Marta Vila-Pueyo

Genome-wide association analysis identifies susceptibility loci for migraine without aura

Migraine without aura is the most common form of migraine, characterized by recurrent disabling headache and associated autonomic symptoms. To identify common genetic variants associated with this migraine type, we analyzed genome-wide association data of 2,326 clinic-based German and Dutch individuals with migraine without aura and 4,580 population-matched controls. We selected SNPs from 12 loci with 2 or more SNPs associated with P values of <1 × 10−5 for replication testing in 2,508 individuals with migraine without aura and 2,652 controls. SNPs at two of these loci showed convincing replication: at 1q22 (in MEF2D; replication P = 4.9 × 10−4; combined P = 7.06 × 10−11) and at 3p24 (near TGFBR2; replication P = 1.0 × 10−4; combined P = 1.17 × 10−9). In addition, SNPs at the PHACTR1 and ASTN2 loci showed suggestive evidence of replication (P = 0.01; combined P = 3.20 × 10−8 and P = 0.02; combined P = 3.86 × 10−8, respectively). We also replicated associations at two previously reported migraine loci in or near TRPM8 and LRP1. This study identifies the first susceptibility loci for migraine without aura, thereby expanding our knowledge of this debilitating neurological disorder.

Biallelic SZT2 Mutations Cause Infantile Encephalopathy with Epilepsy and Dysmorphic Corpus Callosum

Epileptic encephalopathies are genetically heterogeneous severe disorders in which epileptic activity contributes to neurological deterioration. We studied two unrelated children presenting with a distinctive early-onset epileptic encephalopathy characterized by refractory epilepsy and absent developmental milestones, as well as thick and short corpus callosum and persistent cavum septum pellucidum on brain MRI. Using whole-exome sequencing, we identified biallelic mutations in seizure threshold 2 (SZT2) in both affected children. The causative mutations include a homozygous nonsense mutation and a nonsense mutation together with an exonic splice-site mutation in a compound-heterozygous state. The latter mutation leads to exon skipping and premature termination of translation, as shown by RT-PCR in blood RNA of the affected boy. Thus, all three mutations are predicted to result in nonsense-mediated mRNA decay and/or premature protein truncation and thereby loss of SZT2 function. Although the molecular role of the peroxisomal protein SZT2 in neuronal excitability and brain development remains to be defined, Szt2 has been shown to influence seizure threshold and epileptogenesis in mice, consistent with our findings in humans. We conclude that mutations in SZT2 cause a severe type of autosomal-recessive infantile encephalopathy with intractable seizures and distinct neuroradiological anomalies.

Replication study of previous migraine genome-wide association study findings in a Spanish sample of migraine with aura

Background Migraine is a common disabling condition that affects approximately 15% of the population. Several genome-wide association studies have attempted to identify susceptibility variants involved in migraine, reporting several candidate loci for the disorder. Methods In order to replicate findings from previous genome-wide association studies, a case–control association study was performed. Twelve single nucleotide polymorphisms were genotyped in a Spanish sample of 512 migraine with aura patients and 535 migraine-free controls. Results Nominal associations were found for single nucleotide polymorphisms rs2651899 (within the PRDM16 gene), rs10166942 (near TRPM8), rs12134493 (close to TSPAN2) and rs10504861 (near MMP16) in our migraine with aura sample. Conclusions Our study provides suggestive replication, in a Spanish migraine with aura sample, of four genome-wide association study findings previously reported in common migraine. However, larger sample sets should be explored to confirm our results.

Candidate-gene association study searching for genetic factors involved in migraine chronification

Introduction Chronic migraine (CM) is at the severe end of the clinical migraine spectrum, but its genetic background is unknown. Our study searched for evidence that genetic factors are involved in the chronification process. Methods We initially selected 144 single-nucleotide polymorphisms (SNPs) from 48 candidate genes, which we tested for association in two stages: The first stage encompassed 262 CM patients, the second investigated 226 patients with high-frequency migraine (HFM). Subsequently, SNPs with p values < 0.05 were forwarded to the replication stage containing 531 patients with CM or HFM. Results Eight SNPs were significantly associated with CM and HFM in the two-stage phase. None survived replication in the third stage. Discussion We present the first comprehensive genetic association study for migraine chronification. There were no significant findings. Future studies may benefit from larger, genome-wide data sets or should use other genetic approaches to identify genetic factors involved in migraine chronification.

