Fitusiran reduces bleeding in factor X-deficient mice.

ABSTRACT: Factor X (FX) deficiency is a rare bleeding disorder manifesting a bleeding tendency caused by low FX activity levels. We aim to explore the use of fitusiran (an investigational small interfering RNA that silences antithrombin expression) to increase thrombin generation and the in vivo hemostatic potential under conditions of FX deficiency. We therefore developed a novel model of inducible FX deficiency, generating mice expressing <1% FX activity and antigen (f10low mice). Compared with control f10WT mice, f10low mice had sixfold and fourfold prolonged clotting times in prothrombin time and activated partial prothrombin time assays, respectively (P < .001). Thrombin generation was severely reduced, irrespective of whether tissue factor or factor XIa was used as an initiator. In vivo analysis revealed near-absent thrombus formation in a laser-induced vessel injury model. Furthermore, in 2 distinct bleeding models, f10low mice displayed an increased bleeding tendency compared with f10WT mice. In the tail-clip assay, blood loss was increased from 12 ± 16 µL to 590 ± 335 µL (P < .0001). In the saphenous vein puncture (SVP) model, the number of clots generated was reduced from 19 ± 5 clots every 30 minutes for f10WT mice to 2 ± 2 clots every 30 minutes (P < .0001) for f10low mice. In both models, bleeding was corrected upon infusion of purified FX. Treatment of f10low mice with fitusiran (2 × 10 mg/kg at 1 week interval) resulted in 17 ± 6% residual antithrombin activity and increased thrombin generation (fourfold and twofold to threefold increase in endogenous thrombin potential and thrombin peak, respectively). In the SVP model, the number of clots was increased to 8 ± 6 clots every 30 minutes (P = .0029). Altogether, we demonstrate that reduction in antithrombin levels is associated with improved hemostatic activity under conditions of FX deficiency.

Five new F10 variants in hereditary factor x deficiency detected by high-throughput sequencing.

INTRODUCTION: Factor X deficiency is a rare inherited bleeding disorder. To date, 181 variants are reported in the recently updated F10-gene variant database. AIM: This study aimed to describe new F10 variants. METHOD: The F10 gene was analysed in 16 consecutive families with FX deficiency by a targeted high-throughput sequencing approach, including F10, F9, F8 genes, and 78 genes dedicated to haematological malignancies. RESULTS: We identified 19 variants (17 missense, one nonsense and one frameshift) and two copy number variations. Two patients presenting a combined FVII-FX deficiency showed a loss of one F10 gene copy (del13q34) associated with a missense variant on the remaining allele, leading to a FX:C significantly lower than the FVII:C level and explaining their unusual bleeding history. We reported five novel variants. Three missense variants (p.Glu22Val affecting the signal peptide cleavage site, p.Cys342Tyr removing the disulphide bond between the FX heavy and light chains, and p.Val385Met located in FX peptidase S1 domain) were detected at compound heterozygosis status in three patients with severe bleeding symptoms and FX:C level below 10 IU/dL. Two truncating variants p.Tyr279* and p.Thr434Aspfs*13 leading to an altered FX protein were found at heterozygous state in two patients with mild bleeding history. CONCLUSION: This study showed the feasibility and the interest of high-throughput sequencing approach for rare bleeding disorders, enabling the report of F10 gene screening in a 3-weeks delay, suitable for clinical use. The description of five new variants may contribute to a better understanding of the phenotype-genotype correlation in FX deficiency.

A novel factor modulating X chromosome dosage compensation in Anopheles.

Dosage compensation (DC), a process countering chromosomal imbalance in individuals with heteromorphic sex chromosomes, has been molecularly characterized only in mammals, Caenorhabditis elegans, and fruit flies.1 In Drosophila melanogaster males, it is achieved by an approximately 2-fold hypertranscription of the monosomic X chromosome mediated by the MSL complex.2,3 The complex is not assembled on female X chromosomes because production of its key protein MSL-2 is prevented due to intron retention and inhibition of translation by Sex-lethal, a female-specific protein operating at the top of the sex determination pathway.4 It remains unclear how DC is mechanistically regulated in other insects. In the malaria mosquito Anopheles gambiae, an approximately 2-fold hypertranscription of the male X also occurs5 by a yet-unknown molecular mechanism distinct from that in D. melanogaster.6 Here we show that a male-specifically spliced gene we call 007, which arose by a tandem duplication in the Anopheles ancestral lineage, is involved in the control of DC in males. Homozygous 007 knockouts lead to a global downregulation of the male X, phenotypically manifested by a slower development compared to wild-type mosquitoes or mutant females-however, without loss of viability or fertility. In females, a 007 intron retention promoted by the sex determination protein Femaleless, known to prevent hypertranscription from both X chromosomes,7 introduces a premature termination codon apparently rendering the female transcripts non-productive. In addition to providing a unique perspective on DC evolution, the 007, with its conserved properties, may represent an important addition to a genetic toolbox for malaria vector control.

