Isolation and characterization of a hereditary abnormal antithrombin III 'Antithrombin III Toyama'

Utility of the SERPINC1 Gene Test in Ischemic Stroke Patients With Antithrombin Deficiency

Objective

Antithrombin (AT) plays a critical role in the coagulation system, and its deficiency induces hypercoagulability. AT deficiency is caused not only by inherited variants in the SERPINC1 gene but also by acquired conditions. Therefore, AT deficiency alone could not ensure the presence of the SERPINC1 mutation. We evaluated the utility of the SERPINC1 gene test in ischemic stroke, an important clinical type of arterial thrombosis.

Methods

This retrospective, observational study investigated symptomatic patients who underwent the SERPINC1 gene test because of decreased AT activity (<80%) during 2009-2021 at a tertiary hospital. For the detection of sequence variants in the SERPINC1 gene, direct Sanger sequencing and multiplex ligation-dependent probe amplification were performed. The phenotypes of patients with SERPINC1 gene mutations were examined, and the conditions associated with the pathogenic variants were analyzed.

Results

In our cohort (n = 19), 13 of 19 patients (68.4%) had the pathogenic variant of the SERPINC1 gene. Ischemic stroke (n = 7) was significantly associated with the pathogenic variants (p = 0.044), and the pathogenicity detection rate was 100%. For any kind of arterial thrombosis (n = 8), the detection rate of the pathogenic variant was 87.5%, but was not statistically significant (p = 0.177). The detection rates of the pathogenic variant in ischemic stroke or arterial thrombosis groups were both higher than those in the venous thrombosis-only group (54.5%).

Conclusion

The SERPINC1 gene test was useful in determining the cause of AT deficiency-related arterial thrombosis, especially ischemic stroke. We propose the diagnostic flow of SERPINC1-related ischemic stroke.

Familial Thrombophilia: A Review Analysis

The correct approach to the management of the asymptomatic carrier with a recognized inherited thrombophilic disorder is uncertain because reliable in formation of the risk of spontaneous (unprovoked) throm bosis in these disorders is not available. To determine the best available estimate of the annual incidence of spon taneous thrombosis in asymptomatic carriers of disorders that have been linked to familial thrombophilia, we per formed a literature review. Using Medline search from 1965 to 1992, supplemented by manual searches, we re trieved all articles that presented data on antithrombin III, protein C, protein S, dysfibrinogenemia, plasmino gen, histidine-rich glycoprotein, heparin cofactor II, and fibrinolysis in relation to thrombosis. Publications were included in the analysis if they (1) reported one or more probands with thrombotic disease and a heterozygous biochemical abnormality of the hemostatic system, (2) assessed the presence of this abnormality in family mem bers independent of the presence or absence of a history of thrombotic disease, and (3) assessed the presence of a history of thrombotic disease in all available family mem bers. The biochemical status and clinical details of all family members reported were extracted from each eligi ble article. For each abnormality the odds ratio for throm bosis was compared in family members with and without the biochemical abnormality. If applicable, thrombosis- free survival and age-specific incidences of thrombosis were calculated. The thrombotic episodes were classified as spontaneous or secondary to a recognized risk factor, and the proportion of spontaneous episodes was calcu lated. The influence of diagnostic suspicion bias in symp tomatic patients with a family history of thrombosis was reduced by recalculating the absolute incidence of throm bosis from the odds ratio after adjusting the incidence of venous thrombosis in nonaffected family members to that observed in the general population. Statistically signifi cant associations between the presence of a biochemical abnormality and a history of venous thrombosis were found for antithrombin III deficiency types 1 and 2a and 2b, protein C deficiency type 1, and protein S deficiency type I. Dysfibronogenemia was statistically significantly associated with venous as well as arterial thrombosis. Thirty-five to 67% of the events were classified as being provoked, as they occurred following exposure to a rec ognized risk factor for thrombosis. The recalculated an nual incidence of spontaneous thrombosis was 0.6 to 1.6%/year. It is concluded that this relatively low inci dence does not warrant life-long continuous use of anti coagulant prophylaxis since the reported risk of major and fatal bleeding associated with the use of oral antico agulants is 2-3 and 0.4%/year, respectively.

