PROJECT SUMMARY Alzheimer’s disease is the most common age-related neurodegenerative disorder with ~5.4 million Americans living with Alzheimer’s disease. Central to Alzheimer’s disease is the ongoing loss of neuronal plasticity which impairs cognitive functions and eventually disrupts basic brain functions, resulting in death. Yet, we still lack significant disease-modifying interventions for the disease. Thus, new approaches are needed to identify the mechanisms involved in Alzheimer’s disease pathogenesis. Key clues come from evidence that exposures to environmental neurotoxicants are causally linked to a higher incidence of Alzheimer’s disease. Moreover, there are sex differences in Alzheimer’s disease with women more affected compared to men. Finally, one of the most salient consequences of Alzheimer’s pathology is the loss of neuroplasticity and neurodegeneration, which strongly correlates with memory loss as well as cognitive and motor decline. Together, these findings extend our existing NIEHS-funded R01 (R01ES034037) whose focus is to investigate mechanisms by which the vesicular glutamate transporter 2 (VGLUT2) mediates selective vulnerability to neurodegeneration in males and females caused by exposure to environmental toxicants including pesticides. To adapt the core concepts of our R01 to Alzheimer’s disease, we established an experimental system where we can convert human fibroblasts from Alzheimer’s disease patients and age-matched unaffected individuals directly into induced neurons (iNs). This approach enables the iNs to retain the epigenetic and transcriptomic age signatures similar to those of the aging human brain and has proven vital for modeling the pathology for age-related neurodegenerative disorders like Alzheimer’s disease. Critically, we can generate several unique patient-derived iNs of sporadic and familial Alzheimer’s disease from male and female patients, enabling us to recapitulate key aspects of human Alzheimer’s disease pathophysiology. In parallel, we developed new live-cell and cryo-electron tomography approaches in primary neurons and iNs to study activity-driven local translation – a process that is central to synaptic plasticity and which is lost in Alzheimer’s disease. In this supplement, we will take advantage of innovative new tools and our team’s expertise in neurodegeneration to answer several fundamental questions: 1) whether pesticides exacerbate mitochondrial oxidative stress in Alzheimer’s disease patient neurons to increase Alzheimer’s pathology (e.g., amyloid-b and tau accumulation) and accelerate cell loss; 2) if pesticide exposures impact mitochondrial function and cell plasticity differently in male vs female Alzheimer’s iNs; and 3) if modifying VGLUT2 expression alters pesticide-induced neurodegeneration in male vs female Alzheimer’s patient iNs. We hypothesize pesticide-induced mitochondrial dysfunction initiate or exacerbate accumulation of pathological hallmarks of Alzheimer’s disease, culm...