Molecular analysis of cluster headache

CLOCK gene circannual expression in cluster headache

BACKGROUND

Cluster headache is a primary headache disorder characterized by bouts with circadian and circannual patterns. The CLOCK gene has a central role in regulating circadian rhythms. Here, we investigate the circannual CLOCK expression in a population of cluster headache patients in comparison to matched controls.

METHODS

Patients with cluster headache were sampled two to four times over at least one year, both in or outside bouts, one week after each solstice and equinox. The expression of CLOCK was measured by quantitative real-time polymerase chain reaction (RT-PCR) in the peripheral blood.

RESULTS

This study included 50 patients and 58 matched controls. Among the patient population, composed of 42/50 males (84%) with an average age of 44.6 years, 45/50 (90%) suffered from episodic cluster headache. Two to four samples were collected from each patient adding up to 161 samples, 36 (22.3%) of which were collected within a bout. CLOCK expression for cluster headache patients was considerably different from that of the control population in winter (p-value mean = 0.006283), spring (p-value mean = 0.000006) and summer (p-value mean = 0.000064), but not in autumn (p-value mean = 0.262272). For each season transition, the variations in CLOCK expression were more pronounced in the control group than in the cluster headache population. No statistically significant differences were found between bout and non-bout samples. No individual factors (age, sex, circadian chronotype, smoking and coffee habits or history of migraine) were related to CLOCK expression.

CONCLUSIONS

We observed that CLOCK expression in cluster headache patients fluctuates less throughout the year than in the control population. Bout activity and lifestyle factors do not seem to influence CLOCK expression.

The genetics and chronobiology of cluster headache

BACKGROUND/HYPOTHESIS

Cluster headache displays uniquely rhythmic patterns in its attack manifestation. This strong chronobiological influence suggests that part of the pathophysiology of cluster headache is distinctly different from migraine and has prompted genetic investigations probing these systems.

METHODS

This is a narrative overview of the cluster headache chronobiological phenotype from the point of view of genetics covering existing knowledge, highlighting the specific challenges in cluster headache and suggesting novel research approaches to overcome these.

RESULTS

The chronobiological features of cluster headache are a hallmark of the disorder and while discrepancies between study results do exist, the main findings are highly reproducible across populations and time. Particular findings in subgroups indicate that the heritability of the disorder is linked to chronobiological systems. Meanwhile, genetic markers of circadian rhythm genes have been implicated in cluster headache, but with conflicting results. However, in two recently published genome wide association studies two of the identified four loci include genes with an involvement in circadian rhythm, MER proto-oncogene, tyrosine kinase and four and a half LIM domains 5. These findings strengthen the involvement of circadian rhythm in cluster headache pathophysiology.

CONCLUSION/INTERPRETATION

Studying chronobiology and genetics in cluster headache presents challenges unique to the disorder. Researchers are overcoming these challenges by pooling various data from different cohorts and performing meta-analyses providing novel insights into a classically enigmatic disorder. Further progress can likely be made by combining deep pheno- and genotyping.

Genetic overlap between temporomandibular disorders and primary headaches: A systematic review

Primary headache disorders (PHD), specifically migraine, are strongly associated with temporomandibular disorders (TMD), sharing some patterns of orofacial pain. Both disorders have significant genetic contributions already studied. PRISMA guidelines were followed to conduct this systematic review, which comprehensively summarize and discuss the genetic overlap between TMD and PHD to aid future research in potential therapy targets. This review included eight original articles published between 2015 and 2020, written in English and related to either TMD and/or PHD. The genes simultaneously assessed in PHD and TMD studies were COMT, MTHFR, and ESR1. COMT was proved to play a critical role in TMD pathogenesis, as all studies have concluded about its impact on the occurrence of the disease, although no association with PHD was found. No proof on the impact of MTHFR gene regulation on either TMD or PHD was found. The most robust results are concerning the ESR1 gene, which is present in the genetic profile of both clinical conditions. This novel systematic review highlights not only the need for a clear understanding of the role of ESR1 and COMT genes in pain pathogenesis, but it also evaluates their potential as a promising therapeutic target to treat both pathologies.

The differentially expressed proteins related to clinical viral encephalitis revealed by proteomics

To screen out the prospective biomarkers of viral encephalitis (VE), analyze the biological process and signaling pathways involved by differentially expressed proteins (DEPs). A total of 11 cerebrospinal fluid (CSF) samples with VE and 5 with non-nervous system infection were used to perform label-free proteomic techniques. Then, the bioinformatic analysis of DEPs was applied by Interproscan software. Moreover, 73 CSF samples in the VE group and 53 in the control group were used to verify the changes of some DEPs by enzyme-linked immunosorbent assay (ELISA). Thirty-nine DEPs were identified, including 18 upregulated DEPs and 21 downregulated DEPs. DEPs were mainly enriched in cell adhesion molecules by Kyoto Encyclopedia of Genes and Genomes analysis pathway analysis. The DEPs related to axon tissue were obviously downregulated and the most significant downregulated proteins were neurexin 3, neurofascin, and neuroligin 2 (NLGN2). Moreover, the protein expression of NLGN2 in the VE group was significantly higher than that in the control group by ELISA. The correlation analysis of NLGN2 in the VE group revealed that there was a weak positive correlation with CSF protein and a weak negative correlation with CSF chloride. The clinical VE may be closely related to NLGN2 and the cell adhesion molecule pathway.

