Genetic determinants of hair color and Parkinson's disease risk

Parkinson Disease Genetics Extended to African and Hispanic Ancestries in the VA Million Veteran Program

Background and Objectives

Nearly all genetic analyses of Parkinson disease (PD) have been in populations of European ancestry. We sought to test the ability of a machine learning method to extract accurate PD diagnoses from an electronic medical record (EMR) system, to see whether genetic variants identified in European populations generalize to individuals of African and Hispanic ancestries, and to compare the rates of PD across ancestries.

Methods

A machine learning method using natural language processing was applied to EMRs of US veterans participating in the VA Million Veteran Program (MVP) to identify individuals with PD. These putative cases were vetted via blind chart review by a movement disorder specialist. A polygenic risk score (PRS) of 90 established genetic variants whose genotypes were imputed from a customized Axiom Biobank Array was evaluated in different case groups.

Results

The EMR prediction scores had a distinct trimodal distribution, with 97% of the high group and only 30% of the middle group having a credible diagnosis of PD. Using the 3,542 cases from the high group matched 4:1 to controls, the PRS was highly predictive in individuals of European ancestry (n = 3,137 cases; OR = 1.82; p = 8.01E-48), and nearly identical effect sizes were seen in individuals of African (n = 184; OR = 2.07; p = 3.4E-4) and Hispanic ancestries (n = 221; OR = 2.13; p = 3.9E-6). The PRS was much less predictive for the 2,757 European ancestry cases who had an ICD code for PD but for whom the machine learning method had a lower confidence in their diagnosis. No novel ancestry-specific genetic variants were identified. Individuals with African ancestry had one-quarter the rate of PD compared with European or Hispanic ancestries aged 60-70 years and one half the rate in the 70-80 years age range. African American cases had a higher proportion of their DNA originating in Europe compared with African American controls.

Discussion

Machine learning can reliably classify PD using data from a large EMR. Larger studies of non-European populations are required to confirm the generalizability of PD risk variants identified in populations of European ancestry and the increased risk coming from a higher proportion of European DNA in African Americans.

Hair color, family history of melanoma, and the risk of Parkinson's disease: An analysis update

BACKGROUND

A shared biological component between melanoma and Parkinson's disease (PD) has been suggested. Yet, epidemiological evidence is scarce.

OBJECTIVE

To examine the association of hair color and family history of melanoma, two strong predictors of melanoma risk, with the occurrence of PD.

METHODS

We followed 131,342 women and men for ∼30 years for the development of PD. We calculated the cumulative incidence of PD from ages 40 to 90 according to hair color, and estimated the hazard ratio of PD according to hair color and family history of melanoma.

RESULTS

Hair color was not strongly associated with the risk of PD, especially at advanced ages. In contrast, individuals with a family history of melanoma had a 1.4-fold higher risk of PD compared to those without a history.

CONCLUSIONS

Our results support the hypothesis of a shared biological component between PD and melanoma. Both pigmentary and non-pigmentary pathways may play a role.

Racial and Ethnic Disparities in Parkinson Disease: A Call to Action

Health disparities are pervasive in the United States. In the field of Parkinson disease (PD), profound racial and ethnic disparities exist in diagnosis, treatment, and research participation, leading to differential health outcomes and lack of generalizable research data. Racial and ethnic disparities not only limit our understanding of this complex heterogeneous disorder but also hamper our ability to provide new evidence-based care for America's most vulnerable populations. In this report, we summarize findings from our comprehensive white paper for the Michael J. Fox Foundation that reviews the current state of knowledge on racial and ethnic disparities in PD care in the following areas: epidemiology, etiology, phenotype and diagnosis, treatment, and research. We also identify knowledge gaps and necessary policy changes to ensure equitable, high-value care for all persons with PD. These strategies are designed to help identify and reduce health disparities among persons with PD and may serve as a model for other neurologic diseases.

Chemiexcitation: Mammalian Photochemistry in the Dark†

Light is one way to excite an electron in biology. Another is chemiexcitation, birthing a reaction product in an electronically excited state rather than exciting from the ground state. Chemiexcited molecules, as in bioluminescence, can release more energy than ATP. Excited states also allow bond rearrangements forbidden in ground states. Molecules with low-lying unoccupied orbitals, abundant in biology, are particularly susceptible. In mammals, chemiexcitation was discovered to transfer energy from excited melanin, neurotransmitters, or hormones to DNA, creating the lethal and carcinogenic cyclobutane pyrimidine dimer. That process was initiated by nitric oxide and superoxide, radicals triggered by ultraviolet light or inflammation. Several poorly understood chronic diseases share two properties: inflammation generates those radicals across the tissue, and cells that die are those containing melanin or neuromelanin. Chemiexcitation may therefore be a pathogenic event in noise- and drug-induced deafness, Parkinson's disease, and Alzheimer's; it may prevent macular degeneration early in life but turn pathogenic later. Beneficial evolutionary selection for excitable biomolecules may thus have conferred an Achilles heel. This review of recent findings on chemiexcitation in mammalian cells also describes the underlying physics, biochemistry, and potential pathogenesis, with the goal of making this interdisciplinary phenomenon accessible to researchers within each field.

Melanin and Neuromelanin: Linking Skin Pigmentation and Parkinson's Disease

Neuromelanin-containing dopaminergic neurons in the substantia nigra pars compacta (SNpc) are the most vulnerable neurons in Parkinson's disease (PD). Recent work suggests that the accumulation of oxidized dopamine and neuromelanin mediate the convergence of mitochondrial and lysosomal dysfunction in patient-derived neurons. In addition, the expression of human tyrosinase in mouse SNpc led to the formation of neuromelanin resulting in the degeneration of nigral dopaminergic neurons, further highlighting the importance of neuromelanin in PD. The potential role of neuromelanin in PD pathogenesis has been supported by epidemiological observations, whereby individuals with lighter pigmentation or cutaneous malignant melanoma exhibit higher incidence of PD. Because neuromelanin and melanin share many functional characteristics and overlapping biosynthetic pathways, it has been postulated that genes involved in skin pigmentation and melanin formation may play a role in the susceptibility of vulnerable midbrain dopaminergic neurons to neurodegeneration. Here, we highlight potential mechanisms that may explain the link between skin pigmentation and PD, focusing on the role of skin pigmentation genes in the pathogenesis of PD. We also discuss the importance of genetic ancestry in assessing the contribution of pigmentation-related genes to risk of PD. © 2022 International Parkinson and Movement Disorder Society.

