K196E Mutation Research Articles

Effects of low-dose combined oral contraceptives and protein S K196E mutation on anticoagulation factors: a prospective observational study.

The association between low-dose combined oral contraceptives (COCs) and anticoagulation factors in Japanese women has been rarely studied. A total of 394 Japanese women with a new beginning cycle of COC use were enrolled, of whom 335 women visited the clinic within 4weeks after starting the first cycle of COC. Visits occurred in the active phase (272 women) and the placebo phase (63 women). Free protein S (PS) antigen and activity levels and antithrombin activity levels decreased significantly in both the active and placebo phase groups. Protein C (PC) activity levels increased significantly in both groups. Larger reductions in free PS antigen and activity levels occurred with COC comprising either 30µg ethinylestradiol/desogestrel or 20µg ethinylestradiol/drospirenone than that comprising 35µg ethinylestradiol/norethisterone. In four women with the Japanese-specific PS K196E mutation, mean PS activity was 65% before COC use and 57% during COC use, indicating further decrease with COC use. In conclusion, decreased antigen and activity levels of PS and antithrombin and increased activity levels of PC were observed even during the first cycle of low-dose COC use. The effects on PS and PC activities were also observed in the hormone-free interval.

Protein S K196E mutation reduces its cofactor activity for APC but not for TFPI

BackgroundProtein S (PS) is an anticoagulant molecule that functions as a cofactor for activated protein C (APC) in the inactivation of activated coagulation factors Va (FVa) and VIIIa. It also serves as a cofactor for tissue factor pathway inhibitor (TFPI) in the efficient inhibition of factor Xa (FXa). The Lys196‐to‐Glu (K196E, Tokushima) mutation in the EGF‐2 domain of PS is a genetic risk factor for venous thromboembolism (VTE) in the Japanese population. ObjectivesTo investigate the molecular basis of the thrombophilic phenotype of Japanese patients carrying the PS K196E mutation. MethodsWe expressed recombinant human PS wild‐type (PS‐K) and K196E‐mutant (PS‐E) in CHO cells, and purified them by Ni2+‐affinity and anion exchange column chromatography. We investigated the anticoagulant functions of PS‐K and PS‐E by measuring APC cofactor activity, TFPI cofactor activity, affinity for the β chain of complement component C4b‐binding protein (C4BP), and cleavage by thrombin. ResultsPS‐E had approximately 40% APC cofactor activity compared with PS‐K in a clotting‐based assay and a FVa inactivation assay. The TFPI cofactor activity of PS‐E in the FXa inactivation assay was equivalent to that of PS‐K in the absence and presence of coagulation factor V. The strengths of PS‐E and PS‐K binding to the β chain of C4BP were comparable, and both were equally cleaved by thrombin. ConclusionsThe PS K196E mutation increases the risk of VTE because of reduced APC cofactor activity but does not alter various other properties, including the TFPI cofactor activity.

静脈血栓塞栓症の遺伝的リスクであるプロテインS K196E 変異検出ELISA の開発

静脈血栓塞栓症の遺伝的リスクであるプロテインS K196E 変異検出ELISA の開発

Exacerbated venous thromboembolism in mice carrying a protein S K196E mutation

AbstractProtein S (PS) acts as an anticoagulant cofactor for activated protein C in regulation of blood coagulation. The K196E mutation in PS is a race-specific genetic risk factor for venous thromboembolism with a prevalence of ∼2% within the Japanese population. To evaluate the thrombosis risk of the PS-K196E mutation, we generated PS-K196E knockin mice and heterozygous PS-deficient mice. We analyzed their thrombotic states, comparing with mice carrying the factor V Leiden mutation (FV-R504Q), a race-specific genetic risk for venous thrombosis in whites. PS-K196E mice grew normally but had decreased activated protein C cofactor activity in plasma. Purified recombinant murine PS-K196E showed the same decreased activated protein C cofactor activity. A deep vein thrombosis model of electrolytic inferior vena cava injury and pulmonary embolism models induced by infusion of tissue factor or polyphosphates revealed that PS-K196E mice, heterozygous PS-deficient mice, and FV-R504Q mice were much more susceptible to venous thrombosis compared with wild-type mice. Transient middle cerebral artery ischemia-reperfusion injury model studies demonstrated that both PS-K196E mice and heterozygous PS-deficient mice had cerebral infarction similar to wild-type mice, consistent with human observations. Our in vitro and in vivo results support a causal relationship between the PS-K196E mutation and venous thrombosis and indicate that PS-K196E mice can provide an in vivo evaluation system to help uncovering racial differences in thrombotic diseases.