No significant association between SNPs in the CLOCK and ADH4 genes and susceptibility to cluster headaches: A systematic review and meta-analysis

BACKGROUND

The circadian locomotor output cycles kaput (CLOCK) gene and the alcohol dehydrogenase 4 (ADH4) gene are promising candidates for susceptibility to cluster headaches (CH). Associations of the three single nucleotide polymorphisms (SNPs)-CLOCK SNP rs1801260 and ADH4 SNPs rs1800759, and rs1126671-with CH were studied previously, but the results were inconsistent.

METHODS

Associations between the three SNPs (rs1801260, rs1126671, and rs1800759) and CH risk were separately assessed by pooled odds ratios (ORs) along with 95% confidence intervals (95% CIs) based on five different genetic models. Methodological quality was assessed using the Newcastle-Ottawa Quality Assessment Scale (NOS). All statistical analyses were carried out with RevMan 5.3 software.

RESULTS

Eight studies involving 1437 CH patients and 2541 healthy controls were selected for quantitative synthesis, from five studies on CLOCK rs1801260, five on ADH4 rs1800759, and three on ADH4 rs1126671. Our pooled data did not support associations between the three SNPs (rs1801260 in the CLOCK gene, rs1800759 and rs1126671 in the ADH4 gene) and susceptibility to CH (rs1801260: OR 1.10, 95% CI: 0.95-1.28; p = 0.19; rs1800759: OR 1.06, 95% CI: 0.93-1.22; p = 0.37; and rs1126671: OR 1.09, 95% CI: 0.92-1.28; p = 0.32).

CONCLUSION

We found no significant associations between the three SNPs (rs1801260 in the CLOCK gene and rs1800759 and rs1126671 in the ADH4 gene) and the susceptibility to CH across both Caucasian and Asian ethnicities in our meta-analysis.

Structure, function, and pathology of Neurexin-3

Neurexin-3 is primarily localized in the presynaptic membrane and forms complexes with various ligands located in the postsynaptic membrane. Neurexin-3 has important roles in synapse development and synapse functions. Neurexin-3 mediates excitatory presynaptic differentiation by interacting with leucine-rich-repeat transmembrane neuronal proteins. Meanwhile, neurexin-3 modulates the expression of presynaptic α-amino-3-hydroxy-5-methyl-4-isoxazole propionic acid receptors and γ-aminobutyric acid A receptors by interacting with neuroligins at excitatory and inhibitory synapses. Numerous studies have documented the potential contribution of neurexin-3 to neurodegenerative and neuropsychiatric disorders, such as Alzheimer's disease, addiction behaviors, and other diseases, which raises hopes that understanding the mechanisms of neurexin-3 may hold the key to developing new strategies for related illnesses. This review comprehensively covers the literature to provide current knowledge of the structure, function, and clinical role of neurexin-3.

The clinical characteristics of familial cluster headache

Background

A positive family history predisposes to the development of cluster headache. The distinct characteristics of familial cluster headache have yet to be confirmed, however, evidence suggests a younger age of onset and higher proportion of females in this subgroup.

Objectives

To assess the rate and mode of inheritance of familial cluster headache in a tertiary referral centre for headache. To describe the clinical features of familial cluster headache.

Methods

A retrospective study conducted between 2007 and 2017. Cluster headache was confirmed in probands and affected relatives. Differences in demographics, clinical characteristics, and response-to-treatment in familial cluster headache were delineated through multivariate analysis using a control cohort of 597 patients with sporadic cluster headache.

Results

Familial cluster headache was confirmed in 48 (7.44%) patients and predominantly reflected an autosomal dominant mode of inheritance with reduced penetrance. Familial cases were more likely to report nasal blockage (OR 4.06, 95% CI; 2.600–6.494, p < 0.001) during an attack and a higher rate of concurrent short-lasting unilateral neuralgiform headache with conjunctival injection and tearing (OR 3.76, 95% CI; 1.572–9.953, p = 0.004).

Conclusion

These findings add to evidence suggesting a genetic component to cluster headache. Here, we demonstrated prominent nasal blockage, and a higher occurrence of concomitant short-lasting unilateral neuralgiform headache with conjunctival injection and tearing in this subgroup, further delineating the phenotype.

