Summary statistics from a genome-wide association study of narcolepsy

Type 1 narcolepsy (T1N) is a neurological condition, in which the death of
hypocretin-producing neurons in the lateral hypothalamus leads to
excessive daytime sleepiness and symptoms of abnormal Rapid Eye Movement
(REM) sleep. Known triggers for narcolepsy are influenza-A infection and
associated immunization during the 2009 H1N1 influenza pandemic. Here, we
genotyped all remaining consented narcolepsy cases worldwide and assembled
this with the existing genotyped individuals. We used this multi-ethnic
sample in genome wide association study (GWAS) to dissect disease
mechanisms and interactions with environmental triggers (5,339 cases and
20,518 controls). Overall, we found significant associations with HLA (2
GWA significant subloci) and 11 other loci. Six of these other loci have
been previously reported
(TRA, TRB, CTSH, IFNAR1, ZNF365 and P2RY11) and five are new (PRF1, CD207, SIRPG, IL27 and ZFAND2A). Strikingly, in vaccination-related cases, GWA significant effects were found in HLA, TRA, and in a novel variant near SIRPB1. Furthermore, IFNAR1-associated polymorphisms regulated dendritic cell response to influenza-A infection in vitro (p-value =1.92*10-25). A partitioned heritability analysis indicated specific enrichment of functional elements active in cytotoxic and helper T cells. Furthermore, functional analysis showed the genetic variants in TRA and TRB loci act as remarkably strong chain usage QTLs for TRAJ*24 (p-value = 0.0017), TRAJ*28 (p-value = 1.36*10-10) and TRBV*4-2 (p-value = 3.71*10-117). This was further validated in TCR sequencing of 60 narcolepsy cases and 60 DQB1*06:02 positive controls, where chain usage effects were further accentuated. Together these findings show that the autoimmune component in narcolepsy is defined by antigen presentation, mediated through specific T cell receptor chains, and modulated by influenza-A as a critical trigger.