Redheaded women are more sexually active than other women, but it is probably due to their suitors

Women with red hair color, i.e., 1–9% of female Europeans, tend to be the subject of various stereotypes about their sexually liberated behavior. The aim of the present case–control study was to explore whether a connection between red hair color and sexual behavior really exists using data from 110 women (34% redheaded) and 93 men (22% redheaded). Redheadedness in women, correlated with various traits related to sexual life, namely with higher sexual desire as measured by Revised Sociosexual Orientation Inventory, with higher sexual activity and more sexual partners of the preferred gender over the past year, earlier initiation of sexual life, and higher sexual submissiveness. Structural equation modelling, however, showed that sexual desire of redheaded women mediated neither their higher sexual activity nor their higher number of sexual partners. These results indirectly indicate that the apparently more liberated sexual behavior in redheaded women could be the consequence of potential mates’ frequent attempts to have sex with them. Our results contradicted the three other tested models, specifically the models based on the assumption of different physiology, faster life history strategy, and altered self-perception of redheaded women induced by stereotypes about them. Naturally, the present study cannot say anything about the validity of other potential models that were not subjects of testing.

Amount of Melanin Granules in Human Hair Defines the Absorption and Conversion to Heat of Light Energy in the Visible Spectrum

One of the known important functions of hair is protection from extensive sunlight. This protection is accomplished in large part due to natural hair pigmentation which is known to reflect the number of melanin granules (melanosomes) in the hair shaft, and melanin variants. Melanin takes in excessive light energy and converts it to heat in a process called absorption; heat is then dissipated into the environment as infrared radiation, thereby protecting the underlying skin. We used transmission electron microscopy (TEM) to visualize the melanosome counts in samples of human hair, and used thermal microscopy to measure the temperature changes of the samples when exposed to green and blue light lasers. In our experiments green light conversion to heat was highly correlated to the number of melanosomes, whereas blue light conversion to heat was less correlated, which may be because the reddish melanosomes it contains are less effective in absorbing energy from the blue spectrum of light. Anyway, we have shown the metals accumulation in the melanin can be easily visualized with TEM. We confirmed that the amount of melanin granules in human hair defines the conversion to heat of light energy in the visible spectrum.

Genetic diversity of the melanocortin-1 receptor in an admixed population of Rio de Janeiro: Structural and functional impacts of Cys35Tyr variant

The melanocortin-1 receptor (MC1R) is one of the key proteins involved in the regulation of melanin production and several polymorphisms have been associated with different phenotypes of skin and hair color in human and nonhuman species. Most of the knowledge is centered on more homogeneous populations and studies involving an admixed group of people should be encouraged due to the great importance of understanding the human color variation. This work evaluates the MC1R diversity and the possible impacts of MC1R variants in an admixed sample population of Rio de Janeiro, Brazil, which is a product of Native American, African, and European miscegenation. Sequencing of complete coding region and part of the 3´UTR of MC1R gene identified 31 variants including one insertion and three novel synonymous substitutions in sample population grouped according to skin, hair and eye pigmentation levels. In nonmetric multidimensional scaling analysis (NMDS), three main clusters were identified, in which the Brazilian dark skin group remained in the African cluster whereas the intermediate and the light skin color phenotype in the European one. None gathered with Asians since their immigration to Brazil was a recent event. In silico analyses demonstrated that Cys35Tyr, Ile155Thr and Pro256Ser, found in our population, have a negative effect on receptor function probably due to changes on the receptor structure. Notably, Cys35Tyr mutation could potentially impair agonist binding. Altogether, this work contributes to the understanding of the genetic background of color variation on an admixed population and gives insights into the damaging effects of MC1R variants.

Whole Exome Sequencing Study in Isolated South-Eastern Moravia (Czechia) Population Indicates Heterogenous Genetic Background for Parkinsonism Development

Parkinsonism belongs to the most common neurodegenerative disease. Genetic predisposition could be one of the significant risk factor for disease development. It has been described higher prevalence of parkinsonism in large pedigree from southeastern Moravia region. The study aims were to select accessible subfamily trios from the pedigree suitable for segregation genetic analyses to perform whole exome sequencing (WES) in trio individuals and further to evaluate genetic variants in the each trio. We used IonTorrent platform for WES for five subfamily trios (1–5). Each trio included two affected and one healthy person (as control). Found variants were filtered with respect to MAF < 1% (minor allele frequency), variants effect (based on prediction tools) and disease filter (Parkinsonism responsible genes). Finally, the variants from each trio were assessed with respect to the presence in the patients. There were found no one founder mutation in the subfamilies from the pedigree. Trio 1 shares two variants with trio 2:MC1R:c.322G > A (p.A108T) and MTCL1:c.1445C > T (p.A482V), trio 3 shares two variants with trio 5: DNAJC6:c.1817A > C (p.H606P) and HIVEP3:c.3856C > A (p.R1286W). In trios 4 and 5, there were found two variants in gene CSMD1:c.3335A > G (p.E1112G) and c.4071C > G (p.I1357M) respectively. As the most potentially damaging, we evaluated the non-shared variant SLC18A2:c.583G > A (p.G195S). The variant could affect dopamine transport in dopaminergic neurons. The study of the parkinsonism genetic background in isolated Moravian population suggested that there could be significant accumulation of many risk genetic factors. For verification of the variants influence, it would be appropriate to perform a more extensive population study and suitable functional analysis.

Parkinson's Disease in African Americans: A Review of the Current Literature

Parkinson’s disease (PD) is the second most common neurodegenerative disease, though evidence suggests that this disorder does not affect all racial groups similarly. Research in African Americans, in particular, has been conflicting. Some studies have found similar prevalence rates in African Americans and whites whereas other studies have found much lower prevalence and incidence rates in African Americans. A few studies identify potential factors underlying these discrepancies, including biologic differences as well as disparities in healthcare access. However, African Americans remain underrepresented in research studies, which make understanding the underlying reasons for these differences difficult. The purpose of this paper is to summarize existing research in African Americans with PD, highlight some of the reasons why differences exist in diagnostic rates of PD in this population, and briefly discuss interventions that may need to be made in order to ensure adequate care is provided to these patients.

Parkinson's disease and cancer: a systematic review and meta-analysis of over 17 million participants

OBJECTIVE

To systematically review and qualitatively evaluate epidemiological evidence on associations between Parkinson's disease (PD) and cancer via meta-analysis.

DATA SOURCES

MEDLINE via PubMed, Web of Science and EMBASE, until March 2021.

STUDY SELECTION

Included were publications that (1) were original epidemiological studies on PD and cancer; (2) reported risk estimates; (3) were in English. Exclusion criteria included: (1) review/comments; (2) biological studies; (3) case report/autopsy studies; (4) irrelevant exposure/outcome; (5) treated cases; (6) no measure of risk estimates; (7) no confidence intervals/exact p values and (8) duplicates.

DATA EXTRACTION AND SYNTHESIS

PRISMA and MOOSE guidelines were followed in data extraction. Two-step screening was performed by two authors blinded to each other. A random-effects model was used to calculate pooled relative risk (RR).