Evidence That HFE H63D Variant Is a Potential Disease Modifier in Cluster Headache

Cluster headache (CH) is a primary headache disorder with a complex genetic background. Several studies indicate a potential link between iron homeostasis and the pathophysiology of primary headaches. The HFE gene encodes for a protein involved in iron metabolism, while genetic variants in HFE have been associated with hereditary hemochromatosis (HH), an iron overload disorder. The objective of the current study was to examine the association of the more common HFE H63D variant, with the susceptibility to develop CH and diverse clinical phenotypes in a population of Southeastern European Caucasian (SEC) origin. Genomic DNA samples from 128 CH patients and 294 neurologically healthy controls were genotyped for the HFE rs1799945 (H63D) variant. H63D genotypic and allelic frequency distribution did not differ significantly between patients and controls (p > 0.05). Subgroup analysis revealed a significantly more frequent occurrence of the variant G allele in chronic compared to episodic CH patients, indicative for a possible correlation of the HFE gene with the susceptibility for disease chronification. Although homozygosity for the less prevalent H63D variant G allele was minimal in the CH cohort, the results of the present study are in accordance with previous studies in CH and migraine patients, suggesting that HFE H63D variant modifies the disease clinical characteristics. Hence, despite the absence of a per se association with CH susceptibility in the current SEC cohort, variability in HFE gene may be potentially regarded as a disease modifier genetic factor in CH.

Gene polymorphism association studies in cluster headache: A field synopsis and systematic meta-analyses

BACKGROUND

A plethora of studies have attempted to identify genetic determinants of disease susceptibility and treatment response of patients with cluster headache (CH), but results are often conflicting, and no comprehensive overview with a quantitative summary of the evidence in this field is available.

METHODS

A systematic search of relevant publications was performed without any language restrictions on PubMed, Web of Knowledge, Cochrane Library, and OpenGrey, up to December 2020. A standardized data extraction form was used to collect relevant data from each included study. Meta-analyses were conducted for gene polymorphisms investigated in at least two studies and the Bayesian false discovery probability (BFDP) test was applied to the pooled odds ratios (ORs) to assess the credibility of the observed associations.

RESULTS

Among the 27 articles identified by the systematic review, 17 studies evaluating 12 single nucleotide polymorphisms (SNPs) were included in the quantitative data analysis. The pooled results showed no significant association with CH risk of 10 SNPs, including five SNPs of HCRTR2 (rs2653349, rs2653342, rs3122156, rs10498801, and rs3800539), two SNPs of ADH4 (rs1800759 and rs1126671), CLOCK rs1801260, and two SNPs (rs1006417 and ADCYAP1R1 rs12668955) previously identified by a genome-wide association study (GWAS). Conversely, the pooled results revealed the association of the HCRTR2 rs9357855 A allele with a higher risk of CH (A vs. G, OR: 1.33, 95% CI: 1.04-1.72, p = 0.026), and of GNB3 rs5443 with a higher response rate of patients with CH to triptan drugs (CT+TT vs. CC, OR: 1.96, 95% CI: 1.04-3.72, p = 0.038). However, assuming a prior probability of 0.001, the respective BFDP values being higher than 0.8 (BFDP_rs9357855  = 0.998; BFDP_rs5443  = 0.998) revealed lack of noteworthy results.

CONCLUSIONS

Well-designed GWASs and large replication studies are still needed to identify reliable genetic variants of disease susceptibility and treatment response of patients with CH.

Genetic Susceptibility Loci in Genomewide Association Study of Cluster Headache

Objective

Identifying common genetic variants that confer genetic risk for cluster headache.

Methods

We conducted a case–control study in the Dutch Leiden University Cluster headache neuro‐Analysis program (LUCA) study population (n = 840) and unselected controls from the Netherlands Epidemiology of Obesity Study (NEO; n = 1,457). Replication was performed in a Norwegian sample of 144 cases from the Trondheim Cluster headache sample and 1,800 controls from the Nord‐Trøndelag Health Survey (HUNT). Gene set and tissue enrichment analyses, blood cell‐derived RNA‐sequencing of genes around the risk loci and linkage disequilibrium score regression were part of the downstream analyses.

Results

An association was found with cluster headache for 4 independent loci (r² < 0.1) with genomewide significance (p < 5 × 10⁻⁸), rs11579212 (odds ratio [OR] = 1.51, 95% confidence interval [CI] = 1.33–1.72 near RP11‐815 M8.1), rs6541998 (OR = 1.53, 95% CI = 1.37–1.74 near MERTK), rs10184573 (OR = 1.43, 95% CI = 1.26–1.61 near AC093590.1), and rs2499799 (OR = 0.62, 95% CI = 0.54–0.73 near UFL1/FHL5), collectively explaining 7.2% of the variance of cluster headache. SNPs rs11579212, rs10184573, and rs976357, as proxy SNP for rs2499799 (r² = 1.0), replicated in the Norwegian sample (p < 0.05). Gene‐based mapping yielded ASZ1 as possible fifth locus. RNA‐sequencing indicated differential expression of POLR1B and TMEM87B in cluster headache patients.

