The Wnt/β-catenin pathway and Nanog are key regulators of embryonic stem cell (ESC) pluripotency and the reprogramming of somatic cells. Here, we demonstrate that the repression of Dkk1 by Nanog, which leads indirectly to β-catenin activation, is essential for reprogramming after fusion of ESCs overexpressing Nanog. In addition, β-catenin is necessary in Nanog-dependent conversion of preinduced pluripotent stem cells (pre-iPSCs) into iPSCs. The activation of β-catenin by Nanog causes fluctuations of β-catenin in ESCs cultured in serum plus leukemia inhibitory factor (serum+LIF) medium, in which protein levels of key pluripotency factors are heterogeneous. In 2i+LIF medium, which favors propagation of ESCs in a ground state of pluripotency with many pluripotency genes losing mosaic expression, we show Nanog-independent β-catenin fluctuations. Overall, we demonstrate Nanog and β-catenin cooperation in establishing naive pluripotency during the reprogramming process and their correlated heterogeneity in ESCs primed toward differentiation.

This work was funded by an ERC grant (242630-RERE) (M.P.C.), an HFSP grant (M.P.C.), the Ministerio de Ciencia e Inovación SAF2011-28580 (M.P.C.), Fundacio La Marató de TV3 (M.P.C.), AXA Research Fund (M.P.C.), an EMBO Long-Term Fellowship (L.M.), and Wolfson Foundation and BBSRC Alert 13 capital grant (BB/L014181/1) (Bristol University)