[GWAS of Rheumatoid Arthritis and Drug Discovery]

We have conducted genome-wide association studies (GWAS) for rheumatoid arthritis (RA). We previously found that myelin basic protein (MBP) is associated with RA. One of the MBP isoforms (Golli-MBP) is expressed not only in nerve cells, but also in hematopoietic cells, and may negatively regulate T-cell receptor signaling. We expanded the GWAS level by collaborating with laboratories in Japan and then throughout the world. Meta-analysis of GWAS data resulted in the identification of -100 genomic loci associated with RA development. The -100 genomic loci contain -400 candidate genes, and it is not easy to find out which genes actually play important roles in RA. By incorporating available public databases, we succeeded in narrowing down the susceptibility genes from 377 to 98. We also showed that regulatory T cells are associated with RA based on the combination of the histone methylation database and our mega-GWAS results. Protein-protein interaction and drug discovery databases gave us information that some of the drugs have already been developed as therapeutic medicines for RA, and some of them were used for diseases other than RA. These drugs may be used for RA in the near future (drug repurposing). The combination of biological databases and GWAS results may be a novel method to identify new therapeutic targets.