UCLA

Parkinson's disease (PD) is a neurodegenerative disorder that affects millions of people worldwide and is characterized by a loss of dopaminergic neurons along with other deficits. While rare inheritable forms of PD exist, the vast majority of cases are sporadic and their etiology remains poorly understood. Epidemiological studies have increasingly linked exposures to environmental toxins, including a variety of pesticides, to an increased risk of contracting PD. However, it remains unclear as to the mechanism by which these pesticides cause neurotoxicity and the extent to which individual genetic variability plays a role. Alterations in the vesicular monoamine transporter (VMAT) gene, which packages dopamine and other amines into synaptic vesicles, have been shown to affect PD susceptibility in animal models and epidemiological studies alike. Using live-imaging techniques at the Drosophila melanogaster neuromuscular junction, I investigated the functional consequences of altered VMAT trafficking at an intact synapse. I show that mutations in putative VMAT trafficking domains result in abnormal protein localization during synaptic vesicle exo- and endocytosis, in a manner that is dependent on nerve terminal identity. Using the same approach, I show that the PD-linked pesticide ziram differentially disrupts neuronal activity and synaptic vesicle cycling at functionally distinct nerve terminals. In particular, I demonstrate that endocytosis at aminergic nerve terminals is particularly sensitive to both disruption of VMAT trafficking motifs and exposure to ziram, and that ziram appears to selectivity induce the spontaneous depolarization of these terminals. Additionally, using traditional toxicological approaches, I developed a novel model of paraquat and maneb induced PD in Drosophila melanogaster and demonstrate the general utility of this model for interrogating specific mechanisms implicated in PD etiology. This dissertation discusses my research using Drosophila melanogaster to address basic biological questions fundamental to understanding gene-environment interactions implicated in PD.