Hanna Harno

Testing of Variants of the MTHFR and ESR1 Genes in 1798 Finnish Individuals Fails to Confirm the Association with Migraine with Aura

Among the few independently replicated genetic associations in migraine are polymorphisms in the methylenetetrahydrofolate reductase (MTHFR) and oestrogen receptor (ESR1) genes. We studied the contribution of these genes to migraine susceptibility by genotyping six MTHFR and 26 ESR1 polymorphisms in 898 unrelated migraine with aura (MA) patients and in 900 unrelated healthy controls. There were no differences in the genotype distributions of the previously migraine-associated SNPs C677T (MTHFR) and G2014A (ESR1) between cases and controls (P-values 0.83 and 0.55, respectively). Thus, we were not able to replicate the previous findings, although our study had considerable power. However, five of the ESR1 SNPs (rs6557170, rs2347867, rs6557171, rs4870062 and rs1801132) that were in strong linkage disequilibrium were nominally associated with MA (uncorrected P-values 0.007-0.034). These results did not, however, remain significant after taking multiple testing into account. Thus it seems unlikely that the studied genes are involved in migraine susceptibility, at least in this sample.

Subclinical vestibulocerebellar dysfunction in migraine with and without aura

Objective: In patients with migraine, neurotologic symptoms and signs occur commonly. The authors’ aim was to determine whether neurotologic findings are in accordance with the type of migraine and whether test findings differ from those of healthy controls. Methods: The authors examined 36 patients with various types of migraine classified by International Headache Society criteria. Comprehensive neurotologic tests were performed between attacks: video-oculography (VOG), electronystagmography, static posturography, and audiometry on 12 patients with migraine with aura (MA) and 24 patients with migraine without aura (MO). Results were compared to those of test-specific nonmigrainous control groups. Only eight migraineurs (six with MA and two with MO) had vertigo or dizziness. Results: Despite the absence of clinical neurotologic symptoms, most of the patients with migraine (83%) showed abnormalities in at least one of these tests. Both migraine types differed significantly from the control group (in VOG, in saccadic accuracy, and in static posturography). Vestibular findings tended to be more severe in MA than in MO. Conclusions: These data suggest that interictal neurotologic dysfunction in MA and MO share similar features and that the defective oculomotor function is mostly of vestibulocerebellar origin.

A novel missense ATP1A2 mutation in a Finnish family with familial hemiplegic migraine type 2.

Familial hemiplegic migraine (FHM), a rare autosomal dominant subtype of migraine with aura, has been linked to two chromosomal loci, 19p13 and 1q23. Mutations in the Na+,K+-ATPase α2 subunit gene, ATP1A2, on 1q23 have recently been shown to cause familial hemiplegic migraine type 2 (FHM2). We sequenced the coding regions of this gene in a Finnish chromosome 1q23-linked FHM family with associated symptoms such as coma and identified a novel A1033G mutation in exon 9. This mutation results in a threonine-to-alanine substitution at codon 345. This residue is located in a highly conserved N-terminal region of the M4–5 loop of the Na+,K+-ATPase. Furthermore, the T345A mutation co-segregated with the disorder in our family and was not present in 132 healthy Finnish control individuals. For these reasons it is most likely the FHM-causing mutation in this family.

Chromosome 19p13 loci in Finnish migraine with aura families.

Chromosomal area 19p13 contains two migraine associated genes: a Cav2.1 (P/Q‐type) calcium channel α1 subunit gene, CACNA1A, and an insulin receptor gene, INSR. Missense mutations in CACNA1A cause a rare Mendelian form of migraine, familial hemiplegic migraine type 1 (FHM1). Contribution of CACNA1A locus has also been studied in the common forms of migraine, migraine with (MA) and without aura (MO), but the results have been contradictory. The role of INSR is less well established: A region on 19p13 separate from CACNA1A was recently reported to be a major locus for migraine and subsequently, the INSR gene was associated with MA and MO. Our aim was to clarify the role of these loci in MA families by analyzing 72 multigenerational Finnish MA families, the largest family sample so far. We hypothesized that the potential major contribution of the 19p13 loci should be detected in a family sample of this size, and this was confirmed by simulations. We genotyped eight polymorphic microsatellite markers surrounding the INSR and CACNA1A genes on 757 individuals. Using parametric and non‐parametric linkage analysis, none of the studied markers showed any evidence of linkage to MA either under locus homogeneity or heterogeneity. However, marginally positive lod scores were observed in three families, and thus for these families the results remain inconclusive. The overall conclusion is that our study did not provide evidence of a major MA susceptibility region on 19p13 and thus we were not able to replicate the INSR locus finding.

Novel splice site CACNA1A mutation causing episodic ataxia type 2

Abstract.Episodic ataxia type 2 (EA-2) is an autosomal dominant neurological disorder, characterized by episodes of ataxia, vertigo, nausea, nystagmus, and fatigue, associated with acetazolamide responsiveness. The disease is caused by mutations in the P/Q-type calcium channel Cav2.1 subunit gene, CACNA1A, located on chromosome 19p13.2. We analyzed a family with 13 affected individuals for linkage to this locus and reached a two-point maximum LOD score of 4.48. A novel CACNA1A mutation, IVS36–2A>G, at the 3′ acceptor splice site of intron 36 was identified by sequencing. It is the first described CACNA1A acceptor splice site mutation and the most C-terminal EA-2-causing mutation reported to date.

