Generation of two induced pluripotent stem cell lines and the corresponding isogenic controls from Parkinson's disease patients carrying the heterozygous mutations c.1290A > G (p.T351A) or c.2067A > G (p.T610A) in the RHOT1 gene encoding Miro1.

in Stem cell research (2023), 69

Primary skin fibroblasts from two Parkinson's disease (PD) patients carrying distinct heterozygous mutations in the RHOT1 gene encoding Miro1, namely c.1290A > G (Miro1 p.T351A) and c.2067A > G (Miro1 p ... [more ▼]

Primary skin fibroblasts from two Parkinson's disease (PD) patients carrying distinct heterozygous mutations in the RHOT1 gene encoding Miro1, namely c.1290A > G (Miro1 p.T351A) and c.2067A > G (Miro1 p.T610A), were converted into induced pluripotent stem cells (iPSCs) by episomal reprogramming. The corresponding isogenic gene-corrected lines have been generated using CRISPR/Cas9 technology. Here, we provide a comprehensive characterization and quality assurance of both isogenic pairs, which will be used to study Miro1-related molecular mechanisms underlying neurodegeneration in iPSC-derived neuronal models (e.g., midbrain dopaminergic neurons and astrocytes). [less ▲]

Functional and Molecular Properties of DYT-SGCE Myoclonus-Dystonia Patient-Derived Striatal Medium Spiny Neurons.

in International journal of molecular sciences (2021), 22(7),

Myoclonus-dystonia (DYT-SGCE, formerly DYT11) is characterized by alcohol-sensitive, myoclonic-like appearance of fast dystonic movements. It is caused by mutations in the SGCE gene encoding ε-sarcoglycan ... [more ▼]

Myoclonus-dystonia (DYT-SGCE, formerly DYT11) is characterized by alcohol-sensitive, myoclonic-like appearance of fast dystonic movements. It is caused by mutations in the SGCE gene encoding ε-sarcoglycan leading to a dysfunction of this transmembrane protein, alterations in the cerebello-thalamic pathway and impaired striatal plasticity. To elucidate underlying pathogenic mechanisms, we investigated induced pluripotent stem cell (iPSC)-derived striatal medium spiny neurons (MSNs) from two myoclonus-dystonia patients carrying a heterozygous mutation in the SGCE gene (c.298T>G and c.304C>T with protein changes W100G and R102X) in comparison to two matched healthy control lines. Calcium imaging showed significantly elevated basal intracellular Ca(2+) content and lower frequency of spontaneous Ca(2+) signals in SGCE MSNs. Blocking of voltage-gated Ca(2+) channels by verapamil was less efficient in suppressing KCl-induced Ca(2+) peaks of SGCE MSNs. Ca(2+) amplitudes upon glycine and acetylcholine applications were increased in SGCE MSNs, but not after GABA or glutamate applications. Expression of voltage-gated Ca(2+) channels and most ionotropic receptor subunits was not altered. SGCE MSNs showed significantly reduced GABAergic synaptic density. Whole-cell patch-clamp recordings displayed elevated amplitudes of miniature postsynaptic currents and action potentials in SGCE MSNs. Our data contribute to a better understanding of the pathophysiology and the development of novel therapeutic strategies for myoclonus-dystonia. [less ▲]

Discordant Monozygotic Parkinson Disease Twins: Role of Mitochondrial Integrity

in Annals of Neurology (2020)

Objective Even though genetic predisposition has proven to be an important element in Parkinson's disease (PD) etiology, monozygotic (MZ) twins with PD displayed a concordance rate of only about 20 ... [more ▼]

Objective Even though genetic predisposition has proven to be an important element in Parkinson's disease (PD) etiology, monozygotic (MZ) twins with PD displayed a concordance rate of only about 20% despite their shared identical genetic background. Methods We recruited 5 pairs of MZ twins discordant for idiopathic PD and established skin fibroblast cultures to investigate mitochondrial phenotypes in these cellular models against the background of a presumably identical genome. To test for genetic differences, we performed whole genome sequencing, deep mitochondrial DNA (mtDNA) sequencing, and tested for mitochondrial deletions by multiplex real‐time polymerase chain reaction (PCR) in the fibroblast cultures. Further, the fibroblast cultures were tested for mitochondrial integrity by immunocytochemistry, immunoblotting, flow cytometry, and real‐time PCR to quantify gene expression. Results Genome sequencing did not identify any genetic difference. We found decreased mitochondrial functionality with reduced cellular adenosine triphosphate (ATP) levels, altered mitochondrial morphology, elevated protein levels of superoxide dismutase 2 (SOD2), and increased levels of peroxisome proliferator‐activated receptor‐gamma coactivator‐α (PPARGC1A) messenger RNA (mRNA) in skin fibroblast cultures from the affected compared to the unaffected twins. Further, there was a tendency for a higher number of somatic mtDNA variants among the affected twins. Interpretation We demonstrate disease‐related differences in mitochondrial integrity in the genetically identical twins. Of note, the clinical expression matches functional alterations of the mitochondria [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 ▲]

PINK1 loss-of-function mutations affect mitochondrial complex I activity via NdufA10 ubiquinone uncoupling.

