Shared loci for migraine and epilepsy on chromosomes 14q12-q23 and 12q24.2-q24.3.

OBJECTIVES: To describe clinical characteristics and to identify susceptibility loci for epilepsy and migraine in a Finnish family with a complex phenotype. METHODS: Participating family members were interviewed and medical files were reviewed. The seizure classification was made according to International League Against Epilepsy criteria. Migraine diagnosis was made using the validated Finnish Migraine Specific Questionnaire for Family Studies and criteria according to the current International Classification of Headache Disorders-II. DNA samples were obtained from 56 family members and nonparametric genome-wide linkage analyses were performed using 382 polymorphic microsatellite markers. The most promising loci were fine-mapped with additional microsatellite markers. RESULTS: Clinical data were obtained from 60 family members of whom 12 (20%) had idiopathic epileptic seizures. Eight of those 12 (67%) also had migraine. Altogether 33 of the 60 family members (55%) had migraine. Significant evidence of linkage was found between a locus on 14q12-q23 and migraine (p = 0.0001). Suggestive evidence of linkage in this region was also found for epilepsy with generalized tonic-clonic seizures (p = 0.0034). In addition, significant evidence of linkage was found at a locus on 12q24.2-q24.3 (p < 0.001) for migraine alone and for the combined phenotype of migraine and epilepsy. CONCLUSIONS: Our data suggest the occurrence of common susceptibility loci for epilepsy and migraine on chromosomes 14q12-q23 and 12q24.2-q24.3, implicating a shared genetic etiology for these 2 diseases.

Receptor for advanced glycation end-products (RAGE) provides a link between genetic susceptibility and environmental factors in type 1 diabetes.

AIMS/HYPOTHESIS: This group of studies examines human genetic susceptibility conferred by the receptor for advanced glycation end-products (RAGE) in type 1 diabetes and investigates how this may interact with a western environment. METHODS: We analysed the AGER gene, using 13 tag SNPs, in 3,624 Finnish individuals from the FinnDiane study, followed by AGER associations with a high risk HLA genotype (DR3)-DQA1*05-DQB1*02/DRB1*0401-DQB1*0302 (n = 546; HLA-DR3/DR4), matched in healthy newborn infants from the Finnish Type 1 Diabetes Prediction and Prevention (DIPP) Study (n = 373) using allelic analysis. We also studied islets and circulating RAGE in NODLt mice. RESULTS: The rs2070600 and rs17493811 polymorphisms predicted increased risk of type 1 diabetes, whereas the rs9469089 SNP was related to decreased risk, on a high risk HLA background. Children from the DIPP study also showed a decline in circulating soluble RAGE levels, at seroconversion to positivity for type 1 diabetes-associated autoantibodies. Islet RAGE and circulating soluble RAGE levels in prediabetic NODLt mice decreased over time and were prevented by the AGE lowering therapy alagebrium chloride. Alagebrium chloride also decreased the incidence of autoimmune diabetes and restored islet RAGE levels. CONCLUSIONS/INTERPRETATION: These studies suggest that inherited AGER gene polymorphisms may confer susceptibility to environmental insults. Declining circulating levels of soluble RAGE, before the development of overt diabetes, may also be predictive of clinical disease in children with high to medium risk HLA II backgrounds and this possibility warrants further investigation in a larger cohort.

Migraine with aura is a risk factor for cervical artery dissection: a case-control study.

BACKGROUND: Cervical artery dissection (CAD) is the most common single etiology for stroke in young adults. Migraine, especially with aura (MA), is a known risk factor for ischemic stroke. The association between CAD and migraine was suggested based on a few small studies, but there are no large-scale case-control data, and the mechanisms are not yet clear. METHODS: We compared the lifetime prevalence of migraine and migraine characteristics in 313 CAD patients with 313 healthy age- and sex-matched controls. We also analyzed clinical and radiological characteristics of CAD with respect to migraine subtypes to investigate whether clear phenotypical associations can be found that might help in the search for a possible shared genetic background for migraine and CAD. RESULTS: Migraine was clearly more common in CAD patients than in controls (36 vs. 23%; OR 2.15; 95% CI 1.48-3.14), and the association was also highly significant for MA (23 vs. 12%; OR 2.41; 95% CI 1.53-3.80). Percentages of reported migraine history and MA of CAD patients vs. controls compared separately for both sexes were as follows: for women, migraine 54 vs. 35% (OR 2.30; 95% CI 1.28-4.13), MA 35 vs. 18% (OR 2.79; 95% CI 1.40-5.59); for men, migraine 27 vs. 16% (OR 2.02; 95% CI 1.23-3.31), MA 16 vs. 10% (OR 2.21; 95% CI 1.19-4.11). Over 60% of the CAD patients with still active migraine at the time of dissection reported later alleviation of migraine activity. CONCLUSION: Our observations suggest that patients with CAD are a significant link between ischemic stroke and migraine. This connection may represent a common pathophysiological or genetic background, or both. Migraine activity appears to be alleviated by CAD.

