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Keywords:

  • ES cells;
  • Pluripotency;
  • β-catenin;
  • Lrh-1;
  • Oct4

Abstract

Delineating the signaling pathways that underlie ESC pluripotency is paramount for development of ESC applications in both the research and clinical settings. In culture pluripotency is maintained by leukemia inhibitory factor (LIF) stimulation of two separate signaling axes: Stat3/Klf4/Sox2 and PI3K/Tbx3/Nanog, which converge in the regulation of Oct4 expression. However, LIF signaling is not required in vivo for self-renewal, thus alternate signaling axes likely mediate these pathways. Additional factors that promote pluripotency gene expression have been identified, including the direct regulation of Oct4 by liver receptor homolog-1 (Lrh-1) and β-catenin regulation of Nanog. Here, we present genetic, molecular, and pharmacological studies identifying a signaling axis in which β-catenin promotes pluripotency gene expression in an Lrh-1-dependent manner. Furthermore, Lrh-1 was identified as a novel β-catenin target gene, and Lrh-1 regulation is required for maintaining proper levels of Oct4, Nanog, and Tbx3. Elucidation of this pathway provides an alternate mechanism by which the primary pluripotency axis may be regulated in vivo and may pave the way for small molecule applications to manipulate pluripotency or improve the efficiency of somatic cell reprogramming. STEM CELLS 2010;28:1794–1804