New susceptibility locus for obesity and dyslipidaemia on chromosome 3q22.3

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 Role of R-Ras Proteins in Normal and Pathologic Migration and Morphologic Change

The contributions that the R-Ras subfamily [R-Ras, R-Ras2/teratocarcinoma 21 (TC21), and M-Ras] of small GTP-binding proteins make to normal and aberrant cellular functions have historically been poorly understood. However, this has begun to change with the realization that all three R-Ras subfamily members are occasionally mutated in Noonan syndrome (NS), a RASopathy characterized by the development of hematopoietic neoplasms and abnormalities affecting the immune, cardiovascular, and nervous systems. Consistent with the abnormalities seen in NS, a host of new studies have implicated R-Ras proteins in physiological and pathologic changes in cellular morphology, adhesion, and migration in the cardiovascular, immune, and nervous systems. These changes include regulating the migration and homing of mature and immature immune cells, vascular stabilization, clotting, and axonal and dendritic outgrowth during nervous system development. Dysregulated R-Ras signaling has also been linked to the pathogenesis of cardiovascular disease, intellectual disabilities, and human cancers. This review discusses the structure and regulation of R-Ras proteins and our current understanding of the signaling pathways that they regulate. It explores the phenotype of NS patients and their implications for the R-Ras subfamily functions. Next, it covers recent discoveries regarding physiological and pathologic R-Ras functions in key organ systems. Finally, it discusses how R-Ras signaling is dysregulated in cancers and mechanisms by which this may promote neoplasia.

MRLocus: Identifying causal genes mediating a trait through Bayesian estimation of allelic heterogeneity

Expression quantitative trait loci (eQTL) studies are used to understand the regulatory function of non-coding genome-wide association study (GWAS) risk loci, but colocalization alone does not demonstrate a causal relationship of gene expression affecting a trait. Evidence for mediation, that perturbation of gene expression in a given tissue or developmental context will induce a change in the downstream GWAS trait, can be provided by two-sample Mendelian Randomization (MR). Here, we introduce a new statistical method, MRLocus, for Bayesian estimation of the gene-to-trait effect from eQTL and GWAS summary data for loci with evidence of allelic heterogeneity, that is, containing multiple causal variants. MRLocus makes use of a colocalization step applied to each nearly-LD-independent eQTL, followed by an MR analysis step across eQTLs. Additionally, our method involves estimation of the extent of allelic heterogeneity through a dispersion parameter, indicating variable mediation effects from each individual eQTL on the downstream trait. Our method is evaluated against other state-of-the-art methods for estimation of the gene-to-trait mediation effect, using an existing simulation framework. In simulation, MRLocus often has the highest accuracy among competing methods, and in each case provides more accurate estimation of uncertainty as assessed through interval coverage. MRLocus is then applied to five candidate causal genes for mediation of particular GWAS traits, where gene-to-trait effects are concordant with those previously reported. We find that MRLocus's estimation of the causal effect across eQTLs within a locus provides useful information for determining how perturbation of gene expression or individual regulatory elements will affect downstream traits. The MRLocus method is implemented as an R package available at https://mikelove.github.io/mrlocus.

Selective role of Nck1 in atherogenic inflammation and plaque formation

Although the Canakinumab Anti-Inflammatory Thrombosis Outcomes Study (CANTOS) established the role of treating inflammation in atherosclerosis, our understanding of endothelial activation at atherosclerosis-prone sites remains limited. Disturbed flow at atheroprone regions primes plaque inflammation by enhancing endothelial NF-κB signaling. Herein, we demonstrate a role for the Nck adaptor proteins in disturbed flow-induced endothelial activation. Although highly similar, only Nck1 deletion, but not Nck2 deletion, limited flow-induced NF-κB activation and proinflammatory gene expression. Nck1-knockout mice showed reduced endothelial activation and inflammation in both models, disturbed flow- and high fat diet-induced atherosclerosis, whereas Nck2 deletion did not. Bone marrow chimeras confirmed that vascular Nck1, but not hematopoietic Nck1, mediated this effect. Domain-swap experiments and point mutations identified the Nck1 SH2 domain and the first SH3 domain as critical for flow-induced endothelial activation. We further characterized Nck1's proinflammatory role by identifying interleukin 1 type I receptor kinase-1 (IRAK-1) as a Nck1-selective binding partner, demonstrating that IRAK-1 activation by disturbed flow required Nck1 in vitro and in vivo, showing endothelial Nck1 and IRAK-1 staining in early human atherosclerosis, and demonstrating that disturbed flow-induced endothelial activation required IRAK-1. Taken together, our data reveal a hitherto unknown link between Nck1 and IRAK-1 in atherogenic inflammation.