Interpretation

This genomewide association study (GWAS) identified and replicated genetic risk loci for cluster headache with effect sizes larger than those typically seen in complex genetic disorders. ANN NEUROL 2021;90:203–216

The molecular clock gene cryptochrome 1 (CRY1) and its role in cluster headache

Background

Cluster headache is a severe primary headache disorder commonly featuring a strikingly distinct circadian attack pattern. Therefore, the circadian system has been suggested to play a crucial role in the pathophysiology of cluster headache. Cryptochromes are key components of the molecular clock generating circadian rhythms and have previously been shown to be associated with several psychiatric disorders, including seasonal affective disorder, bipolar disorder, and depression.

Methods

In this case-control study, we investigated the role of cryptochrome (CRY) genes in cluster headache by screening 628 cluster headache patients and 681 controls from Sweden for four known genetic variants in the CRY1 (rs2287161 and rs8192440) and CRY2 (rs10838524 and rs1554338) genes. In addition, we analyzed CRY1 gene expression in primary fibroblast cell lines from eleven patients and ten controls.

Results

The exonic CRY1 variant rs8192440 was associated with cluster headache on allelic level (p=0.02) and this association was even more pronounced in a subgroup of patients with reported diurnal rhythmicity of attacks (p=0.002). We found a small significant difference in CRY1 gene expression between cluster headache patients and control individuals (p=0.04), but we could not identify an effect of the associated variant rs8192440 on CRY1 expression.

Conclusions

We discovered a disease-associated variant in the CRY1 gene and slightly increased CRY1 gene expression in tissue from cluster headache patients, strengthening the hypothesis of circadian dysregulation in cluster headache. How this gene variant may contribute to the pathophysiology of the disease remains subject to further studies.

Family History of Cluster Headache: A Systematic Review

Importance

Genetic and environmental factors are thought to contribute to cluster headache, and cluster headache can affect multiple members of a family. A thorough understanding of its inheritance is critical to understanding the pathogenesis of this debilitating disease.

Objective

To systematically review family history rates and inheritance patterns of cluster headache.

Evidence Review

A systematic review was performed in PubMed, Embase, and Cochrane Library. Search criteria were created by a librarian. Articles published between 1985 and 2016, after the publication date of a large review in 1985, were analyzed independently by 2 neurologists to identify family history rates and pedigrees. Pedigrees were analyzed by a genetic counselor.

Findings

A total of 1995 studies were found (1988 through the search criteria and 7 through other means). Forty articles met inclusion criteria: 22 large cohort studies, 1 twin-based study, and 17 case reports or small case series. Across the 22 large cohort studies, the positive family history rate of cluster headache varied between 0% and 22%, with a median of 8.2%. The largest 5 studies, of 1134, 785, 693, 609, and 500 probands each, had a positive family history in 18.0% (numerator not provided), 5.1% (40 of 785 cases), 10.0% (numerator not provided), 2.0% (12 of 609 cases), and 11.2% (56 of 500 cases), respectively. No meta-analysis was performed, given differences in methodologies. Separately, 1 twin-based study examined 37 twin pairs and reported a concordance rate of 5.4% (2 pairs). Finally, 67 pedigrees were identified. Most pedigrees (46 of 67 [69%]) were consistent with an autosomal dominant pattern, but 19 of 67 (28%) were consistent with an autosomal recessive inheritance pattern; 10 pedigrees of probable or atypical cluster headache were identified, and all were consistent with an autosomal dominant inheritance pattern. The sex ratio for cluster headache in identified pedigrees was 1.39 (103:74) in affected men and boys compared with affected women and girls, which is lower than that of the general cluster headache population.

Conclusions and Relevance

Cluster headache is an inherited disorder in a subset of families and is associated with multiple hereditary patterns. There is an unexpectedly high preponderance of women and girls with familial cluster headache; genetic subanalyses limited to female participants are necessary to further explore this observation, because these data are otherwise masked by the higher numbers of male participants with cluster headache. Overall, this systematic review supports the notion that familial cluster headache is likely the result of multiple susceptibility genes as well as environmental factors.

No Association Between G1246A Polymorphism in HCRTR2 Gene and Risk of Cluster Headache: Evidence From an Updated Meta-Analysis of Observational Studies

Background: The hypocretin receptor 2 (HCRTR2) gene may play a pathological role in cluster headache (CH). However, the conclusions of published reports on the relationship between the G1246A polymorphism (rs2653349) in the HCRTR2 gene and risk of CH remain controversial. This purpose of this article is to comprehensively study the current evidence and assess the association between G1246A polymorphism (rs2653349) in the HCRTR2 gene and risk of CH.

