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See detailMitochondrial DNA depletion in respiratory chain-deficient Parkinson disease neurons.
Grünewald, Anne UL; Rygiel, Karolina A.; Hepplewhite, Philippa D. et al

in Annals of Neurology (2016), 79(3), 366-378

OBJECTIVE: To determine the extent of respiratory chain abnormalities and investigate the contribution of mitochondrial DNA (mtDNA) to the loss of respiratory chain complexes (CI-IV) in the substantia ... [more ▼]

OBJECTIVE: To determine the extent of respiratory chain abnormalities and investigate the contribution of mitochondrial DNA (mtDNA) to the loss of respiratory chain complexes (CI-IV) in the substantia nigra (SN) of idiopathic Parkinson disease (IPD) patients at the single-neuron level. METHODS: Multiple-label immunofluorescence was applied to postmortem sections of 10 IPD patients and 10 controls to quantify the abundance of CI-IV subunits (NDUFB8 or NDUFA13, SDHA, UQCRC2 and COXI), and mitochondrial transcription factors (TFAM and TFB2M) relative to mitochondrial mass (Porin and GRP75) in dopaminergic neurons. To assess the involvement of mtDNA in respiratory chain deficiency in IPD, SN neurons, isolated with laser-capture microdissection, were assayed for mtDNA deletions, copy number and presence of transcription/replication-associated 7S DNA employing a triplex real-time PCR assay. RESULTS: While mitochondrial mass was unchanged in single SN neurons from IPD patients, we observed a significant reduction in the abundances of CI and II subunits. At single-cell level, CI and II deficiencies were correlated in patients. The CI deficit concomitantly occurred with low abundances of the mtDNA transcription factors TFAM and TFB2M, which also initiate transcription-primed mtDNA replication. Consistent with this, real-time PCR analysis revealed fewer transcription/replication-associated mtDNA molecules and an overall reduction in mtDNA copy number in patients. This effect was more pronounced in single IPD neurons with severe complex I deficiency. INTERPRETATION: Respiratory chain dysfunction in IPD neurons not only involves CI, but also extends to CII. These deficiencies are possibly a consequence of the interplay between nDNA and mtDNA-encoded factors mechanistically connected via TFAM. This article is protected by copyright. All rights reserved. [less ▲]

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See detailFrontotemporal dementia and its subtypes: a genome-wide association study.
Ferrari, Raffaele; Hernandez, Dena G.; Nalls, Michael A. et al

in Lancet neurology (2014), 13(7), 686-99

BACKGROUND: Frontotemporal dementia (FTD) is a complex disorder characterised by a broad range of clinical manifestations, differential pathological signatures, and genetic variability. Mutations in three ... [more ▼]

BACKGROUND: Frontotemporal dementia (FTD) is a complex disorder characterised by a broad range of clinical manifestations, differential pathological signatures, and genetic variability. Mutations in three genes-MAPT, GRN, and C9orf72-have been associated with FTD. We sought to identify novel genetic risk loci associated with the disorder. METHODS: We did a two-stage genome-wide association study on clinical FTD, analysing samples from 3526 patients with FTD and 9402 healthy controls. To reduce genetic heterogeneity, all participants were of European ancestry. In the discovery phase (samples from 2154 patients with FTD and 4308 controls), we did separate association analyses for each FTD subtype (behavioural variant FTD, semantic dementia, progressive non-fluent aphasia, and FTD overlapping with motor neuron disease [FTD-MND]), followed by a meta-analysis of the entire dataset. We carried forward replication of the novel suggestive loci in an independent sample series (samples from 1372 patients and 5094 controls) and then did joint phase and brain expression and methylation quantitative trait loci analyses for the associated (p<5 x 10(-8)) single-nucleotide polymorphisms. FINDINGS: We identified novel associations exceeding the genome-wide significance threshold (p<5 x 10(-8)). Combined (joint) analyses of discovery and replication phases showed genome-wide significant association at 6p21.3, HLA locus (immune system), for rs9268877 (p=1.05 x 10(-8); odds ratio=1.204 [95% CI 1.11-1.30]), rs9268856 (p=5.51 x 10(-9); 0.809 [0.76-0.86]) and rs1980493 (p value=1.57 x 10(-8), 0.775 [0.69-0.86]) in the entire cohort. We also identified a potential novel locus at 11q14, encompassing RAB38/CTSC (the transcripts of which are related to lysosomal biology), for the behavioural FTD subtype for which joint analyses showed suggestive association for rs302668 (p=2.44 x 10(-7); 0.814 [0.71-0.92]). Analysis of expression and methylation quantitative trait loci data suggested that these loci might affect expression and methylation in cis. INTERPRETATION: Our findings suggest that immune system processes (link to 6p21.3) and possibly lysosomal and autophagy pathways (link to 11q14) are potentially involved in FTD. Our findings need to be replicated to better define the association of the newly identified loci with disease and to shed light on the pathomechanisms contributing to FTD. FUNDING: The National Institute of Neurological Disorders and Stroke and National Institute on Aging, the Wellcome/MRC Centre on Parkinson's disease, Alzheimer's Research UK, and Texas Tech University Health Sciences Center. [less ▲]

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See detailSingle-cell expression profiling of dopaminergic neurons combined with association analysis identifies pyridoxal kinase as Parkinson's disease gene.
Elstner, Matthias; Morris, Christopher M.; Heim, Katharina et al

in Annals of neurology (2009), 66(6), 792-8

OBJECTIVE: The etiology of Parkinson disease (PD) is complex and multifactorial, with hereditary and environmental factors contributing. Monogenic forms have provided molecular clues to disease mechanisms ... [more ▼]

OBJECTIVE: The etiology of Parkinson disease (PD) is complex and multifactorial, with hereditary and environmental factors contributing. Monogenic forms have provided molecular clues to disease mechanisms but genetic modifiers of idiopathic PD are still to be determined. METHODS: We carried out whole-genome expression profiling of isolated human substantia nigra (SN) neurons from patients with PD vs. controls followed by association analysis of tagging single-nucleotide polymorphisms (SNPs) in differentially regulated genes. Association was investigated in a German PD sample and confirmed in Italian and British cohorts. RESULTS: We identified four differentially expressed genes located in PD candidate pathways, ie, MTND2 (mitochondrial, p = 7.14 x 10(-7)), PDXK (vitamin B6/dopamine metabolism, p = 3.27 x 10(-6)), SRGAP3 (axon guidance, p = 5.65 x 10(-6)), and TRAPPC4 (vesicle transport, p = 5.81 x 10(-6)). We identified a DNA variant (rs2010795) in PDXK associated with an increased risk of PD in the German cohort (p = 0.00032). This association was confirmed in the British (p = 0.028) and Italian (p = 0.0025) cohorts individually and reached a combined value of p = 1.2 x 10(-7) (odds ratio [OR], 1.3; 95% confidence interval [CI], 1.18-1.44). INTERPRETATION: We provide an example of how microgenomic genome-wide expression studies in combination with association analysis can aid to identify genetic modifiers in neurodegenerative disorders. The detection of a genetic variant in PDXK, together with evidence accumulating from clinical studies, emphasize the impact of vitamin B6 status and metabolism on disease risk and therapy in PD. [less ▲]

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