MRAS Genetic Variation Is Associated with Atherothrombotic Stroke in the Han Chinese Population

MRAS in coronary artery disease-Unchartered territory

Genome-wide association studies (GWAS) have identified coronary artery disease (CAD) susceptibility locus on chromosome 3q22.3. This locus contains a cluster of several genes that includes muscle rat sarcoma virus (MRAS). Common MRAS variants are also associated with CAD causing risk factors such as hypertension, dyslipidemia, obesity, and type II diabetes. The MRAS gene is an oncogene that encodes a membrane-bound small GTPase. It is involved in a variety of signaling pathways, regulating cell differentiation and cell survival (mitogen-activated protein kinase [MAPK]/extracellular signal-regulated kinase and phosphatidylinositol 3-kinase) as well as acute phase response signaling (tumor necrosis factor [TNF] and interleukin 6 [IL6] signaling). In this review, we will summarize the role of genetic MRAS variants in the etiology of CAD and its comorbidities with the focus on tissue distribution of MRAS isoforms, cell type/tissue specificity, and mode of action of single nucleotide variants in MRAS associated complex traits. Finally, we postulate that CAD risk variants in the MRAS locus are specific to smooth muscle cells and lead to higher levels of MRAS, particularly in arterial and cardiac tissue, resulting in MAPK-dependent tissue hypertrophy or hyperplasia.

The Effect of AMBP SNPs, Their Haplotypes, and Gene-Environment Interactions on the Risk of Atherothrombotic Stroke Among the Chinese Population

Background/Objectives: Ischemic stroke (IS) is a severe and complex disorder with high morbidity and mortality rates and it has been associated with both environmental and genetic predisposing factors. The purpose of this study was to evaluate the association of the alpha-1-microglobulin/bikunin precursor (AMBP) gene polymorphisms with IS and any possible interactions between specific AMBP alleles and traditional risk factors among a Han Chinese cohort. Materials and Methods: We conducted a candidate gene study designed to characterize nine (9) single nucleotide polymorphisms (SNPs) of the AMBP gene among 195 patients with atherothrombotic stroke (ATS) (a major subtype of IS) and 184 nonstroke controls. Allelic and genotypic frequency differences were evaluated using a logistic regression model. False discovery rate (FDR) correction for multiple comparisons was used. The interactional analyses were performed using the multifactor dimensionality reduction test. Results: We found an association between the rs2567698 CC genotype (odds ratio [OR], 95% confidence interval [CI]: 2.176, 1.159-4.086) and the T allele (OR, 95% CI: 0.654, 0.446-0.960) with risk of ATS in men. However, these associations did not survive FDR correction. In haplotype analyses, the GCCCCCCCC haplotype had a higher frequency (OR, 95% CI: 2.191, 1.048-4.580) in ATS in the ≥45 years of age subgroup, whereas the GCCTCCCCC haplotype decreased the risk for ATS (OR, 95% CI: 0.543, 0.345-0.853) in men. In addition, we also found interactions for ATS risk between SNPs in the AMBP gene and modifiable risk factors for ATS, including: rs11788411 and hypertension in the overall population and women; rs2251680 and hypertension in subjects aged 45 years and older, as well as the interaction among hypertension and the rs2567698 and rs10817564 genotypes in men. Conclusion: Our results show a possible association between AMBP SNP haplotypes and gene-environment interactions with ATS susceptibility in a Han Chinese cohort.

MRAS: A Close but Understudied Member of the RAS Family

MRAS is the closest relative to the classical RAS oncoproteins and shares most regulatory and effector interactions. However, it also has unique functions, including its ability to function as a phosphatase regulatory subunit when in complex with SHOC2 and protein phosphatase 1 (PP1). This phosphatase complex regulates a crucial step in the activation cycle of RAF kinases and provides a key coordinate input required for efficient ERK pathway activation and transformation by RAS. MRAS mutations rarely occur in cancer but deregulated expression may play a role in tumorigenesis in some settings. Activating mutations in MRAS (as well as SHOC2 and PP1) do occur in the RASopathy Noonan syndrome, underscoring a key role for MRAS within the RAS-ERK pathway. MRAS also has unique roles in cell migration and differentiation and has properties consistent with a key role in the regulation of cell polarity. Further investigations should shed light on what remains a relatively understudied RAS family member.

