Mitochondrial and Clearance Impairment in p.D620N VPS35 Patient-Derived Neurons

in Movement Disorders (2020)

Background: VPS35 is part of the retromer complex and is responsible for the trafficking and recycling of proteins implicated in autophagy and lysosomal degradation, but also takes part in the degradation ... [more ▼]

Background: VPS35 is part of the retromer complex and is responsible for the trafficking and recycling of proteins implicated in autophagy and lysosomal degradation, but also takes part in the degradation of mitochondrial proteins via mitochondria-derived vesicles. The p.D620N mutation of VPS35 causes an autosomal-dominant form of Parkinson’s disease (PD), clinically representing typical PD. Objective: Most of the studies on p.D620N VPS35 were performed on human tumor cell lines, rodent models overexpressing mutant VPS35, or in patient-derived fibroblasts. Here, based on identified target proteins, we investigated the implication of mutant VPS35 in autophagy, lysosomal degradation, and mitochondrial function in induced pluripotent stem cell-derived neurons from a patient harboring the p.D620N mutation. Methods: We reprogrammed fibroblasts from a PD patient carrying the p.D620N mutation in the VPS35 gene and from two healthy donors in induced pluripotent stem cells. These were subsequently differentiated into neuronal precursor cells to finally generate midbrain dopaminergic neurons. Results: We observed a decreased autophagic flux and lysosomal mass associated with an accumulation of α-synuclein in patient-derived neurons compared to controls. Moreover, patient-derived neurons presented a mitochondrial dysfunction with decreased membrane potential, impaired mitochondrial respiration, and increased production of reactive oxygen species associated with a defect in mitochondrial quality control via mitophagy. Conclusion: We describe for the first time the impact of the p.D620N VPS35 mutation on autophago-lysosome pathway and mitochondrial function in stem cell-derived neurons from an affected p.D620N carrier and define neuronal phenotypes for future pharmacological interventions [less ▲]

Generation of two iPS cell lines (HIHDNDi001-A and HIHDNDi001-B) from a Parkinson's disease patient carrying the heterozygous p.A30P mutation in SNCA.

in Stem cell research (2020), 48

Dermal fibroblasts from a patient carrying a heterozygous c.88G > C mutation in the SNCA gene that encodes alpha-synuclein were reprogrammed to pluripotency by retroviruses. This pathogenic mutation ... [more ▼]

Dermal fibroblasts from a patient carrying a heterozygous c.88G > C mutation in the SNCA gene that encodes alpha-synuclein were reprogrammed to pluripotency by retroviruses. This pathogenic mutation generates the p.A30P form of the alpha-synuclein protein leading to autosomal dominantly inherited Parkinson's disease (PD). Two clonal iPS cell lines were generated (A30P-3 and A30P-4) and characterised by validating the silencing of viral transgenes, the expression of endogenous pluripotency genes, directed differentiation into three germ layers in-vitro and a stable molecular genotype. These iPSC lines will serve as a valuable resource in determining the role of the p.A30P SNCA mutation in PD pathogenesis. [less ▲]

Using High-Content Screening to Generate Single-Cell Gene-Corrected Patient-Derived iPS Clones Reveals Excess Alpha-Synuclein with Familial Parkinson's Disease Point Mutation A30P.

in Cells (2020), 9(9),

The generation of isogenic induced pluripotent stem cell (iPSC) lines using CRISPR-Cas9 technology is a technically challenging, time-consuming process with variable efficiency. Here we use fluorescence ... [more ▼]

The generation of isogenic induced pluripotent stem cell (iPSC) lines using CRISPR-Cas9 technology is a technically challenging, time-consuming process with variable efficiency. Here we use fluorescence-activated cell sorting (FACS) to sort biallelic CRISPR-Cas9 edited single-cell iPSC clones into high-throughput 96-well microtiter plates. We used high-content screening (HCS) technology and generated an in-house developed algorithm to select the correctly edited isogenic clones for continued expansion and validation. In our model we have gene-corrected the iPSCs of a Parkinson's disease (PD) patient carrying the autosomal dominantly inherited heterozygous c.88G>C mutation in the SNCA gene, which leads to the pathogenic p.A30P form of the alpha-synuclein protein. Undertaking a PCR restriction-digest mediated clonal selection strategy prior to sequencing, we were able to post-sort validate each isogenic clone using a quadruple screening strategy prior to generating footprint-free isogenic iPSC lines, retaining a normal molecular karyotype, pluripotency and three germ-layer differentiation potential. Directed differentiation into midbrain dopaminergic neurons revealed that SNCA expression is reduced in the gene-corrected clones, which was validated by a reduction at the alpha-synuclein protein level. The generation of single-cell isogenic clones facilitates new insights in the role of alpha-synuclein in PD and furthermore is applicable across patient-derived disease models. [less ▲]

Variants in Miro1 cause alterations of ER-mitochondria contact sites in fibroblasts from Parkinson's disease patients

in Journal of Clinical Medicine (2019)

Background: Although most cases of Parkinson´s disease (PD) are idiopathic with unknown cause, an increasing number of genes and genetic risk factors have been discovered that play a role in PD ... [more ▼]

Background: Although most cases of Parkinson´s disease (PD) are idiopathic with unknown cause, an increasing number of genes and genetic risk factors have been discovered that play a role in PD pathogenesis. Many of the PD‐associated proteins are involved in mitochondrial quality control, e.g., PINK1, Parkin, and LRRK2, which were recently identified as regulators of mitochondrial‐endoplasmic reticulum (ER) contact sites (MERCs) linking mitochondrial homeostasis to intracellular calcium handling. In this context, Miro1 is increasingly recognized to play a role in PD pathology. Recently, we identified the first PD patients carrying mutations in RHOT1, the gene coding for Miro1. Here, we describe two novel RHOT1 mutations identified in two PD patients and the characterization of the cellular phenotypes. Methods: Using whole exome sequencing we identified two PD patients carrying heterozygous mutations leading to the amino acid exchanges T351A and T610A in Miro1. We analyzed calcium homeostasis and MERCs in detail by live cell imaging and immunocytochemistry in patient‐derived fibroblasts. Results: We show that fibroblasts expressing mutant T351A or T610A Miro1 display impaired calcium homeostasis and a reduced amount of MERCs. All fibroblast lines from patients with pathogenic variants in Miro1, revealed alterations of the structure of MERCs. Conclusion: Our data suggest that Miro1 is important for the regulation of the structure and function of MERCs. Moreover, our study supports the role of MERCs in the pathogenesis of PD and further establishes variants in RHOT1 as rare genetic risk factors for neurodegeneration. [less ▲]