title: Nkx1-2 is a transcriptional repressor and is essential for the activation of Brachyury in P19 mouse embryonal carcinoma cell.
abstract: Activation of Wnt/β-catenin signaling is crucial for the differentiation of pluripotent stem cells, namely the epiblast, embryonic stem, and embryonal carcinoma cells, into mesendoderm. However, downstream events of Wnt/β-catenin signaling that control the formation of mesendoderm are still unclear. In the present study, we used mouse P19 embryonal carcinoma cells as a model, and identified a homeodomain protein Nkx1-2 as a key regulator of mesendoderm formation. In the mouse embryo, Nkx1-2 was expressed in the primitive streak, in which the nascent mesendoderm emerges. In P19 cells, the expression of Nkx1-2 was activated by Wnt/β-catenin signaling independently of Brachyury, an evolutionary conserved early mesendoderm gene. In contrast, the expression of Nkx1-2 was both necessary and sufficient for the activation of Brachyury. Nkx1-2 acted as a transcriptional repressor to mediate the action of Wnt/β-catenin signaling to activate the Brachyury expression. We found Tcf3 as a potential target of gene repression by Nkx1-2, and the down-regulation of Tcf3 was partly required for effective activation of Brachyury by Wnt/β-catenin signaling. These results suggest that Nkx1-2 is a critical component of the gene regulatory network that operates downstream of Wnt/β-catenin signaling to regulate the formation of mesendoderm.
authors.affiliation: Institute for Biogenesis Research, Department of Anatomy, Biochemistry and Physiology, University of Hawaii John A. Burns School of Medicine, 651 Ilalo Street, Biosciences Building, Room 163A, Honolulu, Hawaii 96813, USA.
authors.forename: Dana Ann A
authors.initials: DA
authors.lastname: Tamashiro
authors.forename: Vernadeth B
authors.initials: VB
authors.lastname: Alarcon
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Marikawa
mesh_terms: D000818:Animals; D051792:Basic Helix-Loop-Helix Proteins / Q000235:genetics / Q000378:metabolism*; D002454:Cell Differentiation / Q000235:genetics*; D019070:Cell Lineage; D054278:Embryonal Carcinoma Stem Cells / Q000166:cytology / Q000378:metabolism; D005326:Fetal Proteins / Q000235:genetics / Q000378:metabolism*; D053263:Gene Regulatory Networks; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism*; D051379:Mice; D008810:Mice, Inbred C57BL; D008811:Mice, Inbred DBA; D009687:Nuclear Proteins / Q000235:genetics* / Q000378:metabolism*; D020825:T-Box Domain Proteins / Q000235:genetics / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics* / Q000378:metabolism*; D060449:Wnt Signaling Pathway; D000098908:Brachyury Protein
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D005326:Fetal Proteins; D018398:Homeodomain Proteins; D009687:Nuclear Proteins; D020825:T-Box Domain Proteins; D014157:Transcription Factors; D000098908:Brachyury Protein; C109095:Nkx1-2 protein, mouse; C075668:Tcf3 protein, mouse