Materials and Methods: Four electronic databases—ISI Web of Science, CNKI, PubMed, and EMBASE—were comprehensively searched on August 2020 to find and pinpoint all observational articles related to this study. The association between G1246A polymorphism in the HCRTR2 gene and risk of CH under five different genetic models was evaluated based on the summary odds ratio and corresponding 95 confidence interval (95% CI). Methodological quality was assessed based on the Newcastle–Ottawa Scale (NOS). To assist the analysis, RevMan 5.3 software was used to perform subgroup and sensitivity analyses. Egger's and Begg's tests were then conducted to evaluate and assess publication bias. Finally, a meta-regression was carried out by residual (restricted) maximum likelihood (REML).

Results: Eight observation studies containing 3,161 healthy controls and 1,964 patients with CH were identified and to be used for the meta-analysis. With methodological quality NOS assessment, the incorporated studies showed an average score of 6.4 stars. The pooled data didn't support the association between G1246A polymorphism in the HCRTR2 gene and CH vulnerability in the overall population (OR: 0.85, 95% CI 0.69, 1.03; p = 0.10). Subgroup analysis by ethnicity showed no significant association between G1246A and CH in either Caucasians (OR: 0.89, 95% CI 0.77, 1.01; p = 0.08) or Asians (OR: 1.65, 95% CI 0.80, 3.41; p = 0.18). The robustness of the conclusion was tested and confirmed with the leave-one-out sensitivity analysis. Meta-regression analysis showed that chronological order of publication appeared to be significantly associated with the heterogeneity (t = 2.47, p = 0.039; residual I² = 0%, adjusted R² = 100%).

Conclusion: Our present study showed that the G1246A polymorphism in the HCRTR2 gene did not appear to be an accomplice and associated with CH predisposition among either the Asian or Caucasian population.

Prevalence of familial cluster headache: a systematic review and meta-analysis

INTRODUCTION

The population rate of familial cluster headache (CH) has been reported to be as high as 20% however this varies considerably across studies. To obtain a true estimate of family history in CH, we conducted a systematic review and meta-analysis of previously published data.

METHODS

Our systematic review involved a search of electronic databases (Medline, EMBASE, PubMed, CINAHL) to identify and appraise studies of interest utilising the PRISMA (Preferred Reporting Items for Systematic Review and Meta-Analysis) guidelines. To further ameliorate the accuracy of our analysis we included an additional unpublished cohort of CH patients recruited at a tertiary referral centre for headache, who underwent detailed family history with diagnostic verification in relatives. Data was extracted and meta-analysis conducted to provide a true estimation of family history.

RESULTS

In total, we identified 7 studies which fulfilled our inclusion criteria. The estimated true prevalence of CH patients with a positive family history was 6.27% (95% CI:4.65-8.40%) with an overall I² of 73%. Fitted models for gender subgroups showed higher estimates 9.26% (95% CI: 6.29-13.43%) in females. However the I² for the female model was 58.42% and significant (p = 0.047).

CONCLUSION

Our findings estimate a rate of family history in CH to be approximately 6.27% (95% CI: 4.65-8.40%). While estimates were larger for female probands, we demonstrated high heterogeneity in this subgroup. These findings further support a genetic role in the aetiology of CH.

Analysis of HCRTR2, GNB3, and ADH4 Gene Polymorphisms in a Southeastern European Caucasian Cluster Headache Population

Studies point to an increased hereditary risk of cluster headache. HCRTR2 gene rs2653349 and ADH4 gene rs1800759 polymorphisms have been associated with cluster headache susceptibility. Also, GNB3 rs5443 polymorphism, associated with increased signal transduction via GPCRs, seems to influence triptan treatment response. DNA from 114 cluster headache patients and 570 non-related controls, representing a general Southeastern European Caucasian (SEC) population, was extracted from buccal swabs and genotyped using real-time PCR. Gene distribution for the rs2653349 was GG = 79.8%, GA = 18.4%, and AA = 1.8% for patients and GG = 79.1%, GA = 19.1%, and AA = 1.8% for controls. The frequency of the mutated A allele was 11.0% for patients and 11.3% for controls. The frequencies for rs5443 were CC = 44.7%, CT = 44.7%, and TT = 10.5% for patients and CC = 43.9%, CT = 42.6%, and TT = 13.5% for controls. The frequency of the mutated T allele was 32.9% for patients and 34.8% for controls. A 2.7-fold more frequent appearance of the mutated T allele was observed in patients with better triptan treatment response, although not statistically significant. For rs1800759, the frequencies were CC = 36.0%, CA = 43.0%, and AA = 21.0% for patients and CC = 34.0%, CA = 50.2%, and AA = 15.8% for controls. The frequency of the mutated A allele was 42.5% and 40.9% for patients and controls, respectively. The mutated T allele of GNB3 rs5443 polymorphism was more prevalent in patients with better triptan treatment response, indicating a possible trend of association between this polymorphism and triptan treatment response in SEC population. According to our observation, no association of HCRTR2 rs2653349 and ADH4 rs1800759 polymorphisms and cluster headache in SEC population could be documented.