The ANRIL Genetic Variants and Their Interactions with Environmental Risk Factors on Atherothrombotic Stroke in a Han Chinese Population

BACKGROUND

Ischemic stroke (IS) is considered to be a heterogeneous, multifactorial disease with a strong genetic background. This study aims to determine whether variants in the antisense noncoding RNA in the INK4 locus (ANRIL) gene are associated with IS in Han Chinese, as well as whether there is evidence of a gene-environment interactions.

MATERIALS AND METHODS

A case-controlled association study was conducted in which only patients with atherothrombotic stroke (ATS) were enrolled. Multifactor dimensionality reduction model was employed to screen the best interaction combinations among gene and environmental risk factors; RESULTS: A total of 405 subjects (200 cases and 205 controls) and 16 single nucleotide polymorphisms (SNPs) in ANRIL gene were included in this study. The 4 SNPs (rs1537378, rs2184061, rs7044859, and rs7865618) were found to be significantly related to ATS in Chinese Han nationality. In overall people or subjects aged 45 years or older, the GG genotype and G allele of rs1537378, the AA genotype and A allele of rs2184061 and rs7865618, and the AA genotype of rs7044859 increased the risk of ATS. In males, the GG genotype and G allele of rs1537378, the AA genotype and A allele of rs7865618, and the A allele of rs2184061 conferred a susceptibility to ATS. Additionally, the AAAGAGCAAAAAATAG haplotype exhibited an elevated risk of ATS, and a significant interaction was found in ATS susceptibility between ANRIL gene and dyslipidemia; CONCLUSIONS: The ANRIL gene was related to ATS susceptibility in a Han Chinese. Future studies should be performed with larger samples and among different ethnic populations.

The research on association of copy number variation in chromosome 9p21 region with atherothrombotic stroke in the Han Chinese population

BACKGROUND/PURPOSE

The copy number variants (CNVs) contain more genetic information compared with SNPs. The aim of this study was to elucidate whether the CNVs in Chromosome 9p21 region are associated with increased risk of Atherothrombotic stroke (ATS) in a Han Chinese population.

METHODS

A case-controlled association study was conducted in which only patients with ATS were enrolled. The CNVs were detected by the method of multiplex competitive amplification. The differences in distribution of CNVs between cases and controls were analyzed using univariate and multivariate logistic regression analysis. Subgroup analyses were also carried out to determine whether the effect of the CNVs was specific to age and gender among the subjects.

RESULTS

A total of 274 ATS patients and 282 health controls were included in the present study. 4 genes (ANRIL, CDKN2A, CDKN2B, and MTAP) including eight gene fragments in all were analyzed for CNV. The results showed that the copied number of most CNV in the 4 genes is two. There was no significant difference of CNV frequency between groups.

CONCLUSIONS

The obtained data suggested a negative association between CNV of the four genes and ATS. It is necessary to perform sequencing analyses across the entire 9p21 region for detecting rare or uncommon CNV.

A lack of association between the IKZF2 rs12619285 polymorphism and coronary heart disease

The IKZF2 rs12619285 polymorphism is associated with the eosinophil count, which has multidimensional functions in the pathogenesis of coronary heart disease (CHD). The aim of the present study was to investigate the contribution of the IKZF2 rs12619285 polymorphism to the risk of CHD in a Han Chinese population. In total, 721 CHD cases and 631 non-CHD controls were recruited for an association study of the IKZF2 rs12619285 polymorphism. Genotyping was performed using the melting temperature-shift polymerase chain reaction method. No statistically significant association was observed between the IKZF2 rs12619285 polymorphism and CHD (odds ratio, 1.139, 95% confidence interval, 0.927-1.334; P=0.17). In addition, subgroup analyses by gender or age were unable to identify any association between IKZF2 rs12619285 and CHD (P>0.05), and there was no significant correlation between IKZF2 rs12619285 and the severity of CHD (P>0.05). The power of the case-control study was determined to be 63.3%. In addition, the G allele frequency was calculated as 63.6% in the Han Chinese population, which was similar to the 59.3% recorded for the HapMap Chinese population of Han Chinese individuals living in Beijing, compared with 24.3% in European descendents (HapMap-CEU). Therefore, the results indicated that the IKZF2 rs12619285 polymorphism was not associated with CHD in a Han Chinese population. The discrepancy in the association between rs12619285 and CHD may be due to the ethnic differences between Han Chinese and European populations.