Association of the C677T polymorphism in the MTHFR gene with migraine: a meta-analysis

Current Update on Categorization of Migraine Subtypes on the Basis of Genetic Variation: a Systematic Review

Migraine is a complex neurovascular disorder that is characterized by severe behavioral, sensory, visual, and/or auditory symptoms. It has been labeled as one of the ten most disabling medical illnesses in the world by the World Health Organization (Aagaard et al Sci Transl Med 6(237):237ra65, 2014). According to a recent report by the American Migraine Foundation (Shoulson et al Ann Neurol 25(3):252-9, 1989), around 148 million people in the world currently suffer from migraine. On the basis of presence of aura, migraine is classified into two major subtypes: migraine with aura (Aagaard et al Sci Transl Med 6(237):237ra65, 2014) and migraine without aura. (Aagaard K et al Sci Transl Med 6(237):237ra65, 2014) Many complex genetic mechanisms have been proposed in the pathophysiology of migraine but specific pathways associated with the different subtypes of migraine have not yet been explored. Various approaches including candidate gene association studies (CGAS) and genome-wide association studies (Fan et al Headache: J Head Face Pain 54(4):709-715, 2014). have identified the genetic markers associated with migraine and its subtypes. Several single nucleotide polymorphisms (Kaur et al Egyp J Neurol, Psychiatry Neurosurg 55(1):1-7, 2019) within genes involved in ion homeostasis, solute transport, synaptic transmission, cortical excitability, and vascular function have been associated with the disorder. Currently, the diagnosis of migraine is majorly behavioral with no focus on the genetic markers and thereby the therapeutic intervention specific to subtypes. Therefore, there is a need to explore genetic variants significantly associated with MA and MO as susceptibility markers in the diagnosis and targets for therapeutic interventions in the specific subtypes of migraine. Although the proper characterization of pathways based on different subtypes is yet to be studied, this review aims to make a first attempt to compile the information available on various genetic variants and the molecular mechanisms involved with the development of MA and MO. An attempt has also been made to suggest novel candidate genes based on their function to be explored by future research.

Disruption of mitochondrial pyruvate oxidation in dorsal root ganglia drives persistent nociceptive sensitization and causes pervasive transcriptomic alterations

ABSTRACT

Metabolism is inextricably linked to every aspect of cellular function. In addition to energy production and biosynthesis, metabolism plays a crucial role in regulating signal transduction and gene expression. Altered metabolic states have been shown to maintain aberrant signaling and transcription, contributing to diseases like cancer, cardiovascular disease, and neurodegeneration. Metabolic gene polymorphisms and defects are also associated with chronic pain conditions, as are increased levels of nerve growth factor (NGF). However, the mechanisms by which NGF may modulate sensory neuron metabolism remain unclear. This study demonstrated that intraplantar NGF injection reprograms sensory neuron metabolism. Nerve growth factor suppressed mitochondrial pyruvate oxidation and enhanced lactate extrusion, requiring 24 hours to increase lactate dehydrogenase A and pyruvate dehydrogenase kinase 1 (PDHK1) expression. Inhibiting these metabolic enzymes reversed NGF-mediated effects. Remarkably, directly disrupting mitochondrial pyruvate oxidation induced severe, persistent allodynia, implicating this metabolic dysfunction in chronic pain. Nanopore long-read sequencing of poly(A) mRNA uncovered extensive transcriptomic changes upon metabolic disruption, including altered gene expression, splicing, and poly(A) tail lengths. By linking metabolic disturbance of dorsal root ganglia to transcriptome reprogramming, this study enhances our understanding of the mechanisms underlying persistent nociceptive sensitization. These findings imply that impaired mitochondrial pyruvate oxidation may drive chronic pain, possibly by impacting transcriptomic regulation. Exploring these metabolite-driven mechanisms further might reveal novel therapeutic targets for intractable pain.

The impact of genetic factors on the response to migraine therapy

Migraine is a multidimensional disease affecting a large portion of the human population presenting with a variety of symptoms. In the era of personalized medicine, successful migraine treatment presents a challenge, as several studies have shown the impact of a patient's genetic profile on therapy response. However, with the emergence of contemporary treatment options, there is promise for improved outcomes. A literature search was conducted in PubMed and Scopus, in order to obtain studies investigating the impact of genetic factors on migraine therapy outcome. Overall, 23 studies were included in the current review, exhibiting diversity in the treatments used and the genetic variants investigated. Divergent genes were assessed for each category of migraine treatment. Several genetic factors were identified to contribute to the heterogeneous response to treatment. SNPs related to pharmacodynamic receptors, pharmacogenetics and migraine susceptibility loci were the most investigated variants, revealing some interesting significant results. To date, various associations have been recorded correlating the impact of genetic factors on migraine treatment responses. More extensive research needs to take place with the aim of shedding light on the labyrinthine effects of genetic variations on migraine treatment, and, consequently, these findings can promptly affect migraine treatment and improve migraine patients' life quality in the vision of precise medicine.

The Dawn and Advancement of the Knowledge of the Genetics of Migraine

Background: Migraine is a prevalent episodic brain disorder known for recurrent attacks of unilateral headaches, accompanied by complaints of photophobia, phonophobia, nausea, and vomiting. Two main categories of migraine are migraine with aura (MA) and migraine without aura (MO). Main body: Early twin and population studies have shown a genetic basis for these disorders, and efforts have been invested since to discern the genes involved. Many techniques, including candidate-gene association studies, loci linkage studies, genome-wide association, and transcription studies, have been used for this goal. As a result, several genes were pinned with concurrent and conflicting data among studies. It is important to understand the evolution of techniques and their findings. Conclusions: This review provides a chronological understanding of the different techniques used from the dawn of migraine genetic investigations and the genes linked with the migraine subtypes.