Succinate dehydrogenase and MYC-associated factor X mutations in pituitary neuroendocrine tumours.

Pituitary neuroendocrine tumours (PitNETs) associated with paragangliomas or phaeochromocytomas are rare. SDHx variants are estimated to be associated with 0.3-1.8% of PitNETs. Only a few case reports have documented the association with MAX variants. Prolactinomas are the most common PitNETs occurring in patients with SDHx variants, followed by somatotrophinomas, clinically non-functioning tumours and corticotrophinomas. One pituitary carcinoma has been described. SDHC, SDHB and SDHA mutations are inherited in an autosomal dominant fashion and tumorigenesis seems to adhere to Knudson's two-hit hypothesis. SDHD and SDHAF2 mutations most commonly have paternal inheritance. Immunohistochemistry for SDHB or MAX and loss of heterozygosity analysis can support the assessment of pathogenicity of the variants. Metabolomics is promising in the diagnosis of SDHx-related disease. Future research should aim to further clarify the role of SDHx and MAX variants or other genes in the molecular pathogenesis of PitNETs, including pseudohypoxic and kinase signalling pathways along with elucidating epigenetic mechanisms to predict tumour behaviour.

Integrated microarray for identifying the hub mRNAs and constructed miRNA-mRNA network in coronary in-stent restenosis.

As a major complication after percutaneous coronary intervention (PCI) in patients who suffer from coronary artery disease, in-stent restenosis (ISR) poses a significant challenge for clinical management. A miRNA-mRNA regulatory network of ISR can be constructed to better reveal the occurrence of ISR. The relevant data set from the Gene Expression Omnibus (GEO) database was downloaded, and 284 differentially expressed miRNAs (DE-miRNAs) and 849 differentially expressed mRNAs (DE-mRNAs) were identified. As predicted by online tools, 65 final functional genes (FmRNAs) were overlapping DE-mRNAs and DE-miRNAs target genes. In the biological process (BP) terms of gene ontology (GO) functional analysis, the FmRNAs were mainly enriched in the cellular response to peptide, epithelial cell proliferation, and response to peptide hormone. In the Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis, the FmRNAs were mainly enriched in breast cancer, endocrine resistance, and Cushing syndrome. Jun proto-oncogene, activator protein-1 (AP-1) transcription factor subunit (JUN), insulin-like growth factor 1 receptor (IGF1R), member RAS oncogene family (RAB14), specificity protein 1 (SP1), protein tyrosine phosphatase nonreceptor type 1 (PTPN1), DDB1 and CUL4 associated factor 10 (DCAF10), retinoblastoma-binding protein 5 (RBBP5), and eukaryotic initiation factor 4A-I (EIF4A1) were hub genes in the protein-protein interaction network (PPI network). The miRNA-mRNA network containing DE-miRNAs and hub genes was built. Hsa-miR-139-5p-JUN, hsa-miR-324-5p-SP1 axis pairs were found in the miRNA-mRNA network, which could promote ISR development. The aforementioned results indicate that the miRNA-mRNA network constructed in ISR has a regulatory role in the development of ISR and may provide new approaches for clinical treatment and experimental development.

Clotting factor genes are associated with preeclampsia in high-altitude pregnant women in the Peruvian Andes.

