From Cell Stem Cell
By Stuart P. Atkinson
Direct conversion of one somatic cell to another somatic cell type, completely bypassing the pluripotent stage through the forced expression of lineage specific transcription factors has emerged as a large “splinter group” of research, taking many lessons from induced pluripotent stem cell (iPSC) technology. The direct generation of induced neuronal cells (iN) from human fibroblasts has been previously demonstrated in several papers (Ambasuhan et al, Caiazzo et al, Pang et al, Pfisterer et al, Qiang et al, Son et al and Yoo et al.) however fibroblasts represent a heterogeneous mixture of cells, potentially including cells of the neural crest, and so the reprogrammed cell of origin remains undefined. Therefore, researchers from the group of Marius Wernig at the Stanford University School of Medicine, USA, decided to attempt to identify a specific somatic cell type from one germ lineage and reprogram these cells across the germ layer barrier into iN cells. The study, published as a short article in Cell Stem Cell demonstrates the direct conversion of mouse hepatocytes to iN cells and analyses the reprogramming process, demonstrating the faithful silencing of the hepatocyte expression program and the expression of the neuronal expression program (Marro et al).