ELISA-Based Detection System for Protein S K196E Mutation, a Genetic Risk Factor for Venous Thromboembolism.

Protein S (PS) acts as a cofactor for activated protein C in the plasma anticoagulant system. PS Lys196-to-Glu (K196E) mutation is a genetic risk factor for venous thromboembolism in Japanese individuals. Because of the substantial overlap in PS anticoagulant activity between KK (wild-type) and KE (heterozygous) genotypes, it is difficult to identify PS K196E carriers by measuring PS activity. Here, we generated monoclonal antibodies specific to the PS K196E mutant and developed a simple and reliable method for the identification of PS K196E carriers. We immunized mice with a keyhole limpet hemocyanin-conjugated synthetic peptide with Glu196. The hybridoma cells were screened for the binding ability of the produced antibodies to recombinant mutant EGF-like domains of PS (Ile117–Glu283). We obtained three hybridoma cell lines producing PS K196E mutation-specific antibodies. We established a sandwich enzyme-linked immunosorbent assay (ELISA) system in which the PS K196E mutation-specific monoclonal antibody was used as a detection antibody. We measured human plasma samples by using this system and successfully discriminated 11 individuals with the KE genotype from 122 individuals with the KK genotype. The ELISA system using the PS K196E mutation-specific antibody is a useful tool for the rapid identification of PS K196E carriers, who are at a higher risk for venous thromboembolism.

Nonsynonymous mutations in three anticoagulant genes in Japanese patients with adverse pregnancy outcomes

Hereditary thrombophilias may associate with uteroplacental thrombosis leading to adverse pregnancy outcomes. The present study was conducted to reveal the frequency of the low-frequency thrombophilic protein S K196E mutation, as well as the frequency of very rare nonsynonymous mutations in protein S, protein C, and antithrombin genes, in patients with adverse pregnancy outcomes. We enrolled 330 Japanese patients with adverse pregnancy outcomes and divided them into 233 patients with two or more miscarriages and 114 patients with fetal growth restriction (FGR) and/or intrauterine fetal death (IUFD); 17 patients belonged to both groups. We sequenced the entire coding regions of three anticoagulant genes in all 330 patients. We found that protein S K196E mutation was identified in 4 out of 233 patients with recurrent miscarriage and in 2 out of 114 patients with FGR and/or IUFD. The frequencies of this mutation in these patient groups were not different from that in a Japanese general population. Very rare nonsynonymous mutations were identified in 3.3% (11 out of 330) of patients with adverse pregnancy outcomes. Although the low-frequency protein S K196E mutation can increase the risk for venous thromboembolism, it did not increase the risk for adverse pregnancy outcomes even in Japanese.

Genetic analysis of patients with deep vein thrombosis during pregnancy and postpartum

Deep vein thrombosis (DVT) is a serious pregnancy-related complication. Recent studies indicate that the genetic background for DVT differs with ethnicity. In our study, we enrolled 18 consecutive Japanese patients who had developed DVT during pregnancy and postpartum. We performed a genetic analysis of three candidate genes for DVT, protein S, protein C and antithrombin, in these patients. We found that four patients had missense mutations in the protein S gene, including the K196E mutation in two patients, the L446P mutation in one patient, and the D79Y and T630I mutations in one patient, as well as one patient with the C147Y mutation in the protein C gene. All five patients with genetic mutations had DVT in their first two trimesters. Nine of the patients without genetic mutations developed DVT in the first two trimesters, and four in the postpartum period. Thus, genetic mutations in the protein S gene were predominant in pregnant Japanese DVT women, and DVT in pregnant women with genetic mutations occurred more frequently at the early stage of pregnancy than postpartum. Considering the rapid decrease in protein S activity during pregnancy, we may need to assess thrombophilia in women before pregnancy.

Mesenteric Venous Thrombosis in a Child With Type 2 Protein S Deficiency

A 5-year-old girl presented with abdominal pain and bloody stools 2 weeks after suffering from influenza A infection. Enhanced computed tomographic scan showed widespread splanchnic venous thrombosis and small intestine necrosis. She recovered after the necrotic bowel was resected. The patient continues to receive anticoagulant therapy. Thrombophilia screening after the complete resolution consistently showed mildly decreased protein S (PS) activity with normal PS antigen levels. Sequence analysis detected a heterozygous K196E mutation in the PROS1 gene. Type 2 PS deficiency was diagnosed. This is the first report of mesenteric vein thrombosis in a child with a type 2 PS deficiency.