Preeclampsia is a multi-organ complication of pregnancy characterized by sudden hypertension and proteinuria that is among the leading causes of preterm delivery and maternal morbidity and mortality worldwide. The heterogeneity of preeclampsia poses a challenge for understanding its etiology and molecular basis. Intriguingly, risk for the condition increases in high-altitude regions such as the Peruvian Andes. To investigate the genetic basis of preeclampsia in a population living at high altitude, we characterized genome-wide variation in a cohort of preeclamptic and healthy Andean families (n = 883) from Puno, Peru, a city located above 3,800 meters of altitude. Our study collected genomic DNA and medical records from case-control trios and duos in local hospital settings. We generated genotype data for 439,314 SNPs, determined global ancestry patterns, and mapped associations between genetic variants and preeclampsia phenotypes. A transmission disequilibrium test (TDT) revealed variants near genes of biological importance for placental and blood vessel function. The top candidate region was found on chromosome 13 of the fetal genome and contains clotting factor genes PROZ, F7, and F10. These findings provide supporting evidence that common genetic variants within coagulation genes play an important role in preeclampsia. A selection scan revealed a potential adaptive signal around the ADAM12 locus on chromosome 10, implicated in pregnancy disorders. Our discovery of an association in a functional pathway relevant to pregnancy physiology in an understudied population of Native American origin demonstrates the increased power of family-based study design and underscores the importance of conducting genetic research in diverse populations.

Site-specific functional roles of the Factor X activation peptide in the intrinsic tenase-mediated Factor X activation.

The conversion of zymogen Factor X (FX) to an active protease involves the removal of a 52-residue long activation peptide (AP). Through site-directed mutagenesis, we investigate the role of the AP and demonstrate that the high abundance of proline residues is important for efficient proteolysis of FX. Moreover, we identify an essential interaction site for Factor IXa (FIXa) between residues 22 and 30 (AP numbering) and find that the residues between 31 and 41 may provide an important interaction site for the intrinsic tenase complex, composed of Factor IXa (FIXa) and Factor VIIIa (FVIIIa). Finally, we suggest that the carbohydrate chain at Asn-39 restricts the activator specificity, as elimination of this glycosylation site increases the activation rate for activation by FIXa and FXa.

Association of genetic variations in ACE2, TIRAP and factor X with outcomes in COVID-19.

BACKGROUND: Coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), can manifest with varying disease severity and mortality. Genetic predisposition influences the clinical course of infectious diseases. We investigated whether genetic polymorphisms in candidate genes ACE2, TIRAP, and factor X are associated with clinical outcomes in COVID-19. METHODS: We conducted a single-centre retrospective cohort study. All patients who visited the emergency department with SARS-CoV-2 infection proven by polymerase chain reaction were included. Single nucleotide polymorphisms in ACE2 (rs2285666), TIRAP (rs8177374) and factor X (rs3211783) were assessed. The outcomes were mortality, respiratory failure and venous thromboembolism. Respiratory failure was defined as the necessity of >5 litres/minute oxygen, high flow nasal oxygen suppletion or mechanical ventilation. RESULTS: Between March and April 2020, 116 patients (35% female, median age 65 [inter quartile range 55-75] years) were included and treated according to the then applicable guidelines. Sixteen patients (14%) died, 44 patients (38%) had respiratory failure of whom 23 required endotracheal intubation for mechanical ventilation, and 20 patients (17%) developed venous thromboembolism. The percentage of TIRAP polymorphism carriers in the survivor group was 28% as compared to 0% in the non-survivor group (p = 0.01, Bonferroni corrected p = 0.02). Genotype distribution of ACE2 and factor X did not differ between survivors and non-survivors. CONCLUSION: This study shows that carriage of TIRAP polymorphism rs8177374 could be associated with a significantly lower mortality in COVID-19. This TIRAP polymorphism may be an important predictor in the outcome of COVID-19.

Characterization of a Missense Mutation in the Catalytic Domain and a Splicing Mutation of Coagulation Factor X Compound Heterozygous in a Chinese Pedigree.

