Identification of epigenetic marks underlying exercise-induced neuroprotection in Parkinson’s disease

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Abstract This application seeks to map the DNA modification landscape of the mouse genome in response to levels of exercise that are neuroprotective in a toxicant model of Parkinson’s disease (PD). PD is a debilitating neurological disorder that strikes approximately 1-2% of the adult population greater than 50 years of age. Although we have a number of symptomatic treatments for PD, little can be done to prevent its onset or even slow its progression. However, over the past few years, both preclinical and clinical studies have shown that voluntary exercise may offer these benefits. For example, epidemiological studies indicate that aerobic levels of exercise early in life reduce the risk of developing Parkinson's disease (PD) and delay the progression of PD motor symptoms in already diagnosed patients. These epidemiological findings have been replicated in a number of animal studies that demonstrate exercise-induced neuroprotection against the neurotoxicant MPTP. In addition, only a few studies have explored the cellular mechanisms that underlie this protection, focusing their efforts on specific proteins or genes. While there is value to a target-driven approach, exercise modifies many different cellular processes that likely work together in biological networks. As such, defining genome-wide changes in gene regulation will provide a more complete picture of the biological networks underlying exercise-induced neuroprotection. Here, we propose several experiments to determine whether genome-wide changes in DNA modification occur in response to neuroprotective levels of voluntary exercise as well as whether exercise-induced changes in DNA modifications are stable over time, even as exercise- induced neuroprotection is exhausted (a time to be empirically determined). These unanswered questions will be examined in two aims. In SA1, we will use a combination of laser capture microdissection (LCM) and enzymatic methyl-sequencing to map genome-wide DNA modifications of C57BL/6J mice that perform 3 months of aerobic exercise, a duration which is necessary to induce neuroprotection. Using the proposed methods, we will identify exercise-related changes in DNA modifications at both single base pairs and genomic regions in a population of enriched substantia nigra dopaminergic neurons. In SA2, we will 1) identify if and/or when the neuroprotective effects of voluntary exercise are extinguished, and use this information to, 2) identify which exercise-associated changes in DNA modifications persist across time after exercise cessation. We will use targeted capture hybridization sequencing to determine if exercise- associated changes in DNA methylation of SNpc DA neurons isolated by LCM are maintained or reversed after extinguishment of exercise. Completion of these aims will provide a list of candidate genes that are critical for the maintenance of exercise-induced SNpc neuroprotection, thereby providing novel targets for disease modifying therapies.