Neurons were generated from iPSC-derived neural progenitor cells (NPCs) as described by Marchetto et al. with slight modifications [26, 35]. A detailed description of the protocol can be found in Additional file 2. Essentially, the protocol leads to a mixed population of glutamatergic and GABAergic neurons (see Additional file 2), while the ratio of the two neuronal types and subtypes likely vary among samples due to the complexity of differentiation (see below). Neuronal samples were harvested on day 14 following differentiation from NPCs, and RNA was extracted and sent for sequencing. As such, the neurons used here were largely at their early differentiation stages and had not reached the stage that action potentials could be detected.