Genetics of cluster headache

BACKGROUND

Cluster headache is the most severe primary headache disorder. A genetic basis has long been suggested by family and twin studies; however, little is understood about the genetic variants that contribute to cluster headache susceptibility.

METHODS

We conducted a literature search of the MEDLINE database using the PubMed search engine to identify all human genetic studies for cluster headache. In this article we provide a review of those genetic studies, along with an overview of the pathophysiology of cluster headache and a brief review of migraine genetics, which have both been significant drivers of cluster headache candidate gene selection.

RESULTS

The investigation of cluster headache genetic etiology has been dominated by candidate gene studies. Candidate selection has largely been driven by the pathophysiology, such as the striking rhythmic nature of the attacks, which spurred close examination of the circadian rhythm genes CLOCK and HCRTR2. More recently, unbiased genetic approaches such as genome-wide association studies (GWAS) have yielded new genetic avenues of interest including ADCYAP1R1 and MME.

CONCLUSIONS

The majority of candidate genes studied for cluster headache suffer from poor reproducibility. Broader genetic interrogation through larger unbiased GWAS, exome, and whole genome studies may provide more robust candidates, and in turn provide a clearer understanding of the causes of cluster headache.

Analysis of HCRTR2 Gene Variants and Cluster Headache in Sweden

Objective

The purpose of this study was to investigate the HCRTR2 gene variants rs3122156, rs2653342, and rs2653349 in a large homogenous Swedish case‐control cohort in order to further evaluate the possible contribution of HCRTR2 to cluster headache.

Background

Cluster headache is a severe neurovascular disorder and the pathophysiology is not yet fully understood. Due to striking circadian and circannual patterns of this disease, the hypothalamus has been a research focus in cluster headache. Several studies with many different cohorts from Europe have investigated the hypocretin receptor 2 (HCRTR2) gene, which is expressed in the hypothalamus. In particular, one HCRTR2 single nucleotide polymorphism, rs2653349, has been subject to a number of genetic association studies on cluster headache, with conflicting results. Two other HCRTR2 gene variants, rs2653342 and rs2653349, have been reported to be linked to cluster headache in an Italian study.

Methods

We genotyped a total of 517 patients diagnosed with cluster headache and 581 controls, representing a general Swedish population, for rs3122156, rs2653342, and rs2653349 using quantitative real‐time PCR. Statistical analyses of genotype, allele, and haplotype frequencies for the 3 gene variants were performed comparing patients and controls.

Results

For rs3122156, the minor allele frequency in patients was 25.9% compared to 29.9% in controls (P = .0421). However, this significance did not hold after correction for multiple testing. The minor allele frequencies for rs2653342 (14.7% vs 14.7%) and rs2653349 (19.5% vs 18.8%) were similar for patients and controls. Furthermore, we found one haplotype that was significantly less common in patients than controls (P = .0264). This haplotype included the minor allele for rs3122156 and the major alleles for rs2653342 and rs2653349. Significance did not hold after applying a permutation test.

Conclusions

Our data show a trend for association between cluster headache and the HCRTR2 polymorphism rs3122156, where the minor allele seems to be a protective factor. However, the other 2 HCRTR2 gene variants, including the previously reported rs2653349, were not associated with cluster headache in our Swedish material. A comparison with previous studies points to variance in genotype and allele frequencies among the different populations, which most likely contributes to the opposing results regarding rs2653349. Although the results from this study do not strongly support an association, HCRTR2 remains an interesting candidate gene for involvement in the pathophysiology of cluster headache.

Cluster headache

Cluster headache is an excruciating, strictly one-sided pain syndrome with attacks that last between 15 minutes and 180 minutes and that are accompanied by marked ipsilateral cranial autonomic symptoms, such as lacrimation and conjunctival injection. The pain is so severe that female patients describe each attack as worse than childbirth. The past decade has seen remarkable progress in the understanding of the pathophysiological background of cluster headache and has implicated the brain, particularly the hypothalamus, as the generator of both the pain and the autonomic symptoms. Anatomical connections between the hypothalamus and the trigeminovascular system, as well as the parasympathetic nervous system, have also been implicated in cluster headache pathophysiology. The diagnosis of cluster headache involves excluding other primary headaches and secondary headaches and is based primarily on the patient's symptoms. Remarkable progress has been achieved in developing effective treatment options for single cluster attacks and in developing preventive measures, which include pharmacological therapies and neuromodulation.

