title: Gbx2 directly restricts Otx2 expression to forebrain and midbrain, competing with class III POU factors.
abstract: Otx2 plays essential roles in rostral brain development, and its counteraction with Gbx2 has been suggested to determine the midbrain-hindbrain boundary (MHB) in vertebrates. We previously identified the FM enhancer that is conserved among vertebrates and drives Otx2 transcription in forebrain/midbrain from the early somite stage. In this study, we found that the POU homeodomain of class III POU factors (Brn1, Brn2, Brn4, and Oct6) associates with noncanonical target sequence TAATTA in the FM enhancer. MicroRNA-mediated knockdown of Brn2 and Oct6 diminished the FM enhancer activity in anterior neural progenitor cells (NPCs) differentiated from P19 cells. The class III POU factors associate with the FM enhancer in forebrain and midbrain but not in hindbrain. We also demonstrated that the Gbx2 homeodomain recognizes the same target TAATTA in the FM enhancer, and Gbx2 associates with the FM enhancer in hindbrain. Gbx2 misexpression in the anterior NPCs repressed the FM enhancer activity and inhibited Brn2 association with the enhancer, whereas Gbx2 knockdown caused ectopic Brn2 association in the posterior NPCs. These results suggest that class III POU factors and Gbx2 share the same target site, TAATTA, in the FM enhancer and that their region-specific binding restricts Otx2 expression at the MHB.
authors.affiliation: Laboratory for Vertebrate Body Plan, Center for Developmental Biology, RIKEN, Minatojima-minamimachi, Chuo-ku, Kobe, Hyogo, Japan.
authors.forename: Fumitaka
authors.initials: F
authors.lastname: Inoue
authors.forename: Daisuke
authors.initials: D
authors.lastname: Kurokawa
authors.forename: Maiko
authors.initials: M
authors.lastname: Takahashi
authors.forename: Shinichi
authors.initials: S
authors.lastname: Aizawa
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D001665:Binding Sites / Q000235:genetics; D001667:Binding, Competitive; D002460:Cell Line; D017124:Conserved Sequence; D017931:DNA Primers / Q000235:genetics; D004742:Enhancer Elements, Genetic; D018507:Gene Expression Regulation, Developmental; D055785:Gene Knockdown Techniques; D018398:Homeodomain Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics; D008636:Mesencephalon / Q000196:embryology / Q000378:metabolism*; D051379:Mice; D008822:Mice, Transgenic; D008959:Models, Neurological; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D058953:Neural Stem Cells / Q000378:metabolism; D050816:Octamer Transcription Factor-6 / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D051857:Otx Transcription Factors / Q000235:genetics*; D050809:POU Domain Factors / Q000037:antagonists & inhibitors / Q000145:classification / Q000235:genetics / Q000378:metabolism*; D016548:Prosencephalon / Q000196:embryology / Q000378:metabolism*; D017386:Sequence Homology, Amino Acid
chemical_list: D017931:DNA Primers; C052976:FM protein, mouse; C513182:Gbx2 protein, mouse; D018398:Homeodomain Proteins; D008562:Membrane Glycoproteins; D009419:Nerve Tissue Proteins; D051857:Otx Transcription Factors; C497660:Otx2 protein, mouse; D050809:POU Domain Factors; D050816:Octamer Transcription Factor-6; C074066:Pou3f2 protein, mouse