RAC1 and Parkinsonism: By analyzing the number and length of neurites, to explore the capacity of Rac1 in rescuing neuronal degeneration (Online Resource 7), we found a decrease in neurite arborization in PD-derived DAn (Fig. 6b), confirming previous reports showing reduction in neurite length/branching and defects of Rac signaling in LRRK2-associated parkinsonism [53].