M-Ras is Muscle-Ras, Moderate-Ras, Mineral-Ras, Migration-Ras, and Many More-Ras

The Ras family of small GTPases comprises about 36 members in humans. M-Ras is related to classical Ras with regard to its regulators and effectors, but solely constitutes a subfamily among the Ras family members. Although classical Ras strongly binds Raf and highly activates the ERK pathway, M-Ras less strongly binds Raf and moderately but sustainedly activates the ERK pathway to induce neuronal differentiation. M-Ras also possesses specific effectors, including RapGEFs and the PP1 complex Shoc2-PP1c, which dephosphorylates Raf to activate the ERK pathway. M-Ras is highly expressed in the brain and plays essential roles in dendrite formation during neurogenesis, in contrast to the axon formation by R-Ras. M-Ras is also highly expressed in the bone and induces osteoblastic differentiation and transdifferentiation accompanied by calcification. Moreover, M-Ras elicits epithelial-mesenchymal transition-mediated collective and single cell migration through the PP1 complex-mediated ERK pathway activation. Activating missense mutations in the MRAS gene have been detected in Noonan syndrome, one of the RASopathies, and MRAS gene amplification occurs in several cancers. Furthermore, several SNPs in the MRAS gene are associated with coronary artery disease, obesity, and dyslipidemia. Therefore, M-Ras carries out a variety of cellular, physiological, and pathological functions. Further investigations may reveal more functions of M-Ras.

The influence of MRAS gene variants on ischemic stroke and serum lipid levels in Chinese Han population

Previous studies have indicated that muscle RAS oncogene homolog (MRAS) gene played an important role in cardiovascular diseases. However, the effect of MRAS genetic variations on ischemic stroke (IS) is still not clear. The aim of the current study was to investigate the association between the MRAS polymorphism and IS risk in Han populations.Three SNPs (rs40593, rs751357, rs6782181) at MRAS were selected for genotyping in a sample of 240 IS patients and 430 controls. Logistic regression was performed to evaluate the association of 3 SNPs with IS and IS subgroups.No association of MRAS SNPs with IS risk was observed, while G allele of rs40593 was associated with increased risk of cerebral infarction area. Compared with carriers of the AA genotype, the risk of carriers of the AG+GG genotype increased, with an OR (95%CI) of 2.337 (1.175-4.647), P = .016. In relation to lipid profile, rs40593, rs751357, rs6782181 were associated with increased total cholesterol (TC) levels.Summarily, this study suggested that MRAS rs40593 may contribute to the increased risk of area of cerebral infarction of IS in Han population. rs40593, rs751357, and rs6782181 were associated with higher serum TC levels.

Influence of rs1746048 SNPs on clinical manifestations and incidence of acute myocardial infarction in Guangxi Han population

A relationship of the CXCL12 gene rs1746048 SNPs with AMI has been reported in American, European, Caucasian, and Pakistani populations. However, little is known about this association in the Guangxi Han population. In this study, we detect associations between rs1746048 SNPs and susceptibility, risk factors, clinical characteristics, and gene-environment interactions for AMI. 300 AMI patients and 300 healthy controls of Chinese Han were enrolled. Genotyping of rs1746048 SNPs was performed using polymerase chain reaction and restriction fragment length polymorphism (PCR-RFLP) and then confirmed by direct sequencing. Significant differences in both genotypic and allelic frequencies of rs1746048 SNPs between AMI and the control group were not detected (P > 0.05 for each). The frequency of CC genotypes of rs1746048 SNPs was the highest in the 2 h < DT ≤ 6 h subgroup (P < 0.05). The frequencies of the CT genotype and the T allele were significantly higher in the severe complications subgroup of AMI (P < 0.05). There were interactions between the subjects with rs1746048 SNPs and smoking or alcohol consumption (P < 0.017 for each). Rs1746048 SNPs were not correlated with the risk of AMI in present study. For the first time, we discovered that the CC genotype of the rs1746048 SNPs was significantly correlated with DT of AMI; the frequencies of the CT genotype and the minor T allele were positively correlated with the severe complications of AMI. Also, the interaction between the rs1746048 SNPs and smoking or alcohol appears to increase the risk of AMI exposure.

