Objective This work was undertaken in order to identify Parkinson's disease (PD) risk variants in a Latino cohort, to describe the overlap in the genetic architecture of PD in Latinos compared to European‐ancestry subjects, and to increase the diversity in PD genome‐wide association (GWAS) data. Methods We genotyped and imputed 1,497 PD cases and controls recruited from nine clinical sites across South America. We performed a GWAS using logistic mixed models; variants with a p‐value <1 × 10−5 were tested in a replication cohort of 1,234 self‐reported Latino PD cases and 439,522 Latino controls from 23andMe, Inc. We also performed an admixture mapping analysis where local ancestry blocks were tested for association with PD status. Results One locus, SNCA, achieved genome‐wide significance (p‐value <5 × 10−8); rs356182 achieved genome‐wide significance in both the discovery and the replication cohorts (discovery, G allele: 1.58 OR, 95% CI 1.35–1.86, p‐value 2.48 × 10−8; 23andMe, G allele: 1.26 OR, 95% CI 1.16–1.37, p‐value 4.55 × 10−8). In our admixture mapping analysis, a locus on chromosome 14, containing the gene STXBP6, achieved significance in a joint test of ancestries and in the Native American single‐ancestry test (p‐value <5 × 10−5). A second locus on chromosome 6, containing the gene RPS6KA2, achieved significance in the African single‐ancestry test (p‐value <5 × 10−5). Interpretation This study demonstrated the importance of the SNCA locus for the etiology of PD in Latinos. By leveraging the demographic history of our cohort via admixture mapping, we identified two potential PD risk loci that merit further study. ANN NEUROL 2021;90:353–365

We aimed to perform a comprehensive systematic review of the existing ataxia scales. We described the disorders for which the instruments have been validated and used, the time spent in its application, its validated psychometric properties, and their use in studies of natural history and clinical trials. A search from 1997 onwards was performed in the MEDLINE, LILACS, and Cochrane databases. The web sites ClinicalTrials.gov and Orpha.net were also used to identify the endpoints used in ongoing randomized clinical trials. We identified and described the semiquantitative ataxia scales (ICARS, SARA, MICARS, BARS); semiquantitative ataxia and non-ataxia scales (UMSARS, FARS, NESSCA); a semiquantitative non-ataxia scale (INAS); quantitative ataxia scales (CATSYS 2000, AFCS, CCFS and CCFSw, and SCAFI); and the self-performed ataxia scale (FAIS). SARA and ICARS were the best studied and validated so far, and their reliability sustain their use. Ataxia and non-ataxia scores will probably provide a better view of the overall disability in long-term trials and studies of natural history. Up to now, no clear advantage has been disclosed for any of them; however, we recommend the use of specific measurements of gait since gait ataxia is the first significant manifestation in the majority of ataxia disorders and comment on the best scales to be used in specific ataxia forms. Quantitative ataxia scales will be needed to speed up evidence from phase II clinical trials, from trials focused on the early phase of diseases, and for secondary endpoints in phase III trials. Finally, it is worth remembering that estimation of the actual minimal clinically relevant difference is still lacking; this, together with changes in quality of life, will probably be the main endpoints to measure in future therapeutic studies.

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Mutations in Leucine Repeat Rich Kinase 2 (LRRK2), primarily located in codons G2019 and R1441, represent the most common genetic cause of Parkinson’s disease in European-derived populations. However, little is known about the frequency of these mutations in Latin American populations. In addition, a prior study suggested that a LRRK2 polymorphism (p.Q1111H) specific to Latino and Amerindian populations might be a risk factor for Parkinson’s disease, but this finding requires replication. We screened 1734 Parkinson’s disease patients and 1097 controls enrolled in the Latin American Research Consortium on the Genetics of Parkinson’s disease (LARGE-PD), which includes sites in Argentina, Brazil, Colombia, Ecuador, Peru, and Uruguay. Genotypes were determined by TaqMan assay (p.G2019S and p.Q1111H) or by sequencing of exon 31 (p.R1441C/G/H/S). Admixture proportion was determined using a panel of 29 ancestry informative markers. We identified a total of 29 Parkinson’s disease patients (1.7%) who carried p.G2019S and the frequency ranged from 0.2% in Peru to 4.2% in Uruguay. Only two Parkinson’s disease patients carried p.R1441G and one patient carried p.R1441C. There was no significant difference in the frequency of p.Q1111H in patients (3.8%) compared to controls (3.1%; OR 1.02, p = 0.873). The frequency of LRRK2-p.G2019S varied greatly between different Latin American countries and was directly correlated with the amount of European ancestry observed. p.R1441G is rare in Latin America despite the large genetic contribution made by settlers from Spain, where the mutation is relatively common.

Background: Mutations in the glucocerebrosidase (GBA) gene are an important risk factor for Parkinson's disease (PD). However, most GBA genetic studies in PD have been performed in patients of European origin and very few data are available in other populations. Methods: We sequenced the entire GBA coding region in 602 PD patients and 319 controls from Colombia and Peru enrolled as part of the Latin American Research Consortium on the Genetics of Parkinson's disease (LARGE-PD).