Because these findings strongly indicated that, even though SCZD hiPSC lines were capable of generating hippocampal NPCs, there might be defects in the development of these NPCs into DG granule neurons, we assessed the function of SCZD and control hiPSC-derived neurons using calcium imaging. After differentiating SCZD and control hiPSC-derived NPCs for 4 weeks on hippocampal astrocytes, we obtained PROX1+ granule neurons in both groups (Figures 6G and 6H). Calcium imaging of these neural networks at 4 weeks postdifferentiation revealed a significant reduction in the proportion of active neurons in the SCZD group (∼57%) compared to the controls (∼82%) (Figures 6I and 6J), indicating that the deficits in hippocampal neurogenesis by SCZD lines also affected the neural networks formed by SCZD hiPSCs, potentially resulting in the reduction in connectivity observed in our previous work (Brennand et al., 2011).
