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

Abstract

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.

The Role of SOX2 in Maintaining Pluripotency and Differentiation of Human Embryonic Stem Cells

“…Generally, overexpression of Sox2 is required unless the somatic cells already have endogenous Sox2 expression (Hanna et al, 2010;Stadtfeld and Hochedlinger, 2010). Moreover, the level of SOX2 expression has a direct effect on the rate of direct reprogramming of somatic cells to iPSCs (Yamaguchi et al, 2011). These results provide further support for the assumption that SOX2 has a definitive role in the maintenance of ESCs.…”

Direct Lineage Reprogramming: Strategies, Mechanisms, and Applications

“…The use of factor combinations to induce lineage conversion raises an important question: do different expression levels of different exogenous factors affect the outcome of lineage reprogramming? Results from the mechanistic analysis of iPSC reprogramming have provided evidence that factor stoichiometry not only influences the reprogramming process but also the quality of iPSCs (Carey et al, 2011;Papapetrou et al, 2009;Tiemann et al, 2011;Yamaguchi et al, 2011). For example, high levels of exogenous Oct4 and Klf4 protein combined with low levels of Sox2 and c-Myc resulted in the generation of high-quality iPSCs with the ability of generating mice through tetraploid complementation (Carey et al, 2011).…”

A developmental framework for induced pluripotency

“…For example, iPSC-derived secondary fibroblasts carrying doxycycline-inducible OSKM expression cassettes, which achieve a uniform expression of OSKM at levels required for iPSC generation, can be efficiently reprogrammed to pluripotency (Wernig et al, 2008). Additionally, it has been observed that reprogramming efficiency is enhanced by increasing levels of OCT3/4 and KLF4 (Papapetrou et al, 2009;Tiemann et al, 2011) as well as by lowering SOX2 expression (Yamaguchi et al, 2010). It has also been shown that in the early phase of reprogramming towards pluripotency, OCT3/4 and SOX2 promote the expression of mesendodermal and neuroectodermal genes, respectively (Shu et al, 2013), whereas KLF4 can induce the expression of epidermal genes in a context-dependent manner (Kim et al, 2015).…”