Pigmentation genes link Parkinson’s disease to melanoma, opening a window on both etiologies

Risk of Migraine in Europeans with Low Melanin Levels—A Population Based Case-Control Study

Populations with a relatively low concentration of melanin, e.g., inhabitants of Europe, North America, and Australia, are the most vulnerable to the harmful effects of UV radiation. Individuals with fair phototype are at greatest risk of developing skin cancer. Several neurological studies present that light skin may modify the risk of Alzheimer’s and Parkinson’s diseases. However, the relationship between migraine and skin pigmentation has not been investigated yet. The objective of this study is to provide evidence of the relationship between skin pigmentation and migraine prevalence in adults. We examined a group of 148 adults (33 men, 115 women) with migraine and a control group of 107 adults (43 men, 64 women). Parameters of skin pigmentation (melanin index, erythema index, CIElab, and RGB scales) were measured using a DSM II Cortex Technology dermospectrophotometer. Risk of migraine in lightly pigmented adults was elevated. Individuals with a low melanin index had over 3-fold increased risk of migraine (women: OR 3.53, men: OR 3.73). Fair phototype, which results from lightly pigmented skin, was associated with migraine prevalence. Migraineurs should take extra care to protect their skin from the negative effects of solar radiation.

Schizophrenia as Potential Trigger for Melanoma Development and Progression! The Psycho-Neuro-Endocrine-Oncology (P.N.E.O) Network!

BACKGROUND

Skin, nervous tissue, dopamine and melanoma share a common neuroectodermal origin. Hence, processes that modulate nervous tissue formation, patient mental status, motor regulation of individuals, and skin cancerogenesis are inextricably linked. Psycho-neuro-endocrine oncology (or dermato-oncology), i.e. P.N.E.O., is a new model or trend in medicine and science presented for the first time in the world literature by us, that aims to examine the relationship between the mental state, the hormones and the malignant transformation. Schizophrenia and Parkinson's disease are the two main patterns of disease where the main symptoms are related to dopamine levels in the human body. According to our analyses of the available literature, the amount of dopamine is related to the incidence of melanocytic or non-melanocytic cutaneous tumours in patients with central nervous system diseases and those affecting the motor function and coordination. Such patterns of interaction are extremely indicative of the elucidation of the ubiquitous hypothesis or statement: "My illness is on a mental basis, caused by stress …".

CASE PRESENTATION

We present a 44-year-old patient with untreated schizophrenia for approximately 25 years, associated with advanced acral localised melanoma. Schizophrenia is generally associated with a higher level of dopamine, which is also a key precursor to melanin synthesis. After a careful analysis of all literature on melanoma in patients with 1) treated and untreated schizophrenia, 2) those with untreated and untreated forms of Parkinson's disease, it would be logical to conclude that the high level of dopamine in the described patient groups is a risk factor for the development of melanoma.

CONCLUSIONS

The possible mechanisms for the occurrence of malignant melanoma within the so-called psycho/neuro/endocrine oncology (P.N.E.O.), as well as the effective methods of prevention, are under discussion.

New insight into the allosteric effect of L-tyrosine on mushroom tyrosinase during L-dopa production

Kinetics studies of L-tyrosine (LTy) ortho-hydroxylation by mushroom tyrosinase (MT) confirmed that MT was severely, but not completely, inhibited at higher concentrations of LTy. Despite the availability of the crystal structure reports, no allosteric site has been identified on MT. To examine the assumption that a non-specific binding site works as a regulatory site, docking simulations were run for the second molecule of L-tyrosine (LTy₂) on the complexes of the first L-tyrosine molecule (LTy₁) with the heavy chain (H) of MT (LTy₁/HMT) and its dimer with the light chain (Ty₁/LHMT). In both, LTy₂ occupied a non-specific binding site (MTPc). MD simulations revealed LTy₂/HMT/LTy₁ and LTy₂/LHMT/LTy₁ were stable. Binding free-energy analysis supported the formation of LTy₂/HMT/LTy₁ and LTy₂/LHMT/LTy₁ at higher concentrations of LTy and disclosed the importance of ΔE_elec and ΔG_polar during binding of LTy₂ to MTPc. Upon LTy₂ binding to MTPc, the Cu-Cu distance remained unchanged while the spatial position of LTy₁ in the active site (MTPa) changed so that it would not be able to participate in ortho-hydroxylation. This study suggests a tuning role for L chain during binding of the ligands to MTPa and MTPc. Given these results, a plausible mechanism was proposed for the MT substrate inhibition.

