Connie Ha

Adrenoceptor Polymorphisms and the Risk of Cardiac Injury and Dysfunction After Subarachnoid Hemorrhage

Background and Purpose— Cardiac abnormalities occur commonly after subarachnoid hemorrhage (SAH) and may be caused by excessive release of catecholamines from the myocardial sympathetic nerves. We hypothesized that adrenoceptor polymorphisms resulting in greater catecholamine sensitivity would be associated with an increased risk of cardiac injury. Methods— This was a prospective cohort study. The primary outcome variables were the serum level of cardiac troponin I (cTi, abnormal if >1.0 μg/L) and the left ventricular ejection fraction (LVEF, abnormal if <50%). Six adrenoceptor polymorphisms were genotyped: β1AR Arg389Gly, β1AR Ser49Gly, β2AR Gly16Arg, β2AR Gln27Glu, β2AR Thr164Ile, and α2AR del322-325. The effect of each polymorphism on the risk of developing cardiac abnormalities was quantified using multivariable logistic regression. Results— The study included 182 patients. The CC genotype (Arg/Arg) of β1AR Arg389Gly (odds ratio [OR] 3.4, P=0.030) and the CC genotype (Gln/Gln) of β2AR Gln27Glu (OR 3.1, P=0.032) were predictive of cTi release. The presence of the α2AR deletion was predictive of reduced LVEF (OR 4.2, P=0.023). The combination of the β1AR 389 CC and the β2AR 27 CC genotypes resulted in a marked increase in the odds of cTi release (OR 15.5, P=0.012). The combination of the β1AR 389 CC and the α2AR deletion genotypes resulted in a marked increase in the odds of developing a reduced LVEF (OR 10.3, P=0.033). Conclusions— Genetic polymorphisms of the adrenoceptors are associated with an increased risk of cardiac abnormalities after SAH. These data support the hypothesis that cardiac dysfunction after SAH is a form of neurocardiogenic injury.

Rapid DNA mapping by fluorescent single molecule detection

DNA mapping is an important analytical tool in genomic sequencing, medical diagnostics and pathogen identification. Here we report an optical DNA mapping strategy based on direct imaging of individual DNA molecules and localization of multiple sequence motifs on the molecules. Individual genomic DNA molecules were labeled with fluorescent dyes at specific sequence motifs by the action of nicking endonuclease followed by the incorporation of dye terminators with DNA polymerase. The labeled DNA molecules were then stretched into linear form on a modified glass surface and imaged using total internal reflection fluorescence (TIRF) microscopy. By determining the positions of the fluorescent labels with respect to the DNA backbone, the distribution of the sequence motif recognized by the nicking endonuclease can be established with good accuracy, in a manner similar to reading a barcode. With this approach, we constructed a specific sequence motif map of lambda-DNA. We further demonstrated the capability of this approach to rapidly type a human adenovirus and several strains of human rhinovirus.

Tumor Necrosis Factor-α–238G>A Promoter Polymorphism Is Associated With Increased Risk of New Hemorrhage in the Natural Course of Patients With Brain Arteriovenous Malformations

Background and Purpose— Identification of single-nucleotide polymorphisms (SNPs) associated with increased risk of new intracranial hemorrhage (ICH) after brain arteriovenous malformation (BAVM) diagnosis would facilitate risk stratification and identify potential targets for therapeutic intervention. Methods— Patients with BAVM were longitudinally followed. Primary outcome was new ICH after diagnosis; censoring events were last follow-up or any BAVM treatment. We genotyped 4 promoter SNPs in 2 inflammatory cytokine genes: interleukin-6 (IL-6–174G>C; IL-6–572G>C) and tumor necrosis factor-&agr; (TNF-&agr;–238G>A; TNF-&agr;–308G>A). Association of genotype with risk of new ICH was screened using &khgr;2; SNPs associated with new ICH were further characterized using Cox proportional hazards. Results— We genotyped 280 patients (50% female; 59% white, mean±SD age at diagnosis 37±17 years; 40% presenting with ICH). TNF-&agr;–238G>A was associated with increased risk of new ICH after diagnosis (&khgr;2; P=0.003). After adjusting for age, race/ethnicity, and clinical presentation, the risk of new ICH was increased for patients with TNF-&agr;–238 AG genotype (hazard ratio, 4.01; P=0.015). No other SNP was found to be associated with new ICH. Conclusion— A TNF-&agr; SNP was associated with increased risk of new ICH in the natural course of BAVMs. The role of inflammatory cytokines in the pathogenesis of BAVM hemorrhage merits further study.

Polymorphisms in Transforming Growth Factor-β-Related Genes ALK1 and ENG Are Associated With Sporadic Brain Arteriovenous Malformations

Background and Purpose— Mutations in endoglin (ENG) and activin-like kinase (ALK1) cause hereditary hemorrhagic telangiectasias, disorders characterized by pulmonary and brain arteriovenous malformations (BAVMs). We investigated whether polymorphisms in these genes are also associated with sporadic BAVM. Methods— A total of 177 sporadic BAVM patients and 129 controls (all subjects white) were genotyped for 2 variants in ALK1 and 7 variants in ENG. Results— The ALK1 IVS3-35A>G polymorphism was associated with BAVM: (AnyA [AA+AG] genotype: odds ratio, 2.47; 95% CI, 1.38 to 4.44; P=0.002). Two ENG polymorphisms, ENG −1742A>G and ENG 207G>A, showed a trend toward association with BAVM that did not reach statistical significance. Conclusions— A common polymorphism in ALK1 is associated with sporadic BAVM, suggesting that genetic variation in genes mutated in familial BAVM syndromes may play a role in sporadic BAVMs.

