[Genome-Wide Association Studies for life-style related diseases]

After the completion of human genome project, development of single nucleotide polymorphism (SNP) typing technology and collation of information regarding linkage disequilibrium in the human genome have facilitated genome-wide association studies (GWAS) for investigating genes associated with disease susceptibility across the entire human genome. In case of type 2 diabetes, approximately 100 genetic loci have been identified and confirmed as susceptibility to the disease through GWAS in different ethnic groups, including Japanese, European, East Asian and South Asian populations. However, integration of these information accounts for less than 20% of the disease heritability, and thus most of the heritability of type 2 diabetes remain to be identified. Since the rationale of GWAS is based on the hypothesis that common variants contribute to the susceptibility to common diseases, common disease-common variant hypothesis, GWAS have selectively identified common susceptibility variants (allele frequency>=0.05) with lower effect size (odds ratio<1.5), that is a limitation of the GWAS approach. Although GWAS have brought a significant breakthrough in the field of genetic study for life-style related diseases, new approaches other than GWAS, such as whole genome sequencing to identify rare variants with greater effect size or integration of genetic and environmental information, will be required to elucidate a heritability of life-style related diseases completely.