Clinical and genetic analysis in alternating hemiplegia of childhood: Ten new patients from Southern Europe

Alternating hemiplegia of childhood (AHC) is a rare neurodevelopmental disorder featuring attacks of hemiplegia and other paroxysmal and non-paroxysmal manifestations leading to progressive neurological impairment. De novo mutations in ATP1A3 have been identified in up to 80% of patients. AHC is also associated with rare mutations in other genes involved in episodic neurological disorders. We sought to find mutations in ATP1A3, CACNA1A, ATP1A2, SCN1A and SLC2A1 in a cohort of ten unrelated patients from Spain and Greece. All patients fulfilled AHC diagnostic criteria. All five genes were amplified by PCR and Sanger sequenced. Copy number variation (CNV) analysis of SLC2A1 and CACNA1A was performed using two different approaches. We identified three previously described heterozygous missense ATP1A3 mutations (p.Asp801Asn, p.Glu815Lys and p.Gly947Arg) in five patients. No disease-causing mutations were found in the remaining genes. All mutations occurred de novo; carriers presented on average earlier than non-carriers. Intellectual disability was more severe with the p.Glu815Lys variant. A p.Gly947Arg carrier harbored a maternally-inherited CACNA1A p.Ala454Thr variant. Of note, three of our patients exhibited remarkable clinical responses to the ketogenic diet. We confirmed ATP1A3 mutations in half of our patients. Further AHC genetic studies will need to investigate large rearrangements in ATP1A3 or consider greater genetic heterogeneity than previously suspected.

Mutation Spectrum in the CACNA1A Gene in 49 Patients with Episodic Ataxia

Episodic ataxia is an autosomal dominant ion channel disorder characterized by episodes of imbalance and incoordination. The disease is genetically heterogeneous and is classified as episodic ataxia type 2 (EA2) when it is caused by a mutation in the CACNA1A gene, encoding the α1A subunit of the P/Q-type voltage-gated calcium channel Cav2.1. The vast majority of EA2 disease-causing variants are loss-of-function (LoF) point changes leading to decreased channel currents. CACNA1A exonic deletions have also been reported in EA2 using quantitative approaches. We performed a mutational screening of the CACNA1A gene, including the promoter and 3′UTR regions, in 49 unrelated patients diagnosed with episodic ataxia. When pathogenic variants were not found by sequencing, we performed a copy number variant (CNV) analysis to screen for duplications or deletions. Overall, sequencing screening allowed identification of six different point variants (three nonsense and three missense changes) and two coding indels, one of them found in two unrelated patients. Additionally, CNV analysis identified a deletion in a patient spanning exon 35 as a result of a recombination event between flanking intronic Alu sequences. This study allowed identification of potentially pathogenic alterations in our sample, five of them novel, which cover 20% of the patients (10/49). Our data suggest that most of these variants are disease-causing, although functional studies are required.

Transcriptomic Changes in Rat Cortex and Brainstem After Cortical Spreading Depression With or Without Pretreatment With Migraine Prophylactic Drugs

Migraine with aura is a subtype of migraine characterized by transient neurological disturbances that usually precede headache. Cortical spreading depression (CSD) is the likely pathophysiological correlate of the aura phase of migraine, found in common and rare forms of migraine, such as familial hemiplegic migraine. CSD is a depolarization wave that propagates across the cerebral gray matter transiently suppressing neuronal activity. Prophylactic treatments for migraine, such as topiramate or valproate, reduce the number of CSD events. We evaluated changes in gene expression in rat cortex and brainstem after inducing CSD in the cortex, with and without a prophylactic treatment with topiramate or valproate. CSD induction showed similar transcriptomic profiles with and without treatment in cortex, involving genes related to hormone stimulus, apoptosis, synaptic transmission, and interleukin signaling. In brainstem, CSD with and without treatment, although to a lesser extent, also induced gene expression changes involving genes related to apoptosis. Half of the genes altered in brainstem after CSD were also differentially expressed in the same direction in cortex. No differences in gene expression were identified after CSD as a consequence of the treatments, neither in cortex nor in brainstem. PERSPECTIVE Our results suggest that early after triggering the CSD, similar consequences are seen at the genetic level with or without prophylactic treatment. Gene expression changes induced by CSD in cortex and brainstem may help to better understand the underlying mechanisms and identify targets for therapeutic approaches.

EHMTI-0048. Epigenetic changes in a rat model of migraine with aura

Migraine with aura (MA) is a subtype of migraine characterized by reversible neurological disturbances preceding headache. Epigenetic mechanisms are postulated to mediate migraine susceptibility. MA neurophysiological correlate is cortical spreading depression (CSD), a wave of neuronal depolarization and depression that is suppressed by chronic administration of the migraine preventive drugs valproate and topiramate.

EHMTI-0361. Lack of differences in microrna expression profiles of blood cells in migraine

Migraine is a complex and very common neurological disorder. Several genome-wide significant loci have been described in migraine without explaining its whole genetic complexity. microRNAs are small non-coding RNAs involved in the regulation of gene expression that have become prominent candidates to explain the development of different neurological diseases and have also been described as key regulators in nociception.

A loss-of-function CACNA1A mutation causing benign paroxysmal torticollis of infancy

Benign paroxysmal torticollis of infancy (BPTI) is a rare paroxysmal disorder characterized by recurrent episodes of head tilt and accompanying general symptoms which remit spontaneously. The rare association with gain-of-function CACNA1A mutations, similar to hemiplegic migraine, has been reported. We report here two new BPTI patients from the same family carrying a heterozygous mutation in the CACNA1A gene leading to the change p.Glu533Lys. Functional analysis revealed that this mutation induces a loss of channel function due to impaired gating by voltage and much lower current density. Our data suggest that BPTI, a periodic syndrome commonly considered a migraine precursor, con- stitutes an age-specific manifestation of defective neuronal calcium channel activity.