MAIN OUTCOMES AND MEASURES

We included publications that assessed the risk of PD in individuals with vs without cancer and the risk of cancer in individuals with vs without PD.

RESULTS

A total of 63 studies and 17 994 584 participants were included. Meta-analysis generated a pooled RR of 0.82 (n=33; 95% CI 0.76 to 0.88; p<0.001) for association between PD and total cancer, 0.76 (n=21; 95% CI 0.67 to 0.85; p<0.001) for PD and smoking-related cancer and 0.92 (n=19; 95% CI 0.84 to 0.99; p=0.03) for non-smoking-related cancer. PD was associated with an increased risk of melanoma (n=29; pooled RR=1.75; 95% CI 1.43 to 2.14; p<0.001) but not for other skin cancers (n=17; pooled RR=0.90; 95% CI 0.60 to 1.34; p=0.60).

CONCLUSIONS

PD and total cancer were inversely associated. This inverse association persisted for both smoking-related and non-smoking-related cancers. PD was positively associated with melanoma. These results provide evidence for further investigations for possible mechanistic associations between PD and cancer.

PROSPERO REGISTRATION NUMBER

CRD42020162103.

Risk of Nonmelanoma Skin Cancers and Parkinson's Disease-Meta-Analysis and Systematic Review

Simple Summary

Non-melanoma skin cancers (NMSCs) are the most common cancers among fair-skinned people. It is estimated that 2–3 million new cases of NMSCs are diagnosed globally each year. The risk of development increases with age, just like in the case of Parkinson Disease. Due to the general aging of the population and substantially high medical costs of NMSC therapy, NMSCs and Parkinson’s disease (PD) are becoming an increasing health problem. In this paper, we conduct a meta-analysis and systematic review to evaluate the NMSC risk among patients with PD. This study is the first to focus on the effect of different epidemiologic aspects of NMSCs and PD in detail.

Abstract

Patients with Parkinson’s disease (PD) have an increased risk of melanoma compared with the general population. Considering that Nonmelanoma Skin Cancers (NMSCs) share similar risk factors with melanoma, there is a need to understand a possible connection between PD and NMSCs. The aim of the study was the evaluation of NMSC risk among PD patients via meta-analysis and systematic review. A comprehensive search of PubMed, Scopus, and Web of Science databases was conducted, including studies from January 2000 to April 2020. We identified 16 eligible studies including 140291 PD patients. Upon statistical analysis, a significantly higher risk of developing NMSCs in PD patients was found compared with the control group (odds ratio (OR) = 1.25, 95% CI: 1.17–1.33; p < 0.0001). Among all NMSCs, the risk of developing basal cell carcinoma in PD patients was significantly higher (OR = 1.30, 95% confidence interval (CI): 1.15–1.47; p < 0.0001), contrary to squamous cell carcinoma. Further analysis revealed a significantly higher risk of developing NMSCs in patients with previously diagnosed PD (OR = 1.26, 95% CI: 1.19–1.33; p < 0.0001). Our data suggest the necessity for regular skin examination of PD patients, though further studies are required to explore the mechanisms forming this relationship.

Skin conditions in early Parkinson's disease

OBJECTIVE

Skin conditions have been associated with increased risk of Parkinson's disease (PD). Little is known about clinical and biomarker differences according to presence of skin conditions among PD patients. Studying these differences might provide insight into PD pathogenesis.

METHODS

We examined the association between common skin conditions and risk of PD in a case-control study of 423 early drug-naïve PD cases and 196 healthy controls (HC) in the Parkinson's Progression Markers Initiative (PPMI). Among PD participants, we examined if skin conditions were associated with clinical and PD-relevant biomarkers.

RESULTS

Skin conditions occurred more frequently among PD participants (41%) relative to HC (32%). In multivariate analyses, we observed an association between any skin condition and PD (OR = 1.49, 95% CI = 1.03-2.16) and basal cell carcinoma and PD (OR = 2.05, 95% CI = 1.02-4.08). PD participants who reported skin conditions were older (OR = 1.68, 95% CI = 1.21-2.35) more educated (OR = 1.70, 95% CI = 0.99-2.91), had higher Semantic Fluency Test (SFT) scores (OR = 1.45, 95% CI = 1.07-1.96) and Hopkins Verbal Learning Test (HVLT) retention scores (OR = 1.55, 95% CI = 1.09-2.22) compared to PD patients without skin conditions. None of the associations remained significant after Bonferroni correction for multiple comparisons.

CONCLUSIONS

We observed a positive association between any skin condition as well as basal cell carcinoma and PD. PD participants with skin conditions were older, more educated, had higher SFT and HVLT retention scores compared to those without skin conditions. However, all associations were no longer significant after Bonferroni multiple comparisons correction. Observed associations should be confirmed in larger, longitudinal studies.

Body Mass Index and Its Association with Genetically Transmitted Traits

Background

Body mass index (BMI) is a metric widely used to measure the healthy weight of an individual and to predict a person's risk of developing serious illnesses. Study the statistical association between genetically transmitted traits and BMI might be of interest.

Objectives

The present study designed to extend the inadequate evidence concerning the influence of some genetically transmitted traits including ABO blood type, Rh factor, eye color, and hair color on BMI variation.

Methods

A total of 142 undergraduate female students of the Department of Clinical Laboratory Sciences, Faculty of Applied Medical Sciences, King Khalid University, Abha, Saudi Arabia, were participated to investigate the possible linkage between genetic traits and BMI variations. Height and weight are collected from participants for BMI measurement. ABO blood type and Rh factor were determined by antisera.

Results

Out of 142 female students, 48 were categorized in the first tertile (T1: less than 19.8 kg/m²), 50 were categorized in the second tertile (T2: between 19.8 and 23.7 kg/m²), and 44 were categorized in the third tertile (T3: greater than 23.7 kg/m²). Chi-square analysis shows that there were no associations of genetic traits including hair color, eye color, ABO blood type, and Rh blood type with BMI. However, a significant association between hair color and BMI was observed using multinomial logistic regression analysis.

Conclusions

Our data provides a more robust prediction of the relative influence of genetic effects such as hair color on BMI. Future studies may contribute to identifying more association between genes involved in hair pigmentation and BMI variation.

Cancer and Parkinson's Disease: Common Targets, Emerging Hopes

Cancer and neurodegeneration are two major leading causes of morbidity and death worldwide. At first sight, the two fields do not seem to share much in common and, if anything, might be placed on opposite ends of a spectrum. Although neurodegeneration results in excessive neuronal cell death, cancer emerges from increased proliferation and resistance to cell death. Therefore, one might expect significant differences in the underlying pathophysiological mechanisms. However, the more we deepen our understanding of these two types of diseases, the more we appreciate the unexpected overlap between them. Although most epidemiological studies support an inverse association between the risk for development of neurodegenerative diseases and cancer, increasing evidence points to a positive correlation between specific types of cancer, like melanoma, and neurodegenerative diseases, like Parkinson's disease (PD). We believe that deciphering the molecular processes and pathways underlying one of these diseases may significantly increase our understanding about the other. Therefore, the identification of novel biomarkers and therapeutic approaches in cancer, may lead to improved diagnosis and treatment of neurodegeneration, and vice versa. In this Viewpoint, we summarize recent findings connecting both diseases and speculate that insights from one disease may inform on mechanisms, and help identify novel biomarkers and targets for intervention, possibly leading to improved management of both diseases. © 2020 International Parkinson and Movement Disorder Society.