Differences in Allergic Sensitization by Self-reported Race and Genetic Ancestry

BACKGROUND Many allergic conditions occur more frequently in African American patients when compared with white patients; however, it is not known whether this represents genetic predisposition or disparate environmental exposures. OBJECTIVE We sought to assess the relationship of self-reported race and genetic ancestry to allergic sensitization. METHODS We included 601 women enrolled in a population-based cohort study whose self-reported race was African American or white. Genetic ancestry was estimated by using markers that differentiate West African and European ancestry. We assessed the relationship between allergic sensitization (defined as > or =1 allergen-specific IgE results) and both self-reported race and genetic ancestry. Regression models adjusted for sociodemographic variables, environmental exposures, and location of residence. RESULTS The average proportion of West African ancestry in African American participants was 0.69, whereas the mean proportion of European ancestry in white participants was 0.79. Self-reported African American race was associated with allergic sensitization when compared with those who reported being white (adjusted odds ratio, 2.19; 95% CI, 1.22-3.93), even after adjusting for other variables. Genetic ancestry was not significantly associated with allergic sensitization after accounting for location of residence (adjusted odds ratio, 2.09 for urban vs suburban residence; 95% CI, 1.32-3.31). CONCLUSION Self-reported race and location of residence appeared to be more important predictors of allergic sensitization when compared with genetic ancestry, suggesting that the disparity in allergic sensitization by race might be primarily a result of environmental factors rather than genetic differences.

A simple DNA stretching method for fluorescence imaging of single DNA molecules

Stretching or aligning DNA molecules onto a surface by means of molecular combing techniques is one of the critical steps in single DNA molecule analysis. However, many of the current studies have focused on λ-DNA, or other large DNA molecules. There are very few studies on stretching methodologies for DNA molecules generated via PCR (typically smaller than 20 kb). Here we describe a simple method of stretching DNA molecules up to 18 kb in size on a modified glass surface. The very low background fluorescence allows efficient detection of single fluorescent dye labels incorporated into the stretched DNA molecules.

Apolipoprotein E ε2 is associated with new hemorrhage risk in brain arteriovenous malformations: Commentary

OBJECTIVE:Patients with brain arteriovenous malformation (AVM) are at life-threatening risk of intracranial hemorrhage (ICH). Identification of genetic variants associated with increased new ICH risk would facilitate risk stratification and guide therapeutic intervention. METHODS:Brain AVM patients evaluated at University of California, San Francisco or Kaiser Permanente Northern California were followed longitudinally. Primary outcome was new ICH after diagnosis; censoring events were any AVM treatment or last follow-up examination. The association of ApoE ϵ2 and ϵ4 genotype with new ICH was evaluated by Kaplan-Meier survival analysis and further characterized via a Cox proportional hazards model. RESULTS:We genotyped 284 brain AVM patients (50% women; 57% Caucasian; median follow-up time, 0.3 yr) including 18 patients with a history of new ICH). ApoE ϵ2, but not ApoE ϵ4 genotype, was associated with new ICH (P = 0.0052). ApoE ϵ2 carriers had fivefold increased risk of new ICH (hazard ratio, 5.09; 95% confidence interval, 1.46–17.7; P = 0.010; Cox proportional hazards model adjusting for race/ethnicity and clinical presentation). Subset analysis in the largest homogenous ethnic subcohort (Caucasians) confirmed the increased risk of new ICH in ApoE ϵ2 carriers (hazard ratio, 8.71; 95% confidence interval, 1.4–53.9; P = 0.020; multivariate model adjusting for clinical presentation). CONCLUSION:ApoE genotype may influence the risk of ICH in the natural course of brain AVM. The identification of genetic predictors of ICH risk may facilitate estimation of AVM natural history risk and individualize clinical decision-making and therapeutic recommendations.

Genetic Variation in the Proximal Promoter of ABC and SLC Superfamilies: Liver and Kidney Specific Expression and Promoter Activity Predict Variation

Membrane transporters play crucial roles in the cellular uptake and efflux of an array of small molecules including nutrients, environmental toxins, and many clinically used drugs. We hypothesized that common genetic variation in the proximal promoter regions of transporter genes contribute to observed variation in drug response. A total of 579 polymorphisms were identified in the proximal promoters (−250 to +50 bp) and flanking 5′ sequence of 107 transporters in the ATP Binding Cassette (ABC) and Solute Carrier (SLC) superfamilies in 272 DNA samples from ethnically diverse populations. Many transporter promoters contained multiple common polymorphisms. Using a sliding window analysis, we observed that, on average, nucleotide diversity (π) was lowest at approximately 300 bp upstream of the transcription start site, suggesting that this region may harbor important functional elements. The proximal promoters of transporters that were highly expressed in the liver had greater nucleotide diversity than those that were highly expressed in the kidney consistent with greater negative selective pressure on the promoters of kidney transporters. Twenty-one promoters were evaluated for activity using reporter assays. Greater nucleotide diversity was observed in promoters with strong activity compared to promoters with weak activity, suggesting that weak promoters are under more negative selective pressure than promoters with high activity. Collectively, these results suggest that the proximal promoter region of membrane transporters is rich in variation and that variants in these regions may play a role in interindividual variation in drug disposition and response.

Response to Letter by Atanassova

Response: We were interested to read Dr Atanassova’s comments regarding our article. In the design of our study, we excluded patients with a history of myocardial infarction and congestive heart failure (CHF) in order to focus on the pathogenesis of acute cardiac injury and dysfunction. Though subarachnoid hemorrhage (SAH) patients have …