Coronal telencephalic slices (250 μm) were prepared as described previously (Anderson et al., 2001) and maintained in Neurobasal/B27 with 5 ng/ml FGF2 (Promega). hESC-derived NKX2.1::GFP+ cells were isolated by FACS and carefully injected (~ 5,000 cells) into periventricular region of the MGE using an oocyte microinjector (Nanoinject II; Drummond). After 2–6 days cultures were fixed and immunostained. For cell counting, Zone 1 was defined as the region from the ventricular zone of the lateral ganglionic eminence extending to the pallial-subpallial border. Zone 2 was defined as the region from the lateral cortex through the neocortex to the cortical hem.
