Origin and Evolution of Neural Crest Cells in Chordates

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1.The neural crest is a characteristic tissue of vertebrate embryos. Neural crest cells appear on the dorsal side of the neural tube, migrate to various regions of the body, and differentiate into a variety of cells. Thus, the neural crest participates in forming the vertebrate body organization. At first, migration and colonization patterns of neural crest cells were studied in the most primitive vertebrate, the lamprey, using a monoclonal antibody, HNK-1, which stains migratory neural crest cells.(1) In the trunk of lamprey embryos, neural crest cells migrate in three routes ; the dorsolateral route between epidermis and somite, the ventral route between somite and neural tube, and the dorsal route towards the dorsal fin rudiment. In the ventral route, these cells do not migrate ventrally beyond the notochord. This may be related to the absence of sympathetic chains in lampreys. The neural crest cells in the fin rudiment may differentiate into mesenchymal cells and form part of the d … More orsal fin.(2) In lamprey embryos, sensory "doral cells" exist in the neural tube and they are stained with HNK-1. HNK-1-immunoreactive nerve fibers are also detected sub-epidermally and at least some of the fibers originate from dorsal cells. Sensory spinal ganglia are very small in lampreys. Dorsal cells may differentiate from "non-migratory neural crest cells". These observations are relevant to the origin of neural crest and/or placode.2.The migration and colonization patterns of neural crest cells were also studied in the swordtail embryo, using HNK-1 and some antibodies against extracellular matrix molecules.(1) In the trunk of swordtail embryos, three migration routes of neural crest cells are recognized, as in lamprey embryos. Neural crest cells in the ventral route colonize the region below the notochord and differentiate into sympathetic ganglion cells.(2) Extracellular materials such as fibronectin and chondroitin sulfate appear and distribute immunohistochemically, as HNK-1 immunoreactive neural crest cells appear and migrate. Thus, these materials may be intimately related to neural crest cell migration in the teleost as in the higher vertebrate. Less