Nonmuscle myosin II may be one of key regulators of directed cell migration including the migrating mouse MGE cells (Bellion et al., 2005). We found treatment with blebbistatin, a known myosin II inhibitor, completely blocked cell migration, with NKX2-1-GFP+ cells scarcely identified in hCO side under continuous drug treatment (Figure S7D). To monitor the effect of inhibiting myosin II in real-time, we allowed cells to migrate uninterrupted for 2 weeks, then performed live-cell imaging on the hCO side with blebbistatin treatment. We found that soma translocation of interneuron progenitors was dramatically decreased with 50 μM blebbistatin treatment (10.55 ± 2.25%, n=2 hfMCOs, 63 cells in total, mean ± SD) compared with control hfMCOs (41.23 ± 3.20%, n=4 hfMCOs, 79 cells in total, mean ± SD) within 10 hours, and 100 μM blebbistatin treatment completely abolished migration (n=2 hfMCOs, 44 cells in total, mean ± SD) (Figure 7H and 7I; Movie S5 and S6). The average migrating speed of interneuron progenitors was 0.19 ± 0.01 μm/min (n=35 cells from 4 hfMCOs, mean ± SD) (Figure 7J), which was close to the
