Astrocytes are reprogrammed into iPS cells through a neural stem cell-like state

It remains controversial whether the routes from differentiated cells to iPSCs are related to the reverse order of normal developmental processes or independent of them. Here, we generated iPSCs from mouse astrocytes by three (Oct3/4, Klf4 and Sox2 (OKS)), two (OK), or four (OKS plus c-Myc) factors. Sox1, a neural stem cell (NSC)-specific transcription factor, is transiently upregulated during reprogramming and Sox1-positive cells become iPSCs. The upregulation of Sox1 is essential for OK-induced reprogramming. Genome-wide analysis revealed that the gene expression profile of Sox1-expressing intermediate-state cells resembles that of NSCs. Furthermore, the intermediate-state cells are able to generate neurospheres, which can differentiate into both neurons and glial cells. Remarkably, during MEF reprogramming, neither Sox1 upregulation nor an increase in neurogenic potential occurs. Thus, astrocytes are reprogrammed through an NSC-like state, suggesting that reprogramming partially follows the retrograde pathway of normal developmental processes.

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Nakajima-Koyama M, Lee J, Ohta S, Yamamoto T, Nishida E