title: Involvement of a Xenopus nuclear GTP-binding protein in optic primordia formation.
abstract: Using a subtracted Xenopus cDNA library based on the differential sensitivity of anterior and posterior genes to retinoic acid, we isolated a novel Xenopus nuclear GTP-binding protein (XGB). XGB is expressed prominently in the optic primordia at the tailbud stage. The N-terminal region of XGB contains a set of GTP-binding protein motifs, and the C-terminal region contains two putative nuclear localization signals and two coiled regions. A GFP-XGB fusion protein was expressed in the nucleus of NIH3T3 cells where it bound to subnuclear structures. Truncated C-terminal constructs of XGB containing both nuclear localization signal(s) and coiled region(s) suppressed eye formation, whereas neither the N-terminal construct nor constructs with a mutated GTP-binding protein motif affected eye formation. Expression of Pax6 and Rx1 genes, which are crucial for eye development, was reduced in embryos overexpressing the C-terminal constructs of XGB. Suppression of Pax6 and Rx1 at earlier developmental stages as well as perturbation of eye formation at later stages was counteracted by co-expression of wild-type XGB. We conclude that XGB plays a role in the formation of optic primordia through activation of at least two eye field transcription factors.
authors.affiliation: Neuroscience Research Institute, National Institute of Advanced Industrial Science and Technology (AIST) Central 6, 1-1-1 Higashi, Tsukuba 305-8566, Japan.
authors.forename: Yoshiaki
authors.initials: Y
authors.lastname: Tamanoue
authors.forename: Ikuko
authors.initials: I
authors.lastname: Hongo
authors.forename: Harumasa
authors.initials: H
authors.lastname: Okamoto
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018076:DNA, Complementary; D004625:Embryo, Nonmammalian; D047108:Embryonic Development / Q000235:genetics; D005123:Eye / Q000196:embryology* / Q000378:metabolism; D019204:GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D008969:Molecular Sequence Data; D014981:Xenopus / Q000196:embryology* / Q000235:genetics; D029867:Xenopus Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D018076:DNA, Complementary; D029867:Xenopus Proteins; D019204:GTP-Binding Proteins; C518674:XGB protein, Xenopus