Lymphotoxin-alpha C804A polymorphism is a risk factor for stroke. The PROSPER study

Thrombotic and Atherogenetic Predisposition in Polyglobulic Donors

This work analyses the results of research regarding the predisposition of genetic hematological risks associated with secondary polyglobulia. The subjects of the study were selected based on shared laboratory markers and basic clinical symptoms. JAK2 (Janus Kinase 2) mutation negativity represented the common genetic marker of the subjects in the sample of interest. A negative JAK2 mutation hypothetically excluded the presence of an autonomous myeloproliferative disease at the time of detection. The parameters studied in this work focused mainly on thrombotic, immunological, metabolic, and cardiovascular risks. The final goal of the work was to discover the most significant key markers for the diagnosis of high-risk patients and to exclude the less important or only complementary markers, which often represent a superfluous economic burden for healthcare institutions. These research results are applicable as a clinical guideline for the effective diagnosis of selected parameters that demonstrated high sensitivity and specificity. According to the results obtained in the present research, groups with a high incidence of mutations were evaluated as being at higher risk for polycythemia vera disease. It was not possible to clearly determine which of the patients examined had a higher risk of developing the disease as different combinations of mutations could manifest different symptoms of the disease. In general, the entire study group was at risk for manifestations of polycythemia vera disease without a clear diagnosis. The group with less than 20% incidence appeared to be clinically insignificant for polycythemia vera testing and thus there is a potential for saving money in mutation testing. On the other hand, the JAK V617F (somatic mutation of JAK2) parameter from this group should be investigated as it is a clear exclusion or confirmation of polycythemia vera as the primary disease.

Alternative Splicing of Putative Stroke/Vascular Risk Factor Genes Expressed in Blood Following Ischemic Stroke Is Sexually Dimorphic and Cause-Specific

Genome-wide association studies have identified putative ischemic stroke risk genes, yet, their expression after stroke is unexplored in spite of growing interest in elucidating their specific role and identifying candidate genes for stroke treatment. Thus, we took an exploratory approach to investigate sexual dimorphism, alternative splicing, and etiology in putative risk gene expression in blood following cardioembolic, atherosclerotic large vessel disease and small vessel disease/lacunar causes of ischemic stroke in each sex compared to controls. Whole transcriptome arrays assessed 71 putative stroke/vascular risk factor genes for blood RNA expression at gene-, exon-, and alternative splicing-levels. Male (n = 122) and female (n = 123) stroke and control volunteers from three university medical centers were matched for race, age, vascular risk factors, and blood draw time since stroke onset. Exclusion criteria included: previous stroke, drug abuse, subarachnoid or intracerebral hemorrhage, hemorrhagic transformation, infection, dialysis, cancer, hematological abnormalities, thrombolytics, anticoagulants or immunosuppressants. Significant differential gene expression (fold change > |1.2|, p < 0.05, partial correlation > |0.4|) and alternative splicing (false discovery rate p < 0.3) were assessed. At gene level, few were differentially expressed: ALDH2, ALOX5AP, F13A1, and IMPA2 (males, all stroke); ITGB3 (females, cardioembolic); ADD1 (males, atherosclerotic); F13A1, IMPA2 (males, lacunar); and WNK1 (females, lacunar). GP1BA and ITGA2B were alternatively spliced in both sexes (all patients vs. controls). Six genes in males, five in females, were alternatively spliced in all stroke compared to controls. Alternative splicing and exon-level analyses associated many genes with specific etiology in either sex. Of 71 genes, 70 had differential exon-level expression in stroke patients compared to control subjects. Among stroke patients, 24 genes represented by differentially expressed exons were male-specific, six were common between sexes, and two were female-specific. In lacunar stroke, expression of 19 differentially expressed exons representing six genes (ADD1, NINJ2, PCSK9, PEMT, SMARCA4, WNK1) decreased in males and increased in females. Results demonstrate alternative splicing and sexually dimorphic expression of most putative risk genes in stroke patients' blood. Since expression was also often cause-specific, sex, and etiology are factors to consider in stroke treatment trials and genetic association studies as society trends toward more personalized medicine.

Association between lymphotoxin alpha (-252 A/G and -804 C/A) gene polymorphisms and risk of stroke in North Indian population: a hospital-based case-control study

PURPOSE

Lymphotoxin alpha (LTA), a proinflammatory cytokine, plays an important role in promoting atherosclerosis which is an independent risk factor for stroke. Recent genetic studies have suggested that polymorphisms in the LTA gene, which affect its expression and biological function, may contribute to the development of stroke. The aim of this case-control study was to determine the association between LTA (-252 A/G and -804 C/A) gene polymorphisms and risk of stroke.

METHODS

Genotyping was determined by using SNaPshot method for 250 ischemic stroke (IS) patients, 250 age and sex matched IS free controls, 100 intracerebral hemorrhage (ICH) patients and 100 age and sex matched ICH free controls. Conditional logistic regression analysis with adjusting multiple demographic and risk factor variables was used to calculate the strength of association between LTA (-252 A/G and -804 C/A) gene polymorphisms and risk of stroke. The linkage disequilibrium (LD) was analyzed by using HaploView 4.2 software.

