title: Wnt/β-catenin signaling promotes differentiation, not self-renewal, of human embryonic stem cells and is repressed by Oct4.
abstract: Signal transduction pathways play diverse, context-dependent roles in vertebrate development. In studies of human embryonic stem cells (hESCs), conflicting reports claim Wnt/β-catenin signaling promotes either self-renewal or differentiation. We use a sensitive reporter to establish that Wnt/β-catenin signaling is not active during hESC self-renewal. Inhibiting this pathway over multiple passages has no detrimental effect on hESC maintenance, whereas activating signaling results in loss of self-renewal and induction of mesoderm lineage genes. Following exposure to pathway agonists, hESCs exhibit a delay in activation of β-catenin signaling, which led us to postulate that Wnt/β-catenin signaling is actively repressed during self-renewal. In support of this hypothesis, we demonstrate that OCT4 represses β-catenin signaling during self-renewal and that targeted knockdown of OCT4 activates β-catenin signaling in hESCs. Using a fluorescent reporter of β-catenin signaling in live hESCs, we observe that the reporter is activated in a very heterogeneous manner in response to stimulation with Wnt ligand. Sorting cells on the basis of their fluorescence reveals that hESCs with elevated β-catenin signaling express higher levels of differentiation markers. Together these data support a dominant role for Wnt/β-catenin signaling in the differentiation rather than self-renewal of hESCs.
authors.affiliation: Department of Pharmacology, Howard Hughes Medical Institute, and the Institute for Stem Cell and Regenerative Medicine, University of Washington School of Medicine, Seattle, WA 98109, USA.
authors.forename: Kathryn C
authors.initials: KC
authors.lastname: Davidson
authors.forename: Allison M
authors.initials: AM
authors.lastname: Adams
authors.forename: Jamie M
authors.initials: JM
authors.lastname: Goodson
authors.forename: Circe E
authors.initials: CE
authors.lastname: McDonald
authors.forename: Jennifer C
authors.initials: JC
authors.lastname: Potter
authors.forename: Jason D
authors.initials: JD
authors.lastname: Berndt
authors.forename: Travis L
authors.initials: TL
authors.lastname: Biechele
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Taylor
authors.forename: Randall T
authors.initials: RT
authors.lastname: Moon
mesh_terms: D000818:Animals; D002454:Cell Differentiation; D019070:Cell Lineage; D049109:Cell Proliferation; D018920:Coculture Techniques; D053595:Embryonic Stem Cells / Q000166:cytology*; D017930:Genes, Reporter; D006801:Humans; D051379:Mice; D008954:Models, Biological; D050814:Octamer Transcription Factor-3 / Q000378:metabolism*; D015398:Signal Transduction; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*
chemical_list: D050814:Octamer Transcription Factor-3; C494173:POU5F1 protein, human; D051153:Wnt Proteins; D051176:beta Catenin