Dysregulation of synaptic gene expression, perturbations of synaptic vesicle (SV) cycle and synaptic transmission, and a reduction in the number of synapses have been reported in α-synuclein (SNCA) human inducible pluripotent stem cell (hiPSC) models of PD (11), in amyloid-β precursor protein (APP) hiPSC models of AD (12–15), and in a zebrafish genetic model of ALS (16). This evidence concerns the gene APP and Parkinson disease.