A novel risk haplotype of ALOX5AP gene is associated with ischemic stroke in Chinese Han population

Lack of association between ALOX5AP genetic polymorphisms and risk of ischemic stroke: evidence from meta-analyses

BACKGROUND

In recent years, there has been substantial research evaluating the relationship between arachidonate 5-lipoxygenase-activating protein (ALOX5AP) polymorphisms and ischemic stroke (IS). The objective of this study was to systematically review and analyze the existing evidence.

METHODS

A comprehensive search of major electronic databases for studies published between 1990 and 2018 was carried out. Data were synthesized as OR and 95% CI using fixed-effects and random-effects models.

RESULTS

A total of 30 studies were available for analysis. The aggregate sample size across all studies was 32,782 (16,294 cases and 16,488 controls). We found no association of the ALOX5AP rs10507391 (OR=1.03 for A allele vs T allele; 95% CI: 0.93-1.14; P=0.557), rs4769874 (OR=1.13 for A allele vs G allele; 95% CI: 1.00-1.28; P=0.050), rs9551963 (OR=1.03 for A allele vs C allele; 95% CI: 0.96-1.11; P=0.372), rs17222814 (OR=1.09 for A allele vs G allele; 95% CI: 0.96-1.24; P=0.195), rs17222919 (OR=0.89 for G allele vs T allele; 95% CI: 0.75-1.06; P=0.175), and rs4073259 (OR=1.20 for A allele vs G allele; 95% CI: 1.00-1.45; P=0.056) polymorphisms with IS risk. Haplotype analysis also did not yield significant findings for the HapA (rs17222814G-rs10507391T-rs4769874G-rs9551963A; OR=1.20; 95% CI: 0.91-1.56; P=0.192) and HapB (rs17216473A-rs10507391A-rs9315050A-rs17222842G; OR=1.11; 95% CI: 0.90-1.38; P=0.339) haplotypes.

CONCLUSION

Current evidence does not support an association of rs10507391, rs4769874, rs9551963, rs17222814, rs17222919, rs4073259, and HapA and HapB with IS risk.

Allele-specific methylation contributed by CpG-SNP is associated with regulation of ALOX5AP gene expression in ischemic stroke

Previous studies have shown that CpG-SNPs might have influence on gene function via allele-specific DNA methylation (ASM). However, association study between DNA methylation and the promoter CpG-SNPs in ALOX5AP gene with IS has not been reported. The present study aims to explore the relationship among CpG-SNPs, methylation levels, and messenger RNA (mRNA) expression levels of ALOX5AP gene. Firstly, we made a two-stage association study to identify a potential associated CpG-SNP (rs4073259) by SNaPshot genotyping approach (P = 0.015, OR = 0.672, 95% CI 0.487-0.927; P = 0.035, OR = 0.809, 95% CI 0.664-0.985, respectively). In addition, the methylation levels of 17 CpG sites located in the promoter of ALOX5AP were tested by MethylTarget sequencing. The methylation level of GG genotype carriers is significantly higher than those with the AG and AA genotypes (P < 0.05). And the GG genotype carriers with higher DNA methylation levels have a decreased mRNA expression levels of ALOX5AP (P < 0.05). Finally, we found that the G allele with higher methylation level has got a lower transcription activity than the A allele by luciferase assay (P = 0.000).The study provided evidence that IS-associated CpG-SNP rs4073259 may affect the expression level of ALOX5AP through allele-specific methylation and consequently the phenotype of the disease.

