Caroline Ran

Lrrk2 and α-synuclein are co-regulated in rodent striatum

LRRK2, alpha-synuclein, UCH-L1 and DJ-1 are implicated in the etiology of Parkinsons disease. We show for the first time that increase in striatal alpha-synuclein levels induce increased Lrrk2 mRNA levels while Dj-1 and Uch-L1 are unchanged. We also demonstrate that a mouse strain lacking the dopamine signaling molecule DARPP-32 has significantly reduced levels of both Lrrk2 and alpha-synuclein, while mice carrying a disabling mutation of the DARPP-32 phosphorylation site T34A or lack alpha-synuclein do not show any changes. To test if striatal dopamine depletion influences Lrrk2 or alpha-synuclein expression, we used the neurotoxin 6-hydroxydopamine in rats and MitoPark mice in which there is progressive degeneration of dopamine neurons. Because striatal Lrrk2 and alpha-synuclein levels were not changed by dopamine depletion, we conclude that Lrrk2 and alpha-synuclein mRNA levels are possibly co-regulated, but they are not influenced by striatal dopamine levels.

A replication study of GWAS findings in migraine identifies association in a Swedish case-control sample.

BackgroundMigraine is a common neurovascular disorder with symptoms including headache of moderate to severe intensity and recurring attacks. There is no cure for migraine today and the pathology is poorly understood. Common forms of migraine have a complex genetic background and heritability has been estimated to be around 50%. Recent genome-wide association studies (GWAS) on European and American migraine cohorts have led to the identification of new genetic risk factors for migraine.MethodsWe performed an association study in a Swedish population based cohort, investigating the frequency of eight single nucleotide polymorphisms (SNPs) recently identified as genetic risk factors for migraine in three GWAS, using available array data (Illumina Omni Express chip). The eight SNPs were rs2651899, rs3790455, rs10166942, rs7640543, rs9349379, rs1835740, rs6478241 and rs11172113. Because information on rs3790455, rs10166942 and rs7640543 was not directly available, we selected SNPs in high Linkage Disequilibrium (LD) with these three SNPs, and replaced them with rs2274316, rs1003540 and rs4075749, respectively.ResultsWe were able to replicate the association with rs2651899 and found a trend for association with rs1835740 in our Swedish cohort.ConclusionsThis is the first reported genetic association study of a Swedish migraine case control material. We have thus replicated findings of susceptibility loci for migraine in an independent genetic material, thereby increasing knowledge about genetic risk factors for this common neurological disorder.

Strong association between glucocerebrosidase mutations and Parkinson's disease in Sweden

Several genetic studies have demonstrated an association between mutations in glucocerebrosidase (GBA), originally implicated in Gauchers disease, and an increased risk of Parkinsons disease (PD). We have investigated the possible involvement of genetic GBA variations in PD in the Swedish population. Three GBA variants, E326K, N370S, and L444P were screened in the largest Swedish Parkinson cohort reported to date; 1625 cases and 2025 control individuals. We found a significant association with high effect size of the rare variant L444P with PD (odds ratio 8.17; 95% confidence interval: 2.51–26.23; p-value = 0.0020) and a significant association of the common variant E326K (odds ratio 1.60; 95% confidence interval: 1.16–2.22; p-value = 0.026). The rare variant N370S showed a trend for association. Most L444P carriers (68%) were found to reside in northern Sweden, which is consistent with a higher prevalence of Gauchers disease in this part of the country. Our findings support the role of GBA mutations as risk factors for PD and point to lysosomal dysfunction as a mechanism contributing to PD etiology.

Association of a protective paraoxonase 1 (PON1) polymorphism in Parkinson's disease

Pesticide exposure has been suggested to increase the risk to develop Parkinsons disease (PD). The arylesterase paraoxonase 1 (PON1) is mainly expressed in the liver and hydrolyzes organophosphates such as pesticides. The polymorphism Leu54Met (rs854560) in PON1, impairing enzyme activity and leading to decreased PON1 expression levels, has been reported to be associated with Parkinsons disease (PD). PON1 is part of a cluster on chromosome 7q21.3 together with PON2 and PON3. We investigated the occurrence of four additional polymorphisms in PON1 and two in PON2 in a Swedish PD case-control material. We found a significant association (p=0.007) with a PON1 promoter polymorphism, rs854571. The minor allele was more common among controls than PD cases which suggest a protective effect. This is strengthened by the fact that rs854571 is in strong linkage disequilibrium with another PON1 promoter polymorphism, rs854572, reported to increase PON1 gene expression. Our findings support the hypothesis that PON1 is involved in the etiology of PD and that higher PON1 levels are reducing the risk for PD.

