Study of Mitochondrial DNA Mutations in Patients With Migraine With Prolonged Aura

Conserved spatiotemporal expression landscape of dominant tRNA genes in human and mouse

Transfer RNAs are integral for protein synthesis and the interpretation of the information contained in DNA. To date, a few methods, including custom microarrays and custom targeted sequencing, have been used to quantify tRNA. However, methods using available RNA-sequencing data have not yet been reported. We created a bioinformatics pipeline to quantify the highly expressed tRNAs in RNA-Seq effectively, demonstrated by the preserved ratio of the expression levels of two massively duplicated tRNAAla genes in mouse. Using this quantification, we examined the tRNA expression with relation to tissue type and developmental stage in both human and mouse. Heart exhibited the highest overall tRNA expression for both human and mouse. Furthermore, tRNA expression grew to a peak before decreasing steadily with developmental stage, a trend that was conserved in both human and mouse. The two mitochondrial tRNA genes, tRNASer(TCA)(m) and tRNALeu(TTA)(m), which partly contribute to these trends, have been attributed to various human diseases. The tissue-specific high expression of tRNAGln(CAG) and tRNAGln(CAA) in human brains, especially in hindbrain and cerebellum, suggests their important roles in neurological disorders. In summary, our approach revealed conserved spatiotemporal expression of highly expressed tRNAs in both human and mouse. Our method can be applied to other RNA-Seq data to examine the roles of these tRNAs in different human diseases or scientific studies.

A Comprehensive Review on the Role of Genetic Factors in the Pathogenesis of Migraine

Migraine is a common neurovascular condition. This disorder has a complex genetic background. Several single-nucleotide polymorphisms (SNPs) or mutations within genes regulating glutamatergic neurotransmission, cortical excitability, ion channels, and solute carriers have been associated with polygenic and monogenic forms of migraine. SNPs within ACE, DBH, TRPM8, COMT, GABRQ, CALCA, TRPV1, and other genes have been reported to affect the risk of migraine or the associated clinical parameters. The distribution of some HLA alleles within the HLA-DRB1, HLA-DR2, HLA-B, and HLA-C regions have also been found to differ between migraineurs and healthy subjects. In addition, certain mitochondrial DNA changes and polymorphisms in this region have been shown to increase the risk of migraine. A few functional studies have investigated the molecular mechanisms contributing to these genetic factors in the development of migraine. Here we review studies evaluating the role of genetic polymorphisms and mRNA/miRNA dysregulation in migraine.

The metabolic face of migraine - from pathophysiology to treatment

Migraine can be regarded as a conserved, adaptive response that occurs in genetically predisposed individuals with a mismatch between the brain's energy reserve and workload. Given the high prevalence of migraine, genotypes associated with the condition seem likely to have conferred an evolutionary advantage. Technological advances have enabled the examination of different aspects of cerebral metabolism in patients with migraine, and complementary animal research has highlighted possible metabolic mechanisms in migraine pathophysiology. An increasing amount of evidence - much of it clinical - suggests that migraine is a response to cerebral energy deficiency or oxidative stress levels that exceed antioxidant capacity and that the attack itself helps to restore brain energy homeostasis and reduces harmful oxidative stress levels. Greater understanding of metabolism in migraine offers novel therapeutic opportunities. In this Review, we describe the evidence for abnormalities in energy metabolism and mitochondrial function in migraine, with a focus on clinical data (including neuroimaging, biochemical, genetic and therapeutic studies), and consider the relationship of these abnormalities with the abnormal sensory processing and cerebral hyper-responsivity observed in migraine. We discuss experimental data to consider potential mechanisms by which metabolic abnormalities could generate attacks. Finally, we highlight potential treatments that target cerebral metabolism, such as nutraceuticals, ketone bodies and dietary interventions.

Mitochondria in migraine pathophysiology - does epigenetics play a role?

The approximately three times higher rate of migraine prevalence in women than men may result from the mitochondrial transmission of this disease. Studies with imaging techniques suggest disturbances in mitochondrial metabolism in specific regions of the brain in migraine patients. Migraine shares some clinical features with several mitochondrial diseases and many other disorders include migraine headaches. Epigenetic regulation of mitochondrial DNA (mtDNA) is a matter of debate and there are some conflicting results, especially on mtDNA methylation. Micro RNAs (miRNAs) and long-noncoding RNA (lncRNAs) have been detected in mitochondria. The regulation of the miRNA-lncRNA axis can be important for mitochondrial physiology and its impairment can result in a disease phenotype. Further studies on the role of mitochondrial epigenetic modifications in migraine are needed, but they require new methods and approaches.

