Association study of the NRAMP1 gene promoter polymorphism and early-onset type 1 diabetes

Natural resistance-associated macrophage protein 1 (NRAMP1) has an important role in regulating macrophage functions that affect innate resistance as well as immune responses. We analyzed the microsatellite polymorphism in the promoter region of the human NRAMP1 gene in 206 type 1 diabetes patients and 200 normal children to determine whether this polymorphism might be associated with type 1 diabetes in the Japanese population. The frequency of allele 2 (180 bp) of the promoter microsatellite polymorphism of the NRAMP1gene was slightly lower in the early-onset population (2-10 years of age) of type 1 diabetes patients than in controls, although the difference did not reach statistical significance. The association study of the cytotoxic T lymphocyte-associated antigen-4 (CTLA-4) gene, located near the NRAMP1 gene, and type 1 diabetes showed that the CTLA-4 gene significantly contributed to the development of type 1 diabetes, whereas NRAMP1 had an additional effect on the onset of type 1 diabetes in the young population.     

The insulin gene in type 1 diabetes

Insulin is a key autoantigen in the autoimmune process leading to the development of type 1 diabetes. Recent studies in both humans and mice have shown that variation in the expression of the insulin gene, in the thymus rather than the pancreas, contributes to disease susceptibility by affecting self-tolerance to insulin. These findings have brought about a paradigm-shift in our understanding of self-tolerance and autoimmunity to molecules with tissue-restricted expression, which are often the target of autoimmune disease.     

Association of SGK1 gene polymorphisms with type 2 diabetes

The serum and glucocorticoid inducible kinase SGK1 is genomically upregulated by glucocorticoids and in turn stimulates a variety of carriers and channels including the renal epithelial Na(+) channel ENaC and the intestinal Na(+) glucose transporter SGLT1. Twin studies disclosed an association of a specific SGK1 haplotype with moderately enhanced blood pressure in individuals who are carrying simultaneously a homozygous genotype for a variant in intron 6 [I6CC] and a homozygous or heterozygous genotype for the C allele of a polymorphism in exon 8 [E8CC/CT] of the SGK1 gene. A subsequent study confirmed the impact of this risk haplotype on blood pressure. SGK1 knockout mice are resistant to the insulin and high salt induced increase of blood pressure, glucocorticoid induced increase of electrogenic glucose transport, and glucocorticoid induced suppression of insulin release. The present study explored whether the I6CC/E8CC/CT haplotype impacts on the prevalence of type 2 diabetes. The prevalence of the I6CC genotype was 3.1% in a healthy German, 2.4 % in a healthy Romanian and 11.6 % in a healthy African population from Ghana (p=0.0006 versus prevalence in Caucasians). Comparison of genotype frequencies between type 2 diabetic patients and the respective control groups revealed significant differences for the intron 6 T>C variant. Carriers of at least one T allele were protected against type 2 diabetes (Romanians: p=0.023; OR 0.29; 95% CI 0.09-0.89; Germans: p=0.01; OR 0.37; 95% CI 0.17-0.81). The SGK1 risk haplotype (I6CC/E8CC/CT) was significantly (p=0.032; OR 4.31, 95% CI 1.19-15.58) more frequent in diabetic patients (7.2 %) than in healthy volunteers from Romania (1.8%). The observations support the view that SGK-1 may participate in the pathogenesis of metabolic syndrome.     

Association of TNF promoter polymorphisms with type 1 diabetes in the South Croatian population

Type 1 diabetes mellitus (TIDM) is an autoimmune disease characterized by the destruction of pancreatic p cells. Tumor necrosis factor (TNF) is a pleotropic cytokine with potent immunomodulatory and inflammatory activity. Association studies of TNF polymorphisms and type 1 diabetes (TIDM) frequently demonstrated TNF involvement with TIDM. Although TNF may play an important role in the pathogenesis of TIDM, the genetic association of TNF región with the disease has not been conclusive because of the strong linkage disequilibrium with HLA genes. In this study, we examined two TNF promoter variants (rs 1800629 at position -308, and rs361525 at position -238) for TIDM association in 233 patients and 144 controls from the population of South Croatia. A higher frequency of TNF -308 A alíele and also, a more frequent specific -308A -238G haplotype in TIDM patients were observed with a limited significance. However, we did not find strong evidence of association of TNF promoter polymorphisms with TIDM. In order to elucidate the trae contribution of TNF to TIDM susceptibility in our population, more comprehensive studies with HLA adjustment in a larger sample are required.     

