generated iN cells when tested individually (data not shown). Next, we tested whether combinatorial expression of these factors with Ascl1 could further increase the induction of neuron-like cells by infecting TauEGFP MEFs with a pool of Brn2, Myt1l, Zic1, Olig2, and Ascl1 viruses (5F pool). Given its close similarity to Brn2, we did not include Brn4 in the 5F pool. Twelve days after infection, we detected a frequent Tuj1-positive iN cells with highly complex morphologies (Fig. 1f). These 5F-iN cells also expressed the pan-neuronal markers MAP2, NeuN, and synapsin (Fig. 1i–j, n). Similar results were obtained with iN cells derived from Balb/c MEFs (Supplementary Fig. 3a).
