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Background: Moderately elevated blood levels of homocysteine are weakly correlated with coronary heart disease (CHD) risk, but causality remains uncertain. When folate levels are low, the TT genotype of the common C677T polymorphism (rs1801133) of the methylene tetrahydrofolate reductase gene (MTHFR) appreciably increases homocysteine levels, so ''Mendelian randomization'' studies using this variant as an instrumental variable could help test causality. Methods and Findings: Nineteen unpublished datasets were obtained (total 48,175 CHD cases and 67,961 controls) in which multiple genetic variants had been measured, including MTHFR C677T. These datasets did not include measurements of blood homocysteine, but homocysteine levels would be expected to be about 20% higher with TT than with CC genotype in the populations studied. In meta-analyses of these unpublished datasets, the case-control CHD odds ratio (OR) and 95% CI comparing TT versus CC homozygotes was 1.02 (0.98-1.07; p = 0.28) overall, and 1.01 (0.95-1.07) in unsupplemented low-folate populations. By contrast, in a slightly updated meta-analysis of the 86 published studies (28,617 CHD cases and 41,857 controls), the OR was 1.15 (1.09-1.21), significantly discrepant (p = 0.001) with the OR in the unpublished datasets. Within the meta-analysis of published studies, the OR was 1.12 (1.04-1.21) in the 14 larger studies (those with variance of log OR,0.05; total 13,119 cases) and 1.18 (1.09-1.28) in the 72 smaller ones (total 15,498 cases). Conclusions: The CI for the overall result from large unpublished datasets shows lifelong moderate homocysteine elevation has little or no effect on CHD. The discrepant overall result from previously published studies reflects publication bias or methodological problems. [ABSTRACT FROM AUTHOR]

Myocardial infarction (MI) results from complex interactions of multiple genetic and environmental factors. To disclose genetic backgrounds of MI, we performed a large-scale, case-control association study using 52,608 gene-based single-nucleotide polymorphism (SNP) markers, and identified a candidate SNP located on chromosome 3p21.2–p21.1. Subsequent linkage–disequilibrium mapping indicated very significant association between MI and a SNP in exon 2 of the inter-alpha (globulin) inhibitor 3 gene ( ITIH3; χ 2 = 24.88, P = 6.1 × 10−7, 3,353 affected individuals versus 3,807 controls). In vitro functional analyses showed that this SNP enhanced the transcriptional level of the ITIH3 gene. Furthermore, we found expression of the ITIH3 protein in the vascular smooth muscle cells and macrophages in the human atherosclerotic lesions, suggesting ITIH3 SNP to be a novel genetic risk factor of MI. [ABSTRACT FROM AUTHOR]

Through a large-scale case-control association study using 52,608 haplotype-based single nucleotide polymorphism (SNP) markers, we identified a susceptible locus for myocardial infarction (MI) on chromosome 22q12.1. Following linkage disequilibrium (LD) mapping, haplotype analyses revealed that six SNPs in this locus, all of which were in complete LD, showed markedly significant association with MI ( χ 2=25.27, P=0.0000005; comparison of allele frequency, 3,435 affected individuals versus 3,774 controls, in the case of intron 1 5,338 C>T; rs2331291). Within this locus, we isolated a complete cDNA of a novel gene, designated myocardial infarction associated transcript ( MIAT). MIAT has five exons, and in vitro translation assay showed that MIAT did not encode any translational product, indicating that this is likely to be a functional RNA. In vitro functional analyses revealed that the minor variant of one SNP in exon 5 increased transcriptional level of the novel gene. Moreover, unidentified nuclear protein(s) bound more intensely to risk allele than non-risk allele. These results indicate that the altered expression of MIAT by the SNP may play some role in the pathogenesis of MI. [ABSTRACT FROM AUTHOR]