Clinical, Social, and Genetic Factors Associated with Obesity at 12 Months of Age

OBJECTIVE

To examine genomic, social, and clinical risk factors of ≥85 weight for length percentile (WFLP) at 12 months.

STUDY DESIGN

Children in this study had whole-genome sequencing, and clinical and social data were collected. WFLPs at 12 months of age were grouped as follows: (1) <85th, (2) ≥85th to <95th, (3) ≥95th to <99th, and (4) ≥99th. Whole-genome sequencing data were used to analyze rare and common variants, and association of clinical and social factors was examined.

RESULTS

A total of 690 children were included; WFLPs were 422 (61.2%) <85th, 112 (16.2%) ≥85th-<95th, 89 (12.9%) ≥95th-<99th, and 67 (9.7%) ≥99th. Family-related risk factors associated with greater WFLP were greater paternal body mass index, WFLP ≥99th OR 1.10 (1.03-1.16), and greater than recommended weight gain in pregnancy, WFLP ≥85th-<95th OR 1.90 (1.09-3.26). More breast milk at 6 months was protective factor: WFLP ≥85th-<95th, OR 0.98 (0.97-0.99), WFLP ≥95th-<99th OR 0.98 (0.97-0.99), and WFLP ≥99th OR 0.98 (0.96-0.99). Although none of the variants reached genome-wide significance, there was a trend toward increased prevalence of genetic variants within or near genes previously associated with obesity in children with WFLP ≥99th.

CONCLUSION

This cross-sectional study identified several modifiable factors, including increased weight gain in pregnancy and decreased breast milk at 6 months, associated with greater WFLP at 12 months. Strong genetic factors were not identified.

Relationship between Lipid Phenotypes, Overweight, Lipid Lowering Drug Response and KIF6 and HMG-CoA Genotypes in a Subset of the Brisighella Heart Study Population

The existence of genetic traits might explain the susceptibility to develop hypercholesterolemia and the inter-individual differences in statin response. This study was performed to evaluate whether individuals' polymorphisms in HMG-CoA and KIF6 genes are independently associated with hypercholesterolemia, other lipid-associated traits, and statin response in unselected individuals enrolled in the Brisighella heart study (Survey 2012). A total of 1622 individuals, of which 183 under statin medication, were genotyped for a total of five polymorphisms (KIF6 rs20455, rs9471077, rs9462535; HMG-CoA rs3761740, rs3846662). The relationships between the five loci and clinical characteristics were analyzed. The principal basic parameters calculated on 12 h fasting blood included total cholesterol (TC), High Density Lipoprotein Cholesterol (HDL-C), Low-Density Lipoprotein Cholesterol (LDL-C), and triglycerides (TG). Hypercholesterolemia was defined as a TC >200 mg/dL or use of lipid-lowering medication. 965 individuals were characterized by hypercholesterolemia; these subjects were significantly older (p < 0.001), with body mass index (BMI) and waist circumference significantly higher (p < 0.001) compared to the others. HMG-CoA rs3846662 GG genotype was significantly over-represented in the hypercholesterolemic group (p = 0.030). HMG-CoA rs3846662 genotype was associated with the level of TC and LDL-C. Furthermore, in the same subset of untreated subjects, we observed a significant correlation between the KIF6 rs20455 and HDL-C. KIF6 variants were associated with a significantly lower (rs20455) or higher (rs9471077 and rs9462535) risk of obesity, in males only. No association between responsiveness to statins and the polymorphisms under investigation were observed. Our results showed associations between HMG-CoA rs3846662 and KIF6 rs20455 and lipid phenotypes, which may have an influence on dyslipidemia-related events. Moreover, this represents the first study implicating KIF6 variants with obesity in men, and point to the possible involvement of this genetic locus in the known gender-related differences in coronary artery disease.