Genetic association of HCRTR2, ADH4 and CLOCK genes with cluster headache: a Chinese population-based case-control study

Background

Cluster headache (CH), a rare primary headache disorder, is currently thought to be a genetic susceptibility which play a role in CH susceptibility. A large numbers of genetic association studies have confirmed that the HCRTR2 (Hypocretin Receptor 2) SNP rs2653349, and the ADH4 (Alcohol Dehydrogenase 4) SNP rs1126671 and rs1800759 polymorphisms are linked to CH. In addition, the CLOCK (Circadian Locomotor Output Cycles Kaput) gene is becoming a research hotspot for CH due to encoding a transcription factor that serves as a basic driving force for circadian rhythm in humans. The purpose of this study was to evaluate the association between CH and the HCRTR2, ADH4 and CLOCK genes in a Chinese CH case–control sample.

Methods

We genotyped polymorphisms of nine single nucleotide polymorphisms (SNPs) in the HCRTR2, ADH4 and CLOCK genes to perform an association study on a Chinese Han CH case-control sample (112 patients and 192 controls),using Sequenom MALDI-TOF mass spectrometry iPLEX platform. The frequencies and distributions of genotypes and haplotypes were statistically compared between the case and control groups to identify associations with CH. The effects of SNPs on CH were further investigated by multiple logistic regression.

Results

The frequency of the HCRTR2 SNP rs3800539 GA genotype was significantly higher in cases than in controls (48.2% vs.37.0%). The GA genotypes was associated with a higher CH risk (OR = 1.483, 95% CI: 0.564-3.387, p = 0.038), however, after Bonferroni correction, the association lost statistical significance. Haplotype analysis of the HCRTR2 SNPs showed that among eight haplotypes, only H1-GTGGGG was linked to a reduced CH risk (44.7% vs. 53.1%, OR = 0.689, 95% CI =0.491~0.966, p = 0.030). No significant association of ADH4, CLOCK SNPs with CH was statistically detected in the present study.

Conclusions

Association between HCRTR2, ADH4,CLOCK gene polymorphisms and CH was not significant in the present study, however, haplotype analysis indicated H1-GTGGGG was linked to a reduced CH risk.

Electronic supplementary material

The online version of this article (10.1186/s10194-017-0831-1) contains supplementary material, which is available to authorized users.

A genetic CLOCK variant associated with cluster headache causing increased mRNA levels

Background Cluster headache is characterized by recurrent unilateral headache attacks of severe intensity. One of the main features in a majority of patients is a striking rhythmicity of attacks. The CLOCK ( Circadian Locomotor Output Cycles Kaput) gene encodes a transcription factor that serves as a basic driving force for circadian rhythm in humans and is therefore particularly interesting as a candidate gene for cluster headache. Methods We performed an association study on a large Swedish cluster headache case-control sample (449 patients and 677 controls) screening for three single nucleotide polymorphisms (SNPs) in the CLOCK gene implicated in diurnal preference (rs1801260) or sleep duration (rs11932595 and rs12649507), respectively. We further wanted to investigate the effect of identified associated SNPs on CLOCK gene expression. Results We found a significant association with rs12649507 and cluster headache ( p = 0.0069) and this data was strengthened when stratifying for reported diurnal rhythmicity of attacks ( p = 0.0009). We investigated the effect of rs12649507 on CLOCK gene expression in human primary fibroblast cultures and identified a significant increase in CLOCK mRNA expression ( p = 0.0232). Conclusions Our results strengthen the hypothesis of the involvement of circadian rhythm in cluster headache.

A genome-wide analysis in cluster headache points to neprilysin and PACAP receptor gene variants

Background

Cluster Headache (CH) is a severe primary headache, with a poorly understood pathophysiology. Complex genetic factors are likely to play a role in CH etiology; however, no confirmed gene associations have been identified. The aim of this study is to identify genetic variants influencing risk to CH and to explore the potential pathogenic mechanisms.

Methods

We have performed a genome-wide association study (GWAS) in a clinically well-defined cohort of 99 Italian patients with CH and in a control sample of 360 age-matched sigarette smoking healthy individuals, using the Infinium PsychArray (Illumina), which combines common highly-informative genome-wide tag SNPs and exonic SNPs. Genotype data were used to carry out a genome-wide single marker case-control association analysis using common SNPs, and a gene-based association analysis focussing on rare protein altering variants in 745 candidate genes with a putative role in CH.

Results

Although no single variant showed statistically significant association at the genome-wide threshold, we identified an interesting suggestive association (P = 9.1 × 10⁻⁶) with a common variant of the PACAP receptor gene (ADCYAP1R1). Furthermore, gene-based analysis provided significant evidence of association (P = 2.5 × 10⁻⁵) for a rare potentially damaging missense variant in the MME gene, encoding for the membrane metallo-endopeptidase neprilysin.

Conclusions

Our study represents the first genome-wide association study of common SNPs and rare exonic variants influencing risk for CH. The most interesting results implicate ADCYAP1R1 and MME gene variants in CH susceptibility and point to a role for genes involved in pain processing. These findings provide new insights into the pathogenesis of CH that need further investigation and replication in larger CH samples.

