Early somatic cell nuclear transfer experiments in amphibians by Briggs, King and Gurdon have heralded the notion that every somatic cell type can be reprogrammed to pluripotency [1, 2]. Later cell fusion experiments by Blau and colleagues illustrated cell conversions between somatic cell types [1, 2]. Finally, transcription factors have been identified that are sufficient to interconvert closely related cell types such as fibroblasts to muscle cells with MyoD or B-cells into macrophages with CEBPα ([3] and references therein). In 2006, Takahashi and Yamanaka have demonstrated that induced pluripotent stem (iPS) cells can be directly derived from fibroblasts by a combination of just 4 transcription factors Oct4, Sox2, Klf4 and cMyc [4, 5]. The induction of pluripotency in somatic cells is a very dramatic change in cell fates unlike the other cell interconversions reported before. This begged the question whether such dramatic cell lineage changes can also be induced between distantly related somatic cell types. In 2010, we have shown that fibroblasts can be reprogrammed into induced neuronal (iN) cells illustrating that direct lineage conversion is possible even between cell