DNA methylation epigenotype and clinical features of NRAS-mutation(+) colorectal cancer

Sporadic colorectal cancer (CRC) is classified into several molecular subtypes. We previously established two groups of DNA methylation markers through genome‐wide DNA methylation analysis to classify CRC into distinct subgroups: high‐, intermediate‐, and low‐methylation epigenotypes (HME, IME, and LME, respectively). HME CRC, also called CpG island methylator phenotype (CIMP)‐high CRC, shows methylation of both Group 1 markers (CIMP markers) and Group 2 markers, while IME/CIMP‐low CRC shows methylation of Group 2, but not of Group 1 markers, and LME CRC shows no methylation of either Group 1 or Group 2 markers. While BRAF‐ and KRAS‐mutation(+) CRC strongly correlated with HME and IME, respectively, clinicopathological features of NRAS‐mutation(+) CRC, including association with DNA methylation, remain unclear. To characterize NRAS‐mutation(+) CRC, the methylation levels of 19 methylation marker genes (6 Group 1 and 13 Group 2) were analyzed in 61 NRAS‐mutation(+) and 144 NRAS‐mutation(−) CRC cases by pyrosequencing, and their correlation with clinicopathological features was investigated. Different from KRAS‐mutation(+) CRC,NRAS‐mutation(+) CRC significantly correlated with LME. NRAS‐mutation(+) CRC showed significantly better prognosis than KRAS‐mutation(+) CRC (P = 3 × 10⁻⁴). NRAS‐mutation(+) CRC preferentially occurred in elder patients (P = 0.02) and at the distal colon (P = 0.006), showed significantly less lymph vessel invasion (P = 0.002), and correlated with LME (P = 8 × 10⁻⁵). DNA methylation significantly accumulated at the proximal colon. NRAS‐mutation(+) CRC may constitute a different subgroup from KRAS‐mutation(+) CRC, showing significant correlation with LME, older age, distal colon, and relatively better prognosis.

Forearm vasodilator reactivity in healthy male carriers of the 3q22.3 rs9818870 polymorphism

BACKGROUND

A genome wide association study has identified a robust risk locus for cardiovascular disease on 3q22.3. However, the mechanisms by which the [C]/[T] polymorphism rs9818870 increases cardiovascular risk are unknown. This forearm blood flow (FBF) study addressed the question if the genetic association with cardiovascular disease in patients is preceded by incipient vasodilator impairment in young, healthy carriers of this new risk locus on chromosome 3.

MATERIALS AND METHODS

After a pre-screening of 74 subjects 17 male healthy volunteers homozygous/heterozygous for a single nucleotide polymorphism (SNP) risk allele on 3q22.3 and a control group of 17 healthy volunteers not carrying the allele were included into this case-control study.

RESULTS

Forearm vascular endothelium-dependent and -independent vasodilator responses were in the normal range in both groups, although endothelium-dependent FBF reactivity to acetylcholine was significantly higher in SNP carriers of the risk allele.

CONCLUSION

The augmented endothelium-dependent vasodilation of the forearm resistance vasculature does not support the presence of endothelial dysfunction in young SNP carriers and indicates that other mechanisms are responsible for the strong association between coronary artery diseases and the rs9818870 polymorphism, located on 3q22.3.

Genetic insight into the role of MRAS in coronary artery disease risk

The muscle Ras (MRAS) gene polymorphisms have been reported to be associated with coronary artery disease (CAD) in white Europeans. The aim of this study was to ascertain the role of MRAS gene polymorphisms in conferring susceptibility to CAD, and to explore the effect on severity of CAD in Chinese population. We genotyped 5009 Chinese individuals (2466 CAD cases and 2543 controls) for eight single nucleotide polymorphisms (SNPs) around MRAS and used logistic regression analysis to determine whether they were associated with CAD. The association of the SNP loci on the severity of CAD was analyzed using a logistic and linear regression analysis, respectively. Our results revealed that an intron SNP, rs1199337, tends to be marginally associated with CAD as previously reported in Caucasians (nominal P=0.01, OR 1.10, 95% CI 1.01-1.20). However, this association did not retain statistically significant levels after applying Bonferroni's correction for multiple testing (corrected P=0.08). There was no significant association between other loci and CAD (nominal P>0.05). We did not observe any significant association between the SNPs and severity of CAD (all P values>0.05). From the above results, the MRAS gene loci might have a minor effect in conferring susceptibility to CAD in Chinese population.

