title: Dual roles of Oct4 in the maintenance of mouse P19 embryonal carcinoma cells: as negative regulator of Wnt/β-catenin signaling and competence provider for Brachyury induction.
abstract: Transcription factor Oct4 is expressed in pluripotent cell lineages during mouse development, namely, in inner cell mass (ICM), primitive ectoderm, and primordial germ cells. Functional studies have revealed that Oct4 is essential for the maintenance of pluripotency in inner cell mass and for the survival of primordial germ cells. However, the function of Oct4 in the primitive ectoderm has not been fully explored. In this study, we investigated the role of Oct4 in mouse P19 embryonal carcinoma (EC) cells, which exhibit molecular and developmental properties similar to the primitive ectoderm, as an in vitro model. Knockdown of Oct4 in P19 EC cells upregulated several early mesoderm-specific genes, such as Wnt3, Sp5, and Fgf8, by activating Wnt/β-catenin signaling. Overexpression of Oct4 was sufficient to suppress Wnt/β-catenin signaling through its action as a transcriptional activator. However, Brachyury, a key regulator of early mesoderm development and a known direct target of Wnt/β-catenin signaling, was unable to be upregulated in the absence of Oct4, even with additional activation of Wnt/β-catenin signaling. Microarray analysis revealed that Oct4 positively regulated the expression of Tdgf1, a critical component of Nodal signaling, which was required for the upregulation of Brachyury in response to Wnt/β-catenin signaling in P19 EC cells. We propose a model that Oct4 maintains pluripotency of P19 EC cells through 2 counteracting actions: one is to suppress mesoderm-inducing Wnt/β-catenin signaling, and the other is to provide competence to Brachyury gene to respond to Wnt/β-catenin signaling.
authors.affiliation: Department of Anatomy, Biochemistry, and Physiology, Institute for Biogenesis Research, University of Hawaii John A. Burns School of Medicine, Honolulu, HI 96813, USA. marikawa@hawaii.edu
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Marikawa
authors.forename: Dana Ann A
authors.initials: DA
authors.lastname: Tamashiro
authors.forename: Toko C
authors.initials: TC
authors.lastname: Fujita
authors.forename: Vernadeth B
authors.initials: VB
authors.lastname: Alarcon
mesh_terms: D000818:Animals; D055415:Bone Morphogenetic Protein 4 / Q000494:pharmacology; D002454:Cell Differentiation; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D003907:Dexamethasone / Q000494:pharmacology; D054278:Embryonal Carcinoma Stem Cells / Q000166:cytology / Q000378:metabolism*; D004815:Epidermal Growth Factor / Q000378:metabolism; D005326:Fetal Proteins / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental / Q000187:drug effects; D006801:Humans; D008562:Membrane Glycoproteins / Q000378:metabolism; D008648:Mesoderm / Q000166:cytology / Q000196:embryology / Q000378:metabolism; D051379:Mice; D009363:Neoplasm Proteins / Q000378:metabolism; D050814:Octamer Transcription Factor-3 / Q000235:genetics / Q000378:metabolism*; D010446:Peptide Fragments / Q000096:biosynthesis; D039904:Pluripotent Stem Cells / Q000166:cytology / Q000378:metabolism; D034622:RNA Interference; D011993:Recombinant Fusion Proteins / Q000096:biosynthesis; D015398:Signal Transduction; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism*; D015533:Transcriptional Activation; D051153:Wnt Proteins / Q000378:metabolism*; D051176:beta Catenin / Q000378:metabolism*; D000098908:Brachyury Protein
chemical_list: D055415:Bone Morphogenetic Protein 4; D003907:Dexamethasone; D004815:Epidermal Growth Factor; D005326:Fetal Proteins; D008562:Membrane Glycoproteins; D009363:Neoplasm Proteins; D050814:Octamer Transcription Factor-3; D010446:Peptide Fragments; D011993:Recombinant Fusion Proteins; D020825:T-Box Domain Proteins; D051153:Wnt Proteins; D051176:beta Catenin; D000098908:Brachyury Protein; C494174:Pou5f1 protein, mouse; C489450:Tdgf1 protein, mouse