Migraine polygenic risk score associates with efficacy of migraine-specific drugs.

OBJECTIVE: To assess whether the polygenic risk score (PRS) for migraine is associated with acute and/or prophylactic migraine treatment response. METHODS: We interviewed 2,219 unrelated patients at the Danish Headache Center using a semistructured interview to diagnose migraine and assess acute and prophylactic drug response. All patients were genotyped. A PRS was calculated with the linkage disequilibrium pred algorithm using summary statistics from the most recent migraine genome-wide association study comprising ∼375,000 cases and controls. The PRS was scaled to a unit corresponding to a twofold increase in migraine risk, using 929 unrelated Danish controls as reference. The association of the PRS with treatment response was assessed by logistic regression, and the predictive power of the model by area under the curve using a case-control design with treatment response as outcome. RESULTS: A twofold increase in migraine risk associates with positive response to migraine-specific acute treatment (odds ratio [OR] = 1.25 [95% confidence interval (CI) = 1.05-1.49]). The association between migraine risk and migraine-specific acute treatment was replicated in an independent cohort consisting of 5,616 triptan users with prescription history (OR = 3.20 [95% CI = 1.26-8.14]). No association was found for acute treatment with non-migraine-specific weak analgesics and prophylactic treatment response. CONCLUSIONS: The migraine PRS can significantly identify subgroups of patients with a higher-than-average likelihood of a positive response to triptans, which provides a first step toward genetics-based precision medicine in migraine.

Polygenic risk score: use in migraine research.

BACKGROUND: The latest Genome-Wide Association Study identified 38 genetic variants associated with migraine. In this type of studies the significance level is very difficult to achieve (5 × 10- 8) due to multiple testing. Thus, the identified variants only explain a small fraction of the genetic risk. It is expected that hundreds of thousands of variants also confer an increased risk but do not reach significance levels. One way to capture this information is by constructing a Polygenic Risk Score. Polygenic Risk Score has been widely used with success in genetics studies within neuropsychiatric disorders. The use of polygenic scores is highly relevant as data from a large migraine Genome-Wide Association Study are now available, which will form an excellent basis for Polygenic Risk Score in migraine studies. RESULTS: Polygenic Risk Score has been used in studies of neuropsychiatric disorders to assess prediction of disease status in case-control studies, shared genetic correlation between co-morbid diseases, and shared genetic correlation between a disease and specific endophenotypes. CONCLUSION: Polygenic Risk Score provides an opportunity to investigate the shared genetic risk between known and previously unestablished co-morbidities in migraine research, and may lead to better and personalized treatment of migraine if used as a clinical assistant when identifying responders to specific drugs. Polygenic Risk Score can be used to analyze the genetic relationship between different headache types and migraine endophenotypes. Finally, Polygenic Risk Score can be used to assess pharmacogenetic effects, and perhaps help to predict efficacy of the Calcitonin Gene-Related Peptide monoclonal antibodies that soon become available as migraine treatment.

Part I: Pituitary adenylate cyclase-activating polypeptide-38 induced migraine-like attacks in patients with and without familial aggregation of migraine.

Background Intravenous infusion of adenylate cyclase-activating polypeptide-38 (PACAP38) provokes migraine-like attacks in 65-70% of migraine sufferers. Whether aggregation of migraine in first-degree relatives contributes to this discrepancy in PACAP38-induced response is unknown. We hypothesized that genetic enrichment plays a role in triggering of migraine and that migraine without aura patients with a high family load ( ≥ 2 first-degree relatives with migraine) would report more migraine-like attacks after intravenous infusion of human PACAP38. Methods In this study, we allocated 32 previously genotyped migraine without aura patients to receive intravenous infusion of 10 pmol/kg/min PACAP38 and recorded migraine-like attacks including headache characteristics and associated symptoms. Information of familial aggregation was obtained by telephone interview of first-degree relatives using a validated semi-structured questionnaire. Results PACAP38 infusion induced a migraine-like attack in 75% (nine out of 12) of patients with high family load compared to 70% (14 out of 20) with low family load ( P = 0.761). In an explorative investigation, we found that the migraine response after PACAP38 was not associated with the risk allele of rs2274316 ( MEF2D), which confers increased risk of migraine without aura and may regulate PACAP38 expression. Conclusion Migraine response to PACAP38 infusion in migraine without aura patients is not associated with high family load or the risk allele of rs2274316 ( MEF2D).