Ubiquitination in melanoma pathogenesis and treatment

Melanoma is one of the most aggressive skin cancers with fiercely increasing incidence and mortality. Since the progressive understanding of the mutational landscape and immunologic pathogenic factors in melanoma, the targeted therapy and immunotherapy have been recently established and gained unprecedented improvements for melanoma treatment. However, the prognosis of melanoma patients remains unoptimistic mainly due to the resistance and nonresponse to current available drugs. Ubiquitination is a posttranslational modification which plays crucial roles in diverse cellular biological activities and participates in the pathogenesis of various cancers, including melanoma. Through the regulation of multiple tumor promoters and suppressors, ubiquitination is emerging as the key contributor and therefore a potential therapeutic target for melanoma. Herein, we summarize the current understanding of ubiquitination in melanoma, from mechanistic insights to clinical progress, and discuss the prospect of ubiquitination modification in melanoma treatment.

Looking beyond the brain to improve the pathogenic understanding of Parkinson's disease: implications of whole transcriptome profiling of Patients' skin

BACKGROUND

Parkinson's Disease is a progressive neurodegenerative disease, characterized by symptoms of motor impairment, resulting from the loss of dopaminergic neurons in the midbrain, however non-neuronal symptoms are also common. Although great advances have been made in the pathogenic understanding of Parkinson's Disease in the nervous system, little is known about the molecular alterations occurring in other non-neuronal organ systems. In addition, a higher rate of melanoma and non-melanoma skin cancer has been observed in the Parkinson's Disease population, indicating crosstalk between these diseases.

METHODS

To understand the molecular pathogenesis and gene expression alterations of Parkinson's Disease in peripheral tissues, and in order to explore the possible link between skin cancer and neurodegeneration, whole transcriptomic profiling of patients' skin was performed. Skin biopsies from 12 patients and matched controls were collected, and processed with high-throughput RNA-sequencing analysis.

RESULTS

This analysis resulted in a large collection of over 1000 differentially expressed genes, among which clear biological and functional networks could be distinguished. The central functional processes altered in patients skin can be grouped into six broad categories: impaired cellular metabolism and mitochondrial dysfunction, defective protein metabolism, disturbed skin homeostasis, dysfunctional nuclear processes, altered signalling and tumour pathways, as well as disordered immune regulation.

CONCLUSIONS

These results demonstrate that the molecular alterations leading to neurodegeneration in the CNS are systemic and manifest also in peripheral tissues, thereby indicating the presence of "skin-brain" crosstalk in Parkinson's Disease. In addition, the extensive homeostatic imbalance and basal stress can lead to increased susceptibility to external and internal mutagenic hazards in these patients, and thus provide a possible molecular link for the crosstalk between skin cancer and Parkinson's Disease.

Rare variants analysis of cutaneous malignant melanoma genes in Parkinson's disease

A shared genetic susceptibility between cutaneous malignant melanoma (CMM) and Parkinson's disease (PD) has been suggested. We investigated this by assessing the contribution of rare variants in genes involved in CMM to PD risk. We studied rare variation across 29 CMM risk genes using high-quality genotype data in 6875 PD cases and 6065 controls and sought to replicate findings using whole-exome sequencing data from a second independent cohort totaling 1255 PD cases and 473 controls. No statistically significant enrichment of rare variants across all genes, per gene, or for any individual variant was detected in either cohort. There were nonsignificant trends toward different carrier frequencies between PD cases and controls, under different inheritance models, in the following CMM risk genes: BAP1, DCC, ERBB4, KIT, MAPK2, MITF, PTEN, and TP53. The very rare TYR p.V275F variant, which is a pathogenic allele for recessive albinism, was more common in PD cases than controls in 3 independent cohorts. Tyrosinase, encoded by TYR, is the rate-limiting enzyme for the production of neuromelanin, and has a role in the production of dopamine. These results suggest a possible role for another gene in the dopamine-biosynthetic pathway in susceptibility to neurodegenerative Parkinsonism, but further studies in larger PD cohorts are needed to accurately determine the role of these genes/variants in disease pathogenesis.

Cutaneous malignant melanoma and Parkinson disease: Common pathways?

