By assessing multiple positive and negative markers of forebrain progenitors and neurons, the authors show that now-standard, partially directed neocortical differentiation of mouse embryonic stem cells generates neurons that most closely resemble neocortical projection neurons during mid-corticogenesis. These neurons are“stalled” in subtype-specific molecular refinements, as compared to primary, dissociated E15.5 neocortical neurons cultured under the same in vitro conditions.
