We next aimed to gain insight into the nature of the neurons generated and more importantly, to assess the reproducibility of Ngn2-induced production of iN cells from different ES and iPS cell lines. Towards this end, we quantitatively analyzed expression of 73 genes at the single-cell level using fluidigm-dependent mRNA measurements (Pang et al., 2011; Table S1). All fluidigm-mediated quantitative RT-PCR assays were validated using standard curves (Table S1). Analysis of more than 100 individual iN cells revealed a uniform but discrete pattern of gene expression in iN cells derived from H1 ES and two different iPS cell lines (Figs. 3 and S3). Specifically, Ngn2-iN cells expressed at high levels the telencephalic markers Brn-2, Cux1, and FoxG1 that are characteristic of layer 2/3 excitatory cortical neurons, but lacked other prominent forebrain transcription factors (e.g., Tbr1 and Fog2). iN cells consistently expressed AMPA-type glutamate receptors GluA1, A2, and A4, but lacked NMDA-type glutamate receptors 3 weeks after induction (Fig. 3A). Moreover, nearly all iN cells expressed vGlut2, and approximately 20% of iN cells expressed vGlut1. iN cells highly expressed GABAA-receptors but