RESULTS

The distribution of LTA (-252 A/G and -804 C/A) genotypes was consistent with Hardy-Weinberg equilibrium. Adjusted conditional logistic regression analysis showed no significant association between LTA (-252 A/G and -804 C/A) gene polymorphisms and risk of both IS and ICH. Based on Trial of Org 10172 in Acute Stroke Treatment (TOAST) classification, a significant association between LTA -252 A/G gene polymorphism and small vessel disease subtype of IS under dominant model (OR, 2.06; 95% CI, 1.03-4.12; p value 0.04) with the risk of IS was observed. No LD was observed for both single nucleotide polymorphisms (SNPs) in north Indian population.

CONCLUSION

Neither -252 G/A nor -804 C/A polymorphism of the LTA gene was found to be associated with overall stroke as well as any subtype of IS excluding SVD in North Indian population.

Genetic risk factors for perinatal arterial ischemic stroke

The cause of perinatal arterial ischemic stroke is unknown in most cases. We explored whether genetic polymorphisms modify the risk of perinatal arterial ischemic stroke. In a population-based case-control study of 1997-2002 births at Kaiser Permanente Northern California, we identified 13 white infants with perinatal arterial ischemic stroke. Control subjects included 86 randomly selected white infants. We genotyped polymorphisms in nine genes involved in inflammation, thrombosis, or lipid metabolism previously linked with stroke, and compared genotype frequencies in case and control individuals. We tested several polymorphisms: tumor necrosis factor-α -308, interleukin-6, lymphotoxin A, factor V Leiden, methyltetrahydrofolate reductase 1298 and 667, prothrombin 20210, and apolipoprotein E ε2 and ε4 alleles. Patients with perinatal arterial ischemic stroke were more likely than control subjects to demonstrate at least one apolipoprotein E ε4 allele (54% vs 25%, P = 0.03). More patients with perinatal arterial ischemic stroke carried two ε4 alleles than did control subjects (15% vs 2%, P = 0.09), although this finding lacked statistical significance. Proinflammatory and prothrombotic polymorphisms were not associated with perinatal arterial ischemic stroke. The apolipoprotein E polymorphism may confer genetic susceptibility for perinatal arterial ischemic stroke. Larger population-based studies are required to confirm this finding.

Cross-sectional study of risk factors for atherosclerosis in the Azorean population

BACKGROUND

Atherosclerosis-a major cause of vascular disease, including ischemic heart disease (IHD), is a pathology that has a two-fold higher mortality rate in the Azorean Islands compared to mainland Portugal.

AIM

This cross-sectional study investigated the role of genetic variation in the prevalence of atherosclerosis in this population.

SUBJECTS AND METHODS

A total of 305 individuals were characterized for polymorphisms in eight susceptibility genes for atherosclerosis: ACE, PAI1, NOS3, LTA, FGB, ITGB3, PON1 and APOE. Data were analysed with respect to phenotypic characteristics such as blood pressure, lipid profile, life-style risk factors and familial history of myocardial infarction.

RESULTS

In the total sample, frequencies for hypercholestrolemic, hypertensive and obese individuals were 63.6%, 39.3% and 23.3%, respectively. The genetic profile was similar to that observed in other European populations, namely in mainland Portugal. No over-representation of risk alleles was evidenced in this sample.

CONCLUSIONS

One has to consider the possibility of an important non-genetic influence on the high cholesterolemia present in the Azorean population. Since diet is the most important life-style risk factor for dyslipidemia, studies aiming to evaluate the dietary characteristics of this population and its impact on serum lipid levels will be of major importance.

A functional variant in the 3'-UTR of angiopoietin-1 might reduce stroke risk by interfering with the binding efficiency of microRNA 211

Angiopoietin-1 is a vascular strengthening factor during vascular development and a protective factor for pathological vascular inflammation and leakage. Brain vascular leaking and inflammation are two important pathological processes of stroke; therefore, we hypothesized that variants of the microRNA-binding site in angiopoietin-1 would affect its expression and confer a risk of stroke. To test our hypothesis, a predicted microRNA-binding site was found in the 3'-UTR of angiopoietin-1 using bioinformatics; variant rs2507800 was identified to be located in the miR-211-binding site of angiopoietin-1. Secondly, the effects of the identified variant on angiopoietin-1 translation were assessed using a luciferase reporter assay and ELISA. We found that the A allele of rs2507800 suppressed angiopoietin-1 translation by facilitating miR-211 binding, but not the T allele. Subjects carrying the TT genotype had higher plasma angiopoietin-1 levels than those with the A allele. Finally, the association of the variant with stroke was tested in 438 stroke patients and 890 controls, and replicated in an independent population of 1791 stroke patients and 1843 controls. The TT genotype resulted in a significant reduction in overall stroke risk {OR, 0.51 [95% confidence interval (CI), 0.36-0.74], P = 0.0003}, ischemic stroke [OR, 0.56 (95% CI, 0.36-0.85), P = 0.007] and hemorrhagic stroke [OR, 0.46 (95% CI, 0.26-0.80), P = 0.007]. These results were confirmed in an independent study. Our results provide evidence that the TT genotype (rs2507800) in the 3'-UTR of angiopoietin-1 might reduce the risk of stroke by interfering with miR-211 binding.