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Ann Neurol. 2016 Mar;79(3):366-78. doi: 10.1002/ana.24571. Epub 2016 Jan 28.

Mitochondrial DNA Depletion in Respiratory Chain-Deficient Parkinson Disease Neurons.

Author information

1
Wellcome Trust Centre for Mitochondrial Research and Medical Research Council/Biotechnology and Biological Sciences Research Council Centre for Ageing and Vitality, Institute of Neurosciences, Newcastle University, Newcastle upon Tyne, United Kingdom.
2
Institute of Neurogenetics, University of Lübeck, Lübeck, Germany.
3
Molecular and Functional Neurobiology Group, Luxembourg Center for Systems Biomedicine, University of Luxembourg, Campus Belval, Belvaux, Luxembourg.
4
Newcastle Brain Tissue Resource, Campus for Ageing and Vitality, Newcastle University, Newcastle upon Tyne, United Kingdom.
5
Division of Behavioral Medicine, Department of Psychiatry and Department of Neurology, College of Physicians and Surgeons, Columbia University, Columbia University Medical Center, New York, NY.

Abstract

OBJECTIVE:

To determine the extent of respiratory chain abnormalities and investigate the contribution of 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 polymerase chain reaction (PCR) assay.

RESULTS:

Whereas 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 the single-cell level, CI and II deficiencies were correlated in patients. The CI deficiency 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 CI 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.

PMID:
26605748
PMCID:
PMC4819690
DOI:
10.1002/ana.24571
[Indexed for MEDLINE]
Free PMC Article

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