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See detailMitochondrial DNA heteroplasmy distinguishes disease manifestation in PINK1- and PRKN-linked Parkinson's disease 2022.05.17.22275087
Trinh, Joanne; Hicks, Andrew A.; Koenig, Inke R. et al

E-print/Working paper (2022)

Biallelic mutations in PINK1 and PRKN cause recessively inherited Parkinson's disease (PD). Though some studies suggest that PINK1/PRKN monoallelic mutations may not contribute to risk, deep phenotyping ... [more ▼]

Biallelic mutations in PINK1 and PRKN cause recessively inherited Parkinson's disease (PD). Though some studies suggest that PINK1/PRKN monoallelic mutations may not contribute to risk, deep phenotyping assessment showed that PINK1 or PRKN monoallelic pathogenic variants were at a significantly higher rate in PD compared to controls. Given the established role of PINK1 and Parkin in regulating mitochondrial dynamics, we explored mitochondrial DNA (mtDNA) integrity and inflammation as potential disease modifiers in carriers of mutations in these genes. MtDNA integrity, global gene expression and serum cytokine levels were investigated in a large collection of biallelic (n=84) and monoallelic (n=170) carriers of PINK1/PRKN mutations, iPD patients (n=67) and controls (n=90). Affected and unaffected PINK1/PRKN monoallelic mutation carriers can be distinguished by heteroplasmic mtDNA variant load (AUC=0.83, CI:0.74-0.93). Biallelic PINK1/PRKN mutation carriers harbor more heteroplasmic mtDNA variants in blood (p=0.0006, Z=3.63) compared to monoallelic mutation carriers. This enrichment was confirmed in iPSC-derived and postmortem midbrain neurons from biallelic PRKN-PD patients. Lastly, the heteroplasmic mtDNA variant load was found to correlate with IL6 levels in PINK1/PRKN mutation carriers (r=0.57, p=0.0074). PINK1/PRKN mutations predispose individuals to mtDNA variant accumulation in a dose- and disease-dependent manner. MtDNA variant load over time is a potential marker of disease manifestation in PINK1/PRKN mutation carriers.Competing Interest StatementThe authors have declared no competing interest.Funding StatementThe authors wish to thank the many patients and their families who volunteered, and the efforts of the many clinical teams involved. Funding has been obtained from the German Research Foundation (ProtectMove; FOR 2488, GR 3731/5-1; SE 2608/2-1; KO 2250/7-1), the Luxembourg National Research Fund in the ATTRACT (Model-IPD, FNR9631103), NCER-PD (FNR11264123) and INTER programmes (ProtectMove, FNR11250962; MiRisk-PD, C17/BM/11676395, NB 4328/2-1), the BMBF (MitoPD), the Hermann and Lilly Schilling Foundation, the European Community (SysMedPD), the Canadian Institutes of Health Research (CIHR), Peter and Traudl Engelhorn Foundation. Initial studies in Tunisia on familial parkinsonism were in collaboration with Lefkos Middleton, Rachel Gibson, and the GlaxoSmithKline PD Programme Team (2002-2005). We would like to thank Dr Helen Tuppen from the Welcome Trust Centre for Mitochondrial Research, Newcastle University, UK for providing us with the plasmid p7D1. Moreover, this project was supported by the high throughput/high content screening platform and HPC facility at the Luxembourg Centre for Systems Biomedicine, and the University of Luxembourg.Author DeclarationsI confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained.YesThe details of the IRB/oversight body that provided approval or exemption for the research described are given below:University of Lubeck Ethics CommitteeI confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals.YesI understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance).Yes I have followed all appropriate research reporting guidelines and uploaded the relevant EQUATOR Network research reporting checklist(s) and other pertinent material as supplementary files, if applicable.YesAll data produced in the present study are available upon reasonable request to the authors [less ▲]

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See detailA genome on shaky ground: exploring the impact of mitochondrial DNA integrity on Parkinson's disease by highlighting the use of cybrid models.
Lang, Martin; Grünewald, Anne UL; Pramstaller, Peter P. et al

in Cellular and molecular life sciences : CMLS (2022), 79(5), 283

Mitochondria play important roles in the regulation of key cellular processes, including energy metabolism, oxidative stress response, and signaling towards cell death or survival, and are distinguished ... [more ▼]

Mitochondria play important roles in the regulation of key cellular processes, including energy metabolism, oxidative stress response, and signaling towards cell death or survival, and are distinguished by carrying their own genome (mtDNA). Mitochondrial dysfunction has emerged as a prominent cellular mechanism involved in neurodegeneration, including Parkinson's disease (PD), a neurodegenerative movement disorder, characterized by progressive loss of dopaminergic neurons and the occurrence of proteinaceous Lewy body inclusions. The contribution of mtDNA variants to PD pathogenesis has long been debated and is still not clearly answered. Cytoplasmic hybrid (cybrid) cell models provided evidence for a contribution of mtDNA variants to the PD phenotype. However, conclusive evidence of mtDNA mutations as genetic cause of PD is still lacking. Several models have shown a role of somatic, rather than inherited mtDNA variants in the impairment of mitochondrial function and neurodegeneration. Accordingly, several nuclear genes driving inherited forms of PD are linked to mtDNA quality control mechanisms, and idiopathic as well as familial PD tissues present increased mtDNA damage. In this review, we highlight the use of cybrids in this PD research field and summarize various aspects of how and to what extent mtDNA variants may contribute to the etiology of PD. [less ▲]

