BLBD: brainstem predominant Lewy body disease; CCCP: carbonyl cyanide m-chlorophenyl hydrazone; DLB: dementia with Lewy bodies; DLBD: diffuse neocortical Lewy body disease; EOPD: early-onset Parkinson disease; GVB: granulovacuolar degeneration body; LB: Lewy body; LBD: Lewy body disease; mitoQC: mitochondrial quality control; nbM: nucleus basalis of Meynert; PD: Parkinson disease; PDD: Parkinson disease with dementia; p-S65-Ub: PINK1-phosphorylated serine 65 ubiquitin; SN: substantia nigra; TLBD: transitional Lewy body disease; Ub: ubiquitin.

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

Huntington disease (HD) is the most common monogenic neurodegenerative disorder in populations of European ancestry, but occurs at lower prevalence in populations of East Asian or black African descent. New mutations for HD result from CAG repeat expansions of intermediate alleles (IAs), usually of paternal origin. The differing prevalence of HD may be related to the rate of new mutations in a population, but no comparative estimates of IA frequency or the HD new mutation rate are available. In this study, we characterize IA frequency and the CAG repeat distribution in fifteen populations of diverse ethnic origin. We estimate the HD new mutation rate in a series of populations using molecular IA expansion rates. The frequency of IAs was highest in Hispanic Americans and Northern Europeans, and lowest in black Africans and East Asians. The prevalence of HD correlated with the frequency of IAs by population and with the proportion of IAs found on the HD-associated A1 haplotype. The HD new mutation rate was estimated to be highest in populations with the highest frequency of IAs. In European ancestry populations, one in 5,372 individuals from the general population and 7.1% of individuals with an expanded CAG repeat in the HD range are estimated to have a molecular new mutation. Our data suggest that the new mutation rate for HD varies substantially between populations, and that IA frequency and haplotype are closely linked to observed epidemiological differences in the prevalence of HD across major ancestry groups in different countries.

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).

No abstract

No abstract

Huntington disease (HD) is a fatal neurodegenerative disorder caused by a gain-of-function mutation in HTT. Suppression of mutant HTT has emerged as a leading therapeutic strategy for HD, with allele-selective approaches targeting HTT SNPs now in clinical trials. Haplotypes associated with the HD mutation (A1, A2, A3a) represent panels of allele-specific gene silencing targets for efficient treatment of individuals with HD of Northern European and indigenous South American ancestry. Here we extend comprehensive haplotype analysis of the HD mutation to key populations of Southern European, South Asian, Middle Eastern, and admixed African ancestry. In each of these populations, the HD mutation occurs predominantly on the A2 HTT haplotype. Analysis of HD haplotypes across all affected population groups enables rational selection of candidate target SNPs for development of allele-selective gene silencing therapeutics worldwide. Targeting SNPs on the A1 and A2 haplotypes in parallel is essential to achieve treatment of the most HD-affected subjects in populations where HD is most prevalent. Current allele-specific approaches will leave a majority of individuals with HD untreated in populations where the HD mutation occurs most frequently on the A2 haplotype. We further demonstrate preclinical development of potent and selective ASOs targeting SNPs on the A2 HTT haplotype, representing an allele-specific treatment strategy for these individuals. On the basis of comprehensive haplotype analysis, we show the maximum proportion of HD-affected subjects that may be treated with three or four allele targets in different populations worldwide, informing current allele-specific HTT silencing strategies.