Comprehensive genetic testing combined with citizen science reveals a recently characterized ancient MC1R mutation associated with partial recessive red phenotypes in dog

Background

The Melanocortin 1 Receptor (MC1R) plays a central role in regulation of coat color determination in various species and is commonly referred to as the “E (extension) Locus”. Allelic variation of the MC1R gene is associated with coat color phenotypes E^M (melanistic mask), E^G (grizzle/domino) and e^1–3 (recessive red) in dogs. In addition, a previous study of archeological dog specimens over 10,000 years of age identified a variant p.R301C in the MC1R gene that may have influenced coat color of early dogs.

Results

Commercial genotyping of 11,750 dog samples showed the R301C variant of the MC1R gene was present in 35 breeds or breed varieties, at an allele frequency of 1.5% in the tested population. We detected no linkage disequilibrium between R301C and other tested alleles of the E locus. Based on current convention we propose that R301C should be considered a novel allele of the E locus, which we have termed e^A for “e ancient red”. Phenotype analysis of owner-provided dog pictures reveals that the e^A allele has an impact on coat color and is recessive to wild type E and dominant to the e alleles. In dominant black (K^B/*) dogs it can prevent the phenotypic expression of the K locus, and the expressed coat color is solely determined by the A locus. In the absence of dominant black, e^A/e^A and e^A/e genotypes result in the coat color patterns referred to in their respective breed communities as domino in Alaskan Malamute and other Spitz breeds, grizzle in Chihuahua, and pied in Beagle.

Conclusions

This study demonstrates a large genotype screening effort to identify the frequency and distribution of the MC1R R301C variant, one of the earliest mutations captured by canine domestication, and citizen science empowered characterization of its impact on coat color.

Supplementary Information

The online version contains supplementary material available at 10.1186/s40575-020-00095-7.

The Links between Parkinson's Disease and Cancer

Epidemiologic studies indicate a decreased incidence of most cancer types in Parkinson’s disease (PD) patients. However, some neoplasms are associated with a higher risk of occurrence in PD patients. Both pathologies share some common biological pathways. Although the etiologies of PD and cancer are multifactorial, some factors associated with PD, such as α-synuclein aggregation; mutations of PINK1, PARKIN, and DJ-1; mitochondrial dysfunction; and oxidative stress can also be involved in cancer proliferation or cancer suppression. The main protein associated with PD, i.e., α-synuclein, can be involved in some types of neoplastic formations. On the other hand, however, its downregulation has been found in the other cancers. PINK1 can act as oncogenic or a tumor suppressor. PARKIN dysfunction may lead to some cancers’ growth, and its expression may be associated with some tumors’ suppression. DJ-1 mutation is involved in PD pathogenesis, but its increased expression was found in some neoplasms, such as melanoma or breast, lung, colorectal, uterine, hepatocellular, and nasopharyngeal cancers. Both mitochondrial dysfunction and oxidative stress are involved in PD and cancer development. The aim of this review is to summarize the possible associations between PD and carcinogenesis.

Parkinson's disease and skin cancer risk: a nationwide population-based cohort study in Korea

BACKGROUND

Previous studies have reported that patients with Parkinson's disease (PD) have a significantly lower risk of cancer. Studies reporting prevalence of skin cancers in Parkinson's disease mostly involve Caucasians.

OBJECTIVE

A nationwide population-based study was conducted to determine the risk of skin cancer in patients diagnosed with PD in Korea.

METHODS

Data obtained from National Health Insurance Claims records were used to retrieve information about 70 780 patients with newly diagnosed PD between January 2010 and December 2015. The control group included 353 900 sex- and age-matched patients without PD. In this nationwide population-based cohort study, we investigated the association between PD and skin cancer.

RESULTS

The overall hazard ratio (HR) of skin cancers in patients with PD was 1.169 (95% CI, 1.005-1.359) compared with non-PD group. Among patients with PD, males aged above 65 had a 2.8-fold increase in the risk for melanoma development than the non-PD group (HR, 2.825; 95% CI, 1.395-5.721). In addition, female PD patients aged above 65 years showed a 1.3-fold increase in non-melanoma skin cancer risk than the non-PD group (HR, 1.305; 95% 1.073-1.589).

CONCLUSION

Compared with the general population, Korean patients diagnosed with PD had a greater risk of skin cancer. Especially, male patients aged 65 years and above, and diagnosed with PD had a significant risk of melanoma development compared with control.

Association Between Parkinson's Disease and Melanoma: Putting the Pieces Together

Patients with Parkinson’s disease (PD) generally have reduced risk of developing many types of cancers, except melanoma—a malignant tumor of melanin-producing cells in the skin. For decades, a large number of epidemiological studies have reported that the occurrence of melanoma is higher than expected among subjects with PD, and the occurrence of PD is reciprocally higher than expected among patients with melanoma. More recent epidemiological studies further indicated a bidirectional association, not only in the patients themselves but also in their relatives. This association between PD and melanoma offers a unique opportunity to understand PD. Here, we summarize epidemiological, clinical, and biological evidence in regard to shared risk factors and possible underlying mechanisms for these two seemingly distinct conditions.

Overlapping genetic architecture between Parkinson disease and melanoma

Epidemiologic studies have reported inconsistent results regarding an association between Parkinson disease (PD) and cutaneous melanoma (melanoma). Identifying shared genetic architecture between these diseases can support epidemiologic findings and identify common risk genes and biological pathways. Here, we apply polygenic, linkage disequilibrium-informed methods to the largest available case-control, genome-wide association study summary statistic data for melanoma and PD. We identify positive and significant genetic correlation (correlation: 0.17, 95% CI 0.10-0.24; P = 4.09 × 10-06) between melanoma and PD. We further demonstrate melanoma and PD-inferred gene expression to overlap across tissues (correlation: 0.14, 95% CI 0.06 to 0.22; P = 7.87 × 10-04) and highlight seven genes including PIEZO1, TRAPPC2L, and SOX6 as potential mediators of the genetic correlation between melanoma and PD. These findings demonstrate specific, shared genetic architecture between PD and melanoma that manifests at the level of gene expression.

