Genome-wide gene-environment study identifies glutamate receptor gene GRIN2A as a Parkinson's disease modifier gene via interaction with coffee.

Our aim was to identify genes that influence the inverse association of coffee with the risk of developing Parkinson's disease (PD). We used genome-wide genotype data and lifetime caffeinated-coffee-consumption data on 1,458 persons with PD and 931 without PD from the NeuroGenetics Research Consortium (NGRC), and we performed a genome-wide association and interaction study (GWAIS), testing each SNP's main-effect plus its interaction with coffee, adjusting for sex, age, and two principal components. We then stratified subjects as heavy or light coffee-drinkers and performed genome-wide association study (GWAS) in each group. We replicated the most significant SNP. Finally, we imputed the NGRC dataset, increasing genomic coverage to examine the region of interest in detail. The primary analyses (GWAIS, GWAS, Replication) were performed using genotyped data. In GWAIS, the most significant signal came from rs4998386 and the neighboring SNPs in GRIN2A. GRIN2A encodes an NMDA-glutamate-receptor subunit and regulates excitatory neurotransmission in the brain. Achieving P(2df) = 10(-6), GRIN2A surpassed all known PD susceptibility genes in significance in the GWAIS. In stratified GWAS, the GRIN2A signal was present in heavy coffee-drinkers (OR = 0.43; P = 6×10(-7)) but not in light coffee-drinkers. The a priori Replication hypothesis that "Among heavy coffee-drinkers, rs4998386_T carriers have lower PD risk than rs4998386_CC carriers" was confirmed: OR(Replication) = 0.59, P(Replication) = 10(-3); OR(Pooled) = 0.51, P(Pooled) = 7×10(-8). Compared to light coffee-drinkers with rs4998386_CC genotype, heavy coffee-drinkers with rs4998386_CC genotype had 18% lower risk (P = 3×10(-3)), whereas heavy coffee-drinkers with rs4998386_TC genotype had 59% lower risk (P = 6×10(-13)). Imputation revealed a block of SNPs that achieved P(2df)<5×10(-8) in GWAIS, and OR = 0.41, P = 3×10(-8) in heavy coffee-drinkers. This study is proof of concept that inclusion of environmental factors can help identify genes that are missed in GWAS. Both adenosine antagonists (caffeine-like) and glutamate antagonists (GRIN2A-related) are being tested in clinical trials for treatment of PD. GRIN2A may be a useful pharmacogenetic marker for subdividing individuals in clinical trials to determine which medications might work best for which patients.

Risk prediction for complex diseases: application to Parkinson disease.

PURPOSE: The aim of this study was to evaluate the risk of Parkinson disease using clinical and demographic data alone and when combined with information from genes associated with Parkinson disease. METHODS: A total of 1,967 participants in the dbGAP NeuroGenetics Research Consortium data set were included. Single-nucleotide polymorphisms associated with Parkinson disease at a genome-wide significance level in previous genome-wide association studies were included in risk prediction. Risk allele scores were calculated as the weighted count of the minor alleles. Five models were constructed. Discriminatory capability was evaluated using the area under the curve. RESULTS: Both family history and genetic risk scores increased risk for Parkinson disease. Although the fullest model, which included both family history and genetic risk information, resulted in the highest area under the curve, there were no significant differences between models using family history alone and those using genetic information alone. CONCLUSION: Adding genome-wide association study-derived genotypes, family history information, or both to standard demographic risk factors for Parkinson disease resulted in an improvement in discriminatory capacity. In the full model, the contributions of genotype data and family history information to discriminatory capacity were similar, and both were statistically significant. This suggests that there is limited overlap between genetic risk factors identified through genome-wide association study and unmeasured susceptibility variants captured by family history. Our results are similar to those of studies of other complex diseases and indicate that genetic risk prediction for Parkinson disease requires identification of additional genetic risk factors and/or better methods for risk prediction in order to achieve a degree of risk prediction that is clinically useful.Genet Med 2013:15(5):361-367.

Common variation in the LRRK2 gene is a risk factor for Parkinson's disease.

