Molecular and Physiological Responses to Persistent Mitochondrial DNA Damage

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DESCRIPTION (provided by applicant): The goal of this research is to elucidate the physiological and molecular responses that occur in response to persistent mitochondrial DNA (mtDNA) damage. Mitochondrial DNA integrity is critical for human health, and mtDNA is more sensitive than nuclear DNA (nDNA) to many chemicals that cause DNA damage. However, the consequences of unrepaired mtDNA damage are poorly understood. Furthermore, since mitochondria apparently lack the repair proteins that would handle such damage in the nuclear genome, the fate of mtDNA damaged by environmental genotoxins, such as ultraviolet C radiation (UVC) and polycyclic aromatic hydrocarbons, is also poorly understood. This project will elucidate the fate of mtDNA damage and test the hypothesis that severely damaged mtDNA is cleared from the powerful model organism Caenorhabditis elegans by fission/fusion and autophagy. We have recently observed that early life stage exposure to bulky (UVC-induced) mtDNA lesions causes developmental delay in C elegans, and also leads to neurodegeneration in adults, suggesting that C elegans will be an appropriate as well as powerful model for the mammalian response to such damage. To better understand the temporal progression and mechanistic details of the toxicological response to such damage, we will also examine the molecular and physiological consequences of early-life exposure to persistent mtDNA damage. This work will be accomplished via the following three Specific Aims: Specific Aim 1. Test the hypothesis that exposure during early development to persistent mtDNA damage leads to mitochondrial dysfunction. We will measure mitochondrial function and dysfunction in C elegans carrying persistent mtDNA damage. Specific Aim 2. Test the hypothesis that exposure during early development to persistent mtDNA damage leads to neurodegeneration in adults. Many neurodegenerative diseases have environmental components, and exposure to mitochondrial toxicants is associated with neurodegenerative disease. We will test whether early-life exposure of C elegans to persistent mtDNA damage leads to neurodegeneration in later life. Specific Aim 3. Test the hypothesis that bulky DNA adducts present in mitochondrial genomes are removed via mitochondrial fusion, fission and autophagy. This hypothesis will be tested via the use of gene knock-out and gene knock-down technologies. PUBLIC HEALTH RELEVANCE: Mitochondrial DNA integrity is critical for human health, but the mechanisms by which persistent mtDNA damage causes physiological outcomes, and the pathways by which such damage is handled, are unclear. This research will yield information critical to our understanding of the genetic and environmental contributors to diseases caused by mitochondrial dysfunction.