Skin fairness is a better predictor for impaired physical and mental health than hair redness

About 1-2% of people of European origin have red hair. Especially female redheads are known to suffer higher pain sensitivity and higher incidence of some disorders, including skin cancer, Parkinson's disease and endometriosis. Recently, an explorative study performed on 7,000 subjects showed that both male and female redheads score worse on many health-related variables and express a higher incidence of cancer. Here, we ran the preregistered study on a population of 4,117 subjects who took part in an anonymous electronic survey. We confirmed that the intensity of hair redness negatively correlated with physical health, mental health, fecundity and sexual desire, and positively with the number of kinds of drugs prescribed by a doctor currently taken, and with reported symptoms of impaired mental health. It also positively correlated with certain neuropsychiatric disorders, most strongly with learning disabilities disorder and phobic disorder in men and general anxiety disorder in women. However, most of these associations disappeared when the darkness of skin was included in the models, suggesting that skin fairness, not hair redness, is responsible for the associations. We discussed two possible explanations for the observed pattern, the first based on vitamin D deficiency due to the avoidance of sunbathing by subjects with sensitive skin, including some redheads, and second based on folic acid depletion in fair skinned subjects, again including some (a different subpopulation of) redheads. It must be emphasized, however, that both of these explanations are only hypothetical as no data on the concentration of vitamin D or folic acid are available for our subjects. Our results, as well as the conclusions of current reviews, suggest that the new empirical studies on the concentration of vitamin D and folic acids in relation to skin and hair pigmentation are urgently needed.

Interaction between apolipoprotein E genotype and hypertension on cognitive function in older women in the Nurses' Health Study

OBJECTIVE

To examine the interaction between APOE genotypes and both treated and untreated hypertension on cognitive function in an updated analysis of Nurses' Health Study (NHS) data.

DESIGN

At baseline (1995-2001) and 3 biennial follow-up assessments over ~6 years, cognitive function was assessed.

SETTING AND PARTICIPANTS

8300 NHS participants aged 70+ years underwent a cognitive battery, which comprised 6 tests including the Telephone Interview for Cognitive Status (TICS) and tests of verbal memory, category fluency, and working memory.

MEASURES

We estimated the mean differences in average cognitive scores across up to 4 assessments using multiple linear regression. We also tested for interaction between APOE e4 allele carrier status and hypertension overall, as well as for apparently untreated and treated hypertension.

RESULTS

We confirmed that, compared with those with APOE e3/3 genotype, APOE e4 allele carriers scored lower by 0.55 units on the average TICS score (95%CI:-0.67,-0.43). We also observed a significantly worse average TICS score among women with untreated hypertension compared with women without hypertension (difference = -0.23, 95%CI:-0.37,-0.09), while no significant difference was observed for women with treated hypertension. Significant interaction was detected between the APOE e4 allele and untreated hypertension (p-int = 0.02 for the TICS; p-int = 0.045 for global score), but not with treated hypertension. Specifically, compared with normotensive women with the APOE e3/3 genotype, APOE e4 allele carriers with treated hypertension scored lower by 0.50 units (95%CI:-0.69,-0.31); however, the APOE e4 allele carriers with untreated hypertension scored lower by 1.02 units on the TICS score (95%CI:-1.29, -0.76). This interaction of APOE e4 and untreated hypertension was also consistently observed for the global score.

CONCLUSIONS

Women with hypertension and at least one APOE e4 allele had worse average cognitive function compared with women without hypertension with the e3/3 genotype; this difference was amplified among APOE e4 allele carriers with untreated hypertension.

Neuromelanin, aging, and neuronal vulnerability in Parkinson's disease

Neuromelanin, a dark brown intracellular pigment, has long been associated with Parkinson's disease (PD). In PD, neuromelanin-containing neurons preferentially degenerate, tell-tale neuropathological inclusions form in close association with this pigment, and neuroinflammation is restricted to neuromelanin-containing areas. In humans, neuromelanin accumulates with age, which in turn is the main risk factor for PD. The potential contribution of neuromelanin to PD pathogenesis remains unknown because, in contrast to humans, common laboratory animals lack neuromelanin. The recent introduction of a rodent model exhibiting an age-dependent production of human-like neuromelanin has allowed, for the first time, for the consequences of progressive neuromelanin accumulation-up to levels reached in elderly human brains-to be assessed in vivo. In these animals, intracellular neuromelanin accumulation above a specific threshold compromises neuronal function and triggers a PD-like pathology. As neuromelanin levels reach this threshold in PD patients and presymptomatic PD patients, the modulation of neuromelanin accumulation could provide a therapeutic benefit for PD patients and delay brain aging. © 2019 The Author. Movement Disorders published by Wiley Periodicals, Inc. on behalf of International Parkinson and Movement Disorder Society.

Phosphorylation of Parkin at serine 65 is essential for its activation in vivo

Mutations in PINK1 and Parkin result in autosomal recessive Parkinson's disease (PD). Cell culture and in vitro studies have elaborated the PINK1-dependent regulation of Parkin and defined how this dyad orchestrates the elimination of damaged mitochondria via mitophagy. PINK1 phosphorylates ubiquitin at serine 65 (Ser65) and Parkin at an equivalent Ser65 residue located within its N-terminal ubiquitin-like domain, resulting in activation; however, the physiological significance of Parkin Ser65 phosphorylation in vivo in mammals remains unknown. To address this, we generated a Parkin Ser65Ala (S65A) knock-in mouse model. We observe endogenous Parkin Ser65 phosphorylation and activation in mature primary neurons following mitochondrial depolarization and reveal this is disrupted in Parkin ^S65A/S65A neurons. Phenotypically, Parkin ^S65A/S65A mice exhibit selective motor dysfunction in the absence of any overt neurodegeneration or alterations in nigrostriatal mitophagy. The clinical relevance of our findings is substantiated by the discovery of homozygous PARKIN (PARK2) p.S65N mutations in two unrelated patients with PD. Moreover, biochemical and structural analysis demonstrates that the Parkin^S65N/S65N mutant is pathogenic and cannot be activated by PINK1. Our findings highlight the central role of Parkin Ser65 phosphorylation in health and disease.

A Common Variant in the MC1R Gene (p.V92M) is associated with Alzheimer's Disease Risk

Despite the recent identification of some novel risk genes for Alzheimer's disease (AD), the genetic etiology of late-onset Alzheimer's disease (LOAD) remains largely unknown. The inclusion of these novel risk genes to the risk attributable to the APOE gene accounts for roughly half of the total genetic variance in LOAD. The evidence indicates that undiscovered genetic factors may contribute to AD susceptibility. In the present study, we sequenced the MC1R gene in 525 Spanish LOAD patients and in 160 controls. We observed that a common MC1R variant p.V92M (rs2228479), not related to pigmentation traits, was present in 72 (14%) patients and 15 (9%) controls and confers increased risk of developing LOAD (OR: 1.99, 95% CI: 1.08-3.64, p = 0.026), especially in those patients whose genetic risk could not be explained by APOE genotype. This association remains and even increased in the subset of 69 patients with typical AD cerebrospinal fluid profile (OR: 3.40 95% CI: 1.40-8.27, p = 0.007). We did not find an association between p.V92M and age of onset of AD. Further studies are necessary to elucidate the role of MC1R in brain cells through the different MC1R pathways.

