The purpose of this project is to determine how a recently discovered, Parkinson's Disease (PD)- associated, gene variant in human patients contributes to the pathogenesis of PD. The allele under study, in RME-8, is dominant and linked to late-onset PD. RME-8 is a protein localized to endosomes that our lab previously identified as a crucial regulator of transmembrane cargo sorting after endocytosis, determining whether endocytic cargo is recycled or degraded. This is the first instance in which RME-8 has been linked to human neuronal health, though its function in neurons is not yet understood. Preliminary data in vivo in C. elegans, and in primary cultured mouse cortical neurons, indicates that the RME-8 PD-associated allele interferes with retrograde trafficking of late endosomes along the axon toward the cell body of the neuron. Due to the unique architecture of neurons, an inability of cargo to reach the cell body may be exceptionally catastrophic, since the cell body is where degradation and recycling of cargo occurs via the lysosomes and Golgi, respectively. Inability of cargo to traffic back to the cell body may lead to accumulation in the axon, resulting in neuron dysfunction and death. To accomplish this project, I will utilize a dual-model approach of both cultured mouse neurons as well as an in vivo approach in C. elegans, using CRISPR, RNAi, the auxin-inducible degron system, and temperature sensitive loss-of-function alleles. I will determine the effects on retrograde trafficking of late endosomes along the axon using confocal imaging and kymograph analysis, as well determine the effects on degradation and recycling of cargo. Since Parkinson's Disease is caused by the death of dopaminergic neurons, I will analyze changes in dopamine-dependent behaviors in C. elegans and determine the effect of RME-8 perturbation on the lifespan of dopaminergic neurons. Understanding the novel role of RME-8 in maintaining neuronal health leads us closer to understanding the factors that contribute to Parkinson's Disease and therefore closer to determining how to treat patients with PD.
Neurons are extremely long cells of the brain that possess cargoes that must travel long distances to be recycled or degraded. Proteins that are not properly degraded can instead aggregate into large masses within the neuron, preventing the neuron from functioning properly and causing neurodegenerative diseases such as Parkinson's Disease. In this project, I will study how a protein that was recently implicated in causing Parkinson's Disease contributes to neuronal health.