Genetic Variants in the Transcriptional Regulatory Region of the ALOX5AP gene and Susceptibility to Ischemic Stroke in Chinese Populations

No coding sequence variants of the ALOX5AP gene that lead to amino acid substitutions have been identified. A two-stage study design was used to explore the relationship between variants in the transcriptional regulatory region of ALOX5AP gene and ischemic stroke (IS) risk in Chinese populations. IS was determined using CT and/or MRI. First, 18 SNPs, located in the upstream promoter region of ALOX5AP gene, were genotyped in 200 IS patients and 200 controls. And one potential associated SNP (rs17222919) was identified (P = 0.005,OR = 0.623, 95% CI: 0.448~0.866). Next, another independent case-control cohort comprising 810 IS patients and 825 matched controls was recruited to investigate the role of rs17222919, rs9579646 polymorphisms and their haplotypes in IS risk. The G allele frequency of rs17222919 in the IS group was significantly lower than that in control group (P = 0.007, OR = 0.792, 95% CI: 0.669~0.937). T-A and G-A haplotypes were associated with IS (P = 0.001,OR = 1.282, 95% CI:1.100~1.495; P = 0.0001, OR = 0.712, 95% CI: 0.598~0.848; respectively). Our study providesevidence that rs17222919 is a potential genetic protective factor against IS. Furthermore, the T-A haplotype is a risk factor and the G-A haplotype is a protective factor against IS in Chinese population.

A promoter polymorphism (rs17222919, -1316T/G) of ALOX5AP gene is associated with decreased risk of ischemic stroke in two independent Chinese populations

No coding sequence variants of the gene encoding 5-lipoxygenase-activating protein (ALOX5AP) leading to amino acid substitutions have been identified. Therefore, variants in the ALOX5AP promoter region have received attention recently. The purpose of this study was to explore whether the promoter polymorphism rs17222919 is involved in the etiology of ischemic stroke (IS) in the Chinese Han population. We investigated the rs17222919 polymorphism by TaqMan genotyping in two independent Chinese Han samples: the first comprised 910 IS patients and 925 healthy inhabitants from the northern Henan Province, while the second included 1003 IS patients and 889 healthy controls from the southern Henan Province. Functional characterization of rs17222919 was performed by an in vitro luciferase assay. After adjusting for conventional risk factors, the G allele frequencies in the IS groups were significantly lower than that in the control groups of the two independent Chinese cohorts (19.0% vs. 22.9%, P = 0.004, odds ratio (OR) = 0.792, 95% confidence interval (CI) = 0.675-0.929; 18.8% vs. 22.9%, P = 0.002, OR = 0.782, 95% CI = 0.668-0.915, respectively). This was also observed in the large-artery atherosclerosis (LAA) and stroke of other undetermined etiology (SUE) subtypes (P = 0.019, OR = 0.815, 95% CI = 0.687-0.967; P = 0.021, OR = 0.815, 95% CI = 0.685-0.970, respectively). Additionally, the TG genotype and G allele frequencies were significantly lower in the IS compared with the control group in two female cohorts (P<0.05). Finally, the in vitro luciferase assay demonstrated that the G allele has a significantly lower transcription activity than the T allele (P = 0.031). Our study provides evidence that the promoter single nucleotide polymorphism (SNP) rs17222919 is a potential genetic protective factor for IS in the Chinese Han population.

Mitochondrial DNA haplogroup D4b is a protective factor for ischemic stroke in Chinese Han population

Mitochondrial DNA (mtDNA) haplogroups affect the assembly and stability of the mitochondrial respiratory chain, which is potentially related to susceptibility to ischemic stroke (IS). However, the role of mtDNA in IS has not been comprehensively studied. The purpose of this study was to explore whether mtDNA polymorphisms and haplogroups are involved in the etiology of IS in the Chinese Han population. We recruited 200 patients with IS and 200 matched controls and genotyped them for 18 mtDNA single nucleotide polymorphisms defining the major Eastern Asian haplogroups by SNaPshot minisequencing. We also sequenced the hypervariable segment I (HVS-I), position 16051-16400. The prevalence of haplogroup D4b was significantly lower in IS patients than in healthy controls (0 and 8 %, respectively, corrected P = 2 × 10(-5), odds ratio = 0.028, 95 % confidence interval = 0.002-0.468).The positive association between haplogroup D4b and IS may be related to the protective effect of haplogroup D4b against oxidative damage, which decreases the risk of IS. Our study provides the first evidence that haplogroup D4b is a potential genetic protective factor for IS in the Chinese Han population.