References of "Seibler, Philip"
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See detailParkin Deficiency Impairs Mitochondrial DNA Dynamics and Propagates Inflammation.
Wasner, Kobi; Smajic, Semra UL; Ghelfi, Jenny UL et al

in Movement disorders : official journal of the Movement Disorder Society (2022)

BACKGROUND: Mutations in the E3 ubiquitin ligase parkin cause autosomal recessive Parkinson's disease (PD). Together with PTEN-induced kinase 1 (PINK1), parkin regulates the clearance of dysfunctional ... [more ▼]

BACKGROUND: Mutations in the E3 ubiquitin ligase parkin cause autosomal recessive Parkinson's disease (PD). Together with PTEN-induced kinase 1 (PINK1), parkin regulates the clearance of dysfunctional mitochondria. New mitochondria are generated through an interplay of nuclear- and mitochondrial-encoded proteins, and recent studies suggest that parkin influences this process at both levels. In addition, parkin was shown to prevent mitochondrial membrane permeability, impeding mitochondrial DNA (mtDNA) escape and subsequent neuroinflammation. However, parkin's regulatory roles independent of mitophagy are not well described in patient-derived neurons. OBJECTIVES: We sought to investigate parkin's role in preventing neuronal mtDNA dyshomeostasis, release, and glial activation at the endogenous level. METHODS: We generated induced pluripotent stem cell (iPSC)-derived midbrain neurons from PD patients with parkin (PRKN) mutations and healthy controls. Live-cell imaging, proteomic, mtDNA integrity, and gene expression analyses were employed to investigate mitochondrial biogenesis and genome maintenance. To assess neuroinflammation, we performed single-nuclei RNA sequencing in postmortem tissue and quantified interleukin expression in mtDNA/lipopolysaccharides (LPS)-treated iPSC-derived neuron-microglia co-cultures. RESULTS: Neurons from patients with PRKN mutations revealed deficits in the mitochondrial biogenesis pathway, resulting in mtDNA dyshomeostasis. Moreover, the energy sensor sirtuin 1, which controls mitochondrial biogenesis and clearance, was downregulated in parkin-deficient cells. Linking mtDNA disintegration to neuroinflammation, in postmortem midbrain with PRKN mutations, we confirmed mtDNA dyshomeostasis and detected an upregulation of microglia overexpressing proinflammatory cytokines. Finally, parkin-deficient neuron-microglia co-cultures elicited an enhanced immune response when exposed to mtDNA/LPS. CONCLUSIONS: Our findings suggest that parkin coregulates mitophagy, mitochondrial biogenesis, and mtDNA maintenance pathways, thereby protecting midbrain neurons from neuroinflammation and degeneration. © 2022 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society. [less ▲]

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See detailFunctional and Molecular Properties of DYT-SGCE Myoclonus-Dystonia Patient-Derived Striatal Medium Spiny Neurons.
Kutschenko, Anna; Staege, Selma; Grütz, Karen et al

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 ▲]

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See detailDiscordant Monozygotic Parkinson Disease Twins: Role of Mitochondrial Integrity
Dulovic-Mahlow, Marija; König, Inke R.; Trinh, Joanne et al

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 ▲]

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See detailMitochondrial Mechanisms of LRRK2 G2019S Penetrance
Delcambre, Sylvie UL; Ghelfi, Jenny UL; Ouzren, Nassima et al

in Frontiers in Neurology (2020)

Several mutations in leucine-rich repeat kinase-2 (LRRK2) have been associated with Parkinson’s disease (PD). The most common substitution, G2019S, interferes with LRRK2 kinase activity, which is ... [more ▼]

Several mutations in leucine-rich repeat kinase-2 (LRRK2) have been associated with Parkinson’s disease (PD). The most common substitution, G2019S, interferes with LRRK2 kinase activity, which is regulated by autophosphorylation. Yet, the penetrance of this gain-of-function mutation is incomplete, and thus far, few factors have been correlated with disease status in carriers. This includes (i) LRRK2 autophosphorylation in urinary exosomes, (ii) serum levels of the antioxidant urate, and (iii) abundance of mitochondrial DNA (mtDNA) transcription-associated 7S DNA. In light of a mechanistic link between LRRK2 kinase activity and mtDNA lesion formation, we previously investigated mtDNA integrity in fibroblasts from manifesting (LRRK2+/PD+) and non-manifesting carriers (LRRK2+/PD−) of the G2019S mutation as well as from aged-matched controls. In our published study, mtDNA major arc deletions correlated with PD status, with manifesting carriers presenting the highest levels. In keeping with these findings, we now further explored mitochondrial features in fibroblasts derived from LRRK2+/PD+ (n = 10), LRRK2+/PD− (n = 21), and control (n = 10) individuals. In agreement with an accumulation of mtDNA major arc deletions, we also detected reduced NADH dehydrogenase activity in the LRRK2+/PD+ group. Moreover, in affected G2019S carriers, we observed elevated mitochondrial mass and mtDNA copy numbers as well as increased expression of the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), which regulates antioxidant signaling. Taken together, these results implicate mtDNA dyshomeostasis—possibly as a consequence of impaired mitophagy—in the penetrance of LRRK2-associated PD. Our findings are a step forward in the pursuit of unveiling markers that will allow monitoring of disease progression of LRRK2 mutation carriers [less ▲]