Interaction between caffeine and polymorphisms of glutamate ionotropic receptor NMDA type subunit 2A (GRIN2A) and cytochrome P450 1A2 (CYP1A2) on Parkinson's disease risk

BACKGROUND

Caffeine intake has been inversely associated with Parkinson's disease (PD) risk. This relationship may be modified by polymorphisms of glutamate ionotropic receptor NMDA type subunit 2A (GRIN2A) and cytochrome P450 1A2 (CYP1A2), but the results of previous studies have been inconsistent.

METHOD

We examined the interaction of caffeine intake with GRIN2A-rs4998386 and CYP1A2-rs762551 polymorphisms in influencing PD risk among 829 incident cases of PD and 2,754 matched controls selected among participants in the following 3 large prospective ongoing cohorts: the Nurses' Health Study, the Health Professionals' Follow-up Study, and the Cancer Prevention Study II Nutrition Cohort. Matching factors included cohort, birth year, source of DNA, date of DNA collection, and race. Relative risks and 95% confidence intervals were estimated using conditional logistic models. Interactions were tested both on the multiplicative scale and on the additive scale.

RESULTS

Overall, caffeine intake was associated with a lower PD risk (adjusted relative risk for highest versus lowest tertile = 0.70; 95% confidence interval, 0.57-0.86; p < .001). In analyses stratified by the GRIN2A-rs4998386 genotype, the multivariable-adjusted relative risk of PD comparing the highest to the lowest tertile of caffeine was 0.69 (95% confidence interval, 0.55-0.88; p < .01) among individuals homozygous for the C allele, and 0.85 (95% confidence interval, 0.55-1.32; p = .47; p_RERI  = .43) among carriers for the T allele. Interactions between caffeine and GRIN2A were not significant in either the multiplicative or additive scales. We also did not observe significant interactions for CYP1A2-rs762551 and incident PD risk.

CONCLUSION

Our findings do not support the hypothesis of an interaction between the GRIN2A-rs4998386 or CYP1A2-rs762551 polymorphism and caffeine intake in determining PD risk. © 2018 International Parkinson and Movement Disorder Society.

Health status by gender, hair color, and eye color: Red-haired women are the most divergent

Red hair is associated in women with pain sensitivity. This medical condition, and perhaps others, seems facilitated by the combination of being red-haired and female. We tested this hypothesis by questioning a large sample of Czech and Slovak respondents about the natural redness and darkness of their hair, their natural eye color, their physical and mental health (24 categories), and other personal attributes (height, weight, number of children, lifelong number of sexual partners, frequency of smoking). Red-haired women did worse than other women in ten health categories and better in only three, being particularly prone to colorectal, cervical, uterine, and ovarian cancer. Red-haired men showed a balanced pattern, doing better than other men in three health categories and worse in three. Number of children was the only category where both male and female redheads did better than other respondents. We also confirmed earlier findings that red hair is naturally more frequent in women than in men. Of the ‘new’ hair and eye colors, red hair diverges the most from the ancestral state of black hair and brown eyes, being the most sexually dimorphic variant not only in population frequency but also in health status. This divergent health status may have one or more causes: direct effects of red hair pigments (pheomelanins) or their by-products; effects of other genes that show linkage with genes involved in pheomelanin production; excessive prenatal exposure to estrogen (which facilitates expression of red hair during fetal development and which, at high levels, may cause health problems later in life); evolutionary recentness of red hair and corresponding lack of time to correct negative side effects; or genetic incompatibilities associated with the allele Val92Met, which seems to be of Neanderthal origin and is one of the alleles that can cause red hair.

Biological and Clinical Implications of Comorbidities in Parkinson's Disease

A wide spectrum of comorbidities has been associated with Parkinson's disease (PD), a progressive neurodegenerative disease that affects more than seven million people worldwide. Emerging evidence indicates that chronic diseases including diabetes, depression, anemia and cancer may be implicated in the pathogenesis and progression of PD. Recent epidemiological studies suggest that some of these comorbidities may increase the risk of PD and precede the onset of motor symptoms. Further, drugs to treat diabetes and cancer have elicited neuroprotective effects in PD models. Nonetheless, the mechanisms underlying the occurrence of these comorbidities remain elusive. Herein, we discuss the biological and clinical implications of comorbidities in the pathogenesis, progression, and clinical management, with an emphasis on personalized medicine applications for PD.

Genome-wide Pleiotropy Between Parkinson Disease and Autoimmune Diseases

Importance

Recent genome-wide association studies (GWAS) and pathway analyses supported long-standing observations of an association between immune-mediated diseases and Parkinson disease (PD). The post-GWAS era provides an opportunity for cross-phenotype analyses between different complex phenotypes.

Objectives

To test the hypothesis that there are common genetic risk variants conveying risk of both PD and autoimmune diseases (ie, pleiotropy) and to identify new shared genetic variants and their pathways by applying a novel statistical framework in a genome-wide approach.

Design, Setting, and Participants

Using the conjunction false discovery rate method, this study analyzed GWAS data from a selection of archetypal autoimmune diseases among 138 511 individuals of European ancestry and systemically investigated pleiotropy between PD and type 1 diabetes, Crohn disease, ulcerative colitis, rheumatoid arthritis, celiac disease, psoriasis, and multiple sclerosis. NeuroX data (6927 PD cases and 6108 controls) were used for replication. The study investigated the biological correlation between the top loci through protein-protein interaction and changes in the gene expression and methylation levels. The dates of the analysis were June 10, 2015, to March 4, 2017.

Main Outcomes and Measures

The primary outcome was a list of novel loci and their pathways involved in PD and autoimmune diseases.

Results

Genome-wide conjunctional analysis identified 17 novel loci at false discovery rate less than 0.05 with overlap between PD and autoimmune diseases, including known PD loci adjacent to GAK, HLA-DRB5, LRRK2, and MAPT for rheumatoid arthritis, ulcerative colitis and Crohn disease. Replication confirmed the involvement of HLA, LRRK2, MAPT, TRIM10, and SETD1A in PD. Among the novel genes discovered, WNT3, KANSL1, CRHR1, BOLA2, and GUCY1A3 are within a protein-protein interaction network with known PD genes. A subset of novel loci was significantly associated with changes in methylation or expression levels of adjacent genes.

Conclusions and Relevance

The study findings provide novel mechanistic insights into PD and autoimmune diseases and identify a common genetic pathway between these phenotypes. The results may have implications for future therapeutic trials involving anti-inflammatory agents.

