title: The structure and expression of the Xenopus Krox-20 gene: conserved and divergent patterns of expression in rhombomeres and neural crest.
abstract: Recent studies in the chick have indicated that rhombomeres (r) are segments that underlie the patterning of hindbrain nerves. These segments may also be important for the specification of branchial arch structures since alternating rhombomeres, r2, r4 and r6, each contribute crest to a specific arch. Krox-20 has been implicated in the segmental patterning of the hindbrain in the mouse by its expression prior to segment formation in alternating domains, which later correspond to r3 and r5. Here, we describe the sequence and developmental expression of the Xenopus Krox-20 gene, XKrox-20. Alternating domains of XKrox-20 expression appear in the early neurula, later correspond to r3 and r5, and persist until late tadpole stages. In contrast to this conserved spatial expression in rhombomeres, we find a pattern in the neural crest of Xenopus that appears different from that found in the mouse: expression occurs in crest that migrates from r5 into the third visceral arch. We speculate that this may reflect a distinct route of neural crest migration due to anatomical differences between these systems, rather than a difference in the site of origin of Krox-20-expressing crest.
authors.affiliation: Laboratory of Eukaryotic Molecular Genetics, National Institute for Medical Research, London, UK.
authors.forename: L C
authors.initials: LC
authors.lastname: Bradley
authors.forename: A
authors.initials: A
authors.lastname: Snape
authors.forename: S
authors.initials: S
authors.lastname: Bhatt
authors.forename: D G
authors.initials: DG
authors.lastname: Wilkinson
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D002490:Central Nervous System / Q000196:embryology*; D004247:DNA / Q000302:isolation & purification*; D004268:DNA-Binding Proteins / Q000235:genetics*; D051767:Early Growth Response Protein 2; D005786:Gene Expression Regulation; D017403:In Situ Hybridization; D008969:Molecular Sequence Data; D009024:Morphogenesis / Q000235:genetics; D009432:Neural Crest / Q000196:embryology*; D016415:Sequence Alignment; D014157:Transcription Factors / Q000235:genetics*; D014981:Xenopus / Q000196:embryology / Q000235:genetics*
chemical_list: D004268:DNA-Binding Proteins; C497329:EGR2 protein, Xenopus; D051767:Early Growth Response Protein 2; D014157:Transcription Factors; D004247:DNA