Oct4 and Its Pseudogenes Confuse Stem Cell Research

Octamer-binding transcription factor 4 (Oct4) encodes a POU-domain transcription factor (Scholer et al., 1990Scholer H.R. Ruppert S. Suzuki N. Chowdhury K. Gruss P. Nature. 1990; 344: 435-439Crossref PubMed Scopus (594) Google Scholar). The gene is specifically expressed in embryonic stem (ES) cells but can also be detected in adult stem cells such as bone marrow-derived mesenchymal stem cells (Pochampally et al., 2004Pochampally R.R. Smith J.R. Ylostalo J. Prockop D.J. Blood. 2004; 103: 1647-1652Crossref PubMed Scopus (203) Google Scholar). Expression of Oct4 is downregulated during stem cell differentiation. Oct4 plays a critical role in maintaining pluripotency and self-renewal of ES cells (Niwa et al., 2000Niwa H. Miyazaki J. Smith A.G. Nat. Genet. 2000; 24: 372-376Crossref PubMed Scopus (2896) Google Scholar, Pesce and Scholer, 2001Pesce M. Scholer H.R. Stem Cells. 2001; 19: 271-278Crossref PubMed Scopus (670) Google Scholar), but its utility as a marker of pluripotency has been challenged recently by studies suggesting that it is expressed in a variety of differentiated cells, including peripheral blood mononuclear cells (PBMCs) (Tai et al., 2005Tai M.H. Chang C.C. Kiupel M. Webster J.D. Olson L.K. Trosko J.E. Carcinogenesis. 2005; 26: 495-502Crossref PubMed Scopus (518) Google Scholar, Zangrossi et al., 2007Zangrossi S. Marabese M. Broggini M. Giordano R. D'Erasmo M. Montelatici E. Intini D. Neri A. Pesce M. Rebulla P. Lazzari L. Stem Cells. 2007; 25: 1675-1680Crossref PubMed Scopus (144) Google Scholar). However, detection of Oct4 expression by RT-PCR could be prone to artifacts generated by pseudogene transcripts. We therefore have analyzed the sequences of human Oct4 and its pseudogenes and designed PCR primers that can avoid false positive detection of Oct4 expression.