BACKGROUND: Common variants in the LRRK2 gene influence the risk of Parkinson's disease (PD) in Asians, but whether the same is true in European-derived populations is less clear. METHODS: We genotyped 66 LRRK2 tagging single-nucleotide polymorphisms (SNPs) in 575 PD patients and 689 controls from the northwestern United States (tier 1). PD-associated SNPs (P < .05) were then genotyped in an independent sample of 3617 cases and 2512 controls from the United States and Spain (tier 2). Logistic regression was used to model additive SNP genotype effects adjusted for age and sex among white individuals. RESULTS: Two regions showed independent association with PD in tier 1, and SNPs in both regions were successfully replicated in tier 2 (rs10878226, combined odds ratio [OR], 1.20; 95% confidence interval [CI], 1.08-1.33; P = 6.3 × 10(-4); rs11176013, OR, 0.89; CI, 0.83-0.95; P = 4.6 × 10(-4)). CONCLUSIONS: Our data suggest that common variation within LRRK2 conveys susceptibility for PD in individuals of European ancestry.

Contralateral prophylactic mastectomy.

BACKGROUND: Contralateral prophylactic mastectomy (CPM) is often discussed as a treatment option for women with a diagnosis of unilateral breast cancer. The purpose of this study was to identify the prevalence of pathology within the specimen at the time of CPM and to evaluate potential risk factors. METHODS: Patients with a unilateral breast malignancy who underwent CPM were identified from the database of Scott and White Breast Cancer Clinic. A retrospective cohort study comparing disease status and various exposure parameters was conducted via chart review. RESULTS: Of the 301 patients who met the inclusion criteria, there were 14 cases (4.7%) with malignancy and 45 cases (15.0%) with moderate-to-high risk lesions. Multivariate analysis demonstrated 2 independent factors predictive of malignant or moderate-to-high risk lesions: age >54 years and lobular histology in the original specimen. CONCLUSIONS: The prevalence of malignant and premalignant lesions at the time of CPM was nearly 1 in 5.

Monitoring and reducing exposure of infants to pollutants in house dust.

The health risks to babies from pollutants in house dust may be 100 times greater than for adults. The young ingest more dust and are up to ten times more vulnerable to such exposures. House dust is the main exposure source for infants to allergens, lead, and PBDEs, as well as a major source of exposure to pesticides, PAHs, Gram-negative bacteria, arsenic, cadmium, chromium, phthalates, phenols, and other EDCs, mutagens, and carcinogens. Median or upper percentile concentrations in house dust of lead and several pesticides and PAHs may exceed health-based standards in North America. Early contact with pollutants among the very young is associated with higher rates of chronic illness such as asthma, loss of intelligence, ADHD, and cancer in children and adults. The potential of infants, who live in areas with soil contaminated by automotive and industrial emissions, can be given more protection by improved home cleaning and hand washing. Babies who live in houses built before 1978 have a prospective need for protection against lead exposures; homes built before 1940 have even higher lead exposure risks. The concentration of pollutants in house dust may be 2-32 times higher than that found in the soil near a house. Reducing infant exposures, at this critical time in their development, may reduce lifetime health costs, improve early learning, and increase adult productivity. Some interventions show a very rapid payback. Two large studies provide evidence that home visits to reduce the exposure of children with poorly controlled asthma triggers may return more than 100% on investment in 1 yr in reduced health costs. The tools provided to families during home visits, designed to reduce dust exposures, included vacuum cleaners with dirt finders and HEPA filtration, allergy control bedding covers, high-quality door mats, and HEPA air filters. Infants receive their highest exposure to pollutants in dust at home, where they spend the most time, and where the family has the most mitigation control. Normal vacuum cleaning allows deep dust to build up in carpets where it can be brought to the surface and become airborne as a result of activity on the carpet. Vacuums with dirt finders allow families to use the three-spot test to monitor deep dust, which can reinforce good cleaning habits. Motivated families that receive home visits from trained outreach workers can monitor and reduce dust exposures by 90% or more in 1 wk. The cost of such visits is low considering the reduction of risks achieved. Improved home cleaning is one of the first results observed among families who receive home visits from MHEs and CHWs. We believe that proven intervention methods can reduce the exposure of infants to pollutants in house dust, while recognizing that much remains to be learned about improving the effectiveness of such methods.

Glucocerebrosidase gene mutations: a risk factor for Lewy body disorders.

