Deyo-Svendsen, Matthew

Abstract The advancement in genotyping technology and large SNP arrays has led to an increase in the number of genome-wide association studies (GWAS) for various complex traits. These GWAS have resulted in the implication of over 1500 SNPs for association with disease traits. However, the SNPs identified from these GWAS are not necessarily the functional variants. Therefore, the next phase in GWAS will involve the validation, augmentation and refining of these putative regions or loci. One possible “next phase” approach would be to catalog all variants found in the study subjects within the loci of interest using sequencing technology, followed by the association analysis. However, sequencing a locus in a large number of subjects is still relatively expensive. By sequencing only a portion of the samples for the follow-up of signals from GWAS, followed by imputation in the remaining samples, one can significantly reduced the cost to localize the punitive variant involved in the etiology of complex phenotypes. A potentially attractive alternative option would be to impute based only on the 1000 Genomes Project; however, this has the drawbacks of using a reference population that does not necessarily match with disease status and LD pattern. Therefore, we conducted a study to investigate the ability to carry-out genotype imputation using a reference panel consisting of sequencing data for a fraction of the study participants. The various approaches were implemented using data from the candidate gene sequencing study conducted at the Mayo Clinic and the 1000 Genomes Project. Our results show that imputation of untyped markers based on sequencing a portion of the study participants is a reasonable, cost-saving, approach for disease mapping and the refinement of putative regions detected with GWAS. We recommend a few guidelines in designing sequencing studies to take advantage of the recent advances in genotype imputation: (1) Select the largest and most diverse reference panel for sequencing, with respect to both haplotypes and phenotypes. One can also use the 1000 Genomes Project in addition to the sequencing of a portion of the study participants; (2) Genotype as many “anchor” markers as possible, in that, the number of markers genotyped on all subjects impacts accuracy. Therefore, additional genotyping of a few common SNP markers not already genotyped on all subjects using a cost effective platform may be needed if the GWAS SNP array does not provide adequate coverage in the locus to be sequenced. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 101st Annual Meeting of the American Association for Cancer Research; 2010 Apr 17-21; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2010;70(8 Suppl):Abstract nr 4738.