounding amino acids, which resulted in decreased protein stability.

CONCLUSION

The heterozygous c.911G>A (Gly276Glu) mutation of the F5 gene probably underlies the decreased level of FⅤin the proband.

The duplication mutation of Quebec platelet disorder dysregulates PLAU, but not C10orf55, selectively increasing production of normal PLAU transcripts by megakaryocytes but not granulocytes

Quebec Platelet disorder (QPD) is a unique bleeding disorder that markedly increases urokinase plasminogen activator (uPA) in megakaryocytes and platelets but not in plasma or urine. The cause is tandem duplication of a 78 kb region of chromosome 10 containing PLAU (the uPA gene) and C10orf55, a gene of unknown function. QPD increases uPA in platelets and megakaryocytes >100 fold, far more than expected for a gene duplication. To investigate the tissue-specific effect that PLAU duplication has on gene expression and transcript structure in QPD, we tested if QPD leads to: 1) overexpression of normal or unique PLAU transcripts; 2) increased uPA in leukocytes; 3) altered levels of C10orf55 mRNA and/or protein in megakaryocytes and leukocytes; and 4) global changes in megakaryocyte gene expression. Primary cells and cultured megakaryocytes from donors were prepared for quantitative reverse polymerase chain reaction analyses, RNA-seq and protein expression analyses. Rapidly isolated blood leukocytes from QPD subjects showed only a 3.9 fold increase in PLAU transcript levels, in keeping with the normal to minimally increased uPA in affinity purified, QPD leukocytes. All subjects had more uPA in granulocytes than monocytes and minimal uPA in lymphocytes. QPD leukocytes expressed PLAU alleles in proportions consistent with an extra copy of PLAU on the disease chromosome, unlike QPD megakaryocytes. QPD PLAU transcripts were consistent with reference gene models, with a much higher proportion of reads originating from the disease chromosome in megakaryocytes than granulocytes. QPD and control megakaryocytes contained minimal reads for C10orf55, and C10orf55 protein was not increased in QPD megakaryocytes or platelets. Finally, our QPD megakaryocyte transcriptome analysis revealed a global down regulation of the interferon type 1 pathway. We suggest that the low endogenous levels of uPA in blood are actively regulated, and that the regulatory mechanisms are disrupted in QPD in a megakaryocyte-specific manner.

Platelet-delivered therapeutics

We have proposed that modified platelets could potentially be used to correct intrinsic platelet defects as well as for targeted delivery of therapeutic molecules to sights of vascular injury. Ectopic expression of proteins within α-granules prior to platelet activation has been achieved for several proteins, including urokinase, factor (F) VIII, and partially for FIX. Potential uses of platelet-directed therapeutics will be discussed, focusing on targeted delivery of urokinase as a thromboprophylactic agent and FVIII for the treatment of hemophilia A patients with intractable inhibitors. This presentation will discuss new strategies that may be useful in the care of patients with vascular injury as well as remaining challenges and limitations of these approaches.

[Analysis of a consanguineous pedigree featuring hereditary coagulation factor Ⅴ deficiency]

OBJECTIVE

To screen potential mutation and explore the underlying mechanism for a consanguineous pedigree featuring hereditary coagulation factor Ⅴ (FⅤ) deficiency.

METHODS

Clinical diagnosis was validated by coagulant parameter assays of prothrombin time (PT), activated partial thromboplastin time (APTT), fibrinogen (FIB), FⅤ procoagulant activity (FⅤ:C) and FⅤ antigen (FⅤ:Ag). Potential mutations of the F5 gene in the proband and his family members were analyzed by direct DNA sequencing of PCR products of all exons, exon-intron boundaries and 3', 5' untranslated regions. Suspected mutation was confirmed by reverse sequencing.

RESULTS

The PT and APTT in the proband were significantly prolonged, which measured 23.5 s (reference range 11.8-14.8 s) and 50.5 s (reference range 27.0-41.0 s), respectively. FⅤ activity and FⅤ antigen of the proband were significantly reduced to 8% and <1%, respectively. PT and APTT in the younger sister of the proband were also significantly prolonged (24.1 s and 62.4 s, respectively). Her FⅤ activity and FⅤ antigen were also significantly decreased (7% and <1%, respectively). PT and APTT of other family members were within the normal range. The homozygous missence mutation causing T→C transition at position 29170 in exon 5 of F5 gene has resulted in a Phe190Ser substitution in the proband. His younger sister was also homozygous for Phe190Ser. Heterozygosity for Phe190Ser was confirmed in his elder brother, elder sister, two daughters and niece, and their FⅤ activity were slightly decreased (57%, 73%, 72%, 66% and 75%, respectively). A normal wild type was observed in two younger brothers of the proband, and their FⅤ activity and FⅤ antigen were in the normal range.

CONCLUSION

Homozygous missence mutation of Phe190Ser has been found in above family featuring hereditary FⅤ deficiency. The homozygous missence mutation was inherited from the parents by consanguineous marriage. Phe190Ser probably underlies may underlie the pathogenesis of hereditary FⅤ deficiency in this pedigree.