OCT4 Activity during Conversion of Human Intermediately Reprogrammed Stem Cells to iPS Cells through MET

• Published in: Development (Cambridge)
• Main Authors: Teshigawara, Rika, Hirano, Kunio, Nagata, Shogo, Ainscough, Justin, Tada, Takashi
• Format: Journal Article
• Language: English; Japanese
• Published: 01.01.2015
• ISSN: 0950-1991; 1477-9129
• DOI: 10.1242/dev.130344

To facilitate understanding the mechanisms of somatic reprogramming to human induced Pluripotent Stem Cells (iPSCs), we have established intermediately Reprogrammed Stem Cells (iRSCs), human mesenchymal cells that express exogenous Oct4/Sox2/Klf4/c-Myc (OSKM) and endogenous SOX2/NANOG. iRSCs can be stably maintained at low density. At high density, however, they are induced to enter Mesenchymal-to-Epithelial Transition (MET), resulting in reprogramming to an iPSC state. Morphological changes through MET correlate with silencing of exogenous OSKM, and up-regulation of endogenous OCT4. A CRISPR/Cas9-mediated GFP knock-in visualized the temporal regulation of endogenous OCT4 in cells converting from iRSC to iPSC state. OCT4 activation coincident with OSKM silencing occurred prior to entering MET. Notably, OCT4 instability was frequently observed in cells of developing post-MET colonies until a late stage (>200 cells), demonstrating that OCT4-activated post-MET cells switched from asymmetric to symmetric cell division in late stage reprogramming.