We previously observed that Ngn2, or Neurod1, rapidly converted ES and iPS cells into glutamatergic iN cells13. Notably, we also found that forced expression of Ascl1—a basic helix–loop–helix (bHLH) factor not conventionally associated with cell fate determination of glutamatergic neurons—induces excitatory iN cells from human PSCs with slower conversion kinetics14. In an effort to improve Ascl1-mediated neuronal induction, we found that coexpression of the zinc finger protein Myt1-like (Myt1l) greatly accelerated the appearance of morphologically complex iN cells (Supplementary Fig. 1).