BACKGROUND: Congenital coagulation factor X (FX) deficiency is a rare bleeding disorder with an incidence of one in one million caused by mutations in the FX-coding gene(F10), leading to abnormal coagulation activity and a tendency for severe hemorrhage. Therefore, identifying mutations in FX is important for diagnosing congenital FX deficiency. RESULTS: Genetic analysis of the proband identified two single-base substitutions: c.794T > C: p.Ile265Thr and c.865 + 5G > A: IVS7 + 5G > A. His FX activity and antigen levels were < 1% and 49.7%, respectively; aPTT and PT were prolonged to 65.3 and 80.5 s, respectively. Bioinformatics analysis predicted the two novel variants to be pathogenic. In-vitro expression study of the missense mutation c.794T > C: p.Ile265Thr showed normal synthesis and secretion. Activation of FXs by RVV, FVII/TF, and FVIII/FIX all showed no obvious difference between the variant and the reference. However, clotting activity by PT and aPTT assays and activity of thrombin generation in a TGA assay all indicated reduced activity of the mutant FX-Ile265Thr compared to FX-WT. Minigene assay showed a normal splicing mode c.865 + 5G > A: IVS7 + 5G > A, which is inconsistent with clinical phenotype. CONCLUSIONS: The heterozygous variants c.794T > C: p.Ile265Thr or c.865 + 5G > A: IVS7 + 5G > A indicate mild FX deficiency, but the compound heterozygous mutation of the two causes severe congenital FX deficiency. Genetic analysis of these two mutations may help characterize the bleeding tendency and confirm congenital FX deficiency. In-vitro expression and functional study showed that the low activity of the mutant FX-Ile265Thr is caused by decrease in its enzyme activity rather than self-activation. The minigene assay help us explore possible mechanisms of the splicing mutation. However, more in-depth mechanism research is needed in the future.

Blood coagulation factor X: molecular biology, inherited disease, and engineered therapeutics.

Blood coagulation factor X/Xa sits at a pivotal point in the coagulation cascade and has a role in each of the three major pathways (intrinsic, extrinsic and the common pathway). Due to this central position, it is an attractive therapeutic target to either enhance or dampen thrombin generation. In this brief review, I will summarize key developments in the molecular understanding of this critical clotting factor and discuss the molecular basis of FX deficiency, highlight difficulties in expressing recombinant factor X, and detail two factor X variants evaluated clinically.

A Compound Heterozygosis of Two Novel Mutations Causes Factor X Deficiency in a Chinese Pedigree.

BACKGROUND: Mutations in the F10-coding gene can cause factor X (FX) deficiency, leading to abnormal coagulation activity and severe tendency for hemorrhage. Therefore, identifying mutations in F10 is important for diagnosing congenital FX deficiency. METHODS: We studied a 63-year-old male patient with FX deficiency and 10 of his family members. Clotting and immunological methods were used to determine activated partial thromboplastin time (aPTT), prothrombin time (PT), thrombin time (TT), fibrinogen levels, FX activity, and FX antigen levels. The platelet count was determined. A mixing study was performed to eliminate the presence of coagulation factor inhibitors and lupus anticoagulant. Mutations were searched using whole-exome sequencing and certified by Sanger sequencing. RESULTS: Genetic analysis of the proband identified two single-base substitutions: c.1085G>A (p.Ser362Asn) and c.1152C>A (p.Tyr384Ter, termination codon, caused by the DNA sequence TAA). His FX activity and antigen levels were 1.7% and 408.53 pg/mL, respectively; aPTT and PT were 52.3 and 48.0 s, respectively. One brother had the same compound heterozygous mutations, and his FX activity and antigen levels were 1.3% and 465.47 pg/mL, respectively; his aPTT and PT were 65.2 and 54.5 s, respectively. His mother, another brother, and one sister were heterozygous for c.1085G>A (p.Ser362Asn), and his daughter and grandson (6 years old) were heterozygous for c.1152C>A (p.Tyr384Ter). CONCLUSION: The heterozygous variants p.Ser362Asn or p.Tyr384Ter indicate mild FX deficiency, but the compound heterozygous mutation of the two causes severe congenital FX deficiency and bleeding. Genetic analysis of these two mutations may help characterize the bleeding tendency and confirm congenital FX deficiency.

A mutated factor X activatable by thrombin corrects bleedings in vivo in a rabbit model of antibody-induced hemophilia A.

Rendering coagulation factor X sensitive to thrombin was proposed as a strategy that can bypass the need for factor VIII. In this paper, this non-replacement strategy was evaluated in vitro and in vivo in its ability to correct factor VIII but also factor IX, X and XI deficiencies. A novel modified factor X, named Actiten, was generated and produced in the HEK293F cell line. The molecule possesses the required post-translational modifications, partially keeps its ability to be activated by RVV-X, factor VIIa/tissue factor, factor VIIIa/factor IXa and acquires the ability to be activated by thrombin. The potency of the molecule was evaluated in respective deficient plasmas or hemophilia A plasmas, for some with inhibitors. Actiten corrects dose dependently all the assayed deficient plasmas. It is able to normalize the thrombin generation at 20 µg/mL showing however an increased lagtime. It was then assayed in a rabbit antibody-induced model of hemophilia A where, in contrast to recombinant factor X wild-type, it normalized the bleeding time and the loss of hemoglobin. No sign of thrombogenicity was observed and the generation of activated factor X was controlled by the anticoagulation pathway in all performed coagulation assays. This data indicates that Actiten may be considered as a possible non replacement factor to treat hemophilia's with the advantage of being a zymogen correcting bleedings only when needed.