Migraine and thyroid dysfunction: Co-occurrence, shared genes and biological mechanisms

BACKGROUND AND PURPOSE

Migraine and thyroid dysfunction, particularly hypothyroidism, are common medical conditions and are known to have high heritability. Thyroid function measures, thyroid stimulating hormone (TSH) and free thyroxine (fT4), are also known to be genetically influenced. Although observational epidemiological studies report an increased co-occurrence of migraine and thyroid dysfunction, a clear and combined interpretation of the findings is currently lacking. A narrative review is provided of the epidemiological and genetic association evidence linking migraine, hypothyroidism, hyperthyroidism and thyroid hormones TSH and fT4.

METHODS

An extensive literature search was conducted in the PubMed database for epidemiological, candidate gene and genome-wide association studies using the terms migraine, headache, thyroid hormones, TSH, fT4, thyroid function, hypothyroidism and hyperthyroidism.

RESULTS

Epidemiological studies suggest a bidirectional relationship between migraine and thyroid dysfunction. However, the nature of the relationship remains unclear, with some studies suggesting migraine increases the risk for thyroid dysfunction whilst other studies suggest the reverse. Early candidate gene studies have provided nominal evidence for MTHFR and APOE, whilst more recently genome-wide association studies have provided robust evidence for THADA and ITPK1 being associated with both migraine and thyroid dysfunction.

CONCLUSIONS

These genetic associations improve our understanding of the genetic relationship between migraine and thyroid dysfunction, provide an opportunity to develop biomarkers to identify migraine patients most likely to benefit from thyroid hormone therapy, and indicate that further cross-trait genetic studies have excellent potential to provide biological insight into their relationship and inform clinical interventions.

Update on Findings about Sudden Sensorineural Hearing Loss and Insight into Its Pathogenesis

Sudden sensorineural hearing loss (SSNHL) is routinely encountered and is one of the most common emergent diseases in otolaryngology clinics. However, the etiology of SSNHL remains unclear. Due to the inaccessibility of the living human inner ear for biopsy, studies investigating the etiology of SSNHL have been performed by analyzing data obtained from examinations using peripheral blood or imaging. We updated the findings obtained from serological, magnetic resonance imaging, genetic, and viral examinations to reveal the etiology of SSNHL. Regarding viral examination, we focused on sensorineural hearing loss associated with coronavirus disease (COVID-19) because the number of correlated reports has been increasing after the outbreak. The updated findings revealed the following three possible mechanisms underlying the development of SSNHL: thrombosis and resulting vascular obstruction in the cochlea, asymptomatic viral infection and resulting damage to the cochlea, and cochlear inflammation and resulting damage to the cochlea. Thrombosis and viral infection are predominant, and cochlear inflammation can be secondarily induced through viral infection or even thrombosis. The findings about sensorineural hearing loss associated with COVID-19 supported the possibility that asymptomatic viral infection is one of the etiologies of SSNHL, and the virus can infect inner ear tissues and directly damage them.

Glucose-Related Traits and Risk of Migraine—A Potential Mechanism and Treatment Consideration

Migraine and glucose-related (glycaemic) traits (fasting glucose, fasting insulin, and type 2 diabetes) are common and complex comorbid disorders that cause major economic and social burdens on patients and their families. Studies on the relationship between migraine and glucose-related traits have yielded inconsistent results. The purpose of this review is to synthesise and discuss the information from the available literature on the relationship between fasting glucose, fasting insulin, and type 2 diabetes (T2D) with migraine. Publications on migraine and fasting glucose, migraine and fasting insulin, and migraine and T2D were identified from a PubMed and Google Scholar database search and reviewed for this article. Multiple publications have suggested that the comorbidity of migraine and glucose-related traits may have a similar complex pathogenic mechanism, including impaired glucose homeostasis, insulin resistance, reduced cerebrovascular reactivity, abnormal brain metabolism, shared genetic factors, neurotransmitters, and sex hormones. Furthermore, several studies have found a bi-directional link between migraine with insulin resistance and T2D. There is strong evidence for a biological association between migraine headache and glucose-related traits, and burgeoning evidence for shared genetic influences. Therefore, genetic research into these comorbid traits has the potential to identify new biomarkers and therapeutic targets and provide biological insight into their relationships. We encourage healthcare professionals to consider the co-occurrence of migraine with glucose-related traits in the evaluation and treatment of their patients.

Analysis of the DNA methylation pattern of the promoter region of calcitonin gene-related peptide 1 gene in patients with episodic migraine: An exploratory case-control study

Recent studies suggested that epigenetic mechanisms, including DNA methylation, may be involved in migraine pathogenesis. The calcitonin gene-related peptide (CGRP), encoded by calcitonin gene-related peptide 1 (CALCA) gene, plays a key role in the disease. The aim of the study was to evaluate DNA methylation of CALCA gene in patients with episodic migraine. 22 patients with episodic migraine (F/M 15/7, mean age 39.7 ± 13.4 years) and 20 controls (F/M 12/8, mean age 40.5 ± 14.8 years) were recruited. Genomic DNA was extracted from peripheral blood. Cytosine-to-thymine conversion was obtained with sodium bisulfite. The methylation pattern of two CpG islands in the promoter region of CALCA gene was analyzed. No difference of methylation of the 30 CpG sites at the distal region of CALCA promoter was observed between migraineurs and controls. Interestingly, in patients with episodic migraine the methylation level was lower in 2 CpG sites at the proximal promoter region (CpG -1461, p = 0.037, and -1415, p = 0.035, respectively). Furthermore, DNA methylation level at different CpG sites correlates with several clinical characteristics of the disease, as age at onset, presence of nausea/vomiting, depression and anxiety (p < 0.05). In conclusion, we found that DNA methylation profile in two CpG sites at the proximal promoter region of CALCA is lower in migraineurs when compared to controls. Intriguingly, the -1415 hypomethylated unit is located at the CREB binding site, a nuclear transcription factor. In addition, we found a correlation between the level of CALCA methylation and several clinical features of migraine. Further studies with larger sample size are needed to confirm these results.

