Acquired Mitochondrial DNA Mutations in the Brain
Principal Investigator: David K Simon
Abstract: Mitochondrial complex I (CI) activity appears to play a key role in the pathogenesis of Parkinson?s disease (PD). Cl activity is impaired in the substantia nigra (SN) in PD, and Cl inhibitors induce parkinsonism when systemically administered in animals. Indirect evidence suggests a role for mitochondrial DNA (mtDNA) mutations. However, detection of these mutations may not be possible by standard screening techniques, particularly if they are present at low mutational burdens. We hypothesize that numerous acquired mutations, each individually present at a low mutational burden, could reach a sufficient aggregate burden to cause mitochondrial dysfunction. Such mutations are hypothesized to result from oxidative damage to mtDNA. Brain levels of 8-hydroxy-2?deoxyguanosine (OH8dG), a marker of oxidative DNA damage associated with point mutations, are 16-fold higher in mtDNA than in nuclear DNA, increase with aging, and increase further in PD. We have developed a protocol for detecting mtDNA mutations present at extremely low mutational burdens. We propose to determine the frequency of oxidative stress-induced mtDNA mutations in frontal cortex and substantia nigra in controls and in PD. Using Laser Capture Microdissection (Arcturus), we will examine the specific subpopulation of neurons susceptible in PD. Single-cell PCR will allow us to address the question of accumulation of individual acquired mutations within single neurons. We also propose to establish an in vitro system for analyzing the induction of oxidative stress-induced mutations in dividing and in post-mitotic cells by exposure to hydrogen peroxide or to agents that inhibit mtDNA repair. Collaborations have been established which will make the proposed studies possible. These studies will lay the foundation for future studies addressing the role of acquired mtDNA mutations in aging and in neurodegenerative diseases.
Funding Period: 2002-08-01 - 2007-05-31
more information: NIH RePORT
- Somatic mitochondrial DNA mutations in early Parkinson and incidental Lewy body diseaseMichael T Lin
Department of Neurology and Neuroscience, Weill Cornell Medical College, New York, NY, USA
Ann Neurol 71:850-4. 2012..We show for the first time that mtDNA mutation levels in substantia nigra neurons are significantly elevated in this group of early PD and ILBD cases...
- Mitochondrial complex I gene variant associated with early age at onset in spinocerebellar ataxia type 2David K Simon
Department of Neurology, Beth Israel Deaconess Medical Center, 77 Avenue Louis Pasteur, Room HIM 847, Boston, MA 02115, USA
Arch Neurol 64:1042-4. 2007..We hypothesized that this variant might have a protective effect on the central nervous system and therefore might delay the onset of symptoms in spinocerebellar ataxia type 2 (SCA2)...