Given the protracted maturation of Nkx2.1-GFP+, putative interneuron precursors in vivo, we were surprised to obtain morphological, marker-based and physiological evidence of interneuron-like differentiation in the co-culture system. We next tested whether similar results can be obtained with growing the same Nkx2.1::GFP+ cells on cultures enriched for human cortical projection neurons. The human cortical feeders were obtained upon differentiation of hESCs (modified XLSB conditions) followed by FACS for CD44−/CD184+/CD24+ neurons (Yuan et al., 2011) (Figure S5A–D). The cortical identity of the hESC-derived neurons was confirmed by the expression of VGLUT1, MAP2, CTIP2, and SATB2. Only very few GFAP+ or Nestin+ cells were present under those conditions (Figure S5E–T).
