Oct4-Sox2-Nanog transcriptional networks are critical for the maintenance of embryonic stem (ES) cell self-renewal and induction of pluripotency. However, in transcription factor-induced reprogramming of somatic cells into induced pluripotent stem cells (iPSCs), Nanog is initially dispensable and Oct4 remains the sole factor that could not be substituted/omitted. Here, we show that mouse fibroblasts could be reprogrammed into iPSCs by Nanog and Bmi1, which replaces Sox2, Klf4, and c-Myc, in the absence of Oct4. Furthermore, we show that in the presence of shh agonists (oxysterol and purmophamine), which replaces the function of Bmi1, a single transcription factor, Nanog is sufficient to reprogram mouse fibroblasts into iPSCs. Nanog-induced iPSCs resemble mESCs in terms of morphology, global gene expression profiles, epigenetic status and pluripotency both in vitro and in vivo. These findings support that Nanog can replace the Oct4 for the somatic cell reprogramming and underlie the mechanisms of Nanog in reprogramming process. (C) 2013 Elsevier Inc. All rights reserved.