Myocardial infarction (MI) is one of the common diseases whose pathogenesis includes genetic factors. To reveal genetic backgrounds of this clinically heterogeneous disorder, we started our case-control association study by examining large-scale gene-based single nucleotide polymorphism (SNP) sets for ∼1,000 patients and controls. As a core genotyping method, a combination of multiplex PCR and Invader method was used, and after genotyping ∼65,000 SNPs, we found two SNPs located within lymphotoxin-α ( LTA) gene showing significant association with MI. LTA is one of the cytokines produced in the early stages of vascular inflammatory processes. These SNPs seem to be involved in inflammation by both qualitatively and quantitatively modifying the function of LTA protein, thereby conferring a risk of MI. The genetic association was further confirmed by other researchers using white European trios. To further understand the roles of LTA protein in the pathogenesis of MI, we searched for proteins that interact directly with LTA protein and identified galectin-2 protein as a binding partner of LTA protein. It is a member of galactose-binding lectin family whose function has not been well characterized. Genetic association study again revealed that an SNP in LGALS2 encoding galectin-2 was also associated with susceptibility to MI. This genetic substitution seemed to affect the transcriptional level of galectin-2, which led to altered secretion of LTA, thereby affecting the degree of inflammation. Thus, our findings indicate the importance of inflammation, especially the LTA cascade, in the pathogenesis of MI. Also, combined strategy of genetic and molecular-cellular biological approaches may be useful for clarification of the pathogenesis of common diseases in general. [ABSTRACT FROM AUTHOR]

Galectins, a family of animal lectins that bind ß-galactoside sugar chains, are thought to have a variety of intra- and extracellular functions. Through a case-control study in the Japanese population and subsequent functional analyses, we previously showed that a functional single nucleotide polymorphism (SNP) in the gene encoding galectin-2 (lectin, galactoside-binding, soluble, 2;LGALS2) is associated with susceptibility to myocardial infarction. As an addition to the genetic information aboutLGALS2reported earlier, we provide here a map of polymorphic sites within an 11-kb region containing the gene encoding a closely related molecule, galectin-1 (lectin, galactoside-binding, soluble, 1;LGALS1). The map includes 14 SNPs and two genetic variations of other types detected in a Japanese population sample. Five of the 14 SNPs were not among those deposited in the dbSNP database in the US National Center for Biotechnology Information and appeared to be novel. We also analyzed linkage disequilibrium (LD) using the 12 SNPs in which minor-allele frequencies were>0.20. Investigation of haplotype structure within theLGALS1locus revealed five common haplotypes covering more than 95% of the test population. One, or a pair, of the SNPs described here might serve as a “tag” for detecting associations between complex diseases and genes in this local segment of chromosome 22q13.1. [ABSTRACT FROM AUTHOR]

Immunoglobulin A (IgA) nephropathy is the most common form of primary glomerulonephritis worldwide. The pathogenesis of IgA nephropathy is unknown, but it is certain that some genetic factors are involved in susceptibility to the disease. Employing a large-scale, case-control association study using gene-based single-nucleotide polymorphism (SNP) markers, we previously reported four candidate genes. We report here an additional significant association between IgA nephropathy and an SNP located in the gene encoding immunoglobulin µ-binding protein 2 (IGHMBP2) at chromosome 11q13.2-q13.4. The association (?2 =17.1,p=0.00003; odds ratio of 1.85 with 95% confidence interval of 1.39-2.50 in a dominant association model) was found using DNA from 465 affected individuals and 634 controls. The SNP (G34448A) caused an amino acid substitution from glutamine to lysine (E928K). As the gene product is involved in immunoglobulin-class switching and patients with the A allele revealed higher serum levels of IgA (p=0.048), the amino acid change might influence a class switch to increase serum IgA levels, resulting in a higher risk of IgA nephropathy. [ABSTRACT FROM AUTHOR]

We identified a total of 187 single-nucleotide polymorphisms (SNPs) at 11 gene loci in the 130-kb region on chromosome 6p21 containing a gene strongly associated with myocardial infarction (MI). By comparing our data with SNPs deposited in the dbSNP database at the National Center for Biotechnology Information, 46 of these SNPs (24.6%) were considered to be novel: four were identified in the P5-1 locus, 14 in the MICB locus, nine in the BAT1 locus, one in the ATP6V1G2 locus, six in the NFKBIL1 locus, one in the LTA locus, one in the TNF locus, five in the LST1 locus, four in the LY117a locus, and one in the AIF-1 locus. The SNP map presented here should provide as useful resource not only for examining the relationships between genotypes and susceptibility to the MI phenotype, but also for scanning of complex diseases mapped to this local segment on chromosome 6. [ABSTRACT FROM AUTHOR]