Relation Between Methylenetetrahydrofolate Reductase Polymorphisms (C677T and A1298C) and Migraine Susceptibility

Migraine is a neurological disorder which impairs the patient's quality of life. Several association studies investigating the association between MTHFR gene C677T and A1298C polymorphisms and susceptibility to migraine were published. But the results were conflicting, so authors performed a meta-analysis of published case control studies to find out the exact association between MTHFR polymorphism and migraine susceptibility. Four databases were searched for suitable studies up to December, 2018. Odds ratios (OR) with 95% confidence intervals (CI) was calculated adopting additive, homozygote, co-dominant, dominant, and recessive genetic models. Results of MTHFR C677T polymorphism studies meta-analysis showed significant association with migraine risk using allele contrast, homozygote, dominant and recessive genetic models (T vs. C: OR = 1.18, 95% CI = 1.00-1.26, p = 0.05; TT vs. CC: OR = 1.24, 95% CI = 1.0-1.5, p = 0.04; CT vs. CC: OR = 1.08, 95% CI = 0.97-1.07, p = 0.25; TT + CT vs. CC: OR = 1.15, 95% CI = 1.0-1.29, p = 0.04; TT vs. CT + CC: OR = 1.97, 95% CI = 1.28-3.42, p = 0.002). However, results of MTHFR A1298 polymorphism studies meta-analysis did not show any association with migraine. Subgroup analysis based on ethnicity and migraine types i.e. migraine with aura (MA) and without aura (MO) were also performed. Results of present meta-analysis indicate overall association between MTHFR C677T polymorphism with migraine in total 24 studies, in Asian population and in MA cases but did not show any association with Caucasian population and MO cases.

Exploring the Hereditary Nature of Migraine

Migraine is a common neurological disorder which affects 15-20% of the population; it has a high socioeconomic impact through treatment and loss of productivity. Current forms of diagnosis are primarily clinical and can be difficult owing to comorbidity and symptom overlap with other neurological disorders. As such, there is a need for better diagnostic tools in the form of genetic testing. Migraine is a complex disorder, encompassing various subtypes, and has a large genetic component. Genetic studies conducted on rare monogenic subtypes, including familial hemiplegic migraine, have led to insights into its pathogenesis via identification of causal mutations in three genes (CACNA1A, ATP1A2 and SCN1A) that are involved in transport of ions at synapses and glutamatergic transmission. Study of familial migraine with aura pedigrees has also revealed other causal genes for monogenic forms of migraine. With respect to the more common polygenic form of migraine, large genome-wide association studies have increased our understanding of the genes, pathways and mechanisms involved in susceptibility, which are largely involved in neuronal and vascular functions. Given the preponderance of female migraineurs (3:1), there is evidence to suggest that hormonal or X-linked components can also contribute to migraine, and the role of genetic variants in mitochondrial DNA in migraine has been another avenue of exploration. Epigenetic studies of migraine have shown links between hormonal variation and alterations in DNA methylation and gene expression. While there is an abundance of preliminary studies identifying many potentially causative migraine genes and pathways, more comprehensive genomic and functional analysis to better understand mechanisms may aid in better diagnostic and treatment outcomes.

Utilization of B12 for the treatment of chronic migraine

Chronic migraine is a particular classification of a headache that is typically unilateral and pulsatile and lasts for at least 3 months. Owing to its high prevalence and detrimental impact on personal, social, and economic aspects of patient lives, much desire has gone into fully understanding the pathogenesis of migraine, and to search for therapeutic agents. In addition to current therapeutics such as triptans, ergotamine, and monoclonal antibodies targeting calcitonin gene-related peptide receptors, vitamin B12 has been investigated for its possible use as a prophylactic agent for migraines. Specifically, the observed effects of vitamin B12 on nitric oxide and homocysteine prompt further investigation of its underlying mechanisms in migraine pathophysiology. In this comprehensive review, we provide a brief overview of migraines and current therapies while focusing on the promising role of vitamin B12 as a possible treatment option for chronic migraine management.

Genetic variants in migraine: a field synopsis and systematic re-analysis of meta-analyses

OBJECTIVE

Numerous genetic variants from meta-analyses of observational studies and GWAS were reported to be associated with migraine susceptibility. However, due to the random errors in meta-analyses, the noteworthiness of the results showing statistically significant remains doubtful. Thus, we performed this field synopsis and re-analysis study to evaluate the noteworthiness using a Bayesian approach in hope of finding true associations.

METHODS

Relevant meta-analyses from observational studies and GWAS examining correlation between all genetic variants and migraine risk were included in our study by a PubMed search. Identification of noteworthy associations were analyzed by false-positive rate probability (FPRP) and Bayesian false discovery probability (BFDP). Using noteworthy variants, GO enrichment analysis were conducted through DAVID online tool. Then, the PPI network and hub genes were performed using STRING database and CytoHubba software.

RESULTS

As for 8 significant genetic variants from observational studies, none of which showed noteworthy at prior probability of 0.001. Out of 47 significant genetic variants in GWAS, 36 were noteworthy at prior probability of 0.000001 via FPRP or BFDP. We further found the pathways "positive regulation of cytosolic calcium ion concentration" and "inositol phosphate-mediated signaling" and hub genes including MEF2D, TSPAN2, PHACTR1, TRPM8 and PRDM16 related to migraine susceptibility.

CONCLUSION

Herein, we have identified several noteworthy variants for migraine susceptibility in this field synopsis. We hope these data would help identify novel genetic biomarkers and potential therapeutic target for migraine.

Advances in genetics of migraine

Background

Migraine is a complex neurovascular disorder with a strong genetic component. There are rare monogenic forms of migraine, as well as more common polygenic forms; research into the genes involved in both types has provided insights into the many contributing genetic factors. This review summarises advances that have been made in the knowledge and understanding of the genes and genetic variations implicated in migraine etiology.

Findings

Migraine is characterised into two main types, migraine without aura (MO) and migraine with aura (MA). Hemiplegic migraine is a rare monogenic MA subtype caused by mutations in three main genes - CACNA1A, ATP1A2 and SCN1A - which encode ion channel and transport proteins. Functional studies in cellular and animal models show that, in general, mutations result in impaired glutamatergic neurotransmission and cortical hyperexcitability, which make the brain more susceptible to cortical spreading depression, a phenomenon thought to coincide with aura symptoms. Variants in other genes encoding ion channels and solute carriers, or with roles in regulating neurotransmitters at neuronal synapses, or in vascular function, can also cause monogenic migraine, hemiplegic migraine and related disorders with overlapping symptoms. Next-generation sequencing will accelerate the finding of new potentially causal variants and genes, with high-throughput bioinformatics analysis methods and functional analysis pipelines important in prioritising, confirming and understanding the mechanisms of disease-causing variants.