DDOST, PRKCSH and LGALS3, which encode AGE-receptors 1, 2 and 3, respectively, are not associated with diabetic nephropathy in type 1 diabetes.

AIMS/HYPOTHESIS: The AGE receptors 1, 2 and 3, which are encoded by DDOST, PRKCSH and LGALS3, respectively, may be involved in the pathogenesis of diabetic complications. We sought to find out whether these genes are associated with diabetic nephropathy, cardiovascular disease and type 1 diabetes or related quantitative traits. METHODS: Using the Tagger program, we selected 28 single nucleotide polymorphisms (SNPs) based on the HapMap Centre d'Etude du Polymorphisme (Utah residents with northern and western European ancestry) data. The SNPs were genotyped in 2,719 Finnish patients with type 1 diabetes and tested for association with diabetic nephropathy (821 cases, 1,060 controls), cardiovascular disease and related quantitative traits. For association analysis with type 1 diabetes, 703 non-diabetic control participants were genotyped. RESULTS: We found evidence of genotype association between diabetic nephropathy and the SNPs rs2170336 in DDOST (p = 0.03), rs311788 in PRKCSH (p = 0.04) and rs311778 in PRKCSH (p = 0.02). However, these associations did not reach the significance limit of 0.0008 adjusted for multiple testing. None of the DDOST, PRKCSH or LGALS3 SNPs were associated with quantitative traits related to diabetic nephropathy, including AER and estimated GFR. No associations were found between the SNPs and cardiovascular disease, blood pressure, serum lipid levels or type 1 diabetes. CONCLUSIONS/INTERPRETATION: The common SNPs tested in DDOST, PRKCSH and LGALS3 do not seem to be associated with diabetic micro- or macrovascular complications or with type 1 diabetes in Finnish patients.

A visual migraine aura locus maps to 9q21-q22.

OBJECTIVE: To identify susceptibility loci for visual migraine aura in migraine families primarily affected with scintillating scotoma type of aura. METHODS: We included Finnish migraine families with at least 2 affected family members with scintillating scotoma as defined by the International Criteria for Headache Disorders-II. A total of 36 multigenerational families containing 351 individuals were included, 185 of whom have visual aura and 159 have scintillating scotoma. Parametric and nonparametric linkage analyses were performed with 378 microsatellite markers. The most promising linkage loci found were fine-mapped with additional microsatellite markers. RESULTS: A novel locus on chromosome 9q22-q31 for migraine aura was identified (HLOD = 4.7 at 104 cM). Fine-mapping identified a shared haplotype segment of 12 cM (9.8 Mb) on 9q21-q22 among the aura affected. Four other loci showed linkage to aura: a locus on 12p13 showed significant evidence of linkage, and suggestive evidence of linkage was detected to loci on chromosomes 5q13, 6q25, and 13q14. CONCLUSIONS: A novel visual migraine aura locus has been mapped to chromosome 9q21-q22. Interestingly, this region has previously been linked to occipitotemporal lobe epilepsy with prominent visual symptoms. Our finding further supports a shared genetic background in migraine and epilepsy and suggests that susceptibility variant(s) to visual aura for both of these traits are located in the 9q21-q22 locus.

Genetic association study of endothelin-1 and its receptors EDNRA and EDNRB in migraine with aura.

The effect of endothelin-1 and its receptors EDNRA and EDNRB in migraine with aura (MA) susceptibility is not established yet. We studied the association between the MA end-diagnosis and three migraine trait components and 32 single nucleotide polymorphisms (SNPs) capturing the variation of endothelin genes in 850 Finnish migraine patients and 890 non-migrainous individuals. The SNPs showing evidence of association were further studied in 648 German migraine patients and 651 non-migrainous individuals. No significant association was detected. However, the homozygous minor genotype (5% in cases) of the EDNRA SNP rs2048894 showed nominal association with MA both in the Finnish sample (P = 0.015) and in the pooled sample [odds ratio (OR) 1.61, 95% confidence interval (CI) 1.12-2.32, P = 0.010] when adjusted for gender and sample origin. The trait age of onset < 20 years was also associated with rs2048894 (OR 1.69, 95% CI 1.13-2.54, P = 0.011) in the pooled sample. To confirm this finding studies on even larger samples are required.

No association of migraine to the GABA-A receptor complex on chromosome 15.