BACKGROUND: Mutations in the glucocerebrosidase (GBA) gene have been reported to modify risk for Parkinson disease (PD) and dementia with Lewy bodies (DLB). However, these findings have not been consistently replicated, and most studies have had substantial methodological shortcomings. OBJECTIVE: To better assess the role of GBA variants in altering risk for Lewy body disorders. DESIGN: Case-control study. SETTING: Four movement disorder clinics in the Seattle, Washington, area. PARTICIPANTS: Seven hundred twenty-one patients with PD, 554 healthy control subjects, and 57 patients with DLB. MAIN OUTCOME MEASURES: Disease status and presence or absence of the 2 most common GBA mutations (N370S and L444P). RESULTS: We observed a significantly higher heterozygote frequency for the 2 mutations in patients with PD (2.9%; P <.001) and those with DLB (3.5%; P = .045) compared with control subjects (0.4%). CONCLUSION: Our findings suggest that GBA mutations exert a large effect on susceptibility for Lewy body disorders at the individual level but are associated with a modest (approximately 3%) population-attributable risk in individuals of European ancestry.

Exploring gene-environment interactions in Parkinson's disease.

The objective of this study was to explore combined effects of four candidate susceptibility genes and two exposures on Parkinson's disease (PD) risk; namely, alpha-synuclein (SNCA) promoter polymorphism REP1, microtubule-associated protein tau (MAPT) H1/H2 haplotypes, apolipoprotein E (APOE) epsilon2/epsilon3/epsilon4 polymorphism, ubiquitin carboxy-terminal esterase L1 (UCHL1) S18Y variant, cigarette smoking and caffeinated coffee consumption. 932 PD patients and 664 control subjects from the NeuroGenetics Research Consortium, with complete data on all six factors, were studied. Uniform protocols were used for diagnosis, recruitment, data collection and genotyping. A logistic regression model which included gene-exposure interactions was applied. Likelihood ratio tests (LRTs) were used for significance testing and Bayesian inference was used to estimate odds ratios (ORs). MAPT (P = 0.007), SNCA REP1 (P = 0.012), smoking (P = 0.001), and coffee (P = 0.011) were associated with PD risk. Two novel interactions were detected: APOE with coffee (P = 0.005), and REP1 with smoking (P = 0.021). While the individual main effects were modest, each yielding OR < 1.6, the effects were cumulative, with some combinations reaching OR = 12.6 (95% CI: 5.9-26.8). This study provides evidence for the long-held notion that PD risk is modulated by cumulative and interactive effects of genes and exposures. Furthermore, the study demonstrates that while interaction studies are useful for exploring risk relationships that might otherwise go undetected, results should be interpreted with caution because of the inherent loss of power due to multiple testing. The novel findings of this study that warrant replication are the evidence for interaction of coffee with APOE, and of smoking with REP1 on PD risk.

Study of istradefylline in patients with Parkinson's disease on levodopa with motor fluctuations.

The objective of this study was to evaluate the efficacy, safety, and tolerability of istradefylline 20 mg once daily versus placebo as an adjunct to levodopa in subjects with Parkinson's disease (PD) who have motor fluctuations. Istradefylline (KW-6002) is an adenosine A(2A) receptor antagonist that in primate models of PD improves motor function without causing or worsening dyskinesia. This 12-week, multicenter, double-blind, placebo-controlled, randomized, Phase 3 study of istradefylline was conducted in subjects experiencing an average daily OFF time of at least 3 hours (116 randomized to istradefylline; 115 to placebo). All were on stable levodopa regimens; 90% were also on stable regimens of other anti-Parkinson's medications. Istradefylline-treated subjects had significant placebo-corrected reductions in daily OFF time from baseline to endpoint: 4.6% (P = 0.03) and 0.7 hours (P = 0.03). For ON time with troublesome dyskinesia, the changes between istradefylline and placebo were not significant. Istradefylline was well tolerated, with 6 (5.2%) istradefylline-treated and 7 (6.1%) placebo-treated subjects withdrawing from the study because of adverse events. Dyskinesia, lightheadedness, tremor, constipation, and weight decrease were reported more often with istradefylline than placebo. We conclude that istradefylline is well tolerated and significantly reduces OFF time as an adjunct to levodopa in PD subjects with motor fluctuations.

