Publications

Abstract

Background

The biological mechanisms of headache chronification are poorly understood. We aimed to identify changes in DNA methylation associated with the transformation from episodic to chronic headache.
Methods

Participants were recruited from the population-based Norwegian HUNT Study. Thirty-six female headache patients who transformed from episodic to chronic headache between baseline and follow-up 11 years later were matched against 35 controls with episodic headache. DNA methylation was quantified at 485,000 CpG sites, and changes in methylation level at these sites were compared between cases and controls by linear regression analysis. Data were analyzed in two stages (Stages 1 and 2) and in a combined meta-analysis.
Results

None of the top 20 CpG sites identified in Stage 1 replicated in Stage 2 after multiple testing correction. In the combined meta-analysis the strongest associated CpG sites were related to SH2D5 and NPTX2, two brain-expressed genes involved in the regulation of synaptic plasticity. Functional enrichment analysis pointed to processes including calcium ion binding and estrogen receptor pathways.
Conclusion

In this first genome-wide study of DNA methylation in headache chronification several potentially implicated loci and processes were identified. The study exemplifies the use of prospectively collected population cohorts to search for epigenetic mechanisms of disease

Abstract

Migraine is a disabling common brain disorder typically characterized by attacks of severe headache and associated with autonomic and neurological symptoms. Its etiology is far from resolved. This review will focus on evidence that epigenetic mechanisms play an important role in disease etiology. Epigenetics comprise both DNA methylation and post-translational modifications of the tails of histone proteins, affecting chromatin structure and gene expression. Besides playing a role in establishing cellular and developmental stage-specific regulation of gene expression, epigenetic processes are also important for programming lasting cellular responses to environmental signals. Epigenetic mechanisms may explain how non-genetic endogenous and exogenous factors such as female sex hormones, stress hormones and inflammation trigger may modulate attack frequency. Developing drugs that specifically target epigenetic mechanisms may open up exciting new avenues for the prophylactic treatment of migraine.

Abstract

Purpose of review: Migraine is a prevalent neurovascular brain disorder with a strong genetic component, and different methodological approaches have been implemented to identify the genes involved. This review focuses on pearls and pitfalls of these approaches and genetic findings in migraine. Summary: Common forms of migraine (i.e. migraine with and without aura) are thought to have a polygenic make-up, whereas rare familial hemiplegic migraine (FHM) presents with a monogenic pattern of inheritance. Until a few years ago only studies in FHM yielded causal genes, which were identified by a classical linkage analysis approach. Functional analyses of FHM gene mutations in cellular and transgenic animal models suggest abnormal glutamatergic neurotransmission as a possible key disease mechanism. Recently, a number of genes were discovered for the common forms of migraine using a genome-wide association (GWA) approach, which sheds first light on the pathophysiological mechanisms involved. Conclusions: Novel technological strategies such as next-generation sequencing, which can be implemented in future genetic migraine research, may aid the identification of novel FHM genes and promote the search for the missing heritability of common migraine.