Jèssica Fernández-Morales

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.

SNP variants within the vanilloid TRPV1 and TRPV3 receptor genes are associated with migraine in the Spanish population.

The transient receptor potential (TRP) superfamily of non‐selective cationic channels are involved in several processes plausibly relevant to migraine pathophysiology, including multimodal sensory and pain perception, central and peripheral sensitization, and regulation of calcium homeostasis. With the aim of identifying single nucleotide polymorphisms (SNPs) in TRP genes that may confer increased genetic susceptibility to migraine, we carried out a case–control genetic association study with replication, including a total of 1,040 cases and 1,037 controls. We genotyped 149 SNPs covering 14 TRP genes with known brain expression. The two‐stage study comprised samples of 555 and 485 Spanish, Caucasian patients, selected according to the ICHD‐II criteria for the diagnosis of migraine without aura (MO) or migraine with aura (MA). In the discovery sample, 19 SNPs in ten TRP genes showed nominal association (P < 0.05) with MO, MA, or overall migraine. In the replication sample, nominal association was confirmed for TRPV3 rs7217270 in MA and TRPV1 rs222741 in the overall migraine group. Risk haplotypes were identified for seven of the genes showing nominal association in the discovery set, but none of them was replicated. The present findings suggest that members of the vanilloid TRPV subfamily of receptors contribute to the genetic susceptibility to migraine in the Spanish population.

Association of a genetic variant in the ALOX5AP with higher risk of ischemic stroke: a case-control, meta-analysis and functional study.

Background: Variants in the 5-lipoxygenase-activating protein (ALOX5AP) and phosphodiesterase 4D (PDE4D) genes have first been associated with ischemic stroke (IS) through whole-genome linkage screens. However, association studies obtained conflicting results. We aimed to investigate the contribution of selected single nucleotide polymorphisms (SNPs) in these genes for the first time in a large Iberian population. Methods: A case-control design was used to analyze one SNP in ALOX5AP and five SNPs in PDE4D in a total of 1,092 IS patients and 781 healthy controls of two different subsets from Spain and Portugal. The analysis was adjusted for confounding variables and the results were integrated in a meta-analysis of all case-control studies. In addition, ALOX5AP gene expression levels were determined in controls and IS cases. Results: A first meta-analysis of both subsets showed that the T allele of the SG13S114 SNP in ALOX5AP was a risk factor for IS after Bonferroni correction [OR = 1.22 (1.06–1.40); p = 0.006]. A second meta-analysis of white populations confirmed these results [OR = 1.18 (1.07–1.31); p = 0.001]. ALOX5AP gene expression analysis in a subset of controls and cases revealed that the SG13S114 genotypes modulate mRNA levels of ALOX5AP (p = 0.001) and mRNA levels were higher in IS cases (2.8 ± 2.4%) than in controls (1.4 ± 1.3%; p = 0.003). No association of the variants in PDE4D with IS was observed in our study. Conclusions: The ALOX5AP SG13S114 variant is an independent risk factor for IS in the Iberian population and is associated with ALOX5AP expression levels. The role of this gene in stroke merits further investigation.

KCNK17 genetic variants in ischemic stroke

BACKGROUND Genetic factors contribute to the development of ischemic stroke (IS). In order to identify susceptibility variants, we analyzed single nucleotide polymorphisms (SNPs) that had been previously linked to stroke in a genome-wide association study. METHODS We analyzed 12 SNPs in a White population comprising IS patients and healthy controls. The analysis was adjusted for confounding variables and stratified by stroke etiology. Functional studies were then performed to elucidate the role of these variants in IS. RESULTS In a preliminary analysis of 268 controls and 531 IS cases, the rs10947803 SNP of KCNK17 (p=0.012) and the rs7506045 of IMPA2 (p=0.040) were associated with IS, although only the KCNK17 gene was an independent risk factor for IS. In a second phase, analysis of 271 new IS cases revealed that the A allele of rs10947803 was associated with stroke after correction for Bonferroni (OR=1.48; 95% CI, 1.14-1.91, p=0.003). Gene expression analysis revealed that KCNK17 mRNA levels were higher in the IS cases in the acute phase than in controls (14+/-78% vs. 91+/-41, p=0.002) but not in the chronic phase (56+/-57%; p=0.230). Moreover, RNA levels depended on the alleles of the rs10947803 SNP in the control group (p=0.021) and in the chronic phase (p=0.033). CONCLUSIONS The A allele of the rs10947803 variant of KCNK17 was associated with increased risk of IS and increased levels of KCNK17 gene expression. The role of this potassium channel gene in IS opens diagnostic and therapeutic expectations and merits further investigation.

CD40-1C>T polymorphism (rs1883832) is associated with brain vessel reocclusion after fibrinolysis in ischemic stroke.