Skin disorders in Parkinson's disease: potential biomarkers and risk factors

Parkinson’s disease (PD) is one of the most common neurodegenerative disorders, characterized by a symptom triad comprising resting tremor, rigidity, and akinesia. In addition, non-motor symptoms of PD are well recognized and often precede the overt motor manifestations. Cutaneous manifestations as markers of PD have long been discussed, and cumulative evidence shows an increased prevalence of certain dermatological disorders in PD. Seborrheic dermatitis is considered to occur as a premotor feature of PD referable to dysregulation of the autonomic nervous system. Also, an increased risk of melanoma has been observed in PD. Light hair color is a known risk factor for melanoma, and interestingly the risk of PD is found to be significantly higher in individuals with light hair color and particularly with red hair. Furthermore, several studies have reported a high prevalence of PD in patients with bullous pemphigoid. Moreover, a 2-fold increase in risk of new-onset PD has been observed in patients with rosacea. Besides the association between PD and various dermatological disorders, the skin may be useful in the diagnosis of PD. Early PD pathology is found not only in the brain but also in extra-neuronal tissues. Thus, the protein α-synuclein, which is genetically associated with PD, is present not only in the CNS but also in the skin. Hence, higher values of α-synuclein have been observed in the skin of patients with PD. Furthermore, an increased risk of PD has been found in the Cys/Cys genotype, which is associated with red hair color. In this review, we summarize the current evidence of the association between PD and dermatological disorders, the cutaneous adverse effects of neurological medications, and describe the potential of skin protein expression and biomarkers in identification of risk and diagnosis of PD.

Red hair, MC1R variants, and risk for Parkinson's disease - a meta-analysis

Several studies have been conducted with mixed results since our initial report of increased Parkinson's disease risk in individuals with red hair and/or red hair‐associated p.R151C variant of the MC1R gene, both of which confer high melanoma risk. We performed a meta‐analysis of six publications on red hair, MC1R, and Parkinson's disease. We found that red hair (pooled odds ratios = 1.68, 95% confidence intervals: 1.07, 2.64) and p.R151C (pooled odds ratios = 1.10, 95% confidence intervals: 1.00, 1.21), but not p.R160W, were associated with greater risk for Parkinson's disease. Our results support potential roles of pigmentation and its key regulator MC1R in the pathogenesis of Parkinson's disease.

The melanoma-linked "redhead" MC1R influences dopaminergic neuron survival

OBJECTIVE

Individuals with Parkinson disease are more likely to develop melanoma, and melanoma patients are reciprocally at higher risk of developing Parkinson disease. Melanoma is strongly tied to red hair/fair skin, a phenotype of loss-of-function polymorphisms in the MC1R (melanocortin 1 receptor) gene. Loss-of-function variants of MC1R have also been linked to increased risk of Parkinson disease. The present study is to investigate the role of MC1R in dopaminergic neurons in vivo.

METHODS

Genetic and pharmacological approaches were employed to manipulate MC1R, and nigrostriatal dopaminergic integrity was determined by comprehensive behavioral, neurochemical, and neuropathological measures.

RESULTS

MC1R^e/e mice, which carry an inactivating mutation of MC1R and mimic the human redhead phenotype, have compromised nigrostriatal dopaminergic neuronal integrity, and they are more susceptible to dopaminergic neuron toxins 6-hydroxydopamine and 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP). Furthermore, a selective MC1R agonist protects against MPTP-induced dopaminergic neurotoxicity.

INTERPRETATION

Our findings reveal a protective role of MC1R in the nigrostriatal dopaminergic system, and they provide a rationale for MC1R as a potential therapeutic target for Parkinson disease. Together with its established role in melanoma, MC1R may represent a common pathogenic pathway for melanoma and Parkinson disease. Ann Neurol 2017;81:395-406.

The p. R151C Polymorphism in MC1R Gene Modifies the Age of Onset in Spanish Huntington's Disease Patients

The expansion of CAG repeats (≥36 CAG) in the HTT gene is the only known genetic cause of Huntington's disease (HD) and the main determinant of the course of the disease. The length of the expanded CAG repeats correlates inversely with the age of onset (AOO) but does not completely determine it. We investigated the role of the melanocortin 1 receptor (MC1R) gene as a modifier factor of AOO in 600 HD patients from Spain. We sequenced the entire region of the MC1R gene and analyzed all the nonsynonymous MC1R genetic variants with a minor allele frequency of at least 0.01 in HD patients. The variability in AOO attributable to the CAG repeats and MC1R polymorphisms was evaluated using a multiple linear regression model. We found that the loss-of-function p. R151C MC1R polymorphism has a significant influence on the AOO (P = 0.004; Bonferroni-corrected P = 0.032) which explains 1.42% of the variance in AOO that cannot be accounted for by the expanded CAG repeat. Our results suggest that the MC1R gene could modify the AOO in Spanish HD patients and encourage the evaluation of loss-of-function MC1R polymorphisms in other HD populations with a higher frequency of these MC1R polymorphisms.

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.

The epidemiology of Parkinson's disease: risk factors and prevention

Since 2006, several longitudinal studies have assessed environmental or behavioural factors that seem to modify the risk of developing Parkinson's disease. Increased risk of Parkinson's disease has been associated with exposure to pesticides, consumption of dairy products, history of melanoma, and traumatic brain injury, whereas a reduced risk has been reported in association with smoking, caffeine consumption, higher serum urate concentrations, physical activity, and use of ibuprofen and other common medications. Randomised trials are investigating the possibility that some of the negative risk factors might be neuroprotective and thus beneficial in individuals with early Parkinson's disease, particularly with respect to smoking (nicotine), caffeine, and urate. In the future, it might be possible to identify Parkinson's disease in its prodromal phase and to promote neuroprotective interventions before the onset of motor symptoms. At this time, however, the only intervention that seems justifiable for the primary prevention of Parkinson's disease is the promotion of physical activity, which is likely to be beneficial for the prevention of several chronic diseases.

Parkinson disease (PARK) genes are somatically mutated in cutaneous melanoma

OBJECTIVE

To assess whether Parkinson disease (PD) genes are somatically mutated in cutaneous melanoma (CM) tissue, because CM occurs in patients with PD at higher rates than in the general population and PD is more common than expected in CM cohorts.

METHODS

We cross-referenced somatic mutations in metastatic CM detected by whole-exome sequencing with the 15 known PD (PARK) genes. We computed the empirical distribution of the sum of mutations in each gene (Smut) and of the number of tissue samples in which a given gene was mutated at least once (SSampl) for each of the analyzable genes, determined the 90th and 95th percentiles of the empirical distributions of these sums, and verified the location of PARK genes in these distributions. Identical analyses were applied to adenocarcinoma of lung (ADENOCA-LUNG) and squamous cell carcinoma of lung (SQUAMCA-LUNG). We also analyzed the distribution of the number of mutated PARK genes in CM samples vs the 2 lung cancers.