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See detailA multi-centre clinico-genetic analysis of the VPS35 gene in Parkinson disease indicates reduced penetrance for disease-associated variants.
Sharma, Manu; Ioannidis, John P. A.; Aasly, Jan O. et al

in Journal of medical genetics (2012), 49(11), 721-6

BACKGROUND: Two recent studies identified a mutation (p.Asp620Asn) in the vacuolar protein sorting 35 gene as a cause for an autosomal dominant form of Parkinson disease . Although additional missense ... [more ▼]

BACKGROUND: Two recent studies identified a mutation (p.Asp620Asn) in the vacuolar protein sorting 35 gene as a cause for an autosomal dominant form of Parkinson disease . Although additional missense variants were described, their pathogenic role yet remains inconclusive. METHODS AND RESULTS: We performed the largest multi-center study to ascertain the frequency and pathogenicity of the reported vacuolar protein sorting 35 gene variants in more than 15,000 individuals worldwide. p.Asp620Asn was detected in 5 familial and 2 sporadic PD cases and not in healthy controls, p.Leu774Met in 6 cases and 1 control, p.Gly51Ser in 3 cases and 2 controls. Overall analyses did not reveal any significant increased risk for p.Leu774Met and p.Gly51Ser in our cohort. CONCLUSIONS: Our study apart from identifying the p.Asp620Asn variant in familial cases also identified it in idiopathic Parkinson disease cases, and thus provides genetic evidence for a role of p.Asp620Asn in Parkinson disease in different populations worldwide. [less ▲]

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See detailLarge-scale replication and heterogeneity in Parkinson disease genetic loci.
Sharma, Manu; Ioannidis, John P. A.; Aasly, Jan O. et al

in Neurology (2012), 79(7), 659-67

OBJECTIVE: Eleven genetic loci have reached genome-wide significance in a recent meta-analysis of genome-wide association studies in Parkinson disease (PD) based on populations of Caucasian descent. The ... [more ▼]

OBJECTIVE: Eleven genetic loci have reached genome-wide significance in a recent meta-analysis of genome-wide association studies in Parkinson disease (PD) based on populations of Caucasian descent. The extent to which these genetic effects are consistent across different populations is unknown. METHODS: Investigators from the Genetic Epidemiology of Parkinson's Disease Consortium were invited to participate in the study. A total of 11 SNPs were genotyped in 8,750 cases and 8,955 controls. Fixed as well as random effects models were used to provide the summary risk estimates for these variants. We evaluated between-study heterogeneity and heterogeneity between populations of different ancestry. RESULTS: In the overall analysis, single nucleotide polymorphisms (SNPs) in 9 loci showed significant associations with protective per-allele odds ratios of 0.78-0.87 (LAMP3, BST1, and MAPT) and susceptibility per-allele odds ratios of 1.14-1.43 (STK39, GAK, SNCA, LRRK2, SYT11, and HIP1R). For 5 of the 9 replicated SNPs there was nominally significant between-site heterogeneity in the effect sizes (I(2) estimates ranged from 39% to 48%). Subgroup analysis by ethnicity showed significantly stronger effects for the BST1 (rs11724635) in Asian vs Caucasian populations and similar effects for SNCA, LRRK2, LAMP3, HIP1R, and STK39 in Asian and Caucasian populations, while MAPT rs2942168 and SYT11 rs34372695 were monomorphic in the Asian population, highlighting the role of population-specific heterogeneity in PD. CONCLUSION: Our study allows insight to understand the distribution of newly identified genetic factors contributing to PD and shows that large-scale evaluation in diverse populations is important to understand the role of population-specific heterogeneity. [less ▲]

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See detailMutations in PINK1 and Parkin impair ubiquitination of Mitofusins in human fibroblasts.
Rakovic, Aleksandar; Grünewald, Anne UL; Kottwitz, Jan et al

in PloS one (2011), 6(3), 16746

PINK1 and Parkin mutations cause recessive Parkinson's disease (PD). In Drosophila and SH-SY5Y cells, Parkin is recruited by PINK1 to damaged mitochondria, where it ubiquitinates Mitofusins and ... [more ▼]

