title: Amphioxus and lamprey AP-2 genes: implications for neural crest evolution and migration patterns.
abstract: The neural crest is a uniquely vertebrate cell type present in the most basal vertebrates, but not in cephalochordates. We have studied differences in regulation of the neural crest marker AP-2 across two evolutionary transitions: invertebrate to vertebrate, and agnathan to gnathostome. Isolation and comparison of amphioxus, lamprey and axolotl AP-2 reveals its extensive expansion in the vertebrate dorsal neural tube and pharyngeal arches, implying co-option of AP-2 genes by neural crest cells early in vertebrate evolution. Expression in non-neural ectoderm is a conserved feature in amphioxus and vertebrates, suggesting an ancient role for AP-2 genes in this tissue. There is also common expression in subsets of ventrolateral neurons in the anterior neural tube, consistent with a primitive role in brain development. Comparison of AP-2 expression in axolotl and lamprey suggests an elaboration of cranial neural crest patterning in gnathostomes. However, migration of AP-2-expressing neural crest cells medial to the pharyngeal arch mesoderm appears to be a primitive feature retained in all vertebrates. Because AP-2 has essential roles in cranial neural crest differentiation and proliferation, the co-option of AP-2 by neural crest cells in the vertebrate lineage was a potentially crucial event in vertebrate evolution.
authors.affiliation: Division of Biology, 139-74, California Institute of Technology, Pasadena 91125, USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Meulemans
authors.forename: Marianne
authors.initials: M
authors.lastname: Bronner-Fraser
mesh_terms: D000557:Ambystoma / Q000196:embryology / Q000235:genetics; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D019521:Body Patterning / Q000235:genetics; D002465:Cell Movement; D002816:Chordata, Nonvertebrate / Q000196:embryology* / Q000235:genetics*; D018076:DNA, Complementary / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics*; D019143:Evolution, Molecular; D018507:Gene Expression Regulation, Developmental; D007798:Lampreys / Q000196:embryology* / Q000235:genetics*; D008969:Molecular Sequence Data; D009432:Neural Crest / Q000196:embryology*; D010802:Phylogeny; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity; D050656:Transcription Factor AP-2; D014157:Transcription Factors / Q000235:genetics*
chemical_list: D018076:DNA, Complementary; D004268:DNA-Binding Proteins; D050656:Transcription Factor AP-2; D014157:Transcription Factors