With respect to common migraine forms, large genome-wide association studies (GWAS) have greatly expanded our knowledge of the genes involved, emphasizing the role of both neuronal and vascular pathways. Dissecting the genetic architecture of migraine leads to greater understanding of what underpins relationships between subtypes and comorbid disorders, and may have utility in diagnosis or tailoring treatments. Further work is required to identify causal polymorphisms and the mechanism of their effect, and studies of gene expression and epigenetic factors will help bridge the genetics with migraine pathophysiology.

Conclusions

The complexity of migraine disorders is mirrored by their genetic complexity. A comprehensive knowledge of the genetic factors underpinning migraine will lead to improved understanding of molecular mechanisms and pathogenesis, to enable better diagnosis and treatments for migraine sufferers.

Thrombophilia Testing in High Pediatric Migraine Risk Children With Migraine

This study sought to investigate the need for thrombophilia screening in pediatric migraineurs. The cohort included 45/824 children (5.5%) aged 3-18 years with migraine who were tested for thrombophilia at a tertiary pediatric headache clinic. Results were analyzed by background factors and indications for screening. Rates of thrombotic factors were compared with a healthy historical control group. At least 1 thrombotic factor was positive in 19/45 patients (42%). The total thrombophilia risk rate was higher in patients with aura (n = 32). Lipoprotein(a) was the factor most often abnormal in the thrombophilia group of all factors tested (8/19, 42%), regardless of migraine type or gender. It was the only factor with a significantly higher prevalence in the migraine than the historical control group. Full thrombophilia testing in migraine in pediatric headache clinics does not seem to be justified. The high prevalence of elevated lipoprotein(a) in children with migraine warrants further investigation.

Targeting MTHFR for the treatment of migraines

INTRODUCTION

Migraine is a common neurovascular disorder classified by the World Health Organization as one of the most debilitating diseases. Migraine is a complex disease and is a consequence of an interaction between genetic, epigenetic and environmental factors. The MTHFR gene is one of the few replicated genetic risk factors for migraine and encodes an enzyme that is crucial for the folate and the methionine cycles. Individuals carrying the T allele of the MTHFR C677T polymorphism have increased plasma concentrations of homocysteine which leads to endothelial cell injury and alterations in coagulant properties of blood. Areas covered: This review focuses on the recent advances in genetics and the role of the MTHFR gene and homocysteine metabolism in migraine etiopathogenesis. The article summarizes the potential of targeting MTHFR and homocysteine for disease prevention. Expert opinion: Determination of MTHFR C677T polymorphisms as well as measurement of homocysteine concentrations may be useful to migraine patients, particularly those suffering from migraine with aura. Preliminary studies support the use of folate, vitamin B6 and vitamin B12 for the prevention of migraine. However, the results of these studies await replication in larger randomized controlled clinical trials.

Genetic bases of the nutritional approach to migraine

Migraine is a common multifactorial and polygenic neurological disabling disorder characterized by a genetic background and associated to environmental, hormonal and food stimulations. A large series of evidence suggest a strong correlation between nutrition and migraine and indicates several commonly foods, food additives and beverages that may be involved in the mechanisms triggering the headache attack in migraine-susceptible persons. There are foods and drinks, or ingredients of the same, that can trigger the migraine crisis as well as some foods play a protective function depending on the specific genetic sensitivity of the subject. The recent biotechnological advances have enhanced the identification of some genetic factors involved in onset diseases and the identification of sequence variants of genes responsible for the individual sensitivity to migraine trigger-foods. Therefore many studies are aimed at the analysis of polymorphisms of genes coding for the enzymes involved in the metabolism of food factors in order to clarify the different ways in which people respond to foods based on their genetic constitution. This review discusses the latest knowledge and scientific evidence of the role of gene variants and nutrients, food additives and nutraceuticals interactions in migraine.

Association of MTHFR gene polymorphisms with migraine in North Indian population

Polymorphisms in MTHFR gene are mostly associated with increased levels of homocysteine in the absence of dietary folate and are a risk factor for complex neurovascular diseases like migraine. The aim of present case-control study was to determine the association between MTHFR gene polymorphisms (C667T; rs 1801133, A1298C; rs 1801131) with migraine susceptibility. In total, 100 patients with migraine (23with MA and 77 with MO) and age-sex matched 100 healthy controls were included in this study from OPD of ESIC Medical College & Hospital, Faridabad. Genotyping was done by PCR-RFLP method. Genotypic and allelic frequencies were compared by SPSS 24 version. Genotypic results indicated a non-significant increase in frequencies of CT and TT in C667T SNP in migraine patients with control (52 and 10% vs. 42 and 7%: p > 0.05), but CC genotype in A1298C was found to be a risk factor in migraine patients than controls (30 vs. 17% respectively: p < 0.05). On comparing migraine subclasses, migraine with aura (MA) and without aura (MO) with control groups, the present study suggests that in MTHFR polymorphisms, the prevalence of 677CT genotype and T allele in C667T SNP influences susceptibility to MA (p < 0.05) but not to MO. Meanwhile, CC genotype in A1298C SNP could be a risk factor for migraine patients without aura (p < 0.05).

The rs4846049 polymorphism in the 3'UTR region of the MTHFR gene increases the migraine susceptibility in an Iranian population

Introduction

Migraine is a painful complex neurovascular disease characterized by recurrent moderate-to-severe headaches. Increased level of homocysteine is related to dilation of cerebral vessels and endothelial injury that could trigger migraine attacks. Functional polymorphisms in the MTHFR gene affect homocysteine metabolism and, therefore, play an important role in the etiology of the disease.

Objectives

We aimed to investigate the possible association between MTHFR gene rs4846049, C677T, and A1298C polymorphisms and the risk of migraine in Iranian population.