Combined effects of smoking, coffee, and NSAIDs on Parkinson's disease risk.

Inverse associations of Parkinson's disease (PD) with cigarette smoking, coffee drinking, and nonsteroidal anti-inflammatory drug (NSAID) use have been reported individually, but their joint effects have not been examined. To quantify associations with PD for the individual, two-way and three-way combinations of these factors, a case-control association study with 1,186 PD patients and 928 controls was conducted. The study setting was the NeuroGenetics Research Consortium. Subjects completed a structured questionnaire regarding smoking, coffee, and NSAID consumption. Odds ratios were calculated using unconditional logistic regression. Smoking, coffee, and over the counter NSAID use as individual factors exhibited significantly reduced risks of 20% to 30%. The two-way and three-way combinations were associated with risk reduction of 37% to 49%, and 62%, respectively. Smoking and coffee exhibited significant inverse risk trends with increasing cumulative exposures, suggesting dose-response relations. With respect to the combination of all three exposures, persons who were at the highest exposure strata for smoking and coffee and used NSAIDs had an estimated 87% reduction in risk (OR = 0.13, 95% CI = 0.06-0.29). Whether this finding reflects true biologic protection needs to be investigated.

Lack of evidence for an association between UCHL1 S18Y and Parkinson's disease.

UCHL1 has been proposed as a candidate gene for Parkinson's disease (PD). A meta-analysis of white and Asian subjects reported an inverse association between the non-synonymous UCHL1 S18Y polymorphism and PD risk. However, this finding was not replicated in a large case-control study and updated meta-analysis restricted to white subjects. We performed a case-control study of 1757 PD patients recruited from movement disorder clinics and 2016 unrelated controls from four regions of the United States. All subjects self-reported as white. We did not observe evidence for an association between S18Y genotypes and PD (overall P-value for association: P = 0.42). After adjustment for age, sex, and recruitment region, the odds ratio for Y/S versus S/S was 0.91 (95% CI: 0.78-1.06) and for Y/Y versus S/S was 0.87 (95% CI: 0.58-1.29). We also did not observe a significant association for recessive or dominant models of inheritance, or after stratification by age at onset, age at blood draw, sex, family history of PD, or recruitment region. Our results suggest that UCHL1 S18Y is not a major susceptibility factor for PD in white populations although we cannot exclude the possibility that the S18Y variant exerts weak effects on risk, particularly in early-onset disease.

Genetic association between alpha-synuclein and idiopathic Parkinson's disease.

Point mutations and copy number variations in SNCA, the gene encoding alpha-synuclein, cause familial Parkinson's disease (PD). A dinucleotide polymorphism (REP1) in the SNCA promoter may be a risk factor for common forms of PD. We studied 1,802 PD patients and 2,129 controls from the NeuroGenetics Research Consortium, using uniform, standardized protocols for diagnosis, subject recruitment, data collection, genotyping, and data analysis. Three common REP1 alleles (257, 259, and 261 bp, with control frequencies of 0.28, 0.65, and 0.06) and several rare alleles (combined frequency <0.01) were detected. We confirmed association of REP1 with PD risk [odds ratio (OR) = 0.86, P = 0.006 for 257-carriers; OR = 1.25, P = 0.022 for 261-carriers]. Using a normalization procedure, we showed that the 257 and 261 alleles are both independently associated with PD risk (for 257, P = 0.002 in overall data, 0.003 in non-familial PD, 0.001 in early-onset PD; for 261, P = 0.056 in overall data, 0.024 in non-familial PD, 0.052 in early-onset PD). The 257-associated risk was consistent with a dominant model [hazard ratio (HR) = 0.99, P = 0.91 for 257/257 vs. 257/X where X denotes all other common alleles; HR = 1.16, P = 0.004 for X/X vs. 257/X]. The 261-associated risk was consistent with a recessive model (HR = 1.89, P = 0.026 for 261/261 vs. 261/X; HR = 0.95, P = 0.42 for X/X vs. 261/X). Genotype-specific mean onset ages (+/-SD) ranged from 54.8 +/- 12.1 for 261/261 to 59.4 +/- 11.5 for 257/257, displaying a trend of decreasing onset age with increasing allele size (P = 0.055). Genetic variation in SNCA and its regulatory regions play an important role in both familial and sporadic PD.

