Genome-wide association study ofHLA-DQB1*06:02negative essential hypersomnia

Essential hypersomnia (EHS), a sleep disorder characterized by excessive daytime sleepiness, can be divided into two broad classes based on the presence or absence of the HLA-DQB1*06:02 allele. HLA-DQB1*06:02 -positive EHS and narcolepsy with cataplexy are associated with the same susceptibility genes. In contrast, there are fewer studies of HLA-DQB1*06:02 negative EHS which, we hypothesized, involves a different pathophysiological pathway than does narcolepsy with cataplexy. In order to identify susceptibility genes associated with HLA-DQB1*06:02 negative EHS, we conducted a genome-wide association study (GWAS) of 125 unrelated Japanese EHS patients lacking the HLA-DQB1*06:02 allele and 562 Japanese healthy controls. A comparative study was also performed on 268 HLA-DQB1*06:02 negative Caucasian hypersomnia patients and 1761 HLA-DQB1*06:02 negative Caucasian healthy controls. We identified three SNPs that each represented a unique locus— rs16826005 ( P = 1.02E-07; NCKAP5 ), rs11854769 ( P = 6.69E-07; SPRED1 ), and rs10988217 ( P = 3.43E-06; CRAT ) that were associated with an increased risk of EHS in this Japanese population. Interestingly, rs10988217 showed a similar tendency in its association with both HLA-DQB1*06:02 negative EHS and narcolepsy with cataplexy in both Japanese and Caucasian populations. This is the first GWAS of HLA-DQB1*06:02 negative EHS, and the identification of these three new susceptibility loci should provide additional insights to the pathophysiological pathway of this condition.