Methods

In this genetic association study, 498 individuals were enrolled, including 223 migraine patients and 275 healthy controls. Genotyping was performed using tetra-primer ARMS-PCR for rs4846049 and PCR-restriction fragment length polymorphism for C677T and A1298C polymorphisms.

Results

The association between rs4846049 and C677T polymorphisms and migraine was observed. For the rs4846049 polymorphism, the association was detected under a dominant model (P=0.007; odds ratio [OR] =0.60; 95% confidence interval [CI], 0.41-0.87), and for the C677T polymorphism, the TT genotype frequency was significantly different in the studied groups (P=0.009; OR =2.48; 95% CI, 1.25-4.92). No significant differences in the genotype or allele frequencies were found for the A1298C polymorphism between the migraineurs and controls.

Conclusion

Present data provide evidence for the association of rs4846049 and C677T polymorphisms in the MTHFR gene and migraine. Further studies are required to validate the significance of the studied genetic variations in diverse ethnic populations.

Genetics of Migraine: Insights into the Molecular Basis of Migraine Disorders

Migraine is a complex, debilitating neurovascular disorder, typically characterized by recurring, incapacitating attacks of severe headache often accompanied by nausea and neurological disturbances. It has a strong genetic basis demonstrated by rare migraine disorders caused by mutations in single genes (monogenic), as well as familial clustering of common migraine which is associated with polymorphisms in many genes (polygenic). Hemiplegic migraine is a dominantly inherited, severe form of migraine with associated motor weakness. Family studies have found that mutations in three different ion channels genes, CACNA1A, ATP1A2, and SCN1A can be causal. Functional studies of these mutations has shown that they can result in defective regulation of glutamatergic neurotransmission and the excitatory/inhibitory balance in the brain, which lowers the threshold for cortical spreading depression, a wave of cortical depolarization thought to be involved in headache initiation mechanisms. Other putative genes for monogenic migraine include KCKN18, PRRT2, and CSNK1D, which can also be involved with other disorders. There are a number of primarily vascular disorders caused by mutations in single genes, which are often accompanied by migraine symptoms. Mutations in NOTCH3 causes cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a hereditary cerebrovascular disease that leads to ischemic strokes and dementia, but in which migraine is often present, sometimes long before the onset of other symptoms. Mutations in the TREX1 and COL4A1 also cause vascular disorders, but often feature migraine. With respect to common polygenic migraine, genome-wide association studies have now identified single nucleotide polymorphisms at 38 loci significantly associated with migraine risk. Functions assigned to the genes in proximity to these loci suggest that both neuronal and vascular pathways also contribute to the pathophysiology of common migraine. Further studies are required to fully understand these findings and translate them into treatment options for migraine patients.

Molecular factors in migraine

Migraine is a common neurological disorder that affects 11% of adults worldwide. This disease most likely has a neurovascular origin. Migraine with aura (MA) and more common form - migraine without aura (MO) - are the two main clinical subtypes of disease. The exact pathomechanism of migraine is still unknown, but it is thought that both genetic and environmental factors are involved in this pathological process. The first genetic studies of migraine were focused on the rare subtype of MA: familial hemiplegic migraine (FHM). The genes analysed in familial and sporadic migraine are: MTHFR, KCNK18, HCRTR1, SLC6A4, STX1A, GRIA1 and GRIA3. It is possible that migraine is a multifactorial disease with polygenic influence.Recent studies have shown that the pathomechanisms of migraine involves both factors responsible for immune response and oxidative stress such as: cytokines, tyrosine metabolism, homocysteine; and factors associated with pain transmission and emotions e.g.: serotonin, hypocretin-1, calcitonin gene-related peptide, glutamate. The correlations between genetic variants of the HCRTR1 gene, the polymorphism 5-HTTLPR and hypocretin-1, and serotonin were observed. It is known that serotonin inhibits the activity of hypocretin neurons and may affect the appearance of the aura during migraine attack.The understanding of the molecular mechanisms of migraine, including genotype-phenotype correlations, may contribute to finding markers important for the diagnosis and treatment of this disease.

Genetic epidemiology of migraine and depression

Background

Migraine and major depressive disorder (commonly referred to as depression) are both common disorders with a significant impact on society. Studies in both clinical and community-based settings have demonstrated a strong relationship between migraine and depression. In addition to complicating the diagnosis, depression that is comorbid with migraine may lower treatment adherence, increase risk of medication overuse and is associated with migraine chronification, thus leading to higher direct and indirect costs and poorer health-related outcomes with increased disability.

Aim

The aim of this review is to summarise the current knowledge on the genetic epidemiology of migraine and depression and the possible biological mechanisms underlying their comorbidity.

Methods

We present a narrative review reporting on the current literature.

Results and conclusions

Epidemiological findings indicate that there is a bidirectional relationship between migraine and depression, with one disorder increasing the risk for the other and vice versa, suggesting shared biological mechanisms. Twin and family studies indicate that this bidirectional relationship can be explained, at least partly, by shared underlying genetically determined disease mechanisms. Although no genes have been robustly associated with the aetiology of both migraine and depression, genes from serotonergic, dopaminergic and GABAergic systems together with variants in the MTHFR and BDNF genes remain strong candidates.

