Project Summary/Abstract Parkinson's disease (PD) is a progressive neurodegenerative disorder that is characterized by α-synuclein-rich neuronal inclusions. Recent genome-wide associated studies (GWAS) and epidemiological studies have identified multiple candidate genes and environmental factors which can modify PD risk. However, studying polygenic interactions with environmental factors has been difficult due to the lack of a model system. However, studies have hinted at a complex relationship between α-synuclein, genetic risk factors, and environmental factors. In our preliminary data, we have established a multiplex model using the Drosophila model of PD. In this model, we express human α-synuclein, simultaneously modify GWAS candidate genes in neurons, and expose adult flies to rotenone. Using a combination of scalable techniques in this model, we identified novel interactions among α-synuclein, environmental factors, and GWAS genes. The overarching hypothesis is a multiplex model, in combination with iPSC-derived neurons, can be used to identify and study the mechanism of novel gene-environment interactions. Further, this model system will identify potential drug targets that can modify the gene-environment interactions. In Aim 1, a series of experiments, including super-resolution microscopy and iPSC-derived tyrosine hydroxylase (TH) neurons, will be performed to characterize the interaction among LRRK2, rotenone, and α-synuclein, which was identified using the multiplex model. Aim 2 will involve understanding the mechanism of interactions among LRRK2, rotenone, and α-synuclein. Previous studies and preliminary experiments have shown that actin hyperstabilization plays a central role in regulating neurotoxicity. Herein biochemical, immunohistological, and neurotoxicity assays will be performed in Drosophila and iPSC-derived TH neurons (obtained disease-causing LRRK2-G2019S and protective LRRK2-R1398H iPSCs) to study the role of actin dynamics in regulating this gene-environment interaction. Aim III will identify a druggable target that can modify the interaction among LRRK2, rotenone, and α-synuclein. Further, we will screen for other PD-related neurotoxicants that interact with LRRK2 and α-synuclein through actin hyperstabilization. Finally, we will genetically and pharmacologically inhibit MRCKα, a kinase that can regulate actin hyperstabilization, in flies, iPSC-derived neurons, and a mouse model. This project may elucidate a novel model system that can be used to identify and study the mechanism of gene- environment interactions. My training during the K99 phase enabled me to transition to an independent position at URMC. I will lead a laboratory investigating the molecular mechanisms of gene-environment interactions in neurodegenerative disorders.