Validity and utility of a LRRK2 G2019S mutation test for the diagnosis of Parkinson's disease.

The G2019S mutation in the LRRK2 gene, the most common known cause of Parkinson's disease (PD), will soon be widely available as a molecular clinical test for PD. The objective of this study was to assess performance characteristics of G2019S as a clinical test for PD in the setting of typical movement disorder clinics in the United States. Subjects included 1,518 sequentially recruited PD patients from seven movement disorder clinics in the United States, and 1,733 unaffected subjects. All 3,251 subjects were genotyped for the G2019S mutation using a TaqMan assay, and mutations were verified by direct sequencing. Test validity estimates were calculated using standard methods. A total of 20/1518 patients and 1/1733 controls carried the G2019S mutation. Specificity was 99.9% (95% CI, 99.6-100%), sensitivity was 1.3% (0.8-2.1%), and the positive likelihood ratio was 22.8. A positive family history of PD increased the positive likelihood ratio to 82.5. Information on gender, age at disease onset, or age at testing did not improve test performance. The gene test was highly accurate in classifying mutation carriers as PD, but it performed poorly in predicting the phenotype of non-mutation carriers. A G2019S molecular test for PD would be highly specific, technically simple, and inexpensive. Test interpretation is straightforward when used for diagnosis of symptomatic individuals, but is more complex for risk assessment and predictive testing in asymptomatic individuals. Test results can have psychological, social, and economical ramifications; thus, proper counseling is essential.

Haptoglobin phenotype modifies serum iron levels and the effect of smoking on Parkinson disease risk.

INTRODUCTION: Haptoglobin is a hemoglobin-binding protein that exists in three functionally different phenotypes, and haptoglobin phenotype 2-1 has previously been associated with Parkinson disease (PD) risk, with mechanisms not elucidated. Some evidence is emerging that low levels of serum iron may increase PD risk. In this study we investigated whether PD patients have lower serum iron and ferritin than controls, and whether this is dependent on haptoglobin phenotype. We also investigated the effect of Hp phenotype as a modifier of the effect of smoking on PD risk. METHODS: The study population consisted of 128 PD patients and 226 controls. Serum iron, ferritin, and haptoglobin phenotype were determined, and compared between PD cases and controls. Stratified analysis by haptoglobin phenotype was performed to determine effect of haptoglobin phenotype on serum iron parameter differences between PD cases and controls and to investigate its role in the protective effect of smoking on PD risk. RESULTS: PD cases had lower serum iron than controls (83.28 ug/100 ml vs 94.00 ug/100 ml, p 0.006), and in particular among subjects with phenotype 2-1. The protective effect of smoking on PD risk resulted stronger in subjects with phenotype 1-1 and 2-2, and weakest among subjects with phenotype 2-1. Ferritin levels were higher in PD cases than controls among subjects of White ethnicity. CONCLUSIONS: Our results report for the first time that the haptoglobin phenotype may be a contributor of iron levels abnormalities in PD patients. The mechanisms for these haptoglobin-phenotype specific effects will have to be further elucidated.

The RAB39B p.G192R mutation causes X-linked dominant Parkinson's disease.

OBJECTIVE: To identify the causal gene in a multi-incident U.S. kindred with Parkinson's disease (PD). METHODS: We characterized a family with a classical PD phenotype in which 7 individuals (5 males and 2 females) were affected with a mean age at onset of 46.1 years (range, 29-57 years). We performed whole exome sequencing on 4 affected and 1 unaffected family members. Sanger-sequencing was then used to verify and genotype all candidate variants in the remainder of the pedigree. Cultured cells transfected with wild-type or mutant constructs were used to characterize proteins of interest. RESULTS: We identified a missense mutation (c.574G > A; p.G192R) in the RAB39B gene that closely segregated with disease and exhibited X-linked dominant inheritance with reduced penetrance in females. The mutation occurred in a highly conserved amino acid residue and was not observed among 87,725 X chromosomes in the Exome Aggregation Consortium dataset. Sequencing of the RAB39B coding region in 587 familial PD cases yielded two additional mutations (c.428C > G [p.A143G] and c.624_626delGAG [p.R209del]) that were predicted to be deleterious in silico but occurred in families that were not sufficiently informative to assess segregation with disease. Experiments in PC12 and SK-N-BE(2)C cells demonstrated that p.G192R resulted in mislocalization of the mutant protein, possibly by altering the structure of the hypervariable C-terminal domain which mediates intracellular targeting. CONCLUSIONS: Our findings implicate RAB39B, an essential regulator of vesicular-trafficking, in clinically typical PD. Further characterization of normal and aberrant RAB39B function might elucidate important mechanisms underlying neurodegeneration in PD and related disorders.