The mechanisms underlying the high prevalence of cutaneous malignant melanoma (CMM) in Parkinson disease (PD) are unclear, but plausibly involve common pathways. 129Ser-phosphorylated α-synuclein, a pathological PD hallmark, is abundantly expressed in CMM, but not in normal skin. In inherited PD, PARK genes harbor germline mutations; the same genes are somatically mutated in CMM, or their encoded proteins are involved in melanomagenesis. Conversely, genes associated with CMM affect PD risk. PD/CMM-targeted cells share neural crest origin and melanogenesis capability. Pigmentation gene variants may underlie their susceptibility. We review putative genetic intersections that may be suggestive of shared pathways in neurodegeneration/melanomagenesis. Ann Neurol 2016;80:811-820.

Cancer in Parkinson's disease

INTRODUCTION

We examined the prevalence of cancer in patients with Parkinson's disease (PD) and controls evaluated at the Mayo Clinic in Jacksonville, Florida, between 2003 and 2014.

METHODS

We retrospectively collected information regarding cancer diagnoses and diagnosis of PD from 971 unrelated PD patients and 478 controls, and all were white. For PD patients, we examined cancers diagnosed before and after PD diagnosis separately in addition to considering all cancer diagnoses.

RESULTS

Twenty different cancers were identified. In PD patients, the most common types of cancer were skin cancer (17.3% overall; 10.6% before PD), followed by nonmelanoma skin cancer (16.0% overall; 9.7% before PD), prostate cancer in men (12.8% overall; 9.2% before PD), breast cancer in women (10.6% overall; 6.3% before PD), and melanoma (2.4% overall; 1.1% before PD). Compared to controls, a significantly lower frequency of nonmelanoma skin cancer (odds ratio [OR]: 0.62, P = 0.0024) and any skin cancer (OR: 0.57, P = 0.0002) was observed in PD patients. These differences were greater when considering only cases with cancers that occurred before PD diagnosis (OR: 0.49, P < 0.0001; OR: 0.45, P < 0.0001, respectively), and there was a lower frequency of melanoma and any cancer preceding PD diagnosis compared to controls (OR: 0.31, P = 0.003; OR: 0.36, P < 0.0001). There was no evidence of a frequency difference for any other cancer.

CONCLUSIONS

PD patients had a lower frequency of skin cancers or any cancer prior to PD diagnosis compared to controls, suggesting that cancer may have a protective effect on PD risk.

Parkinson's disease and cancer: A register-based family study

We wanted to compare cancer incidence rates between Parkinson's disease (PD) patients and persons without PD, as well as between siblings of these groups. We conducted a family-based matched cohort study based on nationwide Swedish health registries and the Swedish Multi-Generation Register. We assessed risk of incident cancer in PD patients (n = 11,786) during 1964-2009 versus a matched cohort of PD-free individuals (n = 58,930) and in siblings of PD patients (n = 16,841) versus siblings of PD-free individuals (n = 84,205). Hazard ratios with 95% confidence intervals were estimated using Cox proportional hazards regression. Cancer occurrence was slightly higher in PD patients than in PD-free individuals (hazard ratio (HR) = 1.05, 95% confidence interval (CI): 1.00, 1.10), largely because of cancers arising within 1 year before or after the index date for PD, but risk of smoking-related cancers was lower (HR = 0.87, 95% CI: 0.79, 0.96). PD patients had a higher risk of melanoma both up to 1 year before the PD index date (HR = 1.53, 95% CI: 1.23, 1.91) and from 1 year after the index date onward (HR = 1.46, 95% CI: 1.01, 2.10). In the sibling comparison, cancer occurrence was largely similar. These results indicate that melanoma risk is higher among PD patients and that mechanisms other than familial ones explain the association.

Susceptibility loci for pigmentation and melanoma in relation to Parkinson's disease