To date, no gene variants predisposing to common forms of migraine have been convincingly identified. Recently, significant linkage to a cluster of gamma-amino butyric acid (GABA)-A receptors on Chr 15q11-q13 was reported. We performed an extensive association study using 898 MA cases and 900 matched controls by covering the same gene cluster with 34 single nucleotide polymorphisms (SNPs). No association to MA was detected, suggesting that common variants of the GABA cluster are unlikely to be major contributors of MA susceptibility.

Association analysis of podocyte slit diaphragm genes as candidates for diabetic nephropathy.

AIMS/HYPOTHESIS: The slit diaphragm is an adhesion and signalling protein complex linking the interdigitating podocyte foot processes in the kidney glomerulus, and mutations in slit diaphragm-associated genes result in severe proteinuria. Here we report a genetic association analysis of four slit diaphragm genes, LRRC7, KIRREL, NPHS2 and ACTN4, in a Finnish diabetic nephropathy cohort. MATERIALS AND METHODS: A total of 40 single nucleotide polymorphisms (SNPs) were genotyped in 1103 patients with type 1 diabetes. The patients were classified according to their renal status, and the genotype data were analysed in a cross-sectional case-control setting. To confirm positive associations, four SNPs were genotyped in 1,025 additional patients with type 1 diabetes. RESULTS: No associations with diabetic nephropathy were observed for any of the analysed SNPs. The SNPs were not associated with the time from the onset of diabetes to the diagnosis of nephropathy or with glomerular filtration rate or AER as quantitative variables. In a sex-specific sub-analysis, the variants rs979972 and rs749701 in the first intron of ACTN4 were nominally associated with diabetic nephropathy in females, with odds ratios of 1.81 (95% CI 1.18-2.79, p = 0.007) and 1.93 (95% CI 1.26-2.96, p = 0.003) respectively. CONCLUSIONS/INTERPRETATION: Our study has not found any evidence that common variants in LRRC7, KIRREL, NPHS2 and ACTN4 contribute to susceptibility to diabetic nephropathy in Finnish patients with type 1 diabetes.

Treatment of hemiplegic migraine with triptans.

The objective of this study was to investigate the efficacy, safety and tolerability of triptans in patients who suffer from familial or sporadic hemiplegic migraine. Seventy-six subjects had used triptans at least once as an abortive treatment. Average triptan response was 6.9 (SD +/-3.1) and adverse event severity 4.9 (SD +/-3.3) on a scale from 0 to 10 (no response or side effect 0, excellent response or unbearable side effects 10). None of the patients had an ischaemic stroke or a heart attack. One patient reported prolonged neurological symptoms, related to a single dose of rizatriptan, but there were no pathological findings in several MRI-scans. Triptans seem to be safe and effective treatment for most hemiplegic migraine patients.

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.

Trait components provide tools to dissect the genetic susceptibility of migraine.

The commonly used "end diagnosis" phenotype that is adopted in linkage and association studies of complex traits is likely to represent an oversimplified model of the genetic background of a disease. This is also likely to be the case for common types of migraine, for which no convincingly associated genetic variants have been reported. In headache disorders, most genetic studies have used end diagnoses of the International Headache Society (IHS) classification as phenotypes. Here, we introduce an alternative strategy; we use trait components--individual clinical symptoms of migraine--to determine affection status in genomewide linkage analyses of migraine-affected families. We identified linkage between several traits and markers on chromosome 4q24 (highest LOD score under locus heterogeneity [HLOD] 4.52), a locus we previously reported to be linked to the end diagnosis migraine with aura. The pulsation trait identified a novel locus on 17p13 (HLOD 4.65). Additionally, a trait combination phenotype (IHS full criteria) revealed a locus on 18q12 (HLOD 3.29), and the age at onset trait revealed a locus on 4q28 (HLOD 2.99). Furthermore, suggestive or nearly suggestive evidence of linkage to four additional loci was observed with the traits phonophobia (10q22) and aggravation by physical exercise (12q21, 15q14, and Xp21), and, interestingly, these loci have been linked to migraine in previous studies. Our findings suggest that the use of symptom components of migraine instead of the end diagnosis provides a useful tool in stratifying the sample for genetic studies.

Novel sequence variants in the human xylosyltransferase I gene and their role in diabetic nephropathy.

AIMS: Decreased content of heparan sulphate proteoglycans (HSPGs) is a characteristic of the glomerular basement membrane (GBM) in diabetes and contributes to the development of diabetic nephropathy (DN). Xylosyltransferase I (XT-I) is the chain-initiating enzyme involved in the biosynthesis of HSPGs. This study investigated a possible association between XYLT-I sequence variants and susceptibility to DN. METHODS: Screening of all XYLT-I exons was performed in 74 caucasians with Type 1 diabetes (48 with and 26 without DN) and in 13 non-diabetic control subjects using denaturing high-performance liquid chromatography. RESULTS: Fifteen XYLT-I sequence variants were identified. Of these, six were previously unknown. There were significant differences in the allele frequencies of the three polymorphisms (c.343G-->T (p.A115S), IVS3+10C-->T, IVS3+30G-->C) in Type 1 diabetic patients and healthy controls. CONCLUSIONS: The occurrence of DN is independent of the XYLT-I variants detected in our study. However, three XYLT-I polymorphisms may be linked to Type 1 diabetes. Since we have previously proposed that one of these polymorphisms was not associated with Type 1 diabetes (Schön S et al. Kidney Int 2005; 68: 1483-1490), larger-scale analysis is clearly necessary to pinpoint the significance of this mutation.

