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 speed observed from living embryo but slower than that obtained from MGE explant culture (Bellion et al., 2005; Yanagida et al., 2012), indicating that the cellular environment of hfMCOs might closely approximate their in vivo counterparts. With myosin II inhibition, the migration speed largely decreased (Figure 7J). Importantly, we found a near-complete blockage in directed movement of leading process, even under lower dosage of blebbistatin (Figure 7K). Instead of forward outgrowth, growth cones under blebbistatin treatment only displayed local swing-like movement without any directional preference (Figure 7L), indicating a critical role of myosin II in growth cone dynamics of migrating interneurons. These results demonstrate that nonmuscle myosin II plays a critical role in soma translocation and growth cone dynamics of migrating human MGE progenitors.
