Pathogenic Pathways in Early-Onset Autosomal Recessive Parkinson's Disease Discovered Using Isogenic Human Dopaminergic Neurons

Abstract

Parkinson's disease (PD) is a complex and highly variable neurodegenerative disease. Familial PD is caused by mutations in several genes with diverse and mostly unknown functions. It is unclear how dysregulation of these genes results in the relatively selective death of nigral dopaminergic neurons (DNs). To address this question, we modeled PD by knocking out the PD genes PARKIN (PRKN), DJ-1 (PARK7), and ATP13A2 (PARK9) in independent isogenic human pluripotent stem cell (hPSC) lines. We found increased levels of oxidative stress in all PD lines. Increased death of DNs upon differentiation was found only in the PARKIN knockout line. Using quantitative proteomics, we observed dysregulation of mitochondrial and lysosomal function in all of the lines, as well as common and distinct molecular defects caused by the different PD genes. Our results suggest that precise delineation of PD subtypes will require evaluation of molecular and clinical data.

Targeting mitophagy in Parkinson's disease

“…PD is a complex disorder with heterogeneity in pathophysiology and clinical presentation. This is clearest in monogenic PD patients; for example Lewy bodies, a hallmark of PD pathology, are not seen in all PINK1, Parkin and LRRK2 associated PD patients (180)(181)(182). Mitochondrial or mitophagy defects may be involved to a different degree in different patients and at different times.…”

Patient-Derived Midbrain Organoids to Explore the Molecular Basis of Parkinson's Disease

“…More recent evolutions of these protocols have confirmed the initial observations, as well as aimed at increasing the quality and reproducibility of hMO ( 67 , 72 – 76 ) and better estimating their yield of mDA neurons. For instance, using a high content image analysis approach, Smits et al ( 73 ) showed that TH+ cells composed 62% of all cells after 1 month of differentiation, while Ahfeldt et al ( 74 ) found using a knock-in TH:tdtomato line, that TH+ cells composed ~38% of total cells at a similar timepoint. Such differences are likely to arise from cell line effects as well as protocol variations.…”

“…More recently, an extensive report from Ahfeldt et al ( 74 ) used hMO to study the roles of 3 severe PD-associated mutations (in PRKN/PARK2, DJ1/PARK7 , and ATP13A2/PARK9 ) through genomic editing of a healthy control hiPSC line. RNAseq analyses of TH+ cells after 1 month of differentiation found that PRKN –/– mDA neurons showed the highest amount of differentially expressed genes (1641) compared to controls.…”

“…In the long run, hMO technology opens up perspectives for personalized medicine. The study by Ahfeldt et al ( 74 ) identified at least two distinct molecular phenotypes in hMO derived from either PRKN −/− , or ATP13A2 / DJ1 mutated lines, indicating that familial PD mutations induce different pathological cascades, which may call for different therapeutic strategies. Furthermore, personalized medicine approaches may also be explored in cases of non-familial PD.…”

The Convergence of Alpha-Synuclein, Mitochondrial, and Lysosomal Pathways in Vulnerability of Midbrain Dopaminergic Neurons in Parkinson’s Disease

“…In addition, theoretical indices derived from DA/metabolites relative ratios have suggested that both reduced vesicular DA uptake and ALDH1A1 activity accounted for DOPAL accumulation in PD putamen ( Goldstein et al, 2013 ). Quantitative proteomics and transcriptomics highlighted mitochondrial and lysosomal dysregulation and differential vulnerability of DAergic neurons derived from several isogenic PD gene knockout pluripotent stem cell lines ( Ahfeldt et al, 2020 ).…”