Background and Purpose-The association between ischemic childhood stroke and thrombophilia has been debated. We studied the prevalence of thrombophilia risk factors in 65 unrelated children with ischemic stroke compared with 145 control subjects. Methods-Patients and control subjects were tested for antithrombin protein C and protein S deficiencies, the presence of antiphospholipid antibodies (APLA), factor V Leiden (FVL), G20210A polymorphism of factor II gene (FII G20210A), and C677T polymorphism of 5,10-methylenetetrahydrofolate reductase gene (C677T MTHFR). Results-Of 65 children, 7 had a stroke in the neonatal/perinatal period and therefore were analyzed separately. Thirty-one of the remaining 58 patients with pediatric stroke (53.4%) were found to have at least 1 thrombophilia marker compared with only 25.5% of control subjects. None of the patients or control subjects had protein S or antithrombin III deficiency. The prevalence of protein C deficiency was higher among pediatric stroke patients than among control subjects, but the difference was not statistically significant (ORϭ7, 95% CI 0.75 to 65.1). Heterozygous FII G20210A and homozygous MTHFR 677T were not associated with an increased risk for stroke (ORϭ1.29, 95% CI 0.2 to 8.2; and ORϭ1.06, 95% CI 0.4 to 2.7, respectively). In contrast, the presence of APLA was associated with a Ͼ6-fold risk of stroke (ORϭ6.08, 95% CI 1.5 to 24.3), and the heterozygosity for FVL increased the risk of stroke by almost 5-fold (ORϭ4.82, 95% CI 1.4 to 16.5). Five patients with pediatric stroke had a combination of Ն2 thrombophilia markers, whereas none of the control subjects had a combination of the markers. Most of the patients with neonatal/perinatal stroke were found to have at least 1 thrombophilia marker. Conclusions-These data suggest that the prevalence of thrombophilia markers is increased in children with stroke compared with control subjects and, specifically, that FVL and APLA contribute significantly to stroke occurrence.

Abstract-The inherited thrombophilias-deficiencies of protein C, protein S, and antithrombin III-and the prothrombotic polymorphisms factor V G1691A and factor II G20210A predispose patients toward venous thromboembolism (VTE). The aim of this study was to determine the prevalence of single and combined prothrombotic factors in patients with idiopathic VTE and to estimate the associated risks. The study group consisted of 162 patients referred for work-up of thrombophilia after documented VTE. The controls were 336 consecutively admitted patients. In all subjects factor V G1691A, factor II G20210A, and methylenetetrahydrofolate reductase (MTHFR) C677T were analyzed by specific polymerase chain reactions and restriction enzymes. Activities of antithrombin III and protein C, free protein S antigen, and lupus anticoagulant were determined in a subset of 109 patients who were not receiving oral anticoagulants. The prevalences of heterozygotes and homozygotes for factor V G1691A and factor II G20210A among patients and controls were 40.1% versus 3.9% and 18.5% versus 5.4%, respectively (Pϭ0.0001). The prevalence of homozygotes for MTHFR C677T in patients was 22.8% and in controls, 14.3% (Pϭ0.025). Heterozygous and homozygous factor V G1691A, factor II G20210A, and homozygous MTHFR C677T were found to be independent risk factors for VTE, with odds ratios of 16.3, 3.6, and 2.1, respectively. Two or more polymorphisms were detected in 27 of 162 patients (16.7%) and in 3 of 336 controls (0.9%). Logistic regression analysis disclosed odds ratios of 58.6 (confidence interval [CI], 22.1 to 155.2) for joint occurrence of factor V and factor II polymorphisms, of 35.0 (CI, 14.5 to 84.7) for factor V and MTHFR polymorphisms, and of 7.7 (CI, 3.0 to 19.6) for factor II and MTHFR polymorphisms. Among 109 patients in whom a complete thrombophilic work-up was performed, 74% had at least 1 underlying defect. These data indicate that in most patients referred for evaluation of thrombophilia due to idiopathic VTE, 1 or more underlying genetic predispositions were discernible. The presence of Ͼ1 of the prothrombotic polymorphisms was associated with a substantial risk of VTE. (Arterioscler Thromb Vasc Biol. 1999;19:511-518.)

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Bernard-Soulier syndrome (BSS) is a rare autosomal recessive bleeding disorder characterized by defects of the GPIb-IX-V complex, a platelet receptor for von Willebrand factor (VWF). Most of the mutations identified in the genes encoding for the GP1BA (GPIbα), GP1BB (GPIbβ), and GP9 (GPIX) subunits prevent expression of the complex at the platelet membrane or more rarely its interaction with VWF. As a consequence, platelets are unable to adhere to the vascular subendothelium and agglutinate in response to ristocetin. In order to collect information on BSS patients, we established an International Consortium for the study of BSS, allowing us to enrol and genotype 132 families (56 previously unreported). With 79 additional families for which molecular data were gleaned from the literature, the 211 families characterized so far have mutations in the GP1BA (28%), GP1BB (28%), or GP9 (44%) genes. There is a wide spectrum of mutations with 112 different variants, including 22 novel alterations. Consistent with the rarity of the disease, 85% of the probands carry homozygous mutations with evidence of founder effects in some geographical areas. This overview provides the first global picture of the molecular basis of BSS and will lead to improve patient diagnosis and management.