AIMS To find genetic predictors of reocclusion after successful fibrinolytic therapy during the acute phase of ischemic stroke. PATIENTS & METHODS This was a case-case prospective study analyzing 236 polymorphisms in a cohort of 222 patients treated with tissue plasminogen activator, from which 16 patients suffered a reocclusion event (7.2%). A predictive scale was generated using independent polymorphisms with a dominant/recessive model and tandem occlusion, weighted by their beta-coefficients in logistic regression. RESULTS Using a dominant/recessive model, the rs1800801 SNP from the MGP gene (odds ratio [OR]: 15.25; 95% CI: 2.23-104.46; adjusted p = 0.006) and the rs1883832 SNP from CD40 gene (OR: 0.077; 95% CI: 0.009-0.66; adjusted p = 0.019) were independently associated with reocclusion after logistic regression adjustment by clinical predictors. In an additive model, only the rs1883832 SNP (OR: 4.43; 95% CI: 1.62-12.15; adjusted p = 0.004) was related to reocclusion occurrence. The predictive model that was generated stratified the reocclusion risk from less than 1% to more than 70%. Reocclusions were associated with neurological worsening at 24 h (patients with reocclusion: 26.7%, versus patients without reocclusion: 4.9%; p = 0.002), as it was seen for MGP -7A>G (AA: 17.2% vs AG+GG: 4.5%; p = 0.027), but not for CD40 1C>T (CC: 4.5% vs CT+TT: 7.7%; p = 0.565). There was an association between CD40 -1C>T genotype and CD40 transcriptional activity in peripheral blood mononuclear cells (median expression values TT: 65.75%, CT: 70.80%, CC: 96.00%; p = 0.023). However, CD40 soluble fraction was not a useful biomarker of reocclusion status. CONCLUSION An association was found between MGP -7A>G and CD40 -1C>T polymorphisms, and reocclusion risk. The predictive scale that was generated permits the stratification of patients by their reocclusion risk with higher accuracy than clinical parameters alone.

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.

A replication study of a GWAS finding in migraine does not identify association in a Spanish case-control sample.

Background: Migraine is a prevalent neurological disorder with a complex genetic background characterized by recurrent episodes of headache. The disease is subclassified into migraine with aura (MA) and migraine without aura (MO). Many association studies have been performed to date to identify genetic risk variants for common migraine, most of them focusing on selected candidate genes, with variable and often inconsistent results. Recently, a clinic-based genome-wide association study for migraine reported a functionally relevant risk variant (SNP rs1835740), involved in glutamate homeostasis, which showed a significant association with MA. We aimed to replicate this finding in a clinic-based study of a Spanish cohort with MA and MO patients. Methods: We genotyped SNP rs1835740 in a Spanish sample of 1521 patients and 1379 screened controls and performed a case-control association study. Conclusion: No association was found between the assayed SNP and any of the clinical groups considered.

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.

Genes involved in hemorrhagic transformations that follow recombinant t‑PA treatment in stroke patients

AIM Despite the benefits of recombinant t-PA (rt-PA) for stroke patients some of them suffer from adverse hemorrhagic transformations (HTs) following treatment. Our objective is to study the transcriptomics of HTs patients. METHODS We studied by microarrays 11 blood samples from patients with stroke that had received rt-PA of whom six of them had suffered a HT. For replication step RNA was collected from 14 new subjects (seven with HT, seven without) and then analyzed by real-time PCR. Four proteins were measured by ELISA in 72 new subjects to analyze their role as potential protein biomarkers. RESULTS The microarray analysis revealed that 14 genes were altered among the HT patients. The replication study confirmed these results for six genes. Two of them (BCL2 and OLFM4) are associated with apoptosis, whereas the other four (LTF, LCN2 [also known as NGAL], CEACAM8 and CRISP3) are involved in the regulation of neutrophil processes. CONCLUSION Our data revealed that genes related to apoptosis and neutrophil regulation pathways could be associated with HTs after rt-PA.

When does chronic migraine strike? A clinical comparison of migraine according to the headache days suffered per month:

Introduction According to the IHCD-3β classification, chronic migraine (CM) is headache occurring on 15 or more days/month. Episodic migraine (EM) can be divided into low frequency (LFEM) and high frequency (HFEM) depending on the headache days suffered per month. Methods We performed a clinical comparison of migraine characteristics according to monthly headache days suffered. Patients were divided into three groups: LFEM (1–9 headache days/month), HFEM (10–14 headache days/month) and CM (≥15 headache days/month). Results The analysis included 1109 patients. Previously reported differences between EM and CM were replicated. However, there were three times more clinical differences between LFEM and HFEM than between HFEM and CM (15 vs. 6). A new model that takes 10 headache days as a cut-off value for CM would have a minimally higher predictive capacity (72.8%) and no statistical differences (71.8%) when comparing it to the current classification. Conclusions HFEM patients have few clinical differences compared with CM patients. This includes the poor outcomes regarding headache-related disability and impact on daily life. According to these findings, neurologists and headache specialists should consider that the emotional and functional impact in HFEM patients could be as disabling as in those with CM.