Association between the MARS rs6782181 polymorphism and serum lipid levels

Little is known about the association between the muscle Ras (MRAS) gene rs6782181 polymorphism and serum lipid levels. The aim of the present study was to investigate the association between the MRAS rs6782181 polymorphism and serum lipid levels in the Mulao and Han populations. A total of 632 subjects of Han and 629 unrelated subjects of Mulao nationalities were randomly selected from our previous stratified randomized samples. Genotypes of the MARS rs6782181 polymorphism were determined via polymerase chain reaction and restriction fragment length polymorphism. The subjects with GG genotype had higher serum total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL-C), and apolipoprotein (Apo) B levels in Han, and higher serum TC and LDL-C levels in Mulao than the subjects with AA/AG genotypes (P < 0.05-0.01). Subgroup analyses showed that the subjects with GG genotype had higher TC, TG, high-density lipoprotein cholesterol (HDL-C), LDL-C, ApoAI and ApoB in Han males, lower ApoAI and the ratio of ApoAI to ApoB in Han females; and higher LDL-C levels in Mulao males but not in Mulao females than the subjects with AG/AA genotypes. The association of the MARS rs6782181 polymorphism and serum lipid levels is different between the Mulao and Han populations, or between males and females in the both ethnic groups. There may be an ethnic- and/or sex-specific association between the MRAS rs6782181 polymorphism and serum lipid levels in our study populations.

A study of the role of GATA4 polymorphism in cardiovascular metabolic disorders

BACKGROUND

The study was designed to evaluate the association of GATA4 gene polymorphism with coronary artery disease (CAD) and its metabolic risk factors, including dyslipidaemic disorders, obesity, type 2 diabetes and hypertension, following a preliminary study linking early onset of CAD in heterozygous familial hypercholesterolaemia to chromosome 8, which harbours the GATA4 gene.

RESULTS

We first sequenced the whole GATA4 gene in 250 individuals to identify variants of interest and then investigated the association of 12 single-nucleotide polymorphisms (SNPs) with the disease traits using Taqman chemistry in 4,278 angiographed Saudi individuals. Of the studied SNPs, rs804280 (1.14 (1.03 to 1.27); p = 0.009) was associated with CAD (2,274 cases vs 2,004 controls), hypercholesterolaemia (1,590 vs 2,487) (1.61 (1.03-2.52); p = 0.037) and elevated low-density lipoprotein-cholesterol (hLDLC) (575 vs 3,404) (1.87 (1.10-3.15); p = 0.020). Additionally, rs3729855_T (1.52 (1.09-2.11; p = 0.013)) and rs17153743 (AG + GG) (2.30 (1.30-4.26); p = 0.005) were implicated in hypertension (3,312 vs 966), following adjustments for confounders. Furthermore, haplotypes CCCGTGCC (χ2 = 4.71; p = 0.041) and GACCCGTG (χ2 = 3.84; p = 0.050) constructed from the SNPs were associated with CAD and ACCCACGC (χ2 = 6.58; p = 0.010) with myocardial infarction, while hypercholesterolaemia (χ2 = 3.86; p = 0.050) and hLDLC (χ2 = 4.94; p = 0.026) shared the AACCCATGT, and AACCCATGTC was associated with hLDLC (χ2 = 4.83; p = 0.028). A 10-mer GACCCGCGCC (χ2 = 7.59; p = 0.006) was associated with obesity (1,631 vs 2,362), and the GACACACCC (χ2 = 4.05; p = 0.044) was implicated in type 2 diabetes mellitus 2,378 vs 1,900).

CONCLUSION

Our study implicates GATA4 in CAD and its metabolic risk traits. The finding also points to the possible involvement of yet undefined entities related to GATA4 transcription activity or gene regulatory pathways in events leading to these cardiovascular disorders.