Citations

Aggregated α-synuclein (α-SYN) proteins, encoded by the SNCA gene, are hallmarks of Lewy body disease (LBD), affecting multiple brain regions. However, the specific mechanisms underlying α-SYN pathology in cortical neurons, crucial for LBD-associated dementia, remain unclear. Here, we recapitulated α-SYN pathologies in human induced pluripotent stem cells (iPSCs)–derived cortical organoids generated from patients with LBD with SNCA gene triplication. Single-cell RNA sequencing, combined with functional and molecular validation, identified synaptic and mitochondrial dysfunction in excitatory neurons exhibiting high expression of the SNCA gene, aligning with observations in the cortex of autopsy-confirmed LBD human brains. Furthermore, we screened 1280 Food and Drug Administration–approved drugs and identified four candidates (entacapone, tolcapone, phenazopyridine hydrochloride, and zalcitabine) that inhibited α-SYN seeding activity in real-time quaking-induced conversion assays with human brains, reduced α-SYN aggregation, and alleviated mitochondrial dysfunction in SNCA triplication organoids and excitatory neurons. Our findings establish human cortical LBD models and suggest potential therapeutic drugs targeting α-SYN aggregation for LBD.

AbstractBackgroundLoss of function mutations in PINK1 and PRKN are the most common causes of early‐onset Parkinson disease (PD). The encoded ubiquitin (Ub) kinase PINK1 and the E3 Ub ligase PRKN together regulate the autophagic degradation of dysfunctional mitochondria, termed mitophagy. During this cytoprotective process, PINK1 and PRKN identify and jointly decorate damaged mitochondria with phosphorylated Ub (pS65‐Ub) that serves as the mitophagy tag. Accumulating evidence suggest a pathogenic role for impaired mitophagy in PD and related neurodegenerative conditions. This is in line with our previous finding of increased levels of the mitophagy marker pS65‐Ub in the hippocampus of postmortem Lewy body disease (LBD) brain.MethodWe performed a genome‐wide association study (GWAS) of hippocampal pS65‐Ub level to identify novel regulators of the PINK1‐PRKN‐directed mitophagy in LBD. In our two‐stage GWAS, we obtained 1,012 autopsy confirmed LBD samples (754 discovery stage, 258, replication stage) from Caucasian participants of European ancestry. Using an established, mostly automated workflow, hippocampal sections were immunostained for pS65‐Ub, scanned, and quantified with unbiased algorithms.ResultOur findings identified that APOE rs429358 (β: 0.50, 95% CI: 0.41 to 0.69, p = 8.67×10−25) was very strongly associated with pS65‐Ub levels in LBD brain. The APOE4 genotype is known to exacerbate Aβ and tau deposition. We did observe strong correlations of pS65‐Ub levels with both tau tangle and senile plaque density in the entire LBD cohort. Nevertheless, the increased pS65‐Ub levels in APOE4‐carrying LBD brains were also independent of Aβ and tau deposition in a subgroup (N = 175) with medium levels of these pathologies. To further explore APOE4 effects on mitophagy outside disease context, this observation was also confirmed in APOE‐targeted replacement mice and in induced pluripotent stem cell‐derived astrocytes.ConclusionOur findings nominate a novel mitophagy regulator in LBD brain and highlight a strong association of APOE4 with mitophagy alteration. Our results suggested that APOE4 may mediate mitophagy defects through two mechanisms, by aggravating Alzheimer’s‐type pathologies and also independent of them. With APOE4 being the strongest known risk factor for Alzheimer’s disease and dementia with Lewy bodies, our findings suggest a common mechanistic link underscoring the importance of mitochondrial quality control.

AbstractBackgroundAs 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.ObjectiveThe 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.MethodsWe 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.ResultsWe 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.ConclusionsWithin 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.

Loss of either PINK1 or PRKN causes an early onset Parkinson’s disease (PD) phenotype. Functionally, PINK1 and PRKN work together to mediate stress-activated mitochondrial quality control. Upon mitochondrial damage, PINK1, a ubiquitin kinase and PRKN, a ubiquitin ligase, decorate damaged organelles with phosphorylated ubiquitin for sequestration and degradation in lysosomes, a process known as mitophagy. While several genetic mutations are established to result in loss of mitophagy function, many others have not been extensively characterized and are of unknown significance. Here, we analyzed a set of twenty variants, ten in each gene, focusing on understudied variants mostly from the Parkinson’s progressive marker initiative, with sensitive assays to define potential functional deficits. Our results nominate specific rare genetic PINK1 and PRKN variants that cause loss of enzymatic function in line with a potential causative role for PD. Additionally, we identify several variants with intermediate phenotypes and follow up on two of them by gene editing midbrain-derived neuronal precursor cells. Thereof derived isogenic neurons show a stability defect of the rare PINK1 D525N mutation, while the common PINK1 Q115L substitution results in reduced kinase activity. Our strategy to analyze variants with sensitive functional readouts will help aid diagnostics and disease treatment in line with current genomic and therapeutic advances.

Parkinson’s disease (PD) is generally considered a sporadic disorder, but a strong genetic background is often found. The aim of this study was to identify the underlying genetic cause of PD in two affected siblings and to subsequently assess the role of mutations in Cathepsin B (CTSB) in susceptibility to PD. A typical PD family was identified and whole-exome sequencing was performed in two affected siblings. Variants of interest were validated using Sanger sequencing. CTSB p.Gly284Val was genotyped in 2077 PD patients and 615 unrelated healthy controls from the Czech Republic, Ireland, Poland, Ukraine, and the USA. The gene burden analysis was conducted for the CTSB gene in an additional 769 PD probands from Mayo Clinic Florida familial PD cohort. CTSB expression and activity in patient-derived fibroblasts and controls were evaluated by qRT-PCR, western blot, immunocytochemistry, and enzymatic assay. The CTSB p.Gly284Val candidate variant was only identified in affected family members. Functional analysis of CTSB patient-derived fibroblasts under basal conditions did not reveal overt changes in endogenous expression, subcellular localization, or enzymatic activity in the heterozygous carrier of the CTSB variant. The identification of the CTSB p.Gly284Val may support the hypothesis that the CTSB locus harbors variants with differing penetrance that can determine the disease risk.