title: Possible role of Hes5 for the rostrocaudal polarity formation of the tectum.
abstract: The alar plate of the mesencephalon differentiates into the optic tectum. Retinal fibers project to the tectum topographically in a retinotopic manner. Engrailed (En) is responsible for the tectum polarity formation and regionalization. Former study indicated the presence of the molecule whose expression is repressed by En and that represses the isthmus-related gene expression. To isolate such molecules, we constructed a subtracted library between cDNA population of the normal rostral mesencephalon and of the rostral mesencephalon that misexpresses En2. From the library, we isolated cHes5, a chicken homolog of Drosophila hairy/Enhancer of split. cHes5 begins to be expressed in the rostral part of the E2 mesencephalon, and spreads to caudal mesencephalon by E3. To our expectation, cHes5 expression was repressed by En2. Furthermore, misexpression of cHes5 in the mesencephalon inhibited expression of ephrinA2, a marker of caudal mesencephalon. An active repressor form of Hes5, which is a chimeric molecule of Hes5 and repressor domain of En2, showed a similar but more severe phenotype. The results indicate that Hes5 is regulated by En and is responsible for rostral identity of mesencephalon by repressing ephrinA2.
authors.affiliation: Laboratory for Vertebrate Body Plan, Center for Developmental Biology, RIKEN Kobe, 2-2-3 Minatojima, Minami-machi, Chuo-ku, Kobe, Hyogo 650-0047, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Kimura
authors.forename: Tatsuya
authors.initials: T
authors.lastname: Katahira
authors.forename: Isato
authors.initials: I
authors.lastname: Araki
authors.forename: Harukazu
authors.initials: H
authors.lastname: Nakamura
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002642:Chick Embryo; D003001:Cloning, Molecular; D018076:DNA, Complementary; D004268:DNA-Binding Proteins / Q000235:genetics / Q000502:physiology*; D018274:Electroporation; D036383:Ephrin-A2 / Q000235:genetics; D020869:Gene Expression Profiling; D018507:Gene Expression Regulation, Developmental; D015723:Gene Library; D018398:Homeodomain Proteins / Q000502:physiology; D017403:In Situ Hybridization; D008636:Mesencephalon / Q000196:embryology / Q000378:metabolism; D008969:Molecular Sequence Data; D012097:Repressor Proteins / Q000235:genetics / Q000502:physiology*; D017386:Sequence Homology, Amino Acid; D013477:Superior Colliculi / Q000196:embryology* / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D036383:Ephrin-A2; D018398:Homeodomain Proteins; D012097:Repressor Proteins