Recognition memory for hand positions and spatial locations in patients with Huntington's disease: differential visuospatial memory impairment?

Allocentric and egocentric memory was investigated in patients with Huntington's disease (HD) and matched controls. Patients with HD and age- and education-matched healthy normal controls (NC) were administered two visuospatial recognition memory tasks, one assessing memory for hand positions (egocentric) and the other assessing memory for spatial locations (allocentric). HD patients showed normal primacy and recency effects, but their overall performance was impaired relative to controls on both tasks. Correlation analyses indicated that HD patients' performance on the Hand Position Memory task, but not the Spatial Location Memory task, was associated with global cognitive status (Mattis Dementia Rating Scale) and disease severity (Shoulson and Fahn Rating Scale), and HD patients' performances on the two tasks were not associated. Results provide preliminary support for the role of the caudate nucleus in both allocentric and egocentric spatial memory.

Association mapping of the PARK10 region for Parkinson's disease susceptibility genes.

BACKGROUND: Previous studies indicate that as many as six genes within the PARK10 region (RNF11, UQCRH, HIVEP3, EIF2B3, USP24, ELAVL4) might modify susceptibility or age at onset in Parkinson's disease (PD). METHODS: We sought to identify new PD susceptibility genes and to validate previously nominated candidate genes within the PARK10 region using a two-stage design. We used data from a large, publicly-available genome-wide association study (GWAS) in the discovery stage (n = 2000 cases and 1986 controls) and data from three independent studies for the replication stage (total n = 2113 cases and 2095 controls). Marker density was increased by imputation using HapMap 3 and 1000 Genomes reference panels, and over 40,000 single nucleotide polymorphisms (SNPs) were used in the final analysis. The association between each SNP and PD was modeled using logistic regression with an additive allele dosage effect and adjusted for sex, age, and axes of geographical variation. RESULTS: Although the discovery stage yielded promising findings for SNPs in several novel genes, including DAB1, none of the results were validated in the replication stage. Furthermore, in meta-analyses across all datasets no genes within PARK10 reached significance after accounting for multiple testing. CONCLUSION: Our results suggest that common variation in the PARK10 region is not associated with PD risk. However, additional studies are needed to assess the role of PARK10 in modifying age at onset and to determine whether rare variants in this region might affect PD susceptibility.

Evaluation of the test of significant toxicity for determining the toxicity of effluents and ambient water samples.

The test of significant toxicity (TST) is a hypothesis-testing approach based on bioequivalence developed by the U.S. Environmental Protection Agency (U.S. EPA) for analyzing whole-effluent toxicity (WET) and ambient toxicity data. The present study compares results of acute and chronic toxicity tests of effluent, storm-water, and ambient (i.e., receiving-water) samples using both the TST and the standard no-observed-effect concentration (NOEC) approach. Valid WET data were analyzed from 890 tests provided by more than 25 dischargers in California and Washington, USA, representing the majority of test methods used in the U.S. WET program. An additional 3,201 freshwater chronic toxicity tests, obtained from ambient monitoring programs in California, were also analyzed. The TST and NOEC approaches both declared a low number (<6.5%) of tests toxic if effects were below the unacceptable toxicity regulatory management decision (RMD) of 25% effect in chronic tests or 20% effect in acute tests. However, those test methods having generally lower within-test variability and greater test power (e.g., urchin fertilization test) had a much lower percentage of tests declared toxic than the NOEC approach when effects were below the unacceptable toxicity RMD. In addition, the TST showed fewer tests to be nontoxic than NOEC if the test exhibited effects greater than the toxicity RMD (0.1 and 9.6% for TST and NOEC, respectively, for effluents and 0 and 9.5%, respectively, for ambient samples). Our results demonstrate that the TST is more likely to identify a toxic sample when effects are fairly substantial (≥ 25% effect in chronic testing and ≥ 20% effect in acute tests) and less likely to identify a sample as toxic when effects are negligible (≤ 10% effect). Furthermore, these results demonstrate that appropriate WET data interpretation benefits from having well-designed test methods with sufficient power to identify significant toxicity or biologically insignificant effects when they occur.

