MECP2 and atypical Rett syndrome: More specifically, to demonstrate the in vitro patient‐specific treatment of Rett syndrome, we generated induced pluripotent stem cell‐derived neural progenitor cells (iPSC‐NPCs) obtained from a Rett syndrome patient (RTT‐NPCs) and designed two plasmids to cut and replace the mutated MeCP2 gene (Figure 1c).