Direct conversion of fibroblasts into stably expandable neural stem cells

Recent advances have suggested that direct induction of neural stem cells could provide an alternative to derivation from somatic tissues or pluripotent cells. Here we show direct derivation of stably expandable NS cells from mouse fibroblasts through a curtailed version of reprogramming to pluripotency. By constitutively inducing Sox2, Klf4, and c-Myc while strictly limiting Oct4 activity to the initial phase of reprogramming, we generated neurosphere-like colonies that could be expanded for more than 50 passages and do not depend on sustained expression of the reprogramming factors. These induced NS (iNS) cells uniformly display morphological and molecular features of NS cells such as the expression of Nestin, Pax6, and Olig2 and have a similar genome-wide transcriptional profile to brain-derived NSCs. iNS cells can differentiate into neurons, astrocytes and oligodendrocytes in vitro and in vivo. Our results demonstrate that functional neural stem cells can be generated from somatic cells by factor-driven induction. mRNA extracted from Murine Embryonic Fibroblasts (MEF), murine Embryonic Stem Cell (ES), murine Neuronal Stem Cell (NS) and three murine induces Neuronal Stem Cell clones 2, 3 and 5 (iNS2, iNS3, iNS5) has been hybridized on Illumina MouseWG6 V2 arrays for genome wide expression analysis. Samples were run at least as triple, MEF, iNS3, iNS5 as quadruple technical replicates. Differential gene expression analysis has been performed on the grouped expression data with the Murine Embryonic Fibroblasts group as the reference.