Therapeutic advances to treat Parkinson disease (PD) are incumbent upon the identification and mechanistic understanding of cellular factors that influence neuronal survival. We have exploited attributes of the nematode model system, Caenorhabditis elegans, to develop assays that facilitate the screening and isolation of conserved genetic factors that mediate clinical hallmarks of PD, including intracellular aggregation of a-synuclein (a-syn) and dopamine (DA) neuron loss. This R15 application extends prior studies where we have identified neuroprotective targets for translational development and established genetic platforms to evaluate functional modifiers of age-dependent neurodegeneration. Increasing evidence is mounting for a significant role for lysosomal function as a mechanism influencing PD. In this context, a focal point of this application is the ULK2 protein - a human ortholog of the worm unc-51 gene product, a kinase implicated in autophagy, as well as axon elongation and guidance. We previously uncovered a neuroprotective activity for ULK2 in enhancing DA neuron survival in transgenic nematodes. Our data took on greater significance following the report of a human genome-wide association study that also identified a polymorphism in ULK2 as being associated with PD patients. We propose to advance our understanding of ULK2-mediated neuroprotection through a series of structure-function analyses, as well as evaluation of modifiers of ULK2, to mechanistically define the role of ULK2 kinase activity in attenuating neurodegeneration. C. elegans is also among the best-understood animal models in terms of aging mechanisms, with extensive sets of factors implicated in lifespan identified. Thus, as aging represents an unequivocal and defined risk factor for PD, we will use functional genomic screening via RNA interference (RNAi) in C. elegans to knockdown hundreds of genes previously linked to aging-associated pathways to evaluate their distinct contribution to a-syn misfolding and clearance. Preliminary studies in our lab have shown that specific mutations in key components of the daf-2/insulin-like signaling pathway of C. elegans result in substantial effects on DA neuron survival. We have generated a series of transgenic nematode strains to facilitate functional analysis of a-syn modifiers in the context of their potential dependence on this pathway, as well as in autophagy. Transgenic and mutant worms will be generated to examine gene targets from RNAi screening for their impact on DA neuroprotection. This systematic approach provides an unprecedented opportunity to discern age-associated regulators of neurodegeneration that may represent genetic susceptibly markers for PD onset or progression. Collectively, these studies represent an integrated research plan designed to rapidly define the significance of previously uncharacterized factors influencing neurodegeneration. Moreover, our experimental strategy coincides with the specific criteria of the R15 AREA program, as the broader impacts of this application involve extensive undergraduate and graduate student training opportunities in an environment ideally suited to student-centered research.
Over 1 million Americans have been diagnosed with Parkinson's Disease (PD) - the most common movement disorder for which a cure has eluded medical science for decades. This application addresses an unmet challenge of discerning genetic factors that may contribute to this neurodegenerative disease, while accelerating our understanding of underlying cellular mechanisms of PD. In this research, we use a simple animal model system to explore the well-established but poorly understood relationship of aging to PD, in addition to genetic factors that mediate the survival of dopamine-producing neurons. The experimental strategy outlined integrates student-centered research in the context of a systematic approach involving genetic and genomic analysis to uncover mechanisms that facilitate identification of new therapeutic targets with the potential to combat PD.
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