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Impact of SNPs on methylation readouts by Illumina HM450K Array. Methylation profiles in European and Asian populations

ABSTRACT: We performed a comparative study of European and Asian populations using Illumina HM450K. We found that the majority of Infinium probes, which differentiated two examined groups, had SNPs in their target sequence. We investigated the impact of those SNPs on methylation readouts by Illumina HM450K Array. Our study clearly demonstrates that SNP variation existing in the genome, if not accounted for, may lead to false interpretation of the methylation signal differences suggested by some of the Illumina Infinium probes.

ORGANISM(S): Homo sapiens

PROVIDER: GSE73901 | GEO | 2015/12/03

SECONDARY ACCESSION(S): PRJNA298364

REPOSITORIES: GEO

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Project description:Background: The mechanisms of how genetic variants (SNPs) identified in genome-wide association studies act to influence body mass remain unknown for most of these SNPs, which continue to puzzle the scientific community. Recent evidence points to epigenetic and chromatin state of the genome to have an important role. Methods: 355 healthy young individuals were genotyped for 52 known obesity-associated SNPs and we obtained DNA methylation levels in their blood using the Illumina 450K BeadChip. Associations between alleles and methylation at proximal cytosine residues were tested using a linear model adjusted for age, sex, weight category and a proxy for blood cell type counts. For replication in other tissues, we used two open-access datasets (skin fibroblasts, n=62; four brain regions, n=121-133) and an additional dataset in subcutaneous and visceral fat (n=149). Results: We found that alleles at 28 of these obesity-associated SNPs associate with methylation levels at 107 proximal CpG sites. Out of 107 CpG sites, 38 are located in gene promoters, including genes strongly implicated in obesity (MIR148A, BDNF, PTPMT1, NR1H3, MGAT1, SCGB3A1, HOXC12, PMAIP1, PSIP1, RPS10-NUDT3, RPS10, SKOR1, MAP2K5, SIX5, AGRN, IMMP1L, ELP4, ITIH4, SEMA3G, POMC, ADCY3, SSPN, LGR4, TUFM, MIR4721, SULT1A1, SULT1A2, APOBR, CLN3, SPNS1,SH2B1, ATXN2L, and IL27). Interestingly, the associated SNPs are in known eQTLs for some of these genes. We also found that the 107 CpGs are enriched in enhancers in peripheral blood mononuclear cells. Finally, our results indicate that some of these associations are not be blood-specific as we successfully replicated four associations in skin fibroblasts. Conclusions: Our results strongly suggest that many obesity-associated SNPs are associated with proximal gene regulation, which was reflected by association of obesity risk allele genotypes with differential DNA methylation. This study highlights the importance of DNA methylation and other chromatin marks as a way to understand the molecular basis of genetic variants associated to human diseases and traits. Bisulphite converted DNA from 355 individuals aged 14-34 were hybridised to the Illumina Infinium 450k Human Methylation Beadchip.

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Impact of SNPs on methylation readouts by Illumina HM450K Array. Methylation profiles in European and Asian populations

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