Investigation of SNP rs2060546 Immediately Upstream to NTN4 in a Danish Gilles de la Tourette Syndrome Cohort.

Gilles de la Tourette syndrome (GTS) is a neuropsychiatric disorder characterized by multiple motor and vocal tics. GTS is a complex disorder, with environmental factors and several genes involved. Although variations within a few genes such as AADAC, NRXN1, SLITRK1, HDC, and IMMP2L have been tentatively associated with GTS (in a small number of patients), the causative genes underlying GTS pathophysiology remain unknown. In a previous genome-wide association study (GWAS) a single nucleotide polymorphism (SNP, rs2060546) near the Netrin-4 (NTN4 - MIM 610401) gene was shown to be associated with GTS [odds ratio (OR) = 1.7; p-value = 5.8 × 10-7] thus warranting further investigations. As NTN4 is one of the axon guidance molecules expressed in the central nervous system and it interacts with the encoded proteins of SLIT and WNT genes guiding the growth cone toward its target, it is an attractive candidate susceptibility gene for GTS. In this study we attempted to replicate the association of rs2060546 with GTS by genotyping a Danish cohort of 240 GTS patients and 1006 healthy controls. Our results did not reveal an association (OR = 1.363; p-value = 0.3329) in the Danish cohort alone, which may be due to the small sample size. However, a meta-analysis including the present cohort and a total of 1316 GTS patients and 5023 controls from the GTS GWAS Replication Initiative (GGRI) and the first GTS-GWAS yielded a significant signal (OR = 3.74; p-value = 0.00018) and same direction of effect in the three cohorts. Thus, our study strengthens the evidence of the possible involvement of NTN4 in GTS etiology, suggesting that further studies in even larger samples and functional studies are warranted to investigate the role of this region in GTS pathogenesis.

The influence of genetic constitution on migraine drug responses.

OBJECTIVE: Specific acute treatments of migraine are 5HT1B/D receptor agonists; triptans and ergotamine, but only two-thirds of patients respond well without side effects. No migraine-prophylactic drugs are specific to migraine. Prophylactic drugs are selected by time-consuming "trial and error." Personalized treatment is therefore much needed. The objective of this study was to test the effect of 12 single nucleotide polymorphisms (SNPs) significantly associated with migraine on migraine drug responses. METHODS: Semi-structured migraine interviews including questions on drug responses, blood samples and genotyping were performed on 1806 unrelated migraine cases recruited from the Danish Headache Center. Association analyses were carried out using logistic regression, assuming an additive model for the genetic effect. The effect on drug responses was tested for a combined genetic score and for each of the 12 SNPs. Significant findings were subsequently tested in an independent replication sample of 392 unrelated Danish migraine cases. RESULTS: A single risk variant, rs2651899 in PRDM16, was significantly associated with efficacy of triptans with an odds ratio (OR) of treatment success of 1.3, and a higher combined genetic score was significantly associated with efficacy of triptans with an OR of success of up to 2.6. A number of SNPs showed nominal preferential association with the efficacy of triptans and others with prophylactic drugs. Analyses of triptans and ergotamine complemented each other and gave a stronger signal when analyzed together. The associations between response to triptans and genetic load and rs2651899 were partially confirmed in the independent sample. CONCLUSION: We show for the first time an association between genetic constitution and migraine drug response. This is a first step toward future individualized medicine.

The association between candidate migraine susceptibility loci and severe migraine phenotype in a clinical sample.

