We generated midbrain dopaminergic neurons obtained from healthy human skin fibroblasts via reprogramming of iPSCs [22-23]. iPSCs were characterized previously for the expression of pluripotency markers, differentiation capacity through embryoid body formation, and normal genomic structure by karyotype analysis [23]. Differentiation of iPSCs into midbrain dopaminergic neurons was achieved by a previously published protocol [24]. Under conventional neuronal culture conditions 200,000 to 300,000 iPSC-derived neurons are plated onto regular unpatterned PDL/laminin-coated coverslips on day 25 to day 30 of differentiation. These conventional culture conditions result in uneven growth and neurite density, while plating cells onto micropatterned surfaces drives neuronal cultures towards a defined growth pattern allowing studies of individual neurons and neuronal networks (Figure 2A). Long-term culturing of human iPSC-derived neurons has not been possible so far due to neuronal clustering of cells during conventional culture conditions (Figure 2B). For micropatterned studies, substrates were either placed into one well of a 24-well plate or pre-designed live cell imaging substrates were used, coated with laminin and 150,000 to 300,000 neurons were seeded on day 25 to day 30 of differentiation. Once