Headache in mitochondrial disorders

Headache is a prominent feature in mitochondrial disorders (MIDs) but no comprehensive overview is currently available. This review aims at summarising and discussing findings concerning type, frequency, pathogenesis, and treatment of headache in MIDs. The most frequent headache types in MIDs are migraine and migraine-like headache (MLH). MLH is classified as secondary headache. More rarely, tension-type headache, trigemino-autonomic headache, or different secondary headaches can be found. Migraine or MLH may manifest with or without aura. MLH is frequently associated with an ongoing or previous stroke-like episode (SLE) or a seizure but may also occur independently of other neurological features. MLH may be associated with prolonged aura or visual phenomena after headache. Except for MLH, treatment of headache in MIDs is not at variance from other causes of headache. Beyond the broadly accepted subtype-related headache treatment, diet, cofactors, vitamins, and antioxidants may provide a supplementary benefit. Midazolam, l-arginine, or l-citrulline may be beneficial for MLH. The pathogenesis of headache in MIDs largely remains unsolved. However, since migraine and MLH respond both to triptanes, a shared pathomechanism is likely. In conclusion, migraine and MLH are the prominent headache types in MIDs. MLH may or may not be associated with current or previous SLEs. MLH is pathophysiologically different from migraine and requires treatment at variance from that of migraine with aura.

Migraine with prolonged aura: phenotype and treatment

We review the published literature on migraine with prolonged aura (PA), specifically with regards to the phenotype and treatment options. PA is not uncommon. A recent study found that about 17% of migraine auras are prolonged and that 26% of patients with migraine with aura have experienced at least one PA. The characteristics of PA are similar to most typical auras with the exception of a higher number of aura symptoms (in particular sensory and/or dysphasic). There are no well-established treatments at present which target the aura component of migraine. Other than case reports, there have been open-label studies of lamotrigine and greater occipital nerve blocks. The only randomised, blinded, controlled trial to date has been of nasal ketamine showing some reduction in aura severity but not duration. A small open-labelled pilot study of amiloride was also promising. Larger randomised, controlled trials are needed to establish whether any of the existing or novel compounds mentioned are significantly effective and safe.

Sex Differences in the Transmission of Migraine

Consistent evidence demonstrates that migraine is far more common in women than in men, but the explanations for this preponderance have not been systematically evaluated. We examined whether the female preponderance is attributable to genetic factors using data from a controlled family study which included 260 probands and their 1232 first-degree adult relatives. We found that although the risk of migraine was three times greater among the relatives of probands with migraine compared with controls, there was no differential risk of migraine among the relatives of male vs. female probands with migraine. Taking these data together with other family studies, we conclude that the increased risk of migraine in females is likely to result from increased exposure to non-familial endogenous or exogenous risk factors for migraine that lower the threshold for expression of migraine in women.

Prevalence of migraine in persons with the 3243A>G mutation in mitochondrial DNA

BACKGROUND AND PURPOSE

Over the last three decades mitochondrial dysfunction has been postulated to be a potential mechanism in migraine pathogenesis. The lifetime prevalence of migraine in persons carrying the 3243A>G mutation in mitochondrial DNA was investigated.

METHODS

In this cross-sectional study, 57 mDNA 3243A>G mutation carriers between May 2012 and October 2014 were included. As a control group, a population-based cohort from our epidemiological studies on migraine in Danes was used. History of headache and migraine was obtained by telephone interview, based on a validated semi-structured questionnaire, performed by trained physicians.

RESULTS

The prevalence of migraine is significantly higher in persons carrying the 3243A>G mutation than in controls (58% vs. 18%; P < 0.001). This applies for both subforms of migraine, migraine without aura (47% vs. 12%; P < 0.001) and migraine with aura (18% vs. 6%; P < 0.001), and in females (58% vs. 24%; P < 0.001) and males (58% vs. 12%; P < 0.001) for any migraine.

CONCLUSIONS

A high prevalence of migraine in persons with the mDNA 3243A>G mutation was found. This finding suggests a clinical association between a monogenetically inherited disorder of mitochondrial dysfunction and susceptibility to migraine. Mitochondrial DNA aberrations may contribute to the pathogenesis of migraine.

No evidence of association between common European mitochondrial DNA variants in Alzheimer, Parkinson, and migraine in the Spanish population

Certain mitochondrial DNA (mtDNA) variants and haplogroups have been found to be associated with neurological disorders. Several studies have suggested that mtDNA variation could have an etiologic role in these disorders by affecting the ATP production on high-energy demanding organs, such as the brain. We have analyzed 15 mtDNA SNPs (mtSNPs) in five cohorts of cases presenting Alzheimer disease (AD), Parkinson disease (PD), and migraine, and in controls, to evaluate the role mtDNA variation in disease risk. Association tests were undertaken both for mtSNPs and mitochondrial haplogroups. No significant association was detected for any mtSNP or haplogroup in AD and PD cohorts. Two mtSNPs were associated with one migraine cohort after correcting for multiple tests, namely, T4216C and G13708A and haplogroup J (FDR q-value = 0.02; Santiago's cohort). However, this association was not confirmed in a second replication migraine series. A review of the literature reveals the existence of inconsistent findings and methodological shortcomings affecting a large proportion of mtDNA association studies on AD, PD, and migraine. A detailed inspection of the literature highlights the need for performing more rigorous methodological and statistical standards in mtDNA genetic association studies aimed to avoid false positive results of association between mtDNA variants and neurological diseases.

