We next asked whether human ESC-derived putative cortical interneuron precursors (day 10-18 group) exhibit the characteristic migratory potential observed for primary cortical interneurons in the mouse (Anderson et al., 1997) and human (Letinic et al., 2002) brain. In both species, major subclasses of cortical interneurons undergo tangential migration on their way from the ventral telencephalon into the cortex (Anderson et al., 1997; Fertuzinhos et al., 2009; Letinic et al., 2002). NKX2.1::GFP+ cells at day 32 of differentiation were collected by FACS and injected into forebrain slices isolated from embryonic day 13.5 mouse embryos. The cell injection was carefully targeted to the medial ganglionic eminence under microscopic visual guidance (Figure 3H). The migratory potential of NKX2.1::GFP+ cells and their ability to reach the cortex (see Zone 2 in Figure 3H) was assessed for each treatment group (2-18, 6-18 and 10-18 of SHH treatment; Figure 3I–L) At day 2 (Figure 3M) and, more pronounced at day 6 (Figure 3N) after injection, GFP+ cells were observed migrating from the injection site towards the cortex (zone 2). Remarkably, human cells from the 10-18 treatment,
