title: XBF-1, a winged helix transcription factor with dual activity, has a role in positioning neurogenesis in Xenopus competent ectoderm.
abstract: Neuronal differentiation in the vertebrate nervous system is temporally and spatially controlled by mechanisms which are largely unknown. Here we investigate the role of XBF-1, an anterior neural plate-specific winged helix transcription factor, in controlling the pattern of neurogenesis in Xenopus ectoderm. We show that, in the anterior neural plate of normal embryos, prospective neurogenesis is positioned at the anterior boundary of the XBF-1 expression domain. By misexpressing XBF-1 in the posterior neural plate we show that a high dose of XBF-1 has a dual effect; it suppresses endogenous neuronal differentiation in high expressing cells and induces ectopic neuronal differentiation in adjacent cells. In contrast, a low dose of XBF-1 does not suppress but instead, expands the domain of neuronal differentiation in the lateral and ventral sides of the embryo. XBF-1 regulates the expression of XSox3, X-ngnr-1, X-Myt-1 and X-&Dgr;-1 suggesting that it acts early in the cascade leading to neuronal differentiation. A fusion of XBF-1 to a strong repressor domain (EnR) mimics most of the XBF-1 effects suggesting that the wild type XBF-1 is a transcriptional repressor. However, fusion of XBF-1 to a strong activation domain (E1A) specifically suppresses neuronal differentiation suggesting that XBF-1 may also work as a transcriptional activator. Based on these findings, we propose that XBF-1 is involved in positioning neuronal differentiation by virtue of its concentration dependent, dual activity, as a suppressor and an activator of neurogenesis.
authors.affiliation: Wellcome/CRC Institute, Tennis Court Road, Cambridge CB2 1QR, UK and Department of Anatomy, Downing Street, Cambridge CB2 3DY, UK.
authors.forename: C
authors.initials: C
authors.lastname: Bourguignon
authors.forename: J
authors.initials: J
authors.lastname: Li
authors.forename: N
authors.initials: N
authors.lastname: Papalopulu
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D002454:Cell Differentiation / Q000235:genetics; D004475:Ectoderm / Q000378:metabolism*; D004625:Embryo, Nonmammalian / Q000166:cytology; D047108:Embryonic Development; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D017403:In Situ Hybridization; D008845:Microinjections; D008969:Molecular Sequence Data; D009419:Nerve Tissue Proteins / Q000235:genetics; D012333:RNA, Messenger / Q000235:genetics; D012097:Repressor Proteins / Q000235:genetics; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism*; D015533:Transcriptional Activation / Q000235:genetics; D014404:Tubulin / Q000235:genetics; D014981:Xenopus / Q000196:embryology*; D029867:Xenopus Proteins
chemical_list: C117087:FOXG1 protein, Xenopus; D009419:Nerve Tissue Proteins; D012333:RNA, Messenger; D012097:Repressor Proteins; D014157:Transcription Factors; D014404:Tubulin; D029867:Xenopus Proteins