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See detailVariants in Miro1 cause alterations of ER-mitochondria contact sites in fibroblasts from Parkinson's disease patients
Berenguer, Clara UL; Grossmann, Dajana; Massart, François UL et al

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 ▲]

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See detailMtDNA deletions discriminate affected from unaffected LRRK2 mutation carriers
Ouzren, Nassima UL; Delcambre, Sylvie UL; Ghelfi, Jenny UL et al

in Annals of Neurology (2019), 86(2), 324-326

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See detailTHAP1, the gene mutated in DYT6 dystonia, autoregulates its own expression.
Erogullari, Alev; Hollstein, Ronja; Seibler, Philip et al

in Biochimica et biophysica acta (2014), 1839(11), 1196-204

THAP1 encodes a transcription factor but its regulation is largely elusive. TOR1A was shown to be repressed by THAP1 in vitro. Notably, mutations in both of these genes lead to dystonia (DYT6 or DYT1 ... [more ▼]

THAP1 encodes a transcription factor but its regulation is largely elusive. TOR1A was shown to be repressed by THAP1 in vitro. Notably, mutations in both of these genes lead to dystonia (DYT6 or DYT1). Surprisingly, expressional changes of TOR1A in THAP1 mutation carriers have not been detected indicating additional levels of regulation. Here, we investigated whether THAP1 is able to autoregulate its own expression. Using in-silico prediction, luciferase reporter gene assays, and (quantitative) chromatin immunoprecipitation (ChIP), we defined the THAP1 minimal promoter to a 480bp-fragment and demonstrated specific binding of THAP1 to this region which resulted in repression of the THAP1 promoter. This autoregulation was disturbed by different DYT6-causing mutations. Two mutants (Ser6Phe, Arg13His) were shown to be less stable than wildtype THAP1 adding to the effect of reduced binding to the THAP1 promoter. Overexpressed THAP1 is preferably degraded through the proteasome. Notably, endogenous THAP1 expression was significantly reduced in cells overexpressing wildtype THAP1 as demonstrated by quantitative PCR. In contrast, higher THAP1 levels were detected in induced pluripotent stem cell (iPS)-derived neurons from THAP1 mutation carriers. Thus, we identified a feedback-loop in the regulation of THAP1 expression and demonstrated that mutant THAP1 leads to higher THAP1 expression levels. This compensatory autoregulation may contribute to the mean age at onset in the late teen years or even reduced penetrance in some THAP1 mutation carriers. [less ▲]

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See detailPINK1 loss-of-function mutations affect mitochondrial complex I activity via NdufA10 ubiquinone uncoupling.
Morais, Vanessa A.; Haddad, Dominik; Craessaerts, Katleen et al

in Science (New York, N.Y.) (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 ▲]

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See detailPhosphatase 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.
Rakovic, Aleksandar; Shurkewitsch, Katharina; Seibler, Philip et al

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 ▲]

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See detailATP13A2 mutations impair mitochondrial function in fibroblasts from patients with Kufor-Rakeb syndrome.
Grünewald, Anne UL; Arns, Bjorn; Seibler, Philip et al

in Neurobiology of Aging (2012), 33(8), 18431-7

Mutations in ATP13A2 cause autosomal-recessive parkinsonism (Kufor-Rakeb syndrome; KRS). Because several other parkinsonism-associated proteins have been connected to mitochondrial function and mitophagy ... [more ▼]

Mutations in ATP13A2 cause autosomal-recessive parkinsonism (Kufor-Rakeb syndrome; KRS). Because several other parkinsonism-associated proteins have been connected to mitochondrial function and mitophagy, we studied the impact of endogenous mutations in ATPase type 13A2 (ATP13A2) on mitochondria in fibroblasts from KRS patients compared with controls. In patients, we detected decreased adenosine triphosphate (ATP) synthesis rates, increased mitochondrial DNA levels, a higher frequency of mitochondrial DNA lesions, increased oxygen consumption rates, and increased fragmentation of the mitochondrial network. Importantly, overexpression of wild-type ATP13A2 rescued the respiration phenotype. These findings collectively suggest that ATP13A2 contributes to the maintenance of a healthy mitochondrial pool, supporting the hypothesis that impaired mitochondrial clearance represents an important pathogenic mechanism underlying KRS. [less ▲]

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See detailEffect of endogenous mutant and wild-type PINK1 on Parkin in fibroblasts from Parkinson disease patients.
Rakovic, Aleksandar; Grünewald, Anne UL; Seibler, Philip et al

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 ▲]

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