Comorbidity in Finnish migraine families

The objective of the study was to investigate comorbidity of migraine in Finnish migraine families. One thousand consecutive participants in the Finnish Migraine Gene Project reported their medical illnesses in addition to migraine and headache. Migraine patients (n=678) reported significantly more hypotension (OR 1.43, CI 95% 1.02–2.01), allergy (OR 1.83, CI 95% 1.34–2.51) and psychiatric disorders (OR 4.09, CI 95% 2.11–7.92) compared to their family members without migraine (n=322). Subgroup analyses demonstrated that especially women and the group fulfilling the criteria for both migraine with and without aura were likely to have additional disorders besides their migraine. Interestingly, male migraineurs with aura reported a significant association with stroke and epilepsy. Familial migraine is comorbid with hypotension, allergy and psychiatric disorders. The association between migraine with aura and stroke and epilepsy among men of the studied families warrants further study. Clinical, pathophysiological and genetic implications of these results are discussed.

Acetazolamide improves neurotological abnormalities in a family with episodic ataxia type 2 (EA-2).

Sirs: Episodic ataxia type 2 (EA-2) is a rare neurological disease characterized by episodes of vertigo, ataxia, nystagmus, nausea, vomiting, fatigue, and often migraine. EA-2 is inherited as an autosomal dominant trait of the CACNA1A gene mutations on chromosome 19p13. CACNA1A encodes the alpha1A-subunit of a voltage dependent P/Q-type calcium channel that is mainly expressed in the Purkinje cells of the cerebellum [8, 11]. Neurological examination of EA-2 patients can vary from normal to severe cerebellar ataxia. On oculomotor studies interictal gazeevoked, rebound, and downbeat nystagmus have been common findings together with saccade hypermetria. These findings localize to the oculomotor region of the posterior vermis and the fastigial nuclei [3, 4, 9]. Acetazolamide is effective in suppressing attacks in EA-2 [2, 4, 7], but has not been shown to improve oculomotor signs in EA-2 [2, 5]. We, therefore, wanted to evaluate the effect of acetazolamide on oculomotor and postural function in an EA-2 family (Fig. 1) with a novel CACNA1A splice site mutation IVS36–2A > G (Kaunisto et al., Neurogenetics, in press). There were 13 affected individuals in the family of whom four were on acetazolamide. The clinical picture of the family has been described in detail earlier (Kaunisto et al., Neurogenetics, in press). The video-oculography (VOG) including recording of spontaneous and provoked nystagmus, ENG (with caloric and saccadic tests), static posturography, and pure tone audiometry were carried out to three EA-2 patients (III-13, III-16, III-22 in Fig. 1) with and without acetazolamide (one week washout time, patient III-22 three days). Their neurological examination and brain MRI were normal.

Decreased cerebellar total creatine in episodic ataxia type 2: A 1H MRS study

Episodic ataxia type 2 (EA2) affects mainly the cerebellum via mutations in the CACNA1A gene. The authors used proton MR spectroscopy to examine cerebellar and thalamic metabolism of nine mostly nonataxic EA2 family members (all with proven CACNA1A mutation) and nine healthy control subjects. Cerebellar total creatine was lower in the patient group (p = 0.005) than in control subjects, possibly reflecting an early sign of calcium channel dysfunction in EA2.

Patients with complex regional pain syndrome overestimate applied force in observed hand actions.

Movement accuracy is ensured by interaction between motor, somatosensory, and visual systems. In complex regional pain syndrome (CRPS), this interaction is disturbed. To explore CRPS patients’ visual perception of actions, we investigated how these patients evaluate the applied force in observed hand actions of another person.

The contribution of CACNA1A, ATP1A2 and SCN1A mutations in hemiplegic migraine: A clinical and genetic study in Finnish migraine families

Objective To study the position of hemiplegic migraine in the clinical spectrum of migraine with aura and to reveal the importance of CACNA1A, ATP1A2 and SCN1A in the development of hemiplegic migraine in Finnish migraine families. Methods The International Classification of Headache Disorders 3rd edition criteria were used to determine clinical characteristics and occurrence of hemiplegic migraine, based on detailed questionnaires, in a Finnish migraine family collection consisting of 9087 subjects. Involvement of CACNA1A, ATP1A2 and SCN1A was studied using whole exome sequencing data from 293 patients with hemiplegic migraine. Results Overall, hemiplegic migraine patients reported clinically more severe headache and aura episodes than non-hemiplegic migraine with aura patients. We identified two mutations, c.1816G>A (p.Ala606Thr) and c.1148G>A (p.Arg383His), in ATP1A2 and one mutation, c.1994C>T (p.Thr665Met) in CACNA1A. Conclusions The results highlight hemiplegic migraine as a clinically and genetically heterogeneous disease. Hemiplegic migraine patients do not form a clearly separate group with distinct symptoms, but rather have an extreme phenotype in the migraine with aura continuum. We have shown that mutations in CACNA1A, ATP1A2 and SCN1A are not the major cause of the disease in Finnish hemiplegic migraine patients, suggesting that there are additional genetic factors contributing to the phenotype.