SNCA variant associated with Parkinson disease and plasma alpha-synuclein level.

BACKGROUND: A functional repeat polymorphism in the SNCA promoter (REP1) conveys susceptibility for Parkinson disease (PD). There is also increasing evidence that single-nucleotide polymorphisms (SNPs) elsewhere in the gene are associated with PD risk. OBJECTIVES: To further explore the association of common SNCA SNPs with PD susceptibility, to determine whether evidence of allelic heterogeneity exists, and to examine the correlation between PD-associated variants and plasma α-synuclein levels. DESIGN: Two-tiered analysis. SETTING: Academic research. PATIENTS: Patients and control subjects from the NeuroGenetics Research Consortium. MAIN OUTCOME MEASURES: We performed a 2-tiered analysis of 1956 patients with PD and 2112 controls from the NeuroGenetics Research Consortium using a comprehensive tag SNP approach. Previously published REP1 genotypes were also included. Plasma α-synuclein was assayed in 86 patients with PD and 78 controls using a highly sensitive Luminex assay. RESULTS: Five of 15 SNPs genotyped were associated with PD under an additive model in tier 1 (α = .05). Of these, 4 were successfully replicated in tier 2. In the combined sample, the most significant marker was rs356219 (odds ratio, 1.41; 95% confidence interval, 1.28-1.55; P = 1.6 × 10(-12)), located approximately 9 kilobases downstream from the gene. A regression model containing rs356219 alone best fit the data. The linkage disequilibrium correlation coefficient between this SNP and REP1 was low (r(2) = 0.09). The risk-associated C allele of rs356219 was also correlated with higher transformed plasma α-synuclein levels in patients under an adjusted additive model (P = .005). CONCLUSIONS: Our data suggest that 1 or more unidentified functional SNCA variants modify risk for PD and that the effect is larger than and independent of REP1. This variant(s), tagged by rs356219, might act by upregulating SNCA expression in a dose-dependent manner.

Elucidating mechanisms of recurrent laryngeal nerve injury during thyroidectomy and parathyroidectomy.

BACKGROUND: Intraoperative nerve monitoring during thyroidectomy, parathyroidectomy, or related central neck procedures can elucidate actual or potential mechanisms of recurrent laryngeal nerve (RLN) injury, especially visually intact nerves, which were previously unknown to the endocrine surgeon. STUDY DESIGN: In this prospective evaluation study, 373 patients underwent 380 consecutive thyroidectomy- or parathyroidectomy-related operations using intraoperative nerve monitoring, with 666 RLNs at risk. The success of visual and functional identification of the RLN, persistent loss of RLN function to nerve stimulation, the mechanism and location of RLN injury, and anatomy of the RLN or technical difficulties that appeared potentially risky for RLN injury were recorded. RESULTS: RLN was identified visually or functionally in 98.2% of nerves at risk. Initial intraoperative injury to the RLN occurred in 25 nerves at risk (3.75%). It was significantly more likely to be a visually intact RLN (n = 22; 3.3%) than a transected RLN (n = 3; 0.45%), p < 0.001. Paralysis persisted in 2 RLNs (0.3%). Visual misidentification accounted for only 1 RLN injury; the most common cause of injury resulted from traction to the anterior motor branch of a bifurcated RLN near the ligament of Berry (n = 7; 28%), then paratracheal lymph node dissection (n = 6; 24%), incorporating ligature (n = 4; 16%), and adherent cancer (n = 4; 16%). Fifty nerves at risk (7.5%) were identified as particularly at risk for injury, most notably those with anatomic variants (n = 26; 52%) and large or vascular thyroid lobes (n = 19; 38%). CONCLUSIONS: RLN injury during thyroidectomy or parathyroidectomy occurs intraoperatively significantly more often to a visually intact RLN than to a transected nerve. The anterior motor branch of an RLN bifurcating near the ligament of Berry is particularly at risk of traction injury.