Enhanced OCT4 transcriptional activity substitutes for exogenous SOX2 in cellular reprogramming.

Adele G Marthaler,Sergiy Velychko,Natalia Tapia,Kenjiro Adachi,Ulf Tiemann,Ingo Kleiter,Guangming Wu,Hans R Schöler,Davood Sabour

doi:10.1038/srep19415

Abstract

Adenoviral early region 1A (E1A) is a viral gene that can promote cellular proliferation and de-differentiation in mammalian cells, features required for the reprogramming of somatic cells to a pluripotent state. E1A has been shown to interact with OCT4, and as a consequence, to increase OCT4 transcriptional activity. Indeed, E1A and OCT4 are sufficient to revert neuroepithelial hybrids to pluripotency, as demonstrated in previous cell fusion experiments. However, the role that E1A might play in the generation of induced pluripotent stem cells (iPSCs) has not been investigated yet. In this report, we show that E1A can generate iPSCs in combination with OCT4 and KLF4, thus replacing exogenous SOX2. The generated iPSCs are bona fide pluripotent cells as shown by in vitro and in vivo tests. Overall, our study suggests that E1A might replace SOX2 through enhancing OCT4 transcriptional activity at the early stages of reprogramming.

Highlights

Somatic cells can acquire a pluripotent fate after ectopic expression of Oct[4], Sox[2], Klf[4], and Myc[1], from which Myc can be omitted[2]
As early region 1A (E1A) have been described to reprogram neuroepithelial-like cells into pluripotency[11], we assessed whether E1A could contribute to induced pluripotent stem cells (iPSCs)
Mouse embryonic fibroblasts (MEFs) containing an Oct4-green fluorescent protein (GFP) reporter construct were transduced using several combinations of retroviral-defective particles coding for Oct[4] (O), Sox[2] (S), Klf[4] (K), and E1A (E) (Fig. 1A)

Summary

Introduction

Somatic cells can acquire a pluripotent fate after ectopic expression of Oct[4], Sox[2], Klf[4], and Myc[1], from which Myc can be omitted[2]. OCT4 and SOX2 together with NANOG co-occupy the core targets of the pluripotency transcriptional network in embryonic stem cells (ESCs)[3], Nanog is not essential to maintain pluripotency[4]. OCT4 and SOX2 proteins dimerize on DNA to activate their target genes in order to specify pluripotency[7]. OCT4 can activate gene transcription when its DNA binding site is located close to the TATA box. OCT4 requires additional factors to induce transcription when the DNA binding sites are distantly located from the TATA element. The adenovirus early region 1A (E1A) protein can function as such a coactivator and can enhance OCT4 transcriptional activity in somatic cells[10]. E1A can enhance OCT4 transactivation activity in somatic cells and both proteins can together reprogram differentiated cells in a cell fusion context. We sought to investigate the potential role of E1A in reprogramming somatic cells into induced pluripotent stem cells (iPSCs)

Methods

Results

Conclusion