Sox2 expression effects on direct reprogramming efficiency as determined by alternative somatic cell fate

Induced pluripotent stem cells (iPSCs) are generated by directly reprogramming somatic cells by forcing them to express the exogenous transcription factors, Oct4, Sox2, Klf4 and c-Myc (OSKM). These cells could potentially be used in clinical applications and basic research. Here, we explored the molecular role of Sox2 by generating iPSCs that expressed Sox2 at various levels. Low Sox2 (LS) expression increased the efficiency of generating partially reprogrammed iPSCs in combination with OKM. Notably, we detected a significant increase in the number of fully reprogrammed iPSCs with three factors of OK and LS. LS expression was linked with the reduced expression of ectoderm and mesoderm marker genes. This indicates that cell differentiation into the ectoderm and mesoderm lineages was impeded during reprogramming. The quality of the iPSCs that was generated by using OK and LS was comparable to that of iPSCs that were produced via conventional OSK as seen by pluripotent marker gene expression and chimera formation. We conclude that Sox2 plays a crucial role in a dose-dependent manner in direct reprogramming of somatic cells to iPSCs.