Challenges in Clinico-Genetic Correlations in Parkinson’s disease (PD): The Role of Copy Number Variants (CNV)

Parkinson’s disease (PD) represents the second most common neurodegenerative disease and remains incurable. Mutations in multiple genes have been linked to monogenic PD (gPD); these monogenic forms, however, represent a small number of cases while in most instances PD appears as idiopathic (iPD). These findings raise the question of whether genetic and idiopathic parkinsonisms constitute the same disease. Nevertheless, monogenic-PD phenotypes and iPD both fulfill MDS criteria for PD, and show evidence of alpha-synuclein aggregates in both conditions. Distinct genetic loci in rare Mendelian forms have been identified as causal mutations, others as possible disease-causing genes, and genome-wide association studies have reported several risk loci, many of them located in the genes associated with the dominant mutations. Not only single-nucleotide polymorphisms (SNPs), but other kinds of DNA molecular defects as well have been spotted as significant disease-causing mutations, including large chromosomal structural rearrangements and copy number variations (CNVs). As their size varies, and detection methodologies have different sensitivity and resolution, CNVs pose a special challenge in genetic studies, and there currently is a debate on the pathogenetic or susceptibility impact of specific CNVs on PD. In this review, through multiple instances of experimental evidence, we analyze the impact on histopathology of the different mutational mechanisms involved in the genesis and etiology of PD. We believe that increasing our knowledge about the changes and implications at tissue level produced by each of those mechanisms will allow to develop much more suitable and personalized potential therapeutic strategies, biomarker identification, as well as disease modeling, agreeing with the precision medicine concept.Fil: Gatto, Emilia Mabel. Instituto de Neurociencias Buenos Aires S. A.; ArgentinaFil: Radrizzani Helguera, Martin. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de San Martín; ArgentinaFil: González Rojas, Natalia. Instituto de Neurociencias Buenos Aires S. A.; ArgentinaFil: Cesarini, Martin Emiliano. Instituto de Neurociencias Buenos Aires S. A.; ArgentinaFil: Etcheverry, José Luis. Instituto de Neurociencias Buenos Aires S. A.; ArgentinaFil: Perandones, Claudia. Dirección Nacional de Instituto de Investigación.Administración Nacional de Laboratorios e Institutos de Salud "Dr. Carlos G. Malbrán"; Argentin

Embracing Monogenic Parkinson's Disease: The MJFF Global Genetic PD Cohort

BACKGROUND: As gene-targeted therapies are increasingly being developed for Parkinson's disease (PD), identifying and characterizing carriers of specific genetic pathogenic variants is imperative. Only a small fraction of the estimated number of subjects with monogenic PD worldwide are currently represented in the literature and availability of clinical data and clinical trial-ready cohorts is limited. OBJECTIVE: The objectives are to (1) establish an international cohort of affected and unaffected individuals with PD-linked variants; (2) provide harmonized and quality-controlled clinical characterization data for each included individual; and (3) further promote collaboration of researchers in the field of monogenic PD. METHODS: We conducted a worldwide, systematic online survey to collect individual-level data on individuals with PD-linked variants in SNCA, LRRK2 VPS35, PRKN, PINK1, DJ-1, as well as selected pathogenic and risk variants in GBA and corresponding demographic, clinical, and genetic data. All registered cases underwent thorough quality checks, and pathogenicity scoring of the variants and genotype-phenotype relationships were analyzed. RESULTS: We collected 3888 variant carriers for our analyses, reported by 92 centers (42 countries) worldwide. Of the included individuals 3185 had a diagnosis of PD (ie, 1306 LRRK2, 115 SNCA, 23 VPS35 429 PRKN, 75 PINK1, 13 DJ-1, and 1224 GBA) and 703 were unaffected (ie, 328 LRRK2, 32 SNCA, 3 VPS35, 1 PRKN, 1 PINK1, and 338 GBA). In total, we identified 269 different pathogenic variants; 1322 individuals in our cohort (34\%) were indicated as not previously published. CONCLUSIONS: Within the MJFF Global Genetic PD Study Group, we (1) established the largest international cohort of affected and unaffected individuals carrying PD-linked variants; (2) provide harmonized and quality-controlled clinical and genetic data for each included individual; (3) promote collaboration in the field of genetic PD with a view toward clinical and genetic stratification of patients for gene-targeted clinical trials. 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society