Non-coding variants in VAMP2 and SNAP25 affect gene expression: potential implications in migraine susceptibility.

Migraine is a common and complex neurological disease potentially caused by a polygenic interaction of multiple gene variants. Many genes associated with migraine are involved in pathways controlling the synaptic function and neurotransmitters release. However, the molecular mechanisms underpinning migraine need to be further explored.Recent studies raised the possibility that migraine may arise from the effect of regulatory non-coding variants. In this study, we explored the effect of candidate non-coding variants potentially associated with migraine and predicted to lie within regulatory elements: VAMP2_rs1150, SNAP25_rs2327264, and STX1A_rs6951030. The involvement of these genes, which are constituents of the SNARE complex involved in membrane fusion and neurotransmitter release, underscores their significance in migraine pathogenesis. Our reporter gene assays confirmed the impact of at least two of these non-coding variants. VAMP2 and SNAP25 risk alleles were associated with a decrease and increase in gene expression, respectively, while STX1A risk allele showed a tendency to reduce luciferase activity in neuronal-like cells. Therefore, the VAMP2_rs1150 and SNAP25_rs2327264 non-coding variants affect gene expression, which may have implications in migraine susceptibility. Based on previous in silico analysis, it is plausible that these variants influence the binding of regulators, such as transcription factors and micro-RNAs. Still, further studies exploring these mechanisms would be important to shed light on the association between SNAREs dysregulation and migraine susceptibility.

Functional characterization of a novel PRRT2 variant found in a Portuguese patient with hemiplegic migraine.

Familial hemiplegic migraine (FHM) is a rare autosomal-dominant form of migraine with aura. Three disease-causing genes have been identified for FHM: CACNA1A, ATP1A2 and SCN1A. However, not all families are linked to one of these three genes.PRRT2 variants were also commonly associated with HM symptoms; therefore, PRRT2 is hypothesized as the fourth gene causing FHM. PRRT2 plays an important role in neuronal migration, spinogenesis, and synapse mechanisms during development and calcium-dependent neurotransmitter release. We performed exome sequencing to unravel the genetic cause of migraine in one family, and a novel PRRT2 variant (c.938C > T;p.Ala313Val) was identified with further functional studies to confirm its pathogenicity. PRRT2-A313V reduced protein stability, led to protein premature degradation by the proteasome and altered the subcellular localization of PRRT2 from the plasma membrane (PM) to the cytoplasm. We identified and characterized for the first time in a Portuguese patient, a novel heterozygous missense variant in PRRT2 associated with HM symptoms. We suggest that PRRT2 should be included in the diagnosis of HM.

A High Methylation Level of a Novel -284 bp CpG Island in the RAMP1 Gene Promoter Is Potentially Associated with Migraine in Women.

Migraine is a complex neurovascular disorder affecting one billion people worldwide, mainly females. It is characterized by attacks of moderate to severe headache pain, with associated symptoms. Receptor activity modifying protein (RAMP1) is part of the Calcitonin Gene-Related Peptide (CGRP) receptor, a pharmacological target for migraine. Epigenetic processes, such as DNA methylation, play a role in clinical presentation of various diseases. DNA methylation occurs mostly in the gene promoter and can control gene expression. We investigated the methylation state of the RAMP1 promoter in 104 female blood DNA samples: 54 migraineurs and 50 controls. We treated DNA with sodium bisulfite and performed PCR, Sanger Sequencing, and Epigenetic Sequencing Methylation (ESME) software analysis. We identified 51 CpG dinucleotides, and 5 showed methylation variability. Migraineurs had a higher number of individuals with all five CpG methylated when compared to controls (26% vs. 16%), although non-significant (p = 0.216). We also found that CpG -284 bp, related to the transcription start site (TSS), showed higher methylation levels in cases (p = 0.011). This CpG may potentially play a role in migraine, affecting RAMP1 transcription or receptor malfunctioning and/or altered CGRP binding. We hope to confirm this finding in a larger cohort and establish an epigenetic biomarker to predict female migraine risk.