INTRODUCTION: The objective of the study was to follow up and to test whether 12 previously identified migraine-associated single nucleotide polymorphisms were associated as risk factors and/or modifying factors for severe migraine traits in a Danish clinic-based population. METHODS: Semi-structured migraine interviews, blood sampling and genotyping were performed on 1806 unrelated migraineurs recruited from the Danish Headache Center. Genotyping was also performed on a control group of 6415 people with no history of migraine. Association analyses were carried out using logistic regression and odds ratios were calculated assuming an additive model for risk. The proxies for severe migraine traits (early onset of migraine; many lifetime attacks, prolonged migraine and tendency to chronification of migraine) were tested against the 12 single nucleotide polymorphisms and a combined genetic score in both a case-control and case-only logistic regression model. RESULTS: We successfully replicated five out of the 12 previously reported loci and confirmed the same direction of effects for all the 12 single nucleotide polymorphisms. In line with the recently published genome-wide association meta-analysis, the associations were significant for all migraine and migraine without aura but not for migraine with typical aura. Two single nucleotide polymorphisms (rs2274316 and rs11172113) conferred risk of many lifetime attacks inthe case-control analysis. In the case-only analysis, only three single nucleotide polymorphisms showed nominal association with many lifetime attacks and prolonged migraine attacks. CONCLUSION: Our study supports previously reported findings on the association of several single nucleotide polymorphisms with migraine. It also suggests that the migraine susceptibility loci may be risk factors for severe migraine traits.

Future possibilities in migraine genetics.

Migraine with and without aura (MA and MO, respectively) have a strong genetic basis. Different approaches using linkage-, candidate gene- and genome-wide association studies have been explored, yielding limited results. This may indicate that the genetic component in migraine is due to rare variants; capturing these will require more detailed sequencing in order to be discovered. Next-generation sequencing (NGS) techniques such as whole exome and whole genome sequencing have been successful in finding genes in especially monogenic disorders. As the molecular genetics research progresses, the technology will follow, rendering these approaches more applicable in the search for causative migraine genes in MO and MA. To date, no studies using NGS in migraine genetics have been published. In order to gain insight into the future possibilities of migraine genetics, we have looked at NGS studies in other diseases and have interviewed three experts in the field of genetics and complex traits. The experts' ideas suggest that the preferred NGS approach depends on the expected effect size and the frequency of the variants of interest. Family-specific variants can be found by sequencing a small number of individuals, while a large number of unrelated cases are needed to find common and rare variants. NGS is currently hampered by high cost and technical problems concurrent with analyzing large amounts of data generated, especially by whole genome sequencing. As genome-wide association chips, exome sequencing and whole genome sequencing gradually become more affordable, these approaches will be used on a larger scale. This may reveal new risk variants in migraine which may offer previously unsuspected biological insights.

Genome-wide association study identifies four loci associated with eruption of permanent teeth.

The sequence and timing of permanent tooth eruption is thought to be highly heritable and can have important implications for the risk of malocclusion, crowding, and periodontal disease. We conducted a genome-wide association study of number of permanent teeth erupted between age 6 and 14 years, analyzed as age-adjusted standard deviation score averaged over multiple time points, based on childhood records for 5,104 women from the Danish National Birth Cohort. Four loci showed association at P<5×10(-8) and were replicated in four independent study groups from the United States and Denmark with a total of 3,762 individuals; all combined P-values were below 10(-11). Two loci agreed with previous findings in primary tooth eruption and were also known to influence height and breast cancer, respectively. The two other loci pointed to genomic regions without any previous significant genome-wide association study results. The intronic SNP rs7924176 in ADK could be linked to gene expression in monocytes. The combined effect of the four genetic variants was most pronounced between age 10 and 12 years, where children with 6 to 8 delayed tooth eruption alleles had on average 3.5 (95% confidence interval: 2.9-4.1) fewer permanent teeth than children with 0 or 1 of these alleles.

Injuries of the hand and forearm in young children caused by steam roller presses in laundries.

Fourteen children (median age 43 months, range 14-82 months; 7 girls and 7 boys) were treated for mangle injuries (one hot steam, and 13 cold roller presses) to the hand and forearm between 1996-2002 at the Department of Hand Surgery, Malmö, Sweden. All children had unilateral skin damage with avulsion or necrosis of skin in nine. Seven of the 14 had signs of compartment and carpal tunnel syndromes and three had fractures (phalanges or hamate bone). Initial treatment included fasciotomy, decompression, and skin revision with split skin grafts and later further skin cover, including one pedicled ulnar flap. IN eight the injuries healed uneventfully, while six had slight consequences (such as minor extension deficit of fingers or slight contracture of the scar). Ten of the 14 children came from immigrant families. Mangle injuries can be prevented through better supervision of children by parents when the mangle is being used, and dissemination of information of the potential hazards in relevant languages in residential areas with large immigrant populations.