Antithrombin III deficiency

A moderate reduction of plasma antithrombin activity is an uncommon but clinically important cause of severe thromboembolic disease. In recent years the molecule responsible for the major part of this activity (antithrombin III) has been extensively characterised and the mode of inheritance of familial deficiencies worked out. Over 30 autosomally dominant inheritable variants have been described, the gene for normal human antithrombin III has been sequenced and this information has provided important insights into the reaction of antithrombin with thrombin and the catalytic role of heparin. Further information has been derived by analogy with other serine proteinase inhibitors, in particular alpha 1 antitrypsin. Recombinant DNA methods have been used to produce functionally active AT III which may, in the future, replace human chromatographically-separated AT III as the treatment of choice for clinically important deficiency states. Newer diagnostic techniques, using restriction fragment length polymorphisms and synthetic oligonucleotide probes, hold the promise of more accurate diagnosis and diagnosis in the antenatal period in families possessing some of the fully characterised variants.

Quantitative and qualitative congenital deficiency of antithrombin III: a new molecular variant called ATIII-Barcelona 2

A Spanish family with a quantitative-qualitative antithrombin III (ATIII) deficiency and thrombotic tendency is reported. The qualitative defect was suggested by the crossed immunoelectrophoresis (CIE) in the presence of heparin in plasma of all those affected. However, the crossed immunoelectrofocusing (CIEF) showed the same ATIII pattern in controls and affected members. Two populations of ATIII were detected by affinity chromatography on heparin-sepharose from affected members' plasma. The ATIII unbound to sepharose beads was devoid of heparin cofactor activity and showed a lack of anodal migration in CIE in the presence of heparin. The ATIII eluted corresponded to normal ATIII. Our data supports the view that an abnormal ATIII molecule is present in all affected family members in the heterozygous state. This is the first reported ATIII variant in which a molecular abnormality produces a lack of affinity for heparin but no changes in its isoelectric point. This familial ATIII deficiency was named ATIII- Barcelona 2.

Interaction of abnormal antithrombin-III Toyama with cultured porcine aortic endothelial cells

The abnormal Antithrombin-III (AT-III) Toyama has no ability to interact with heparin in the mast cells or heparin-like glycosaminoglycans on the surface of vascular endothelial cells, so that it has low heparin cofactor activity. In the present study, we have measured the binding capacity of 125I-labeled AT-III to cultured porcine aortic endothelial cells and estimated the inactivation of thrombin by AT-III in the presence of endothelial cells. The abnormal AT-III Toyama had low binding capacity to endothelial cells and had lower heparin cofactor antithrombin activity in the presence of endothelial cells than that of normal AT-III. Our results suggested that heparin-like glycosaminoglycans on endothelial cells play as important a role as heparin does in the regulation of antithrombin activity.

Antithrombin III microheterogeneity in antithrombin III deficiency and in the antithrombin III abnormality, "antithrombin III Toyama"

Antithrombin III (AT III) microheterogeneity was investigated in 12 cases of congenital AT III deficiency and 2 cases of congenital AT III abnormality by isoelectric focusing (IEF) and immunofixation. In congenital AT III deficiency, IEF and immunofixation revealed AT III as 8 bands which was indistinguishable from normal control in terms of the number of bands and the isoelectric point (pI) of each band. In the proband of the congenital AT III abnormality, however, IEF and immunofixation showed AT III as 8 bands which shifted slightly but definitely to the acidic side compared to those of normal subjects. This change in pI of the abnormal AT III was considered to reflect the amino acid replacement in the polypeptide chain of the abnormal AT III molecule.