PINK1 and Parkin mutations cause recessive Parkinson's disease (PD). In Drosophila and SH-SY5Y cells, Parkin is recruited by PINK1 to damaged mitochondria, where it ubiquitinates Mitofusins and consequently promotes mitochondrial fission and mitophagy.Here, we investigated the impact of mutations in endogenous PINK1 and Parkin on the ubiquitination of mitochondrial fusion and fission factors and the mitochondrial network structure. Treating control fibroblasts with mitochondrial membrane potential (Deltapsi) inhibitors or H(2)O(2) resulted in ubiquitination of Mfn1/2 but not of OPA1 or Fis1. Ubiquitination of Mitofusins through the PINK1/Parkin pathway was observed within 1 h of treatment. Upon combined inhibition of Deltapsi and the ubiquitin proteasome system (UPS), no ubiquitination of Mitofusins was detected. Regarding morphological changes, we observed a trend towards increased mitochondrial branching in PD patient cells upon mitochondrial stress.For the first time in PD patient-derived cells, we demonstrate that mutations in PINK1 and Parkin impair ubiquitination of Mitofusins. In the presence of UPS inhibitors, ubiquitinated Mitofusin is deubiquitinated by the UPS but not degraded, suggesting that the UPS is involved in Mitofusin degradation. [less ▲]

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See detailMutant Parkin impairs mitochondrial function and morphology in human fibroblasts.
Grünewald, Anne UL; Voges, Lisa; Rakovic, Aleksandar et al

in PloS one (2010), 5(9), 12962

BACKGROUND: Mutations in Parkin are the most common cause of autosomal recessive Parkinson disease (PD). The mitochondrially localized E3 ubiquitin-protein ligase Parkin has been reported to be involved ... [more ▼]

BACKGROUND: Mutations in Parkin are the most common cause of autosomal recessive Parkinson disease (PD). The mitochondrially localized E3 ubiquitin-protein ligase Parkin has been reported to be involved in respiratory chain function and mitochondrial dynamics. More recent publications also described a link between Parkin and mitophagy. METHODOLOGY/PRINCIPAL FINDINGS: In this study, we investigated the impact of Parkin mutations on mitochondrial function and morphology in a human cellular model. Fibroblasts were obtained from three members of an Italian PD family with two mutations in Parkin (homozygous c.1072delT, homozygous delEx7, compound-heterozygous c.1072delT/delEx7), as well as from two relatives without mutations. Furthermore, three unrelated compound-heterozygous patients (delEx3-4/duplEx7-12, delEx4/c.924C>T and delEx1/c.924C>T) and three unrelated age-matched controls were included. Fibroblasts were cultured under basal or paraquat-induced oxidative stress conditions. ATP synthesis rates and cellular levels were detected luminometrically. Activities of complexes I-IV and citrate synthase were measured spectrophotometrically in mitochondrial preparations or cell lysates. The mitochondrial membrane potential was measured with 5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide. Oxidative stress levels were investigated with the OxyBlot technique. The mitochondrial network was investigated immunocytochemically and the degree of branching was determined with image processing methods. We observed a decrease in the production and overall concentration of ATP coinciding with increased mitochondrial mass in Parkin-mutant fibroblasts. After an oxidative insult, the membrane potential decreased in patient cells but not in controls. We further determined higher levels of oxidized proteins in the mutants both under basal and stress conditions. The degree of mitochondrial network branching was comparable in mutants and controls under basal conditions and decreased to a similar extent under paraquat-induced stress. CONCLUSIONS: Our results indicate that Parkin mutations cause abnormal mitochondrial function and morphology in non-neuronal human cells. [less ▲]

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See detailRapid and reliable detection of exon rearrangements in various movement disorders genes by multiplex ligation-dependent probe amplification.
Djarmati, Ana; Guzvic, Miodrag; Grünewald, Anne UL et al

in Movement Disorders (2007), 22(12), 1708-14

Because of the occurrence of different types of mutations, comprehensive genetic testing for Parkinson's disease (PD), dopa-responsive dystonia (DRD), and myoclonus-dystonia (M-D) should include screening ... [more ▼]

Because of the occurrence of different types of mutations, comprehensive genetic testing for Parkinson's disease (PD), dopa-responsive dystonia (DRD), and myoclonus-dystonia (M-D) should include screening for small sequence changes and for large exonic rearrangements in disease-associated genes. In diagnostic and research settings, the latter is frequently omitted or performed by laborious and expensive quantitative real-time PCR (qPCR). Our study aimed to evaluate the utility of a novel method, multiplex ligation-dependent probe amplification (MLPA), in molecular diagnostics of movement disorders. We have analyzed, by MLPA, genomic DNA from 21 patients affected with PD, DRD, or M-D, in which the presence of exon rearrangement(s) (n = 20) or of a specific point mutation (detectable by MLPA, n = 1) had been established previously by qPCR or sequencing. In parallel, we have studied, in a blinded fashion, DNA from 49 patients with an unknown mutational status. Exon rearrangements were evident in 20 samples with previously established mutations; in the 21st sample the known specific point mutation was detected. We conclude that MLPA represents a reliable method for large-scale and cost-effective gene dosage screening of various movement disorders genes. This finding reaches far beyond a simple technical advancement and has two major implications: (1) By improving the availability of comprehensive genetic testing, it supports clinicians in the establishment of a genetically defined diagnosis; (2) By enabling gene dosage testing of several genes simultaneously, it significantly facilitates the mutational analysis of large patient and control populations and thereby constitutes the prerequisite for meaningful phenotype-genotype correlations. [less ▲]

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