Growing evidence suggests that Parkinson's disease (PD) patients have a lower risk for most types of cancer except for melanoma, which has a modest positive association with PD. Pigmentation genes have been hypothesized to contribute to this association. We therefore examined whether genetic susceptibility loci for pigmentation or melanoma was associated with PD risk in 2 large independent datasets. In the Parkinson's Genes and Environment (PAGE) study, we examined 11 single-nucleotide polymorphisms (SNPs) identified from previous genome-wide association studies (GWAS) of pigmentation or melanoma in relation to PD among 808 PD cases and 1623 controls; furthermore, we also examined the colors of hair, eye, or skin and melanoma in relation to PD. In the International Parkinson's Disease Genomic Consortium (IPDGC), we examined a broader selection of 360 pigmentation or melanoma GWAS SNPs in relation to PD among 5,333 PD cases and 12,019 controls. All participants were non-Hispanic Whites. As expected, in the PAGE study, most SNPs were associated with 1 or more pigmentation phenotypes. However, neither these SNPs nor pigmentation phenotypes were associated with PD risk after Bonferroni correction with the exception of rs4911414 at the ASIP gene (p = .001). A total of 18 PD cases (2.2%) and 26 controls (1.6%) had a diagnosis of melanoma with an odds ratio of 1.3 (95% confidence interval: 0.7-2.4). In the IPDGC analysis, none of the 360 SNPs, including rs4911414, were associated with PD risk after adjusting for multiple comparisons. In conclusion, we did not find significant associations between GWAS SNPs of pigmentation or melanoma and the risk for PD.

Abnormal differentiation of dopaminergic neurons in zebrafish trpm7 mutant larvae impairs development of the motor pattern

Transient receptor potential, melastatin-like 7 (Trpm7) is a combined ion channel and kinase implicated in the differentiation or function of many cell types. Early lethality in mice and frogs depleted of the corresponding gene impedes investigation of the functions of this protein particularly during later stages of development. By contrast, zebrafish trpm7 mutant larvae undergo early morphogenesis normally and thus do not have this limitation. The mutant larvae are characterized by multiple defects including melanocyte cell death, transient paralysis, and an ion imbalance that leads to the development of kidney stones. Here we report a requirement for Trpm7 in differentiation or function of dopaminergic neurons in vivo. First, trpm7 mutant larvae are hypomotile and fail to make a dopamine-dependent developmental transition in swim-bout length. Both of these deficits are partially rescued by the application of levodopa or dopamine. Second, histological analysis reveals that in trpm7 mutants a significant fraction of dopaminergic neurons lack expression of tyrosine hydroxylase, the rate-limiting enzyme in dopamine synthesis. Third, trpm7 mutants are unusually sensitive to the neurotoxin 1-methyl-4-phenylpyridinium, an oxidative stressor, and their motility is partially rescued by application of the iron chelator deferoxamine, an anti-oxidant. Finally, in SH-SY5Y cells, which model aspects of human dopaminergic neurons, forced expression of a channel-dead variant of TRPM7 causes cell death. In summary, a forward genetic screen in zebrafish has revealed that both melanocytes and dopaminergic neurons depend on the ion channel Trpm7. The mechanistic underpinning of this dependence requires further investigation.

Melanin affinity and its possible role in neurodegeneration

Certain drugs with melanin affinity are known to have caused pigmentary lesions in the eye and skin. This was the basis for the hypothesis that compounds with melanin affinity may cause damage also in other melanin-bearing tissues such as the substantia nigra. The heterogeneity of compounds that binds to melanin is large. Toxins, drugs, and several other compounds have melanin affinity. Compounds showing the highest affinity are mainly organic amines and metal ions. The binding of toxicants to melanin probably protects the cells initially. However, the binding is normally, slowly reversible and melanin may accumulate the toxicant and gradually release it into the cytosol. Several studies indicate that neuromelanin may play a significant role both in the initiation and in the progression of neurodegeneration. MPTP/MPP(+) that has been causally linked with Parkinsonism has high affinity for neuromelanin, and the induced dopaminergic denervation correlates with the neuromelanin content in the cells. This shows that the toxicological implications of the accumulation of toxicants in pigmented neurons and its possible role in neurodegeneration should not be neglected. Extracellular neuromelanin has been reported to activate dendritic cells and microglia. An initial neuronal damage induced by a neurotoxicant that leaks neuromelanin from the cells may therefore lead to a vicious cycle of neuroinflammation and further neurodegeneration. Although there are many clues to the particular vulnerability of dopaminergic neurons of substantia nigra in Parkinson's disease, the critical factors are not known. Further studies to determine the importance of neuromelanin in neurodegeneration and Parkinson's disease are warranted.