Evolutionary Adaptations in Pseudonaja Textilis Venom Factor X Induce Zymogen Activity and Resistance to the Intrinsic Tenase Complex.

The venom of the Australian snake Pseudonaja textilis comprises powerful prothrombin activators consisting of factor X (v-ptFX)- and factor V-like proteins. While all vertebrate liver-expressed factor X (FX) homologs, including that of P. textilis, comprise an activation peptide of approximately 45 to 65 residues, the activation peptide of v-ptFX is significantly shortened to 27 residues. In this study, we demonstrate that exchanging the human FX activation peptide for the snake venom ortholog impedes proteolytic cleavage by the intrinsic factor VIIIa-factor IXa tenase complex. Furthermore, our findings indicate that the human FX activation peptide comprises an essential binding site for the intrinsic tenase complex. Conversely, incorporation of FX into the extrinsic tissue factor-factor VIIa tenase complex is completely dependent on exosite-mediated interactions. Remarkably, the shortened activation peptide allows for factor V-dependent prothrombin conversion while in the zymogen state. This indicates that the active site of FX molecules comprising the v-ptFX activation peptide partially matures upon assembly into a premature prothrombinase complex. Taken together, the shortened activation peptide is one of the remarkable characteristics of v-ptFX that has been modified from its original form, thereby transforming FX into a powerful procoagulant protein. Moreover, these results shed new light on the structural requirements for serine protease activation and indicate that catalytic activity can be obtained without formation of the characteristic Ile16-Asp194 salt bridge via modification of the activation peptide.

Molecular mechanism of a novel Ser362Asn mutation causing inherited FX deficiency in a Chinese family.

Factor X (FX) deficiency is an inherited autosomal recessive bleeding disorder. Here, we analyzed a proband with FX deficiency in a Chinese family. Genetic analysis revealed that the proband and his affected sister was homozygous for c.1085G>A mutation, corresponding to a Ser362Asn substitution. In vitro expression experiments showed that the FX Ser362Asn mutation led to a significant reduction in activity levels in the culture medium. This Ser to Asn substitution may change the shape of the active site. Moreover, simulations of molecular dynamics indicated that the binding energy of the FX Ser362Asn to the substrate is higher than that of wild type and the side-chain conformation of the catalytic residue His276 (His42) is changed. This impairs the conformational switch of the protein from zymogen to proteinase, thus causing the functional defect of FX protein. Our findings suggest that the Ser362Asn substitution is a pathogenic mutation that causes inherited FX deficiency.

Genetic analysis of a compound heterozygous patient with congenital factor X deficiency and regular replacement therapy with a prothrombin complex concentrate.

Congenital factor X (FX) deficiency is a rare bleeding disorder with an incidence of one in one million. The proband, a 2-year-old girl, exhibited easy bruising and a history of umbilical cord bleeding at birth. Prothrombin time (> 40 s) and activated partial thromboplastin time (65.0 s) were prolonged. Marked declines in FX activity (< 1%) and FX antigen levels (5%) were also observed. Genetic analysis of the proband identified two types of single-base substitutions, c.353G>A (p.Gly118Asp) and c.1303G>A (p.Gly435Ser), indicating compound heterozygous congenital FX deficiency. Genetic analysis of family members revealed that her father and older sister (5-year-old) were also heterozygous for p.Gly118Asp, and that her mother was heterozygous for p.Gly435Ser. To improve the bleeding tendency, the proband received regular replacement of 500 units of PPSB-HT, a prothrombin complex concentrate (PCC). Following continued regular replacement of 500 units of PPSB-HT once per week, the proband has exhibited no bleeding tendencies and no new bruises have been observed. There are no previous report of the use of PPSB-HT for regular FX replacement. Regular replacement therapy with PPSB-HT may be an effective method for preventative control of bleeding tendencies in FX deficiency.

Rare bleeding disorders and advances in gene therapy.