Comparative effect of heparin and heparan sulphate on two abnormal antithrombin III type 3 variants

Two families were found with an antithrombin III that was unresponsive towards heparin (type 3 AT III variants). The abnormal species were purified using affinity chromatography on Sepharose bound anti-AT III antibodies. This yielded active proteins, as judged by their progressive antithrombin activities. In an attempt to explain the thrombotic tendency observed in this abnormality we compared the effect of heparin and heparan sulphate on these abnormal AT III, since, unlike heparin, heparan sulphate is a naturally occurring anticoagulant in the human. In normal plasma the heparan sulphate used in this study had a heparin-like activity of 50 U/mg by anti-F.XA and anti-F.IIa amidolytic assays. Full expression of the heparin cofactor activity in normal plasma could be obtained at a final concentration of 0.024 mg/ml of heparan sulphate (equivalent to 0.007 mg/ml of heparin). At this concentration of heparan sulphate the two abnormal AT III still exhibit a heparin cofactor activity below 10%. This absence of binding of heparan sulphate to abnormal AT III of type 3 could explain why some patients with this abnormality suffer from thrombo-embolic episodes while their AT III acts normally in the absence of heparin.

A functional abnormal antithrombin III (AT III) deficiency: AT III Charleville

An antithrombin III (AT III) functional defect (AT III Charleville) was discovered in a patient presenting with recurrent venous thrombosis. Both anti-activated factor X (anti Xa) and antithrombin activity were decreased, in the absence and in the presence of heparin, while protein concentration was normal in an immunological assay. The abnormal AT III copurified with functional AT III using insolubilized heparin affinity chromatography. Polyacrylamide gel electrophoresis (PAGE) and high pressure liquid chromatography (HPLC) on a TSK column suggest that AT III Charleville forms unstable complexes with thrombin from which a modified protein is rapidly released.

Purification and biological property of heparin cofactor II: activation of heparin cofactor II and antithrombin III by dextran sulfate and various glycosaminoglycans

Heparin cofactor II (HC II) has been purified from human plasma by a modification of the method described by Tollefsen et al. (J. Biol. Chem., 257, 2162, 1982) and abilities of dextran sulfate and various glycosaminoglycans to activate the antithrombin activities of HC II and antithrombin III (AT III) were studied. By the purification method described here, highly purified HC II with the same specific activity as reported by Tollefsen et al. was obtained with a higher yield and in a shorter purification time. Heparin, dextran sulfate and chondroitin polysulfates 1 and 5 activated both HC II and AT III, while dermatan sulfate activated only HC II. Dextran sulfate was almost as active as heparin in the activation of HC II and AT III, indicating that in the interactions of heparin with HC II and AT III, sulfate groups of heparin are more important than carboxyl groups. When mixed with thrombin in the presence of dermatan sulfate, normal human plasma showed antithrombin activity which was not due to AT III but to HC II only. HC II did not inhibit factor Xa or plasmin in the presence of any glycosaminoglycans or dextran sulfate, suggesting that HC II would be a specific inhibitor of thrombin.

Antithrombin III Toyama: replacement of arginine-47 by cysteine in hereditary abnormal antithrombin III that lacks heparin-binding ability

Structural analyses of a hereditary abnormal antithrombin III, antithrombin III Toyama, which has normal progressive antithrombin activity but no heparin cofactor activity, have been carried out to elucidate the molecular abnormality causing recurrent thrombophlebitis of a patient and to identify an amino acid residue essential for the binding with heparin. Abnormal antithrombin III was reduced, S-pyridylethylated, and treated with cyanogen bromide. Eleven fragments were isolated by the combination of Sephadex G-50 gel filtration and reversed-phase HPLC and compared with those from normal antithrombin III. One large fragment (CN-III) that appeared to have a different amino acid composition from that of the corresponding fragment from normal antithrombin III was digested with trypsin, and the digests were separated by HPLC. The abnormal peptide was identified by comparing the peptide map with that from normal antithrombin III. Amino acid sequence analysis of the abnormal peptide indicated that the arginine-47 of normal antithrombin III had been replaced by cysteine in antithrombin III Toyama. One base mutation, C leads to T, in the 5' terminal position of the arginine-47 genetic codon (CGT) is probably responsible for this substitution. These results also suggest that arginine-47 is an essential amino acid residue for the binding with heparin.