The common 5,10-methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism causes decreased activity of this enzyme and can be associated with mild-to-moderate hyperhomocysteinemia in homozygotes, particularly when there is folic acid deficiency, as well as with vascular dementia, arterial thrombosis, venous thrombosis, neural-tube defects, and fetal loss. When folic acid intake is sufficient, homozygotes for MTHFR 677T appear to be protected against colon cancer and acute lymphatic leukemia, and fetuses bearing this genotype have an augmented survival. The distribution of MTHFR 677T is worldwide, but its frequency in different populations varies extensively. In the present study, we addressed the question of whether the MTHFR 677T alteration has an ancestral origin or has occurred repeatedly. We analyzed the frequency distribution of the previously described polymorphism A1298C in exon 7 and of three intronic dimorphisms, in white Israelis (Jews and Arabs), Japanese, and Ghanaian Africans. The 677T allele was, remarkably, associated with one haplotype, G-T-A-C, in white and Japanese homozygotes. Among the Africans, analysis of maximum likelihood also disclosed an association with the G-T-A-C haplotype, although none of the 174 subjects examined was homozygous for MTHFR 677T. These results suggest that the MTHFR 677T alteration occurred on a founder haplotype that may have had a selective advantage.

In Saccharomyces cerevisiae the SAMI and SAM2 genes encode two distinct forms of S-adenosylmethionine (AdoMet) synthetase. In a previous study we cloned and sequenced the SAM] gene (D. Thomas and Y. Surdin-Kerjan, J. Diol. Chem. 262:16704-16709, 1987). In this work, the SAM2 gene was isolated by functional complementation of a yeast double-mutant strain, and its identity was ascertained by gene disruption. It has been sequenced and compared with the SAM] gene. The degree of homology found between the two genes shows that SAM] and SAM2 are duplicated genes. Using strains disrupted in one or the other SAM gene, we have studied the regulation of their expression by measuring the steady-state level of mRNA after growth under different conditions. The results show that the expression of the two SAM genes is regulated differently, SAM2 being induced by the presence of excess methionine in the growth medium and SAM) being repressed under the same conditions. The level of mRNA in the parental strain shows that it is not the sum of the levels found in the two disrupted strains. This raises the question of how the two AdoMet synthetases in S. cerevisiae interact to control AdoMet synthesis.

Inherited factor XI deficiency is an injuryrelated bleeding disorder that is rare in most populations except for Jews, in whom 2 mutations, a stop mutation in exon 5 (type II) and a missense mutation in exon 9 (type III), predominate. Recently, a cluster of 39 factor XI-deficient patients was described in the Basque population of Southwestern France. In this study, we determined the molecular basis of factor XI deficiency in 16 patients belonging to 12 unrelated families of French Basque

Please see also Rosendaal F. R. Clotting and myocardial infarction: a cycle of insights. This issue, pp. 640±642.Summary. Background and purpose: Factor XI (FXI) contributes to thrombin generation thereby affecting ®brin formation and to down regulation of ®brinolysis by activation of thrombinactivatable ®brinolysis inhibitor (TAFI). The purpose of this study was to evaluate whether patients with severe FXI de®-ciency are protected against acute myocardial infarction (AMI). Methods: The incidence of AMI in patients with severe FXI de®ciency (FXI activity less than 15 U dL À1 ) whose age was 35 years or more was compared to the incidence of AMI in age and gender matched persons of the general population. Atherosclerotic risk factors were assessed in FXI de®cient patients and blood was tested for prothrombotic parameters such as FV Leiden, prothrombin G20210A, lupus anticoagulant, and platelet membrane polymorphisms. The common mutations causing FXI de®ciency in Jews were also examined. Results: Of 96 patients with severe FXI de®ciency (55 women and 41 men) 16 had a history of AMI (6 women and 10 men). The median age at the time of AMI was 64.5 for women and 58 for men. The calculated annual rate of AMI in men was similar to the expected in the general Israeli population, whereas in women it was almost 2-fold higher, but this difference did not reach statistical signi®cance. One or more atherosclerotic risk factors were observed in 13 of 16 patients (81.3%) with AMI compared to 44 of 79 patients (55.7%) without AMI (P < 0.001). The frequency distributions of platelet polymorphisms and of prothrombotic polymorphisms were not different between patients with severe FXI de®ciency who experienced or not an AMI. None of the patients had lupus anticoagulant. The common genotypes which cause FXI de®ciency in Jews were similarly distributed in patients with and without AMI. Conclusions: Severe FXI de®ciency does not confer protection against AMI.