in Science (2014), 344(6180), 203-7

Under resting conditions, Pink1 knockout cells and cells derived from patients with PINK1 mutations display a loss of mitochondrial complex I reductive activity, causing a decrease in the mitochondrial ... [more ▼]

Under resting conditions, Pink1 knockout cells and cells derived from patients with PINK1 mutations display a loss of mitochondrial complex I reductive activity, causing a decrease in the mitochondrial membrane potential. Analyzing the phosphoproteome of complex I in liver and brain from Pink1(-/-) mice, we found specific loss of phosphorylation of serine-250 in complex I subunit NdufA10. Phosphorylation of serine-250 was needed for ubiquinone reduction by complex I. Phosphomimetic NdufA10 reversed Pink1 deficits in mouse knockout cells and rescued mitochondrial depolarization and synaptic transmission defects in pink(B9)-null mutant Drosophila. Complex I deficits and adenosine triphosphate synthesis were also rescued in cells derived from PINK1 patients. Thus, this evolutionary conserved pathway may contribute to the pathogenic cascade that eventually leads to Parkinson's disease in patients with PINK1 mutations. [less ▲]

Phosphatase and tensin homolog (PTEN)-induced putative kinase 1 (PINK1)-dependent ubiquitination of endogenous Parkin attenuates mitophagy: study in human primary fibroblasts and induced pluripotent stem cell-derived neurons.

in The Journal of biological chemistry (2013), 288(4), 2223-37

Mutations in the E3 ubiquitin ligase Parkin and the mitochondrial PTEN-induced putative kinase 1 (PINK1) have been identified to cause autosomal recessive forms of familial Parkinson disease, with PINK1 ... [more ▼]

Mutations in the E3 ubiquitin ligase Parkin and the mitochondrial PTEN-induced putative kinase 1 (PINK1) have been identified to cause autosomal recessive forms of familial Parkinson disease, with PINK1 functioning upstream of Parkin in a pathway important for the maintenance of mitochondrial function and morphology. Upon the loss of the mitochondrial membrane potential, Parkin translocates to mitochondria in a PINK1-dependent manner to ubiquitinate mitochondrial proteins. Parkin-mediated polyubiquitination of outer mitochondrial membrane (OMM) proteins recruits the ubiquitin- and LC3-binding adaptor protein p62 to mitochondria and induces mitophagy. Although previous studies examined mitophagy in established cell lines through overexpression approaches, there is an imperative to study the role of endogenous Parkin and PINK1 in human-derived and biologically relevant cell models. Here, we demonstrate in human primary fibroblasts and induced pluripotent stem-derived neurons from controls and PINK1 mutation carriers that endogenous levels of Parkin are not sufficient to initiate mitophagy upon loss of the mitochondrial membrane potential, caused by its (self-)ubiquitination, followed by degradation via the ubiquitin proteasome system. Next, we showed differential PINK1-dependent, Parkin-mediated ubiquitination of OMM proteins, which is Parkin dose-dependent and affects primarily OMM proteins of higher molecular mass. In contrast to the situation fibroblasts, we did not detect mitophagy in induced pluripotent stem-derived neurons even upon overexpression of Parkin. Taken together, our data demonstrate that mitophagy differs between human non-neuronal and neuronal cells and between "endogenous" and "Parkin-overexpressing" cellular models. [less ▲]

Effect of endogenous mutant and wild-type PINK1 on Parkin in fibroblasts from Parkinson disease patients.

in Human molecular genetics (2010), 19(16), 3124-37

Mutations in the PTEN-induced putative kinase 1 (PINK1), a mitochondrial serine-threonine kinase, and Parkin, an E3 ubiquitin ligase, are associated with autosomal-recessive forms of Parkinson disease (PD ... [more ▼]

Mutations in the PTEN-induced putative kinase 1 (PINK1), a mitochondrial serine-threonine kinase, and Parkin, an E3 ubiquitin ligase, are associated with autosomal-recessive forms of Parkinson disease (PD). Both are involved in the maintenance of mitochondrial integrity and protection from multiple stressors. Recently, Parkin was demonstrated to be recruited to impaired mitochondria in a PINK1-dependent manner, where it triggers mitophagy. Using primary human dermal fibroblasts originating from PD patients with various PINK1 mutations, we showed at the endogenous level that (i) PINK1 regulates the stress-induced decrease of endogenous Parkin; (ii) mitochondrially localized PINK1 mediates the stress-induced mitochondrial translocation of Parkin; (iii) endogenous PINK1 is stabilized on depolarized mitochondria; and (iv) mitochondrial accumulation of full-length PINK1 is sufficient but not necessary for the stress-induced loss of Parkin signal and its mitochondrial translocation. Furthermore, we showed that different stressors, depolarizing or non-depolarizing, led to the same effect on detectable Parkin levels and its mitochondrial targeting. Although this effect on Parkin was independent of the mitochondrial membrane potential, we demonstrate a differential effect of depolarizing versus non-depolarizing stressors on endogenous levels of PINK1. Our study shows the necessity to introduce an environmental factor, i.e. stress, to visualize the differences in the interaction of PINK1 and Parkin in mutants versus controls. Establishing human fibroblasts as a suitable model for studying this interaction, we extend data from animal and other cellular models and provide experimental evidence for the generally held notion of PD as a condition with a combined genetic and environmental etiology. [less ▲]