42 hfMCOs that we generated showed migration of NKX2-1-GFP+ cells from hMGEO to hCO. We found that the majority of the migrating cells were confined to the superficial areas of hCOs. Histological analyses confirmed that migration routes of NKX2-1-GFP+ progenitors were outside of cortical VZ-like area (Figure 7E, Figure S7A), which is consistent with the reported pattern of interneuron tangential migration (Ma et al., 2013). Indeed, we found that the migration required the proper development of SVZ/CP-like area in hCOs, without which migration was inefficient. In this condition, migration routes might be altered towards the inner side of hCOs but were excluded from VZ-like area (Figure S7B and S7C).
