Unknown,Transcriptomics,Genomics,Proteomics

Dataset Information

Blood pooling experiments on ophthalmalogic phenotypes with Illumina arrays

ABSTRACT: In this study 3 pooling experiments were performed. In each of the 3 cohorts, a 'case' and a 'control' blood pool was compared - the goal being to identify single nucleotide polymorphisms with significantly different estimated pooling allele frequencies between cases and controls. For cohort 1, 100 individuals with blue eye color were placed in one pool (the 'control' pool) and 100 individuals with brown eye color were placed in another pool ( the 'case' pool). In cohort 2, 131 individuals with age-related macular degeneration were placed in one pool, with 216 control individuals in another pool. In cohort 3, 100 individuals with pseudoexfoliation syndrome were placed in a case pool - in this case the cohort 2 control sample was used as 'controls'. The blue/brown pools were hybridized to Illumina HumanHap550 arrays. The cohort 2 and 3 pools were hybridized to Illumina 1M arrays. After processing, the raw data are summarized to give pooling allele frequency estimates for each pool. The abstract from the paper describing these data is as follows: Genome-wide association studies (GWAS) have now successfully identified important genetic variants associated with many human traits and diseases. The high cost of genotyping arrays in large datasets remains the major barrier to wider utilization of GWAS. We have developed a novel method in which whole blood from cases and controls respectively is pooled prior to DNA extraction for genotyping. We demonstrate proof of principle by clearly identifying the associated variants for eye color, age-related macular degeneration and pseudoexfoliation syndrome in cohorts not previously studied. Blood pooling has the potential to reduce GWAS cost by several orders of magnitude and dramatically shorten gene discovery time. This method has profound implications for translation of modern genetic approaches to a multitude of diseases and traits yet to be analysed by GWAS, and will enable developing nations to participate in GWAS. Pools were typed with Illumina arrays. Estimates of pooling allele frequency were obtained.

ORGANISM(S): Homo sapiens

SUBMITTER: Stuart Macgregor

PROVIDER: E-GEOD-17557 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Publications

Rapid inexpensive genome-wide association using pooled whole blood.

Craig Jamie E JE Hewitt Alex W AW McMellon Amy E AE Henders Anjali K AK Ma Lingjun L Wallace Leanne L Sharma Shiwani S Burdon Kathryn P KP Visscher Peter M PM Montgomery Grant W GW MacGregor Stuart S

Genome research 20091003 11

Genome-wide association studies (GWAS) have now successfully identified important genetic variants associated with many human traits and diseases. The high cost of genotyping arrays in large data sets remains the major barrier to wider utilization of GWAS. We have developed a novel method in which whole blood from cases and controls, respectively, is pooled prior to DNA extraction for genotyping. We demonstrate proof of principle by clearly identifying the associated variants for eye color, age- ...[more]

PMID: 19801603

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Project description:In this study 3 pooling experiments were performed. In each of the 3 cohorts, a 'case' and a 'control' blood pool was compared - the goal being to identify single nucleotide polymorphisms with significantly different estimated pooling allele frequencies between cases and controls. For cohort 1, 100 individuals with blue eye color were placed in one pool (the 'control' pool) and 100 individuals with brown eye color were placed in another pool ( the 'case' pool). In cohort 2, 131 individuals with age-related macular degeneration were placed in one pool, with 216 control individuals in another pool. In cohort 3, 100 individuals with pseudoexfoliation syndrome were placed in a case pool - in this case the cohort 2 control sample was used as 'controls'. The blue/brown pools were hybridized to Illumina HumanHap550 arrays. The cohort 2 and 3 pools were hybridized to Illumina 1M arrays. After processing, the raw data are summarized to give pooling allele frequency estimates for each pool. The abstract from the paper describing these data is as follows: Genome-wide association studies (GWAS) have now successfully identified important genetic variants associated with many human traits and diseases. The high cost of genotyping arrays in large datasets remains the major barrier to wider utilization of GWAS. We have developed a novel method in which whole blood from cases and controls respectively is pooled prior to DNA extraction for genotyping. We demonstrate proof of principle by clearly identifying the associated variants for eye color, age-related macular degeneration and pseudoexfoliation syndrome in cohorts not previously studied. Blood pooling has the potential to reduce GWAS cost by several orders of magnitude and dramatically shorten gene discovery time. This method has profound implications for translation of modern genetic approaches to a multitude of diseases and traits yet to be analysed by GWAS, and will enable developing nations to participate in GWAS.

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.

Dataset Information

Blood pooling experiments on ophthalmalogic phenotypes with Illumina arrays

Publications

Rapid inexpensive genome-wide association using pooled whole blood.

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