Malignant melanoma, breast cancer and other cancers in patients with Parkinson's disease

Previous studies report an atypical cancer pattern among patients with Parkinson's disease. Here, we evaluate the cancer pattern among people diagnosed with Parkinson's disease in an extension of our previous cohort study. For this Danish population-based cohort study, we identified 20,000 people with Parkinson's disease diagnosed in 1977-2006, from the National Danish Hospital Register. Cohort members were followed up for cancer in the Danish Cancer Registry until December 31, 2008, and their incidence rates of cancer were compared to age-, sex- and calendar period-specific rates in the general population as standardized incidence rate ratios (SIRs). In subanalyses, we estimated the risk for cancer among patients with early onset Parkinson's disease and we also compared breast tumor characteristics among women with Parkinson's disease to that of a control group. The overall cancer risk in our cohort was decreased [SIR = 0.86; 95% confidence interval (CI) = 0.83-0.90], as were those for smoking-related (SIR = 0.65; 95% CI = 0.60-0.70) and nonsmoking-related cancers (SIR = 0.79; 95% CI = 0.71-0.86). The cohort had increased risks for malignant melanoma (SIR = 1.41; 95% CI = 1.09-1.80), nonmelanoma skin cancer (SIR = 1.29; 95% CI = 1.18-1.39) and female breast cancer (SIR = 1.17; 95% CI = 1.02-1.34). Among patients with early onset Parkinson's disease, the risk for cancer was comparable to that of the general population. Of breast tumor characteristics, only grade of malignancy differed between Parkinson's disease women and controls. This study confirms a lower cancer risk among people with Parkinson's disease. Increased risks for malignant melanoma, nonmelanoma skin cancer and breast cancer might be due to shared risk factors with Parkinson's disease.

Meta-analysis of the relationship between Parkinson disease and melanoma

OBJECTIVE

To assess the epidemiologic evidence on melanoma in relation to Parkinson disease (PD) via systematic review and meta-analysis.

METHODS

Epidemiologic studies on melanoma and PD were searched using PubMed, Web of Science, Scoups, and Embase (1965 through June 2010). Eligible studies were those that reported risk estimates of melanoma among patients with PD or vice versa. Pooled odds ratios (ORs) with 95% confidence intervals (CIs) were calculated using random-effects models.

RESULTS

We identified 12 eligible publications on melanoma and PD: 8 had fewer than 10 cases with both PD and melanoma, and 7 provided gender-specific results. The pooled OR was 2.11 (95% CI 1.26-3.54) overall, 2.04 (1.55-2.69) for men, and 1.52 (0.85-2.75) for women. Analyses by temporal relationship found that melanoma occurrence was significantly higher after the diagnosis of PD (OR 3.61, 95% CI 1.49-8.77), but not before PD diagnosis (OR 1.07, 95% CI 0.62-1.84). Further analyses revealed that the lack of significance in the latter analysis was due to one study, which when excluded resulted in a significant association (OR 1.44, 95% CI 1.06-1.96). We also analyzed nonmelanoma skin cancers in relation to PD and found no significant relationship (OR 1.11, 95% CI 0.94-1.30).

CONCLUSIONS

Collective epidemiologic evidence supports an association of PD with melanoma. Further research is needed to examine the nature and mechanisms of this relationship.

Epidemiology and etiology of Parkinson's disease: a review of the evidence

The etiology of Parkinson's disease (PD) is not well understood but likely to involve both genetic and environmental factors. Incidence and prevalence estimates vary to a large extent-at least partly due to methodological differences between studies-but are consistently higher in men than in women. Several genes that cause familial as well as sporadic PD have been identified and familial aggregation studies support a genetic component. Despite a vast literature on lifestyle and environmental possible risk or protection factors, consistent findings are few. There is compelling evidence for protective effects of smoking and coffee, but the biologic mechanisms for these possibly causal relations are poorly understood. Uric acid also seems to be associated with lower PD risk. Evidence that one or several pesticides increase PD risk is suggestive but further research is needed to identify specific compounds that may play a causal role. Evidence is limited on the role of metals, other chemicals and magnetic fields. Important methodological limitations include crude classification of exposure, low frequency and intensity of exposure, inadequate sample size, potential for confounding, retrospective study designs and lack of consistent diagnostic criteria for PD. Studies that assessed possible shared etiological components between PD and other diseases show that REM sleep behavior disorder and mental illness increase PD risk and that PD patients have lower cancer risk, but methodological concerns exist. Future epidemiologic studies of PD should be large, include detailed quantifications of exposure, and collect information on environmental exposures as well as genetic polymorphisms.

