The origins of the neural crest. Part II: an evolutionary perspective.
The neural crest and cranial ectodermal placodes are traditionally thought to be unique to vertebrates; however, they must have had evolutionary precursors. Here, we review recent evidence suggesting that such ancestral cell types can be identified in modern non-vertebrate chordates, such as amphioxus (a cephalochordate) and ascidians (urochordates). Hence, migratory neuroectodermal cells may well have been present in the common ancestor of the chordates, such that the possibility of their existence in non-chordate deuterostomes (hemichordates and echinoderms) must also be considered. Finally, we discuss the various non-neuronal cell types produced by the neural crest in order to demonstrate that it is plausible that these different cell types evolved from an ancestral population that was neuronal in nature.
Baker
C V
CV
Division of Biology, Beckman Institute 139-74, California Institute of Technology, Pasadena 91125, USA. cbaker@caltech.edu
Bronner-Fraser
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M
D000818:Animals; D005075:Biological Evolution; D001842:Bone and Bones / Q000196:embryology; D001921:Brain / Q000254:growth & development; D002816:Chordata, Nonvertebrate / Q000196:embryology / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D003804:Dentin / Q000196:embryology / Q000502:physiology; D004625:Embryo, Nonmammalian; D008954:Models, Biological; D009130:Muscle, Smooth / Q000166:cytology / Q000502:physiology; D009420:Nervous System / Q000166:cytology / Q000196:embryology*; D009424:Nervous System Physiological Phenomena; D009432:Neural Crest / Q000196:embryology* / Q000502:physiology*; D009457:Neuroglia / Q000502:physiology; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors; D014561:Urochordata / Q000196:embryology / Q000502:physiology; D014714:Vertebrates
D004268:DNA-Binding Proteins; D000071250:Snail Family Transcription Factors; D014157:Transcription Factors