Genes for familial hemiplegic migraine (FHM) and episodic ataxia type-2 (EA-2) have been mapped to chromosome 19p13. We characterized a brain-specific P/Q-type Ca2+ channel alpha1-subunit gene, CACNL1A4, covering 300 kb with 47 exons. Sequencing of all exons and their surroundings revealed polymorphic variations, including a (CA)n-repeat (D19S1150), a (CAG)n-repeat in the 3'-UTR, and different types of deleterious mutations in FHM and EA-2. In FHM, we found four different missense mutations in conserved functional domains. One mutation has occurred on two different haplotypes in unrelated FHM families. In EA-2, we found two mutations disrupting the reading frame. Thus, FHM and EA-2 can be considered as allelic channelopathies. A similar etiology may be involved in common types of migraine.

IGRAINE IS A COMMON, chronic, multifactorial neurovascular disorder typically characterized by recurrent attacks of disabling headache and autonomic nervous system dysfunction (migraine without aura); up to one third of patients also have neurological aura symptoms (migraine with aura). 1,2 Migraine has been suggested to be an independent risk factor for stroke, but the evidence is conflicting and seems to be restricted to certain subpopulations (eg, women with migraine with aura who are younger than 45 years, particularly ones who smoke or use oral contraceptives [OCs]). 3-9 Case reports on patients with so-called migrainous infarction suggest that the posterior circulation territory (PCT) is most commonly affected. 8,9 However, data are lacking on prevalence of subclinical infarcts in a wide spectrum of migraine patients in the general population. Patients with migraine may also be at increased risk of more diffuse subclinical lesions in the deep white matter or periventricular areas that are only detected on neuroimaging. 10-12 Several clinic-based magnetic resonance imaging (MRI) studies have reported this,

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.

Disorders of the brain can exhibit considerable epidemiological comorbidity and often share symptoms, provoking debate about their etiologic overlap. We quantified the genetic sharing of 25 brain disorders from genome-wide association studies of 265,218 patients and 784,643 control participants and assessed their relationship to 17 phenotypes from 1,191,588 individuals. Psychiatric disorders share common variant risk, whereas neurological disorders appear more distinct from one another and from the psychiatric disorders. We also identified significant sharing between disorders and a number of brain phenotypes, including cognitive measures. Further, we conducted simulations to explore how statistical power, diagnostic misclassification, and phenotypic heterogeneity affect genetic correlations. These results highlight the importance of common genetic variation as a risk factor for brain disorders and the value of heritability-based methods in understanding their etiology.

The prevalence of migraine is higher then previously reported. The coexistence of migraine with and without aura occurs frequently and has implications for future studies on the genetics of migraine.