Possible Involvement of a Mitochondrial Translation Initiation Factor 3 Variant Causing Decreased mRNA Levels in Parkinson's Disease

Genes important for mitochondrial function have been implicated in Parkinsons disease (PD). Mitochondrial translation initiation factor 3 (MTIF3) is a nuclear encoded protein required for the initiation of complex formation on mitochondrial ribosomes. Dysfunction of MTIF3 may impair mitochondrial function and dopamine neurons appear to be particularly vulnerable to oxidative stress, which may relate to their degeneration in PD. An association was recently reported between the synonymous rs7669(C>T) in MTIF3 and PD in a German case-control material. We investigated rs7669 in a Swedish Parkinson case-control material. The study revealed no significant association of the individual genotypes or alleles with PD. When comparing the combined TT/CT-genotypes versus the CC-genotype, we observed a significant association (P = .0473) with PD. We also demonstrated that the TT-genotype causes a significant decrease in MTIF3 mRNA expression compared to the CC-genotype (P = .0163). Our findings support the hypothesis that MTIF3 may be involved in the etiology of PD.

Genetic studies of the protein kinase AKT1 in Parkinson's disease.

The protein kinase AKT1 belongs to the Akt family and is a potent mediator of cell growth and survival and fully activated when phosphorylated. The AKT family has been found to be phosphorylated to a lesser extent in the dopaminergic cells of Parkinsons disease patients compared to control individuals, which might influence cell survival. Several publications support the implication of AKT1 in disorders of the dopaminergic system including bipolar disease and schizophrenia. In 2008 an association study performed in a Greek Parkinsons disease case-control material reported the identification of a protective AKT1 haplotype. Based on their work we have performed a replication study in a Swedish Parkinsons disease cohort. We genotyped the four single nucleotide polymorphims (SNPs): rs2494743, rs2498788, rs2494746 and rs1130214 in a case-control material consisting of 243 Parkinson patients and 315 controls. We did not find any associations with Parkinsons disease for either the individual SNPs or any of the haplotypes. In contrast to previously published results, our data do not support the hypothesis of genetic variants in AKT1 confering protection against Parkinsons disease.

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.

Adh1 and Adh1/4 knockout mice as possible rodent models for presymptomatic Parkinson's disease

Alcohol dehydrogenases (ADH) catalyze the reversible metabolism of many types of alcohols and aldehydes to prevent the possible toxic accumulation of these compounds. ADHs are of interest in Parkinsons disease (PD) since these compounds can be harmful to dopamine (DA) neurons. Genetic variants in ADH1C and ADH4 have been found to associate with PD and lack of Adh4 gene activity in a mouse model has recently been reported to induce changes in the DA system. Adh1 knockout (Adh1-/-) and Adh1/4 double knockout (Adh1/4-/-) mice were investigated for possible changes in DA system related activity, biochemical parameters and olfactory function compared to wild-type (WT) mice. Locomotor activity was tested at ∼7 (adult) and >15 months of age to mimic the late onset of PD. Adh1-/- and Adh1/4-/- mice displayed a significantly higher spontaneous locomotor activity than WT littermates. Both apomorphine and d-amphetamine increased total distance activity in Adh1-/- mice at both age intervals and in Adh1/4-/- mice at 7 months of age compared to WT mice. No significant changes were found regarding olfactory function, however biochemical data showed decreased 3,4-dihydroxyphenylacetic acid (DOPAC)/DA ratios in the olfactory bulb and decreased homovanillic acid (HVA)/DA ratios in the olfactory bulb, frontal cortex and striatum of Adh1/4-/- mice compared to WT mice. Our results suggest that lack of Adh1 alone or Adh1 and Adh4 together lead to changes in DA system related behavior, and that these knockout mice might be possible rodent models to study presymptomatic PD.

Cluster headache – clinical pattern and a new severity scale in a Swedish cohort

Background The aim of this study was to investigate clinical features of a cluster headache cohort in Sweden and to construct and test a new scale for grading severity. Methods Subjects were identified by screening medical records for the ICD 10 code G44.0, that is, cluster headache. Five hundred participating research subjects filled in a questionnaire including personal, demographic and medical aspects. We constructed a novel scale for grading cluster headache in this cohort: The Cluster Headache Severity Scale, which included number of attacks per day, attack and period duration. The lowest total score was three and the highest 12, and we used the Cluster Headache Severity Scale to grade subjects suffering from cluster headache. We further implemented the scale by defining a cluster headache maximum severity subgroup with a high Cluster Headache Severity Scale score ≥ 9. Results A majority (66.7%) of the patients reported that attacks appear at certain time intervals. In addition, cluster headache patients who were current tobacco users or had a history of tobacco consumption had a later age of disease onset (31.7 years) compared to non-tobacco users (28.5 years). The Cluster Headache Severity Scale score was higher in the patient group reporting sporadic or no alcohol intake than in the groups reporting an alcohol consumption of three to four standard units per week or more. Maximum severity cluster headache patients were characterised by higher age at disease onset, greater use of prophylactic medication, reduced hours of sleep, and lower alcohol consumption compared to the non-cluster headache maximum severity group. Conclusion There was a wide variation of severity grade among cluster headache patients, with a very marked impact on daily living for the most profoundly affected.

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

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.