We hypothesize that single genetic factors are insufficient to cause PD — rather, that it is triggered by a combination of genetics, age-related factors, and their effects in different brain cells. Here we propose to dissect the genetic, age-related, and cell-type-specific factors that lead to PD using a collection of genetically diverse stem cells derived from patients. Using advanced methods pioneered by our team, we will convert these stem cells into the different types of brain cells implicated in PD — neurons, microglia, and astrocytes — allowing us to investigate how genetic risk factors, the aging process, and these different cell types interact to trigger disease. We will assess how various combinations of these factors disrupt the function of brain cells using detailed molecular studies, microscopy, genetic manipulations, and biochemical measurements — building a computational network model of the factors that cause PD.