Immunoglobulin A nephropathy (IgAN) is a primary glomerulonephritis of common incidence world-wide whose etiology and pathogenesis remain unresolved, although genetic factors are assumed to be involved in the development and progression of this disease. To identify genetic variations that might confer susceptibility to IgAN, we performed a case-control association study involving 389 Japanese IgAN patients and 465 controls. Genome-wide analysis of approximately 80,000 single-nucleotide polymorphisms (SNPs) identified a significant association between IgAN and six SNPs located in the PIGR (polymeric immuoglob-ulin receptor) gene at chromosome 1q31-q41. One of them, PIGR-17, caused an amino-acid substitution from alanine to valine at codon 580 (χ[SUB2]=13.05, P=0.0003, odds ratio [OR] =1.59, 95% confidence interval [95% CI] =1.24-2.05); the OR of minor homozygotes to other was 2.71 (95% CI=1.31-5.61). Another SNP, PIGR-2, could affect promoter activity (χ[SUB2]=11.95, P=0.00055, OR=1.60, 95% CI=1.22- 2.08); the OR of minor homozygotes to others was 2.08 (95% CI=0.94-4.60). Pairwise analyses demonstrated that all six SNPs were in almost complete linkage disequilibrium. Biopsy specimens from IgAN patients were positively stained by antibody against the secretory component of PIGR, but corresponding tissues from non-IgAN patients were not. Our results suggest that a gene associated with susceptibility to IgAN lies within or close to the PIGR gene locus on chromosome 1q in the Japanese population. [ABSTRACT FROM AUTHOR]

Single-nucleotide polymorphisms (SNPs) can make an important contribution to our understanding of genetic backgrounds that may influence medical conditions and ethnic diversity. We undertook a systematic survey of genomic DNA for SNPs located not only in coding sequences but also in non-coding regions (e.g., introns and 5' flanking regions) of selected genes. Using DNA samples from 48 Japanese patients with rheumatoid arthritis (RA) as templates, we surveyed 41 genes that represent candidates for RA, screening a total of 104 kb of DNA (30 kb of coding sequences and 74 kb of non-coding DNA). Within this 104 kb of genomic sequences we identified 163 polymorphisms (1 per 638 bases on average), of which 142 were single-nucleotide substitutions and the remainder, insertions or deletions. Of the coding SNPs, 52% were non-synonymous substitutions, and non-conservative amino acid changes were observed in a quarter of those. Sixty-nine polymorphisms showed high frequencies for minor alleles (more than 15%) and 20 revealed low frequencies (<5%). Our results indicated a greater average distance between SNPs than others have reported, but this disparity may reflect the type of genes surveyed and/or the relative ethnic homogeneity of our test population. [ABSTRACT FROM AUTHOR]

We constructed a high-density map of single-nucleotide polymorphisms (SNPs) present within a 31-kb region of human chromosome 13q31 that contains the human counterpart of the rabbit ITR gene, which encodes a rhodopsin-like G protein-coupled receptor associated with vascular remodeling. The elements of human ITR cDNA were distributed in 27,452 bp of genomic DNA; the nine exons ranged in size from 50 bp to 2271 bp, with an average size of 392 bp. We isolated a total of 22 SNPs from the ITR locus by systematically screening genomic DNA from 48 healthy Japanese individuals; three SNPs were present in the 5′ flanking region, two in coding elements, 12 in introns, and five in the 3′ untranslated region. By comparing our data with SNPs deposited in the dbSNP database in the National Center for Biotechnology Information, 19 of the 22 SNPs (86) were considered to be novel. The map presented here should help in evaluating the role of human ITR in cardiovascular diseases, in other diseases mapped to this segment on chromosome 13q31, and in a variety of pharmacogenetic effects. [ABSTRACT FROM AUTHOR]

