title: The homeobox gene, Xanf-1, can control both neural differentiation and patterning in the presumptive anterior neurectoderm of the Xenopus laevis embryo.
abstract: From the onset of neurectoderm differentiation, homeobox genes of the Anf class are expressed within a region corresponding to the presumptive telencephalic and rostral diencephalic primordia. Here we investigate functions of the Xenopus member of Anf, Xanf-1, in the differentiation of the anterior neurectoderm. We demonstrate that ectopic Xanf-1 can expand the neural plate at expense of adjacent non-neural ectoderm. In tadpoles, the expanded regions of the plate developed into abnormal brain outgrowths. At the same time, Xanf-1 can inhibit terminal differentiation of primary neurones. We also show that, during gastrula/neurula stages, the exogenous Xanf-1 can downregulate four transcription regulators, XBF-1, Otx-2, Pax-6 and the endogenous Xanf-1, that are expressed in the anterior neurectoderm. However, during further development, when the exogenous Xanf-1 was presumably degraded, re-activation of XBF-1, Otx-2 and Pax-6 was observed in the abnormal outgrowths developed from blastomeres microinjected with Xanf-1 mRNA. Other effects of the ectopic Xanf-1 include cyclopic phenotype and inhibition of the cement gland, both by Otx-2-dependent and -independent mechanisms. Using fusions of Xanf-1 with the repressor domain of Drosophila engrailed or activator domain of herpes virus VP16 protein, we showed that most of the observed effects of Xanf-1 were probably elicited by its functioning as a transcription repressor. Altogether, our data indicate that the repressor function of Xanf-1 may be necessary for regulation of both neural differentiation and patterning in the presumptive anterior neurectoderm.
authors.affiliation: Shemyakin and Ovchinnikov Institute of Bioorganic Chemistry, Russian Academy of Sciences, ul. Mikluho-Maklaya 16/10, V-437 Moscow 117871, Russia.
authors.forename: G V
authors.initials: GV
authors.lastname: Ermakova
authors.forename: E M
authors.initials: EM
authors.lastname: Alexandrova
authors.forename: O V
authors.initials: OV
authors.lastname: Kazanskaya
authors.forename: O L
authors.initials: OL
authors.lastname: Vasiliev
authors.forename: M W
authors.initials: MW
authors.lastname: Smith
authors.forename: A G
authors.initials: AG
authors.lastname: Zaraisky
mesh_terms: D000818:Animals; D019677:Artificial Gene Fusion; D001483:Base Sequence; D019521:Body Patterning / Q000235:genetics; D002454:Cell Differentiation / Q000235:genetics; D017931:DNA Primers / Q000235:genetics; D004475:Ectoderm / Q000166:cytology; D018507:Gene Expression Regulation, Developmental; D005801:Genes, Homeobox; D018398:Homeodomain Proteins / Q000235:genetics* / Q000378:metabolism; D017403:In Situ Hybridization; D008845:Microinjections; D009420:Nervous System / Q000166:cytology / Q000196:embryology* / Q000254:growth & development; D016548:Prosencephalon / Q000196:embryology; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D012097:Repressor Proteins / Q000235:genetics / Q000378:metabolism; D013687:Telencephalon / Q000196:embryology; D029867:Xenopus Proteins; D014982:Xenopus laevis / Q000196:embryology* / Q000235:genetics* / Q000378:metabolism
chemical_list: D017931:DNA Primers; C098129:HESX1 protein, Xenopus; D018398:Homeodomain Proteins; D011993:Recombinant Fusion Proteins; D012097:Repressor Proteins; D029867:Xenopus Proteins