NKX2.1::GFP, are presented in Figure 6F–J. No VIP or calretinin expressing neurons were observed suggesting the lack of cells exhibiting features of the caudal ganglionic eminence (Xu et al., 2004). The derivation of NKX2.1+/PV+ was particularly remarkable given the late developmental expression of this marker in cortical interneurons in vivo (Zecevic et al., 2011). Only a subset of the cells counted as GFP+/PV+ by the automated image analyses (Operetta high content scanner – see Material & Methods) showed high levels of PV expression and exhibited interneuron-like morphologies (about 5% of total GFP+ cells (J)). Our results point to the need to further optimize the derivation of selective cortical interneuron subtypes. However, the fact that PV+ hPSC-derived neurons could be generated at all suggests that the mouse cortical co-culture strategy facilitates expression of cortical interneuron subtype markers.