CpG island methylation pattern in different human tissues and its correlation with gene expression

The study on DNA methylation pattern in different human tissues attracts increasing interest nowadays, but a systematic analysis of CpG island methylation pattern between both somatic tissues and gametocyte is still lacking. In this work, we analyzed the CpG island methylation data of sperm and other 11 somatic tissues from Human Epigenome Project, and found that the CpG island methylation profiles are highly correlated between somatic tissues, while the methylation profile in sperm is quite distinct. Furthermore, we observed that in the six tissues investigated, there is no obvious correlation between the methylation level of promoter CpG islands and corresponding gene expression across different tissues.     

Elevated CpG island methylation of GCK gene predicts the risk of type 2 diabetes in Chinese males

Background

The GCK gene encodes hexokinase 4, which catalyzes the first step in most glucose metabolism pathways. The purpose of our study is to assess the contribution of GCK methylation to type 2 diabetes (T2D).

Methods and results

GCK methylation was evaluated in 48 T2D cases and 48 age- and gender-matched controls using the bisulphite pyrosequencing technology. Among the four CpG sites in the methylation assay, CpG4 and the other three CpGs (CpG1-3) were not in high correlation (r < 0.5). Significantly elevated methylation levels of GCK CpG4 methylation were observed in T2D patients than in the healthy controls (P = 0.004). A breakdown analysis by gender indicated that the association between CpG4 methylation and T2D was specific to males (P = 0.002). It is intriguing that another significant male-specific association was also found between GCK CpG4 methylation and total cholesterol (TC) concentration (r = 0.304, P = 0.036).

Conclusion

Our results showed that elevated GCK CpG4 methylation might suggest a risk of T2D in Chinese males. Gender disparity in GCK CpG4 methylation might provide a clue to elaborate the pathogenesis of T2D.     

Stabilization of G-quadruplex structure on vascular endothelial growth factor gene promoter depends on CpG methylation site and cation type

Background

DNA methylation at the 5-position of cytosine is an epigenetic modification of CpG dinucleotides. In addition to CpG methylation, the G-quadruplex (G4) structure has been reported as a regulator of gene expression. The identification of G4 forming sequences in CpG islands suggests an involvement of CpG-methylated G4 structures in biological processes; however, few reports have addressed the effects of CpG methylation on G4 structure.

Association of lipid metabolism-related gene promoter methylation with risk of coronary artery disease

Molecular Biology Reports - Coronary artery disease (CAD) is a complex disease that is influenced by environmental and genetic factors. Lipid levels are regarded as a major risk factor for CAD, and...     

hMLH1基因启动子CpG岛甲基化致MSI与肿瘤的关系

通过人类错配修复基因( hMLHl)启动子CpG岛甲基化与微卫星不稳定性(MSI)的分析,探讨癌症发病的机制.错配修复基因hMLH1启动子CpG岛甲基化是hMLH1基因失活的重要机制,而hMLH1的表达失活则可导致MSI的产生,促进癌症的发生.根据一系列研究得出结论,在肿瘤组织中hMLH1基因启动子CpG岛甲基化和微卫星不稳定(MSI)有显著相关性,并在癌症早期发生、发展过程中起重要作用.因此临床检测hMLH1基因启动子CpG岛甲基化及微卫星不稳定可能成为癌症鉴别诊断、评价预后、指导化疗的分子标志物之一.     

Global, comparative analysis of tissue-specific promoter CpG methylation

Understanding cell-type-specific epigenetic codes on a global level is a major challenge after the sequencing of the human genome has been completed. Here we applied methyl-CpG immunoprecipitation (MCIp) to obtain comparative methylation profiles of coding and noncoding genes in three human tissues, testis, brain, and monocytes. Forty-four mainly testis-specific promoters were independently validated using bisulfite sequencing or single-gene MCIp, confirming the results obtained by the MCIp microarray approach. We demonstrate the previously unknown somatic hypermethylation at many CpG-rich, testis-specific gene promoters, in particular in ampliconic areas of the Y chromosome. We also identify a number of miRNA genes showing tissue-specific methylation patterns. The comparison of the obtained tissue methylation profiles with corresponding gene expression data indicates a significant association between tissue-specific promoter methylation and gene expression, not only in CpG-rich promoters. In summary, our study highlights the exceptional epigenetic status of germ-line cells in testis and provides a global insight into tissue-specific DNA methylation patterns.