Electronic supplementary material

The online version of this article (doi:10.1186/s10194-016-0705-y) contains supplementary material, which is available to authorized users.

Advances in the understanding of cluster headache

INTRODUCTION

Cluster headache is the worst primary headache form; it occurs in paroxysmal excruciatingly severe unilateral head pain attacks usually grouped in cluster periods. The familial occurrence of the disease indicates a genetic component but a gene abnormality is yet to be disclosed. Activation of trigeminal afferents and cranial parasympathetic efferents, the so-called trigemino-parasympathetic reflex, can explain pain and accompanying oculo-facial autonomic phenomena. In particular, pain in cluster headache is attributed, at least in part, to the increased CGRP plasma levels released by activated trigeminal system. Posterior hypothalamus was hypothesized to be the cluster generator activating the trigemino-parasympathetic reflex. Efficacy of monoclonal antibodies against CRGP is under investigation in randomized clinical trials. Areas covered: This paper will focus on main findings contributing to consider cluster headache as a neurovascular disorder with an origin from within the brain. Expert commentary: Accumulated evidence with hypothalamic stimulation in cluster headache patients indicate that posterior hypothalamus terminates rather than triggers the attacks. More extensive studies on the genetics of cluster headache are necessary to disclose anomalies behind the increased familial risk of the disease. Results from ongoing clinical trials in cluster headache sufferers using monoclonal antibodies against CGRP will open soon a new era.

Screening of Two ADH4 Variations in a Swedish Cluster Headache Case-Control Material

Background

Cluster headache (CH) is a severe neurovascular disorder and an increasing amount of evidence points to a genetic contribution to this disease. When CH was first described, it was observed that alcohol may precipitate an attack during the active phase of the disease. The alcohol dehydrogenase 4 (ADH4) gene encodes an enzyme which contributes to the metabolization of alcohol and is, therefore, an interesting candidate gene for CH. Two Italian groups have reported association of the single nucleotide polymorphism (SNP) rs1126671 located in the ADH4 gene with an increased risk of CH in Italy. In addition, one of the groups found an association between the ADH4 SNP rs1800759 and CH.

Objective

To perform a replication study on the ADH4 SNPs rs1126671 and rs1800759 in a large homogeneous Swedish case–control cohort in order to further investigate the possible contribution of ADH4 to CH.

Methods

A total of 390 unrelated patients diagnosed with CH and 389 controls representing a general Swedish population were recruited to the study. DNA samples from patients and controls were genotyped for the two ADH4 SNPs rs1126671 and rs1800759 using quantitative real‐time polymerase chain reaction. Statistical analyses of genotype, allele and haplotype frequencies for the two SNPs were performed and compared between patients and controls.

Results

For rs1126671, the minor allele frequency (A allele) was 32.8% (n = 254) in controls compared with 31.9% (n = 249) in CH patients. The minor allele frequency (A allele) of rs1800759 was 42.3% (n = 324) in controls and 41.9% (n = 327) in CH patients. Statistical analysis showed no significant differences in allele as well as in genotype or haplotype frequencies between the patient and control group for either SNP. This was also seen after stratifying the patient group for experiencing alcohol as a trigger factor.

Conclusions

The data did not support an association of the ADH4 SNPs rs1126671 and rs1800759 with CH. A comparison with previous studies revealed variance in genotype, allele, and haplotype frequencies among the different populations which might contribute to the contradictory results. Although a significant association with CH in Swedish case–control group was not found, ADH4 as a candidate gene for CH could not be excluded.

Lack of association between cluster headache and PER3 clock gene polymorphism

Background

Cluster headache (CH) is regarded as a chronobiological disorder. The hypothalamic biological clock may thus be involved in the pathophysiology, but few studies have actually investigated this in CH patients. A variable number tandem repeat (VNTR) polymorphism of the PER3 clock gene has been associated to preferred daily rhythm (chronotype) in several studies. We aimed to study the distribution of PER3 VNTR polymorphisms and chronotypes in a CH population.

Methods

We used blood samples from a biobank of CH patients for genetic tests, and invited all tested patients to complete the Horne-Ostberg Morningness-eveningness Questionnaire (MEQ), the Pittsburgh sleep quality Index (PSQI) and the Shift Work Index. Genotypes were compared to a previously tested population of 432 healthy students.

Results

One hundred forty nine patients were genotyped, and we found no difference in PER3 VNTR polymorphisms between patients and controls. Seventy-four patients completed the MEQ (54 men, 20 women, mean age 52.3 years ± 13.4), and chronotypes were as follows: 12 % morning-, 37 % intermediate-, and 51 % evening types. Compared with a previous Danish study of CH patients and controls, there were no difference in chronotype distribution. Sixty percent of patients were defined as bad sleepers (PSQI >5), and 51 % of patients currently employed were shift workers.

Conclusions

No association between CH, PER3 VNTR polymorphism and chronotype was found in this study.