A comprehensive analysis of NDST3 for schizophrenia and bipolar disorder in Han Chinese

A novel susceptibility locus (rs11098403) for schizophrenia and bipolar disorder (BD) was identified in an Ashkenazi Jewish population by a recent large-scale genome-wide association study. The rs11098403 is located in the vicinity of the gene encoding N-deacetylase/N-sulfotransferase (heparan glucosaminyl) 3, (NDST3). This study aimed to replicate the results in a Han Chinese population and then potentially extend these findings. We performed a two-stage study to investigate the association of NDST3 with the schizophrenia and BD risk in the Han Chinese. In stage 1, a total of 632 patients with schizophrenia, 654 patients with BD and 684 healthy controls were recruited from the Shanghai region. In stage 2, 522 schizophrenia patients and 547 normal subjects were enrolled from the Hangzhou region. Then, we conducted a meta-analysis based on the present literature. In stage 1, the single nucleotide polymorphism (SNP) rs11098403 showed a significant association with schizophrenia (corrected P=0.005). The frequency of the rs11098403 G allele was significantly lower among schizophrenia patients than among the controls (odds ratio (OR)=0.68, 95% confidence interval (CI): 0.55-0.84, corrected P=0.002). No significant difference was observed in individual SNP marker genotypes or allele distributions between the BD and control groups. In stage 2, the association of rs11098403 with schizophrenia could be validated (genotypic P=0.001 and allelic P=0.0003). After pooling all data from 1861 patients with schizophrenia and 2081 controls, we observed a significant association of the rs11098403 G allele with schizophrenia (Z=5.56, P<0.001), with an OR=0.70 (95% CI: 0.61-0.79). Then, we performed an expression quantitative trait loci analysis to investigate the functional effect of rs11098403 on NDST3 expression in the brain. We observed a significant association of rs11098403 with NDST3 expression in the hippocampus (P=0.027), although the significance did not survive after multiple testing correction. Our findings provided preliminary evidence that rs11098403 might modify the genetic risk of schizophrenia in the Han Chinese. Further investigations are warranted to identify the precise mechanism regulating brain NDST3 expression in the Han Chinese. These results would help to explain the pathophysiological mechanism of schizophrenia.

The migraine–stroke connection: A genetic perspective

Background

A complex relationship between migraine and vascular disease has long been recognized. The pathophysiological basis underlying this correlation is incompletely understood.

Aim

The aim of this review is to focus on the migraine–vascular disorders connection from a genetic perspective, illustrating potentially shared (molecular) mechanisms.

Results

We first summarize the clinical presentation and genetic basis of CADASIL and other monogenic vascular syndromes with migraine as a prominent disease manifestation. Based on data from transgenic mouse models for familial hemiplegic migraine, we then discuss cortical spreading depression as a potential mechanistic link between migraine and ischemic stroke. Finally, we review data from genome-wide association studies, with a focus on overlapping findings with cervical artery dissection, ischemic stroke in general and cardiovascular disease.

Conclusion

A wealth of data supports a genetic link between migraine and vascular disease. Based on growing high-throughput data-sets, new genotyping techniques and in-depth phenotyping, further insights are expected for the future.

From migraine genes to mechanisms

Migraine is a common multifactorial episodic brain disorder with strong genetic basis. Monogenic subtypes include rare familial hemiplegic migraine, cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy, familial advanced sleep-phase syndrome (FASPS), and retinal vasculopathy with cerebral leukodystrophy. Functional studies of disease-causing mutations in cellular and/or transgenic models revealed enhanced (glutamatergic) neurotransmission and abnormal vascular function as key migraine mechanisms. Common forms of migraine (both with and without an aura), instead, are thought to have a polygenic makeup. Genome-wide association studies have already identified over a dozen genes involved in neuronal and vascular mechanisms. Here, we review the current state of molecular genetic research in migraine, also with respect to functional and pathway analyses. We will also discuss how novel experimental approaches for the identification and functional characterization of migraine genes, such as next-generation sequencing, induced pluripotent stem cell, and optogenetic technologies will further our understanding of the molecular pathways involved in migraine pathogenesis.

Systematic re-evaluation of genes from candidate gene association studies in migraine using a large genome-wide association data set

Background

Before the genome-wide association (GWA) era, many hypothesis-driven candidate gene association studies were performed that tested whether DNA variants in genes that had been selected based on prior knowledge about migraine pathophysiology were associated with migraine. Most studies involved small sample sets without robust replication, thereby making the risk of false-positive findings high. Genome-wide marker data of thousands of migraine patients and controls from the International Headache Genetics Consortium provide a unique opportunity to re-evaluate key findings from candidate gene association studies (and other non-GWA genetic studies) in a much larger data set.

Methods

We selected 21 genes from published candidate gene association studies and six additional genes from other non-GWA genetic studies in migraine. Single nucleotide polymorphisms (SNPs) in these genes, as well as in the regions 500 kb up- and downstream, were inspected in IHGC GWAS data from 5175 clinic-based migraine patients with and without aura and 13,972 controls.

Results

None of the SNPs in or near the 27 genes, including the SNPs that were previously found to be associated with migraine, reached the Bonferroni-corrected significance threshold; neither when analyzing all migraine patients together, nor when analyzing the migraine with and without aura patients or males and females separately.

Conclusion

The available migraine GWAS data provide no clear evidence for involvement of the previously reported most promising candidate genes in migraine.

Migraine genetics: current findings and future lines of research

In the last two decades, migraine research has greatly advanced our current knowledge of the genetic contributions and the pathophysiology of this common and debilitating disorder. Nonetheless, this knowledge still needs to grow further and to translate into more effective treatments. To date, several genes involved in syndromic and monogenic forms of migraine have been identified, allowing the generation of animal models which have significantly contributed to current knowledge of the mechanisms underlying these rare forms of migraine. Common forms of migraine are instead posing a greater challenge, as they may most often stem from complex interactions between multiple common genetic variants, with environmental triggers. This paper reviews our current understanding of migraine genetics, moving from syndromic and monogenic forms to oligogenic/polygenic migraines most recently addressed with some success through genome-wide association studies. Methodological issues in study design and future perspectives opened by biomarker research will also be briefly addressed.

Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism: epidemiology, metabolism and the associated diseases

The Methylenetetrahydrofolate reductase (MTHFR) C677T polymorphism is associated with various diseases (vascular, cancers, neurology, diabetes, psoriasis, etc) with the epidemiology of the polymorphism of the C677T that varies dependent on the geography and ethnicity. The 5,10-Methylenetetrahydrofolate reductase (MTHFR) locus is mapped on chromosome 1 at the end of the short arm (1p36.6). This enzyme is important for the folate metabolism which is an integral process for cell metabolism in the DNA, RNA and protein methylation. The mutation of the MTHFR gene which causes the C677T polymorphism is located at exon 4 which results in the conversion of valine to alanine at codon 222, a common polymorphism that reduces the activity of this enzyme. The homozygous mutated subjects have higher homocysteine levels while the heterozygous mutated subjects have mildly raised homocysteine levels compared with the normal, non-mutated controls. Hyperhomocysteinemia is an emerging risk factor for various cardiovascular diseases and with the increasing significance of this polymorphism in view of the morbidity and mortality impact on the patients, further prevention strategies and nutritional recommendations with the supplementation of vitamin B12 and folic acid which reduces plasma homocysteine level would be necessary as part of future health education. This literature review therefore focuses on the recent evidence-based reports on the associations of the MTHFR C677T polymorphism and the various diseases globally.

