['It is increasingly clear that asthma is not a single disease, but a disorder with vast heterogeneity in pathogenesis, severity, and treatment response. To date, 30 genomewide association studies (GWASs) of asthma have been performed, including by our group. However, most gene variants identified so far confer relatively small increments in risk and explain only a small proportion of familial clustering.', 'To identify additional genetic determinants of susceptibility to asthma using a selected Japanese population with reduced tobacco smoking exposure.', 'We performed a GWAS by genotyping a total of 480\xa0098 single-nucleotide polymorphisms (SNPs) for a Japanese cohort consisting of 734 healthy controls and 240 patients with asthma who had smoked for no more than 10 pack-years. The SNP with the strongest association was genotyped in two other independent Japanese cohorts consisting of a total of 531 healthy controls and 418 patients with asthma who had smoked for no more than 10 pack-years. For the hyaluronan synthase 2 (HAS2) gene, we investigated SNP-gene associations using an expression quantitative trait loci (eQTL) database and also analysed its gene expression profiles in 13 different normal tissues.', 'In the discovery GWAS, a SNP located upstream of HAS2, rs7846389, showed the strongest statistical significance (P\xa0=\xa01.43\xa0×\xa010(-7) ). In the two independent replication cohorts, rs7846389 was consistently associated with asthma (nominal P\xa0=\xa00.0152 and 0.0478 in the first and second replication cohorts, respectively). In the meta-analysis, association of rs7846389 with susceptibility to asthma reached the level of genomewide significance (P\xa0=\xa07.92\xa0×\xa010(-9) ). This variant was strongly correlated with HAS2 mRNA expression. The strongest expression of the gene was detected in the lung.'] Does genomewide association study identify HAS2 as a novel susceptibility gene for adult asthma in a Japanese population?