Migration and colonization patterns of HNK-1-immunoreactive neural crest cells in lamprey and swordtail embryos

Abstract

Migration and colonization patterns of neural crest cells were analyzed histochemically in embryos of the brook lamprey, Lampetra reissneri, and the swordtail, Xiphophorus helleri, using HNK-1 monoclonal antibody, which recognizes migratory neural crest cells and crest derivatives in many groups of vertebrates including teleosts. We demonstrated that HNK-1 recognizes a subpopulation of naural crest cells and crest derivatives in the lamprey as well as in the swordtail. In the trunk of lamprey and swordtail embryos, HNK-1-positive cells were observed in the major migratory pathways of neural crest cells, that is ventral and dorso-lateral pathways. In the swordtail embryos, neural crest cells in the ventral pathway were ubiquitously observed along the rostra-caudal axis at the neural tube level, but at the notochord level their migration was restricted to the middle region of the somite. In the lamprey, by contrast, no HNK-1-immunoreactive neural crest cells migrated ventrally beyond the notochord level in the ventral pathway at axial levels behind the gill pouch region. This migration pattern of neural crest cells in the lamprey trunk might be closely related to the absence of anatomically distinct, sympathetic chains in the lamprey, which is one of characteristic features of the lamprey's body organization. Furthermore, we found dorsal pathways, which extended to the embryonic dorsal fin, of neural crest cells in both swordtail and lamprey embryos. In the lamprey, dorsal cells (Rohon-Beard cells) and cells that resemble chromaffin cells immunoreacted with HNK-1.