Correlations of MTHFR 677C>T polymorphism with cardiovascular disease in patients with end-stage renal disease: a meta-analysis

OBJECTIVE

This meta-analysis was conducted to evaluate the correlations of a common polymorphism (677C>T) in the methylenetetrahydrofolate reductase (MTHFR) gene with risk of cardiovascular disease (CVD) in patients with end-stage renal disease (ESRD).

METHOD

The following electronic databases were searched without language restrictions: Web of Science (1945∼2013), the Cochrane Library Database (Issue 12, 2013), MEDLINE (1966∼2013), EMBASE (1980∼2013), CINAHL (1982∼2013) and the Chinese Biomedical Database (CBM) (1982∼2013). Meta-analysis was performed using STATA statistical software. Odds ratios (ORs) with their 95% confidence intervals (95%CIs) were calculated.

RESULTS

Eight cohort studies met all inclusion criteria and were included in this meta-analysis. A total of 2,292 ESRD patients with CVD were involved in this meta-analysis. Our meta-analysis results revealed that the MTHFR 677C>T polymorphism might increase the risk of CVD in ESRD patients (TT vs. CC: OR = 2.75, 95%CI = 1.35∼5.59, P = 0.005; CT+TT vs. CC: OR = 1.39, 95%CI = 1.09∼1.78, P = 0.008; TT vs. CC+CT: OR = 2.52, 95%CI = 1.25∼5.09, P = 0.010; respectively). Further subgroup analysis by ethnicity suggested that the MTHFR 677C>T polymorphism was associated with an elevated risk for CVD in ESRD patients among Asians (TT vs. CC: OR = 3.38, 95%CI = 1.11∼10.28, P = 0.032; CT+TT vs. CC: OR = 1.44, 95%CI = 1.05∼1.97, P = 0.022; TT vs. CC+CT: OR = 3.15, 95%CI = 1.02∼9.72, P = 0.046; respectively), but not among Africans or Caucasians (all P>0.05).

CONCLUSION

Our findings indicate that the MTHFR 677C>T polymorphism may be associated with an elevated risk for CVD in ESRD patients, especially among Asians.

Effects of MTHFR gene polymorphism on the clinical and electrophysiological characteristics of migraine

Background

It was previously shown that the MTHFR gene polymorphism correlated with an increased risk of migraine, particularly migraine with aura. The substitution of cytosine for thymine at the position 677 of the MTHFR gene leads to formation of the thermolabile form of the protein and development of hyperhomocysteinemia, which increases the probability of migraine. The purpose of this study was to determine whether the replacement of C677T in the gene MTHFR influenced any particular symptoms of the disease.

Methods

We have analyzed clinical and electrophysiological characteristics of 83 patients with migraine (migraine with aura (MA), 19 patients, and migraine without aura (MO), 64 patients, according to the ICHD-II (2003)) taking into account their genotypes of C677T variant of MTHFR.

Results

We have shown that MA was significantly more prevalent among the T-allele carriers (37.2%), as compared to the СС genotype patients (0%), р < 0.0001. Patients with TT genotype were not only more likely to have accompanying symptoms (significant differences were found only for photophobia), but also more sensitive to migraine attack triggers. In RP-VEP test results we observed a trend that the T-allele carriers were presented with the decreased N75/P100 amplitudes and a positive habituation index, as compared to the СС genotype patients.

Conclusions

Thus, according to our data, the MTHFR genotypes are associated with several clinical and electrophysiological characteristics of migraine.

Studies on the pathophysiology and genetic basis of migraine

Migraine is a neurological disorder that affects the central nervous system causing painful attacks of headache. A genetic vulnerability and exposure to environmental triggers can influence the migraine phenotype. Migraine interferes in many facets of people's daily life including employment commitments and their ability to look after their families resulting in a reduced quality of life. Identification of the biological processes that underlie this relatively common affliction has been difficult because migraine does not have any clearly identifiable pathology or structural lesion detectable by current medical technology. Theories to explain the symptoms of migraine have focused on the physiological mechanisms involved in the various phases of headache and include the vascular and neurogenic theories. In relation to migraine pathophysiology the trigeminovascular system and cortical spreading depression have also been implicated with supporting evidence from imaging studies and animal models. The objective of current research is to better understand the pathways and mechanisms involved in causing pain and headache to be able to target interventions. The genetic component of migraine has been teased apart using linkage studies and both candidate gene and genome-wide association studies, in family and case-control cohorts. Genomic regions that increase individual risk to migraine have been identified in neurological, vascular and hormonal pathways. This review discusses knowledge of the pathophysiology and genetic basis of migraine with the latest scientific evidence from genetic studies.

