title: Identification of two NOGO/RTN4 genes and analysis of Nogo-A expression in Xenopus laevis.
abstract: Myelin-associated axon growth inhibitors such as Nogo-A/RTN4-A impair axon regeneration in the adult mammalian central nervous system (CNS). Here, we describe the cloning and expression of two independent Xenopus laevis rtn4 orthologs. As in mammals, alternative transcripts are generated both through differential splicing and promoter usage, giving rise to Xenopus nogo-A, -B, -C and to a new isoform, nogo-N/rtn4-N. Xenopus is therefore the 'lowest' vertebrate where Nogo-A was identified. Xenopus Nogo-A/RTN4-A is predominantly expressed in the nervous system, whereas the other isoforms mainly occur in nonneuronal tissues. Nogo-A/RTN4-A specific antisera detect the protein in myelinated fiber tracts of the spinal cord, hindbrain, optic nerve, tectum opticum and in isolated oligodendrocytes. In addition, subpopulations of CNS neurons are Nogo-A/RTN4-A positive. This expression pattern is consistent with that observed for rat Nogo-A and suggests similar functions. Nogo-A in Xenopus myelin might therefore contribute to the failure of spinal cord regeneration in frogs-a feature that may have evolved during the transition from fish to land vertebrates.
authors.affiliation: Department of Biology, University of Konstanz, 78457 Konstanz, Germany.
authors.forename: Michael
authors.initials: M
authors.lastname: Klinger
authors.forename: Heike
authors.initials: H
authors.lastname: Diekmann
authors.forename: Dietmar
authors.initials: D
authors.lastname: Heinz
authors.forename: Cordula
authors.initials: C
authors.lastname: Hirsch
authors.forename: Sylvia
authors.initials: S
authors.lastname: Hannbeck von Hanwehr
authors.forename: Barbara
authors.initials: B
authors.lastname: Petrausch
authors.forename: Thomas
authors.initials: T
authors.lastname: Oertle
authors.forename: Martin E
authors.initials: ME
authors.lastname: Schwab
authors.forename: Claudia A O
authors.initials: CA
authors.lastname: Stuermer
mesh_terms: D000595:Amino Acid Sequence / Q000235:genetics; D000818:Animals; D001483:Base Sequence / Q000235:genetics; D002454:Cell Differentiation / Q000502:physiology; D002490:Central Nervous System / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D018076:DNA, Complementary / Q000032:analysis / Q000235:genetics; D018507:Gene Expression Regulation, Developmental / Q000235:genetics; D008565:Membrane Proteins / Q000235:genetics; D008969:Molecular Sequence Data; D009185:Myelin Proteins / Q000096:biosynthesis* / Q000235:genetics* / Q000302:isolation & purification; D009413:Nerve Fibers, Myelinated / Q000378:metabolism / Q000648:ultrastructure; D009434:Neural Pathways / Q000166:cytology / Q000254:growth & development / Q000378:metabolism; D000070798:Nogo Proteins; D011817:Rabbits; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D014982:Xenopus laevis / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism
chemical_list: D018076:DNA, Complementary; D008565:Membrane Proteins; D009185:Myelin Proteins; D000070798:Nogo Proteins; C000603197:Rtn4 protein, rat