RESULTS

Somatic CM mutation analysis (n = 246) detected 315,914 mutations in 18,758 genes. Somatic CM mutations were found in 14 of 15 PARK genes. Forty-eight percent of CM samples carried ≥1 PARK mutation and 25% carried multiple PARK mutations. PARK8 mutations occurred above the 95th percentile of the empirical distribution for SMut and SSampl. Significantly more CM samples harbored multiple PARK gene mutations compared with SQUAMCA-LUNG (p = 0.0026) and with ADENOCA-LUNG (p < 0.0001).

CONCLUSIONS

The overrepresentation of somatic PARK mutations in CM suggests shared dysregulated pathways for CM and PD.

The role of the melanoma gene MC1R in Parkinson disease and REM sleep behavior disorder

The MC1R gene, suggested to be involved in Parkinson disease (PD) and melanoma, was sequenced in PD patients (n = 539) and controls (n = 265) from New York, and PD patients (n = 551), rapid eye movement sleep behavior disorder (RBD) patients (n = 351), and controls (n = 956) of European ancestry. Sixty-eight MC1R variants were identified, including 7 common variants with frequency > 0.01. None of the common variants was associated with PD or RBD in the different regression models. In a meta-analysis with fixed-effect model, the p.R160W variant was associated with an increased risk for PD (odds ratio = 1.22, 95% confidence interval = 1.02-1.47, p = 0.03) but with significant heterogeneity (p = 0.048). Removing one study that introduced the heterogeneity resulted in nonsignificant association (odds ratio = 1.11, 95% confidence interval, 0.92-1.35, p = 0.27, heterogeneity p = 0.57). Rare variants had similar frequencies in patients and controls (10.54% and 10.15%, respectively, p = 0.75), and no cumulative effect of carrying more than one MC1R variant was found. The present study does not support a role for the MC1R p.R160W and other variants in susceptibility for PD or RBD.

Morbidity and Mortality in 7,684 Women According to Personal Hair Dye Use: The Copenhagen City Heart Study followed for 37 Years

Background

Permanent hair dye contains aromatic amines which are carcinogenic, and can cause allergic skin reactions. In the long term personal use of hair dye might therefore influence both morbidity and mortality.

Objectives

We tested the hypothesis that personal use of hair dye in women is associated with increased morbidity and mortality in the general population.

Methods

We included 7,684 women from the Copenhagen City Heart Study with information on the use of personal hair dye. We assessed the risk of cancer, skin diseases, other morbidities, and mortality during a median follow-up of 27 years (range 0–37).

Results

The multivariable adjusted hazard ratio for malignant melanoma in women with versus without personal use of hair dye was 2.07 (95% confidence interval 1.25–3.42). There was no increased risk of other cancer types. For other skin diseases and other major causes of morbidity we found no differences between the two groups, except for a minor excess of digestive diseases and increased risk of Parkinson’s disease among women using hair dye. Finally, we found no difference in all-cause mortality comparing women using personal hair dye or not. After correction for multiple comparisons, none of the results remained significant. However, in sensitivity analysis the excess risk of malignant melanoma remained increased with a hazard ratio of 2.58 (95%CI 1.33–5.03) among users of personal hair dye.

Conclusions

Personal use of hair dye does not have major influences on morbidity and mortality. Our finding of a 2-fold risk of malignant melanoma in women using hair dye is hypothesis generating.

MC1R variants in Chinese Han patients with sporadic Parkinson's disease

Recently, a variant p.R160W in the MC1R gene was identified that increased the risk of Parkinson's disease (PD) in Spanish population. To explore whether the MC1R gene variants are associated with sporadic PD in Chinese population, we performed a case-control comparison study for comprehensive MC1R variant screening in 510 Chinese Han patients and 495 healthy controls as ethnically matched controls. We identify 5 nonsynonymous variants, including rs34090186 (p.R67Q), rs2228479 (p.V92M), rs33932559 (p.I120T), rs885479 (p.R163Q), and rs372152373 (p.R223W). However, variants mentioned previously did not show association with PD. Our results suggest that variants in MC1R do not play a major role in PD in the Chinese population.

Frequency and profile of Parkinson's disease prodromi in patients with malignant melanoma

OBJECTIVE

The results of register studies suggest an association between Parkinson's disease (PD) and melanoma. We studied the frequency and profile of early markers of PD in patients with malignant melanoma.

METHODS

100 participants were enrolled in a prospective observational study, of whom 65 had a history of high-risk cutaneous (n=53) or uveal (n=12) melanoma (31 women; age, 61.2±14.9 years) and another 35 served as control participants (19 women; 54.6±20.5 years). Participants underwent assessments of motor function (Unified PD Rating Scale; keyboard tapping test), olfactory function, colour vision, depressive symptoms, the Non-Motor Symptoms Questionnaire, and transcranial brain sonography. Raters were blinded to the diagnosis and clinical data of study participants.

RESULTS

Patients with melanoma showed increased frequency of substantia nigra hyperechogenicity and prodromal motor and non-motor features of PD, especially asymmetric motor slowing and apathy. Hyposmia and colour vision disturbance were, however, infrequent. Larger echogenicity of substantia nigra correlated with lower serum iron in patients with melanoma, similar to previously reported findings in PD, and independently from the earlier findings, with lighter skin pigmentation. Substantia nigra hyperechogenicity, combined with motor asymmetry or hyposmia, was present at baseline in all participants with mild or definite parkinsonism diagnosed after 1 year. Parkinsonism was specifically related to melanoma location at the sun-exposed skin of the head or neck.

CONCLUSIONS

History of melanoma was associated with increased prevalence of prodromal markers of PD. Their predictive value needs to be established in long-term investigations. The similarity of serum iron characteristics found in patients with melanoma and PD deserves further research.

Light pigmentation phenotype is correlated with increased substantia nigra echogenicity

OBJECTIVE

This study was undertaken to address the question of whether pigmentation may be mechanistically linked with Parkinson's disease.

METHODS

In a cross-sectional, observational study, 116 healthy subjects received transcranial sonography of the substantia nigra. Pigmentation phenotype was assessed using the Fitzpatrick skin phototype classification, and five additional phenotypic pigmentation traits as well as a photographic method (Melanin index) in a subgroup of 46 subjects.

RESULTS

Lighter skin phototype was associated with larger echogenic substantia nigra area and increased prevalence of abnormally enlarged echogenic substantia nigra area. The strongest association of substantia nigra echogenicity and phenotypic pigmentation traits was found for hair color and facial tanning.

INTERPRETATION

Findings suggest an increasing prevalence of structural abnormality of substantia nigra with decreasing darkness of skin and thus may provide additional evidence in favor of a pathogenic link of pigmentation and Parkinson's disease.