The 3p21.1-p21.3 Hereditary Vascular Retinopathy Locus Increases the Risk for Raynaud's Phenomenon and Migraine

Previously, we described a large Dutch family with hereditary vascular retinopathy (HVR), Raynaud's phenomenon and migraine. A locus for HVR was mapped on chromosome 3p21.1-p21.3, but the gene has not yet been identified. The fact that all three disorders share a vascular aetiology prompted us to study whether the HVR haplotype also contributed to Raynaud's phenomenon and migraine in this family. Whereas the parent-child transmission disequilibrium test (TDT) did not reach significance, the sibling TDT revealed that the HVR haplotype harbours a susceptibility factor for Raynaud's phenomenon and migraine. Identification of the HVR gene will improve the understanding of the pathophysiology of HVR, Raynaud's phenomenon and migraine.

Shared genetic factors in migraine and depression: evidence from a genetic isolate

OBJECTIVE

To investigate the co-occurrence of migraine and depression and assess whether shared genetic factors may underlie both diseases.

METHODS

Subjects were 2,652 participants of the Erasmus Rucphen Family genetic isolate study. Migraine was diagnosed using a validated 3-stage screening method that included a telephone interview. Symptoms of depression were assessed using the Center for Epidemiologic Studies Depression scale and the depression subscale of the Hospital Anxiety and Depression Scale (HADS-D). The contribution of shared genetic factors in migraine and depression was investigated by comparing heritability estimates for migraine with and without adjustment for symptoms of depression, and by comparing the heritability scores of depression between migraineurs and controls.

RESULTS

We identified 360 migraine cases: 209 had migraine without aura (MO) and 151 had migraine with aura (MA). Odds ratios for depression in patients with migraine were 1.29 (95% confidence interval [CI] 0.98-1.70) for MO and 1.70 (95% CI 1.28-2.24) for MA. Heritability estimates were significant for all migraine (0.56), MO (0.77), and MA (0.96), and decreased after adjustment for symptoms of depression or use of antidepressant medication, in particular for MA. Comparison of the heritability scores for depression between patients with migraine and controls showed a genetic correlation between HADS-D score and MA.

CONCLUSIONS

There is a bidirectional association between depression and migraine, in particular migraine with aura, which can be explained, at least partly, by shared genetic factors.

First mutation in the voltage-gated Nav1.1 subunit gene SCN1A with co-occurring familial hemiplegic migraine and epilepsy

Almost all mutations in the SCN1A gene, encoding the alpha(1) subunit of neuronal voltage-gated Na(V)1.1 sodium channels, are associated with severe childhood epilepsy. Recently, two mutations were identified in patients with pure familial hemiplegic migraine (FHM). Here, we identified a novel SCN1A L263V mutation in a Portuguese family with partly co-segregating hemiplegic migraine and epilepsy. The L263V mutation segregated in five FHM patients, three of whom also had epileptic attacks, occurring independently from their hemiplegic migraine attacks. L263V is the first SCN1A mutation associated with FHM and co-occurring epilepsy in multiple mutation carriers, and is the clearest molecular link between migraine and epilepsy thus far. The results extend the clinical spectrum associated with SCN1A mutations and further strengthen the molecular evidence that FHM and epilepsy share, at least in part, similar molecular pathways.

CACNA1A Mutation Linking Hemiplegic Migraine and Alternating Hemiplegia of Childhood

Familial hemiplegic migraine (FHM) and alternating hemiplegia of childhood (AHC) are severe neurological disorders that share clinical features. Therefore, FHM genes are candidates for AHC. We performed mutation analysis in the CACNA1A gene in a monozygotic twin pair with clinical features overlapping with both AHC and FHM and identified a novel de novo CACNA1A mutation. We provide the first evidence that a CACNA1A mutation can cause atypical AHC, indicating an overlap of molecular mechanisms causing AHC and FHM. These results also suggest that CACNA1A mutation scanning is indicated in patients with a severe neurological phenotype that includes paroxysmal (alternating) hemiplegia.

CACNA1A R1347Q: a frequent recurrent mutation in hemiplegic migraine

Of the 18 missense mutations in the CACNA1A gene, which are associated with familial hemiplegic migraine type 1 (FHM1), only mutations S218L, R583Q and T666M were identified in more than two independent families. Including the four novel families presented here, of which two represent de novo cases, the R1347Q mutation has now been identified in six families. A genotype-phenotype comparison of R1347Q mutation carriers revealed a wide clinical spectrum ranging from (trauma triggered) hemiplegic migraine with and without ataxia, loss of consciousness and epilepsy. R1347Q is the third most frequent mutation in hemiplegic migraine patients and should therefore be screened with priority for confirmation of clinical diagnosis. This study clearly demonstrates that the availability of multiple families better reflects the full clinical spectrum associated with FHM1 mutations.

Systematic analysis of three FHM genes in 39 sporadic patients with hemiplegic migraine

BACKGROUND

Familial (FHM) and sporadic (SHM) hemiplegic migraine are severe subtypes of migraine associated with transient hemiparesis. For FHM, three genes have been identified encoding subunits of a calcium channel (CACNA1A), a sodium-potassium pump (ATP1A2), and a sodium channel (SCN1A). Their role in SHM is unknown. Establishing a genetic basis for SHM may further the understanding of its pathophysiology and relationship with common types of migraine. It will also facilitate the often difficult differential diagnosis from other causes of transient hemiparesis.

METHODS

We systematically scanned 39 well-characterized patients with SHM without associated neurologic features for mutations in the three FHM genes. Functional assays were performed for all new sequence variants.

RESULTS

Sequence variants were identified in seven SHM patients: one CACNA1A mutation, five ATP1A2 mutations, and one SCN1A polymorphism. All six mutations caused functional changes in cellular assays. One SHM patient later changed to FHM because another family member developed FHM attacks.

