Migraine is a debilitating neurological disorder affecting around 1 in 7 people worldwide, but its molecular mechanisms remain poorly understood. Some debate exists over whether migraine is a disease of vascular dysfunction or a result of neuronal dysfunction with secondary vascular changes. Genome-wide association (GWA) studies have thus far identified 13 independent loci associated with migraine. To identify new susceptibility loci, we performed the largest genetic study of migraine to date, comprising 59,674 cases and 316,078 controls from 22 GWA studies. We identified 44 independent single nucleotide polymorphisms (SNPs) significantly associated with migraine risk (P < 5 × 10−8) that map to 38 distinct genomic loci, including 28 loci not previously reported and the first locus identified on chromosome X. In subsequent computational analyses, the identified loci showed enrichment for genes expressed in vascular and smooth muscle tissues, consistent with a predominant theory of migraine that highlights vascular etiologies.

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In a population-based genome-wide analysis including 5122 migraineurs and 18,108 non-migraineurs, rs2651899 (PRDM16), rs10166942 (TRMP8), and rs11172113 (LRP1) were among the top associations (p<5×10−6) with migraine. All three SNPs were significant in meta-analysis among replication cohorts and met genome-wide significance (p<4.3×10−9) in meta-analysis combining discovery and replication cohorts. Rs2651899 and rs10166942 associated with migraine compared to non-migraine headache; none of the three SNPs specifically associated with migraine subtypes or features.

Migraine without aura is the most common form of migraine, characterized by recurrent disabling headache and associated autonomic symptoms. To identify common genetic variants for this migraine type, we analyzed genome-wide association data of 2,326 clinic-based German and Dutch patients and 4,580 population-matched controls. We selected SNPs from 12 loci with two or more SNPs with P-values < 1 × 10 −5 for follow-up in 2,508 patients and 2,652 controls. Two loci, i.e. 1q22 (MEF2D) and 3p24 (near TGFBR2) replicated convincingly (P = 4.9 × 10 −4 , P = 1.0 × 10 −4 , respectively). Meta-analysis of the discovery and replication data yielded two additional genome-wide significant (P < 5 × 10 −8 ) loci in PHACTR1 and ASTN2. In addition, SNPs in two previously reported migraine loci in or near TRPM8 and LRP1 significantly replicated. This study reveals the first susceptibility loci for migraine without aura, thereby expanding our knowledge of this debilitating neurological disorder. Main textMigraine is a disabling episodic neurovascular brain disorder affecting 12% of the general population [1][2][3][4] . Migraine attacks are typically characterized by severe throbbing unilateral headache and nausea, vomiting and photo-and phonophobia (migraine without aura; MO). In up to one third of patients attacks may be associated with neurological aura symptoms (migraine with aura; MA). Previous genome-wide association studies (GWAS) identified a migraine susceptibility locus on chromosome 8q22, close to MTDH, in the clinic-based International Headache Genetics Consortium (IHGC) MA study 5 and three other loci in or near PRDM16, LRP1, and TRPM8 in the population-based migraine Women's Genome Health Study (WGHS) 6 . For TRPM8 there was suggestive association (P < 1 × 10 −5 ) also in the clinic-based IHGC MA GWAS 5 . Here we report the first GWAS in MO, the most common form of migraine. We analyzed two large samples from headache centres in Germany and the Netherlands including 2,326 MO patients and 4,580 population-matched controls (Supplementary Note and Supplementary Fig. 1). A quantile-quantile plot of the joint analysis ( Supplementary Fig. 2) and an overall inflation factor ( 1000) of 1.03 were used as final quality control measures. The discovery dataset identified one genome-wide significant (P < 5 × 10 −8 ) locus on chromosome 1q22 as well as eleven additional loci containing multiple SNPs with suggestive association (P < 1 × 10 −5 ) (Supplementary Table 1). Eighteen SNPs from these 12 loci were taken forward to the replication stage in four Fig. 1 and Supplementary Table 1). Eight SNPs in six loci showed P-values < 0.05 in the replication study, and five of these SNPs also showed P-values < 5 × 10 −8 in the meta-analysis combining the discovery and replication cohorts (Table 1, Fig. 1 and Supplementary Fig. 3). Four loci (1q22, 3p24, 6p24, 9q33) replicated, although replication was less convincing for loci on 6p24 and 9q33 with replication P-values of 0.012 and 0.018, respectively, although P-values were < 5 × ...