An unusual case of episodic SUNCT responding to high doses of topiramate

Trigeminal autonomic cephalalgias (TAC) are rare. Cluster headaches comprise the majority, with short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (SUNCT) being the rarest and shortest in duration. The majority of SUNCT are primary with a few cases occurring secondary to posterior fossa or pituitary lesions. Although activities like exercise or blowing of the nose can trigger SUNCT, onset during orgasm has not been described. Short-lasting aura has been described in TACs including SUNCT, but persistence of focal symptoms and signs without an underlying structural lesion have not been described. Lastly, treatment of SUNCT is difficult, with lamotrigine being the most common effective reported. We report a case of episodic SUNCT with symptoms suggestive of brainstem stroke that completely resolved spontaneously for which no underlying structural cause was found. The onset of first attack occurred during orgasm, and the patient responded to a high dose of topiramate.

Screening for MELAS mutations in young patients with stroke of undetermined origin

PURPOSE: It has been suggested that mitochondrial disease may be responsible for a substantial proportion of strokes of indetermined origin. We have preliminarily screened for MELAS (mitochondrial encephalomyopathy, lactic acidosis, and stroke-like episodes) mutations in young patients with cryptogenic strokes. METHOD: The mitochondrial mutations A3243G and T3271C were investigated in 38 subjects aged less than 46 years. Group 1: 15 patients with cryptogenic strokes; Group 2: 3 patients with diagnosis of MELAS syndrome, including stroke-like episodes; Group 3: 20 healthy subjects. RESULTS: The A3243G mutation was absent in all subjects in Groups 1 and 3 but was present in all subjects in Group 2. CONCLUSION: Our results do not support screening for these mutations to diagnose oligosymptomatic forms of MELAS in cryptogenic strokes in the absence of other features of the syndrome. We suggest that clinical findings should guide mitochondrial genetic testing.

Mitochondrial tRNA gene mutations in patients having mitochondrial disease with lactic acidosis

Lactic acidosis has been associated with a variety of clinical conditions and can be due to mutation in nuclear or mitochondrial genes. We performed mutations screening of all mitochondrial tRNA genes in 44 patients who referred as hyperlactic acidosis. Patients showed heterogeneous phenotypes including Leigh disease in four, MELAS in six, unclassified mitochondrial myopathy in 10, cardiomyopathy in five, MERRF in one, pure lactic acidosis in six, and others in 12 including facio-scaplo-femoral muscular dystrophy (FSFD), familial cerebellar ataxia, recurrent Reye syndrome, cerebral palsy with mental retardation. We measured enzymatic activities of pyruvate dehydrogenase complex, and respiratory chain enzymes. All mitochondrial tRNA genes and known mutation of ATPase 6 were studied by single strand conformation polymorphism (SSCP), automated DNA sequence and PCR-RFLP methods. We have found one patient with PDHC deficiency and six patients with Complex I+IV deficiency, though the most of the patients showed subnormal to deficient state of respiratory chain enzyme activities. We have identified one of the nucleotide changes in 29 patients. Single nucleotide changes in mitochondrial tRNA genes are found in 27 patients and one in ATPase 6 gene in two patients. One of four pathogenic point mutations (A3243G, C3303T, A8348G, and T8993G) was identified in 12 patients who showed the phenotype of Leigh syndrome, MELAS, cardimyopathy and cerebral palsy with epilepsy. Seventeen patients have one of the normal polymorphisms in the mitochondrial tRNA gene reported before. SSCP and PCR-RFLP could detect the heteroplasmic condition when the percentage of mutant up to 5, however, it cannot be observed by direct sequencing method. It is important to screen the mtDNA mutation not only by direct sequence but also by PCR-RFLP and the other sensitive methods to detect the heroplasmy when lactic acidosis has been documented in the patients who are not fulfilled the criteria of mitochondrial disorders.

Visual disturbances and migraine

There is a close relationship between headache and the visual system. Visual symptoms are prominent features of clinical syndromes such as migraine, cluster headache, and the trigeminal autonomic cephalgias. There are also strong links between headache and the visual system on the basis of genetics, molecular biology, neurophysiology, and neuroimaging. Studies of these links are leading to the development of novel therapies for a variety of headache syndromes. This review is designed to summarize the most recent literature on headache and the visual system. A particular emphasis is placed on publications of interest to clinicians.