The role of hyperhomocysteinemia in neurological features associated with coeliac disease

Although a range of neurological and psychiatric disorders are widely reported to be associated with coeliac patients, their pathogenesis remains unclear. Some such disorders are believed to be secondary to vitamin deficiency due to malabsorption, others to immune mechanisms. We hypothesise that hyperhomocysteinemia might, by damaging the blood-brain barrier, expose neuronal tissue to all neuro-irritative metabolites, such as homocysteine itself, a neurotoxic excitatory and proconvulsant amino acid. Neurons respond to these stimuli through hyperexcitability, thereby predisposing subjects to neurological disorders such as epilepsy and headache. Furthermore, persisting endothelial damage may cause blood extravasation and subsequent deposition of calcium salts. We suggest that this might be the pathogenesis of the CEC syndrome, which is characterized by the association of coeliac disease, epilepsy and cerebral calcifications. Indeed, homocysteine plays a well-known role in cardiovascular endothelial dysfunction, with high serum and cerebrospinal fluid levels often being reported in coeliac patients. Moreover, data in the literature show a strong, growing association of homocysteine with epilepsy and migraine in non-coeliac subjects. Despite these findings, homocysteine has never been held directly responsible for neuronal functional features (neuronal hyperexcitability underlying epilepsy and migraine) and structural brain damage (expressed as cerebral calcification) in coeliac patients. Damage to the blood-brain barrier might also facilitate immune reactions against neuronal tissue to a considerable extent. This hypothesis combines the two afore-mentioned theories (vitamin deficiency due to malabsorption and immune mechanisms). We also wish to point out that no studies have yet investigated the prevalence of neuronal hyperexcitability and subclinical electroencephalic abnormalities in children and adults with newly-diagnosed coeliac disease before the introduction of a gluten-free diet, and in particular any changes following the introduction of the diet. We believe that the onset of clinical symptoms such as migraine and convulsions is preceded by a period in which damage is expressed exclusively by subclinical electroencephalic abnormalities; persisting damage to neuronal tissue subsequently leads to clinical manifestations. We propose two types of investigations: the first is to determine whether newly-diagnosed coeliac patients with hyperhomocysteinemia are a subgroup at risk for neurological features (clinical and subclinical); the second is to determine whether appropriate treatment of hyperhomocysteinemia and vitamin B status deficiency improves neurological abnormalities and reduces the risk of cerebral calcifications. The aim of these investigations is to develop new therapeutic strategies designed to prevent neuronal damage and increase the quality of life in children affected by such disorders.

Genes and primary headaches: discovering new potential therapeutic targets

Genetic studies have clearly shown that primary headaches (migraine, tension-type headache and cluster headache) are multifactorial disorders characterized by a complex interaction between different genes and environmental factors. Genetic association studies have highlighted a potential role in the etiopathogenesis of these disorders for several genes related to vascular, neuronal and neuroendocrine functions. A potential role as a therapeutic target is now emerging for some of these genes. The main purpose of this review is to describe new advances in our knowledge regarding the role of MTHFR, KCNK18, TRPV1, TRPV3 and HCRTR genes in primary headache disorders. Involvement of these genes in primary headaches, as well as their potential role in the therapy of these disorders, will be discussed.

Pearls and pitfalls in genetic studies of migraine

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.

Genetic variants in the NOTCH4 gene influence the clinical features of migraine

BACKGROUND

Recent studies suggested an important role for vascular factors in migraine etiopathogenesis. Notch4 belongs to a family of transmembrane receptors that play an important role in vascular development and maintenance. The aim of this study was to test the hypothesis that polymorphisms of the NOTCH4 gene would modify the occurrence and the clinical features of migraine.

FINDINGS

Using a case-control strategy, we genotyped 239 migraine patients and 264 controls for three different non-synonymous polymorphisms (T320A, G835V, R1346P) of the NOTCH4 gene and for the (CTG) n-encoding polyleucine polymorphism in exon 1. Although the analyzed polymorphisms resulted not associated with migraine, the clinical characteristics of our patients were significantly influenced by the different NOTCH4 genotypes. Longer duration of disease and severity of neurovegetative symptoms during headache attacks were associated with the R1346P and G835V polymorphisms, respectively. In female patients, worsening of migraine symptoms at menarche was significantly correlated with T320A polymorphism.

CONCLUSIONS

Our study shows that genetic variations within the NOTCH4 gene significantly modify the clinical characteristics of migraine and may have a role in disease pathogenesis.

Genotypes of the MTHFR C677T and MTRR A66G genes act independently to reduce migraine disability in response to vitamin supplementation

BACKGROUND

Migraine is a chronic disabling neurovascular condition that may in part be caused by endothelial and cerebrovascular disruption induced by hyperhomocysteinaemia. We have previously provided evidence indicating that reduction of homocysteine by vitamin supplementation can reduce the occurrence of migraine in women. The current study examined the genotypic effects of methylenetetrahydrofolate reductase (MTHFR) and methionine synthase reductase (MTRR) gene variants on the occurrence of migraine in response to vitamin supplementation.

METHODS

This was a 6-month randomized, double-blinded placebo-controlled trial of daily vitamin B supplementation (B(6), B(9) and B(12)) on reduction of homocysteine and of the occurrence of migraine in 206 female patients diagnosed with migraine with aura.

RESULTS

Vitamin supplementation significantly reduced homocysteine levels (P<0.001), severity of headache in migraine (P=0.017) and high migraine disability (P=0.022) in migraineurs compared with the placebo effect (P>0.1). When the vitamin-treated group was stratified by genotype, the C allele carriers of the MTHFR C677T variant showed a higher reduction in homocysteine levels (P<0.001), severity of pain in migraine (P=0.01) and percentage of high migraine disability (P=0.009) compared with those with the TT genotypes. Similarly, the A allele carriers of the MTRR A66G variants showed a higher level of reduction in homocysteine levels (P<0.001), severity of pain in migraine (P=0.002) and percentage of high migraine disability (P=0.006) compared with those with the GG genotypes. Genotypic analysis for both genes combined indicated that the treatment effect modification of the MTRR variant was independent of the MTHFR variant.

CONCLUSION

This provided further evidence that vitamin supplementation is effective in reducing migraine and also that both MTHFR and MTRR gene variants are acting independently to influence treatment response in female migraineurs.

Emerging genomic biomarkers in migraine

Migraine is a debilitating neurovascular condition classified as either migraine with aura or migraine without aura. A significant genetic basis has been implicated in migraine and has probed the role of neurotransmitters, hormones and vascular genes in this disorder. The aim of this review is to highlight the recent genetic discoveries contributing to our understanding of the complex pathogenesis of migraine. The current review will discuss the role of neurotransmitter-related genes in migraine, including the recently identified TRESK and variants of the KCNN3 gene, as well as outlining studies investigating hormone receptor genes, such as ESR1 and PGR, and vascular-related genes, including the MTHFR and NOTCH 3 genes.