: Rare bleeding disorders usually begin in childhood and manifest as varying degrees of bleeding, which can be life-threatening in severe cases. With the development of gene editing technology, it is expected that hereditary coagulation factor disorders will someday be fundamentally cured by gene therapy. On account of their rarity, comprehension of these diseases is essential for the application of new treatment strategies. We have compiled the features of some newly discovered mutations of prothrombin, factor VII, and factor X in recent years. In addition, this review introduces the advances and obstacles in gene therapy.

A Thrombin-Activatable Factor X Variant Corrects Hemostasis in a Mouse Model for Hemophilia A.

Engineered recombinant factor X (FX) variants represent a promising strategy to bypass the tenase complex and restore hemostasis in hemophilia patients. Previously, a thrombin-activatable FX variant with fibrinopeptide-A replacing the activation peptide (FX-delAP/FpA) has been described in this regard. Here we show that FX-delAP/FpA is characterized by a sixfold shorter circulatory half-life compared with wild-type FX, limiting its therapeutical applicability. We therefore designed a variant in which the FpA sequence is inserted C-terminal to the FX activation peptide (FX/FpA). FX/FpA displayed a similar survival to wt-FX in clearance experiments and could be converted into FX by thrombin and other activating agents. In in vitro assays, FX/FpA efficiently restored thrombin generation in hemophilia A and hemophilia B plasmas, even in the presence of inhibitory antibodies. Expression following hydrodynamic gene transfer of FX/FpA restored thrombus formation in FVIII-deficient mice in a laser-induced injury model as well as hemostasis in a tail-clip bleeding model. Hemostasis after tail transection in FVIII-deficient mice was also corrected at 5 and 90 minutes after injection of purified FX/FpA. Our data indicate that FX/FpA represents a potential tenase-bypassing agent for the treatment of hemophilia patients with or without inhibitors.

Coagulation factors VII, IX and X are effective antibacterial proteins against drug-resistant Gram-negative bacteria.

Infections caused by drug-resistant "superbugs" pose an urgent public health threat due to the lack of effective drugs; however, certain mammalian proteins with intrinsic antibacterial activity might be underappreciated. Here, we reveal an antibacterial property against Gram-negative bacteria for factors VII, IX and X, three proteins with well-established roles in initiation of the coagulation cascade. These factors exert antibacterial function via their light chains (LCs). Unlike many antibacterial agents that target cell metabolism or the cytoplasmic membrane, the LCs act by hydrolyzing the major components of bacterial outer membrane, lipopolysaccharides, which are crucial for the survival of Gram-negative bacteria. The LC of factor VII exhibits in vitro efficacy towards all Gram-negative bacteria tested, including extensively drug-resistant (XDR) pathogens, at nanomolar concentrations. It is also highly effective in combating XDR Pseudomonas aeruginosa and Acinetobacter baumannii infections in vivo. Through decoding a unique mechanism whereby factors VII, IX and X behave as antimicrobial proteins, this study advances our understanding of the coagulation system in host defense, and suggests that these factors may participate in the pathogenesis of coagulation disorder-related diseases such as sepsis via their dual functions in blood coagulation and resistance to infection. Furthermore, this study may offer new strategies for combating Gram-negative "superbugs".

A Genome Wide Association Study on plasma FV levels identified PLXDC2 as a new modifier of the coagulation process.

BACKGROUND: Factor V (FV) is a circulating protein primarily synthesized in the liver, and mainly present in plasma. It is a major component of the coagulation process. OBJECTIVE: To detect novel genetic loci participating to the regulation of FV plasma levels. METHODS: We conducted the first Genome Wide Association Study on FV plasma levels in a sample of 510 individuals and replicated the main findings in an independent sample of 1156 individuals. RESULTS: In addition to genetic variations at the F5 locus, we identified novel associations at the PLXDC2 locus, with the lead PLXDC2 rs927826 polymorphism explaining ~3.7% (P = 7.5 × 10-15 in the combined discovery and replication samples) of the variability of FV plasma levels. In silico transcriptomic analyses in various cell types confirmed that PLXDC2 expression is positively correlated to F5 expression. SiRNA experiments in human hepatocellular carcinoma cell line confirmed the role of PLXDC2 in modulating factor F5 gene expression, and revealed further influences on F2 and F10 expressions. CONCLUSION: Our study identified PLXDC2 as a new molecular player of the coagulation process.