migration (672 neurospheres analyzed; Figure 3c). Neither mixing control and SZ hiPSC NPCs (marked through reciprocal labeling of lentiviral green fluorescent protein or red fluorescent protein expression) before neurosphere migration (288 neurospheres analyzed; Figures 3d and e) nor culturing lentiviral-green fluorescent protein-labeled neurospheres on healthy cortical murine tissue in slice coculture conditions (147 neurospheres analyzed; Supplementary Figures 6C and D) rescued aberrant migration of SZ NPCs, indicating that this may be a cell-autonomous defect. Using microfluidic devices to probe the migration of single cells, with NPCs from five controls and four patients, we observed reduced migration of SZ hiPSC forebrain NPCs (207±6 migrated cells after 48 h) relative to controls (277±5 migrated cells; P<0.02) (Figures 3f–h). Finally, when migration across discrete micropatterned laminin spots coated on a gold-plated hydrophobic biomaterials surface was assessed, we observed a markedly decreased percentage of neurosphere ‘chaining' between laminin spots in SZ hiPSC forebrain NPCs (SZ 2.8±0.3%) relative to controls (12.8±0.5% P<0.0005) (Figures 3i and j). Reduced migration is unlikely to reflect impaired cellular motility; although we report decreased migration in SZ with three assays (Figure 3), we observed significantly increased migration using a scratch assay (Supplementary Figure 7).
