Transdifferentiation of mouse fibroblasts and hepatocytes to functional neurons.

Nuclear reprogramming by defined transcription factors became of broad interest in 2006 with the work of Takahashi and Yamanaka (Cell 126:663-676, 2006), but the first example of cell fate reshaping via ectopic expression of transcription factor was provided back in 1987 when Davis and colleagues induced features of a muscle cell in fibroblast using the muscle transcription factor MyoD (Davis et al., Cell 51:987-1000, 1987). In 2010 our laboratory described how forced expression of the three neuronal transcription factors Ascl1, Brn2, and Myt1l rapidly converts mouse fibroblasts into neuronal cells that exhibit biochemical and electrophysiological properties of neurons. We named these cells induced neuronal cells (iN cells) (Vierbuchen et al., Nature 463:1035-1041, 2010; Vierbuchen and Wernig, Nat Biotechnol 29:892-907, 2011). Interestingly, iN cells can also be derived from defined endodermal cells such as primary hepatocytes, suggesting the existence of a more general reprogramming paradigm (Marro et al., Cell Stem Cell 9:374-382, 2011). In this chapter we describe the detailed methods used to attain the direct conversion.