The AT2 gene may have a gender-specific effect on kidney function and pulse pressure in type I diabetic patients.

Diabetic nephropathy shows a higher incidence in male subjects, which may in part be owing to genetic factors. The angiotensin II type 2 receptor (AT2), present in the renal glomerulus, may oppose the deleterious effects of the type I receptor (AT1) through vasodilatation and growth inhibition. We determined whether the functional intronic G1675A or A1818T polymorphism of the X-chromosomal AT2 gene is associated with blood pressure levels or with kidney function. We genotyped 996 (538 female/458 male subjects) Finnish patients with type I diabetes from the FinnDiane-study in a cross-sectional study. DNA samples were amplified using standard polymerase chain reaction protocol and the genotypes were determined by the minisequencing method. Male patients with the AA haplotype had a lower glomerular filtration rate (83 +/- 32 vs 94 +/- 34 ml min(-1) 1.73 m(-2), P = 0.008) and a higher pulse pressure (PP) (62 +/- 18 vs 57 +/- 15 mm Hg, P = 0.002; P < 0.05 after adjustment for age) than did those with the GT haplotype. No differences between the genotypes or haplotypes and these variables were evident in females. In males, the G1675A was also an independent variable in a linear regression analysis with PP (r(2) = 0.16, coefficient=3.64, s.e.m.=1.38, P < 0.01) as the dependent variable. These data suggest a gender-specific association between the AT2 gene and kidney function and premature aging of the arterial tree in patients with type I diabetes.

Polymorphisms in the gene encoding angiotensin I converting enzyme 2 and diabetic nephropathy.

AIMS/HYPOTHESIS: Substantial evidence exists for the involvement of the renin-angiotensin system (RAS) in diabetic nephropathy. Angiotensin I converting enzyme 2 (ACE2), a new component of the RAS, has been implicated in kidney disease, hypertension and cardiac function. Based on this, the aim of the present study was to evaluate whether variations in ACE2 are associated with diabetic nephropathy. MATERIALS AND METHODS: We used a cross-sectional, case-control study design to investigate 823 Finnish type 1 diabetic patients (365 with and 458 without nephropathy). Five single-nucleotide polymorphisms (SNPs) were genotyped using TaqMan technology. Haplotypes were estimated using PHASE software, and haplotype frequency differences were analysed using a chi(2)-test-based tool. RESULTS: None of the ACE2 polymorphisms was associated with diabetic nephropathy, and this finding was supported by the haplotype analysis. The ACE2 polymorphisms were not associated with blood pressure, BMI or HbA(1)c. CONCLUSIONS/INTERPRETATION: In Finnish type 1 diabetic patients, ACE2 polymorphisms are not associated with diabetic nephropathy or any studied risk factor for this complication. Further studies are necessary to assess a minor effect of ACE2.

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.

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.

New methods for molecular diagnosis and demonstration of the (CCTG)n mutation in myotonic dystrophy type 2 (DM2).

Myotonic dystrophy types 1 and 2 are autosomal dominant, multisystemic disorders with many similarities in their clinical manifestations. Myotonic dystrophy type 1 is caused by a (CTG)n expansion in the 3' untranslated region of the DMPK gene in 19q13.3 and myotonic dystrophy type 2 by a (CCTG)n expansion in intron 1 of ZNF9 in 3q21.3. However, the clinical diagnosis of myotonic dystrophy type 2 is more complex than that of myotonic dystrophy type 1, and conventional molecular genetic methods used for diagnosing myotonic dystrophy type 1 are insufficient for myotonic dystrophy type 2. Herein we describe two in situ hybridization protocols for the myotonic dystrophy type 2 mutation detection. Chromogenic in situ hybridization was used to detect both the genomic expansion and the mutant transcripts in muscle biopsy sections. Chromogenic in situ hybridization can be used in routine myotonic dystrophy type 2 diagnostics. Fluorescence in situ hybridization on extended DNA fibers was used to directly visualize the myotonic dystrophy type 2 mutation and to estimate the repeat expansion sizes.

Novel splice site CACNA1A mutation causing episodic ataxia type 2.

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 Ca(v)2.1 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.

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.