Prevalence of genetic mutations in protein S, protein C and antithrombin genes in Japanese patients with deep vein thrombosis

Introduction Genetic deficiencies of PROS1, PROC, and SERPINC1 (antithrombin) are risk factors for deep vein thrombosis (DVT). Diagnosis of the inherited deficiencies of these three genes is sometimes difficult because of the phenotypic variability. This study was undertaken to reveal the frequency of nonsynonymous mutations of these three genes in Japanese DVT patients. Patients/Methods One hundred seventy-three DVT patients were registered by the Sub-group of Blood Coagulation Abnormality, from the Study Group of Research on Measures for Intractable Diseases. We sequenced the entire coding regions of the three genes in all DNA samples and identified the nonsynonymous mutations. Results and Conclusions For PROS1 we identified 15 nonsynonymous mutations in 28 DVT patients; for PROC, 10 nonsynonymous mutations in 17 patients; and for SERPINC1, 13 nonsynonymous mutations in 14 patients. Five patients had two mutations in PROS1 and PROC, and all of them had PROS1 K196E mutation. We previously identified one patient with a large PROS1 gene deletion. Thus, 55 out of 173 patients (32%) carried at least one genetic defect in the three genes. The PROS1 K196E mutation found in 15 Japanese DVT patients was the most prevalent. Mutations of PROC K193del and V339M were the second, each found in four patients. Our data suggested that the PROC K193del mutation caused the loss of the anticoagulant activity but not the amidolytic activity. Our effort is the first DNA resequencing study to identify the genetic variations in DVT patients without any consideration of their plasma activities and antigens. To minimize selection bias in a future evaluation of the contribution of genetic deficiency to DVT, we must recruit patients consecutively.

Plasma protein S activity correlates with protein S genotype but is not sensitive to identify K196E mutant carriers.

Protein S (PS) is an anticoagulant protein that functions as a cofactor for activated protein C (APC), and congenital PS deficiency is a well-known risk factor for the development of deep vein thrombosis (DVT). Recently, we and others identified the K196E missense mutation in the second epidermal growth factor-like domain of PS as a genetic risk factor for DVT in the Japanese population. The incidence of this mutation is high in the Japanese population. In the present study, we investigated the relationship between plasma PS activity and the presence of the K196E mutation. We measured PS activity as a cofactor activity for APC in 1,862 Japanese individuals and determined the PS K196E genotype in this population. Individuals heterozygous for the mutant E-allele had lower plasma PS activity than wildtype subjects (mean +/- SD, 71.9 +/- 17.6%, n = 34 vs. 87.9 +/- 19.8%, n = 1,828, P < 0.0001). However, the PS activity of several heterozygous individuals (n = 8) was greater than the population average. In contrast, multiple wildtype subjects (n = 26) had PS activity less than 2 SD below the population mean, indicating that other genetic or environmental factors affect PS activity. Plasma PS activity itself is not suitable for identifying PS 196E carriers and other methods are required for carrier detection.

Genetic Risk Factors for Deep Vein Thrombosis among Japanese: Importance of Protein S K196E Mutation

There is mounting evidence that mutations associated with a given disease arise with different frequencies among ethnic groups, thus ethnicity-specific studies are needed to identify causative mutations and properly assess risk. In particular, ethnic differences in the genetic background of thrombophilia have been reported. We recently conducted a large-scale analysis of the plasma activities of proteins C, S, antithrombin, and plasminogen within the Japanese general population. We found age- and sex-related differences and estimated the prevalence of deficiencies of protein C (0.13%), antithrombin (0.15%), protein S (1.12%), and plasminogen (4.29%). We also evaluated the genetic contribution to deep vein thrombosis and found that protein S mutation K196E is a genetic risk factor in the Japanese population. We estimated allele frequency to be 0.009, suggesting that 1 of 12,000 Japanese may be homozygous for the E allele, thus possibly as many as 10,000 individuals. Accordingly, a substantial proportion of the Japanese population carries the protein S E allele and is at risk of developing deep vein thrombosis. Given the frequency of this mutation and its strong correlation with deep vein thrombosis, it may be valuable to conduct a large-scale screening for this allele and advise concerned persons to avoid environmental risk factors known to be associated with deep vein thrombosis.