The association between Parkinson's disease and melanoma

Parkinson's disease (PD) is a neurodegenerative disorder characterized by a loss of melanin-positive, dopaminergic neurons in the substantia nigra. Although there is convincing epidemiologic evidence of a negative association between PD and most cancers, a notable exception to this is that melanoma, a malignant tumor of melanin-producing cells in skin, occurs with higher-than-expected frequency among subjects with PD and that melanoma patients are more likely to have PD. A clear biological explanation for this epidemiological observation is lacking. Here, we present a comprehensive review of published literature exploring the association between PD and melanoma. On the basis of published findings, we conclude that (i) changes in pigmentation including melanin synthesis and/or melanin synthesis enzymes, such as tyrosinase and tyrosine hydroxylase, play important roles in altered vulnerability for both PD and melanoma; (ii) changes of PD-related genes such as Parkin, LRRK2 and α-synuclein may increase the risk of melanoma; (iii) changes in some low-penetrance genes such as cytochrome p450 debrisoquine hydroxylase locus, glutathione S-transferase M1 and vitamin D receptor could increase the risk for both PD and melanoma and (iv) impaired autophagy in both PD and melanoma could also explain the association between PD and melanoma. Future studies are required to address whether altered pigmentation, PD- or melanoma-related gene changes and/or changes in autophagy function induce oncogenesis or apoptosis. From a clinical point of view, early diagnosis of melanoma in PD patients is critical and can be enhanced by periodic dermatological surveillance, including skin biopsies.

Family history of melanoma and Parkinson disease risk

BACKGROUND

Co-occurrence of Parkinson disease (PD) and melanoma has been reported in numerous studies. If this was due to common genetic mechanisms, a positive family history of melanoma would be associated with an excessive PD risk, independent of environmental risk factors for PD.

METHODS

We prospectively examined associations between a family history of melanoma and PD among 157,036 men and women free of PD at baseline (1990 for men and 1982 for women) who participated in 2 ongoing US cohorts: the Health Professional Follow-up Study and the Nurses' Health Study. Information on family history of melanoma in parents or siblings was assessed via questionnaire. Relative risks and 95% confidence intervals were estimated using Cox proportional hazards models and pooled using a fixed-effects model.

RESULTS

During 14-20 years follow-up, we identified 616 incident PD cases. A family history of melanoma in a first-degree relative was associated with a higher risk of PD (multivariate relative risk = 1.85; 95% confidence interval: 1.2, 2.8; p = 0.004), after adjusting for smoking, ethnicity, caffeine intake, and other covariates. In contrast, we did not observe significant associations between a family history of colorectal, lung, prostate, or breast cancer and PD risk. Interactions between melanoma family history and age, smoking, or caffeine intake were not significant and subgroup analyses according to these factors generated similar results.

CONCLUSIONS

Our findings support the notion that melanoma and Parkinson disease (PD) share common genetic components. The genetic determinants of melanoma could therefore be explored as susceptibility candidate genes for PD.

Genomewide association study for onset age in Parkinson disease

BACKGROUND

Age at onset in Parkinson disease (PD) is a highly heritable quantitative trait for which a significant genetic influence is supported by multiple segregation analyses. Because genes associated with onset age may represent invaluable therapeutic targets to delay the disease, we sought to identify such genetic modifiers using a genomewide association study in familial PD. There have been previous genomewide association studies (GWAS) to identify genes influencing PD susceptibility, but this is the first to identify genes contributing to the variation in onset age.

METHODS

Initial analyses were performed using genotypes generated with the Illumina HumanCNV370Duo array in a sample of 857 unrelated, familial PD cases. Subsequently, a meta-analysis of imputed SNPs was performed combining the familial PD data with that from a previous GWAS of 440 idiopathic PD cases. The SNPs from the meta-analysis with the lowest p-values and consistency in the direction of effect for onset age were then genotyped in a replication sample of 747 idiopathic PD cases from the Parkinson Institute Biobank of Milan, Italy.

RESULTS

Meta-analysis across the three studies detected consistent association (p < 1 x 10(-5)) with five SNPs, none of which reached genomewide significance. On chromosome 11, the SNP with the lowest p-value (rs10767971; p = 5.4 x 10(-7)) lies between the genes QSER1 and PRRG4. Near the PARK3 linkage region on chromosome 2p13, association was observed with a SNP (rs7577851; p = 8.7 x 10(-6)) which lies in an intron of the AAK1 gene. This gene is closely related to GAK, identified as a possible PD susceptibility gene in the GWAS of the familial PD cases.

CONCLUSION

Taken together, these results suggest an influence of genes involved in endocytosis and lysosomal sorting in PD pathogenesis.