The BRCA-1 associated protein gene (BRAP) was recently identified as a susceptibility gene for myocardial infarction (MI). In the present study we aimed to decipher the association between the BRAP polymorphism and carotid atherosclerosis and the mechanism underlying its proatherogenic effect. A total of 1749 stroke/MI-free volunteers received carotid ultrasonic examinations for the measurement of intima-medial thickness (IMT) and plaque. The promoter polymorphism rs11066001 was selected because it affects the transcription of BRAP. We found that the GG genotype was associated with a 1.58-fold increased risk for having at least one plaque compared to carrying the A allele (P = 0.021). When subjects were divided by the cutoff value of IMT above the mean plus 1 standard deviation, there was an overrepresentation of the GG genotype in the subjects with thicker IMT (P = 0.004). The expression of BRAP increased significantly when human aortic smooth muscle cells (HASMCs) were treated with lipopolysaccharide (LPS). HASMCs were transfected with small interfering RNA against BRAP or scrambled sequences before treatment with LPS. Knockdown of BRAP led to attenuated HASMC proliferation and reduced secretion of monocyte chemoattractant protein-1 (MCP-1) and interleukin-8 (IL-8) in response to LPS. Downregulation of BRAP did not affect the protein levels of nuclear factor-κB (NF-κB), but prohibited its nuclear translocation. Coimmunoprecipitation experiments confirmed an interaction between BRAP and the two major components of the IKK signalosome, lκBβ and IKKβ. Collectively, BRAP conferred a risk for carotid plaque and IMT. Inflammatory stimuli upregulated BRAP expression, and BRAP activated inflammatory cascades by regulating NF-κB nuclear translocation. [ABSTRACT FROM AUTHOR]

Lumbar-disc herniation (LDH), one of the most common musculoskeletal diseases, has strong genetic determinants. Recently, several genes that encode extracellular matrix (ECM) proteins in the intervertebral disc have been reported to associate with LDH. Thrombospondins (THBSs) 1 and 2 are good candidates for the LDI-I susceptibility gene: They are intervertebral disc ECM proteins that regulate the effective levels of matrix metalloproteinases (MMPs) 2 and 9, which are key effectors of ECM remodeling. Here, we report that THBS2 is associated with LDH in Japanese populations. An intronic SNP in THBS2 (IVS10-8C → T; rs9406328) showed significant association (p = 0.0000028) with LDH in two independent Japanese populations. This SNP, located in a polypyrimidine tract upstream of the 3' splice site of intron 10, exerts allelic differences on exon 11 skipping rates in vivo, with the susceptibility allele showing increased skipping. Skipping of exon 11 results in decreased THBS2 interaction with MMP2 and MMP9. Further, a missense SNP in MMP9 (Q279R; rs17576) is also strongly associated with LDH in the Japanese population (p = 0.00049) and shows a combinatorial effect with THBS2 (odds ratio 3.03, 95% confidence interval 1.58-5.77). Thus, a splicing-affecting SNP in THBS2 and a missense SNP in MMP9 are associated with susceptibility to LDH. Our data indicate that regulation of intervertebral disc ECM metabolism by the THBS2MMP system plays an essential role in the etiology and pathogenesis of LDH. [ABSTRACT FROM AUTHOR]

Although intensive efforts have been undertaken to elucidate the genetic background of immunoglobulin A ne-phropathy (IgAN), genetic factors associated with the pathogenesis of this disease are still not well understood. We designed a case-control association study that was based on linkage disequilibrium among single-nucleotide polymorphisms (SNPs) in the selectin gene cluster on chromosome 1q24-25, and we found two SNPs in the E-selectin gene (SELE8 and SELE13) and six SNPs in the L-selectin gene (SELL1, SELL4, SELL5, SELL6, SELL10, and SELL11) that were significantly associated with IgAN in Japanese patients. All eight SNPs were in almost complete linkage disequilibrium. SELE8 and SELL10 caused amino acid substitutions from His to Tyr and from Pro to Ser (x² = 9.02, P = .0026, odds ratio = 2.73 [95% confidence interval [CI] 1.38 - 5.38] for His-to-Tyr substitutions; x² = 17.4, P = .000031, odds ratio = 3.61 [95% CI 1.91 - 6.83] for Pro-to-Ser substitutions), and SELL1 could affect promoter activity of the L-selectin gene (x² = 19.5, P = .000010, odds ratio = 3.77 [95% CI 2.02 - 7.05].) The TGT haplotype at these three loci was associated significantly with IgAN (x² = 18.67, P = .000016, odds ratio = 1.88 [95% CI 1.41-2.51]). Our results suggest that these eight SNPs in selectin genes may be useful for screening populations susceptible to the IgAN phenotype that involves interstitial infiltration. [ABSTRACT FROM AUTHOR]