CONCLUSION

We show that FHM genes are involved in at least a proportion of SHM patients without associated neurologic symptoms. Screening of ATP1A2 offers the highest likelihood of success. Because FHM gene mutations were also found in family members with "nonhemiplegic" typical migraine with and without aura, our findings reinforce the hypothesis that FHM, SHM, and "normal" migraine are part of a disease spectrum with shared pathogenetic mechanisms.

Two novel functional mutations in the Na+,K+-ATPase alpha2-subunit ATP1A2 gene in patients with familial hemiplegic migraine and associated neurological phenotypes

Mutations in the ATP1A2 gene, encoding the alpha2-subunit of the Na+,K+-ATPase, are associated with familial hemiplegic migraine type 2. The majority of ATP1A2 mutations were reported in patients with hemiplegic migraine without any additional neurological findings. Here, we report on two novel ATP1A2 mutations that were identified in two Portuguese probands with hemiplegic migraine and interesting additional clinical features. The proband's of family 1 (with a V362E mutation) had mood alterations, classified as a borderline personality. The proband in family 2 (with a P796S mutation) had mild mental impairment, in addition to hemiplegic migraine; more severe mental retardation was observed in his brother, who also had hemiplegic migraine and carried the same mutation. Cell-survival assays clearly showed abnormal functioning of mutant Na+,K+-ATPase, indicating that both ATP1A2 mutants are disease causing. Additionally, our results suggest a possible causal relationship of the ATP1A2 mutations with the complex clinical phenotypes observed in the probands.

Alternating hemiplegia of childhood: no mutations in the glutamate transporter EAAT1

Alternating hemiplegia of childhood (AHC) is a severe brain disorder, mainly characterised by episodes of hemiplegia, progressive mental retardation, and other severe paroxysmal and permanent neurological symptoms. Clinically and genetically, there is some overlap with sporadic (SHM) and familial (FHM) hemiplegic migraine, a severe monogenic subtype of migraine. Although no mutations were detected in the FHM1 CACNA1A and FHM2 ATP1A2 genes in sporadic AHC patients, a mutation was found in the FHM2 ATP1A2 gene in a family with AHC. Recently, a missense mutation was found in the SLC1A3 gene that encodes the glutamate transporter EAAT1, in a patient with alternating hemiplegia, episodic ataxia, seizures, and headache. Because of the remarkable clinical similarities and the potential role of glutamate in AHC, we analysed six sporadic patients with AHC for mutations in the SLC1A3 gene. No mutations were found. The SLC1A3 EAAT1 glutamate transporter gene does not seem to be involved in the pathogenesis of AHC.

Severe episodic neurological deficits and permanent mental retardation in a child with a novel FHM2ATP1A2mutation

OBJECTIVE

Attacks of familial hemiplegic migraine (FHM) are usually associated with transient, completely reversible symptoms. Here, we studied the ATP1A2 FHM2 gene in a young girl with episodes of both very severe and transient neurological symptoms that were triggered by mild head trauma as well as permanent mental retardation. Her family members suffered from hemiplegic and confusional migraine attacks.

METHODS

Mutation analysis of the ATP1A2 gene was performed by direct sequencing of all exons and flanking intronic regions, using genomic DNA of the proband. Functional consequences of the mutation were analyzed by cellular survival assays.

RESULTS

We identified a novel G615R ATP1A2 mutation in the proband and several of her family members. Functional analysis of mutant Na,K-ATPase in cellular survival assays showed a complete loss-of-function effect.

INTERPRETATION

Permanent mental retardation in children may be caused by ATP1A2 mutations.

Alternating hemiplegia of childhood: no mutations in the second familial hemiplegic migraine gene ATP1A2

Alternating hemiplegia of childhood (AHC) is a rare disorder mainly characterised by attacks of hemiplegia and mental retardation. AHC has often been associated with migraine. Previously, we have excluded the involvement of the familial hemiplegic migraine (FHM) CACNA1A gene in four patients with AHC. A second gene for FHM was discovered recently: the ATP1A2 gene on chromosome 1q23, coding for the alpha 2 subunit of Na+,K+-ATPase. We performed a mutation analysis of the ATP1A2 gene in six patients, using direct sequencing, but found no mutations in any of the 23 exons. Other cerebral ion channel genes remain candidate genes for AHC.

[From gene to disease; familial hemiplegic migraine as a result of mutations in a sodium-potassium pump gene]

Familial hemiplegic migraine (FHM) is a rare, autosomal dominant subtype of migraine, associated in half of the families with mutations in the CACNA1A gene located on chromosome 19p13, which encodes the Cav2.1-subunit of brain-specific P/Q-type calcium channels. Recently, mutations in a second gene, ATP1A2 on chromosome 1q23, which encodes a sodium-potassium exchange pump subunit, have been identified. The first functional studies indicate that A TP1A2 FHM mutations result in a loss of function of the pump, leading to an increase in extracellular potassium. This is known to evoke cortical spreading depression, the underlying mechanism of migraine aura.

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 alpha2 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.

Episodic ataxia type 2. Three novel truncating mutations and one novel missense mutation in the CACNA1A gene

We analysed the CACNA1A gene, located on chromosome 19p13, in three unrelated families and one sporadic case with episodic ataxia type 2 (EA-2). In two of the families and the sporadic patient, novel truncating mutations, which disrupt the reading frame and result in a premature stop of the CACNA1A protein, were identified in exons 14, 16 and 26. In the remaining family, a novel missense mutation (H253Y) was found. Of the twenty two EA-2 mutations identified thus far, including those of the present study, seventeen are truncating mutations and five are missense mutations, all resulting in an EA-2 clinical phenotype.