| dc.description | Regulation is the replacement of lost, undifferentiated embryonic cells by neighboring cells in response to environmental signals. Neural crest cells, embryonic cells unique to craniates, are good candidates for studies of regulation because they are pluripotent, and thus might be able to alter their behavior in response to environmental signals. Neural crest cells are classified as cranial, cardiac or trunk according to where they originate along the embryonic axis and the derivatives they form. My study investigated regulation for trunk neural crest (TNC) cells in the zebrafish, Danio rerio. The first part of my study asked 'What are the normal patterns of TNC development, migration and differentiation?' I then addressed the hypothesis that there is regulation for loss of TNC, and that regulation would vary with the amount of premigratory neural crest removed, and the position or stage of removal. Lastly, I asked 'what are potential mechanisms of regulation?' DiI labeling, SEM and snail2 expression in control embryos revealed that TNC cells undergo several successive waves of 'sheet' and 'segmental' migration. Cells labeled at similar axial levels form different derivatives at different stages. Pigment cells served as landmarks for analyzing the effects of TNC extirpation. Regulation occurred on a sliding scale, ranging from complete to incomplete. The amount of TNC removed along the embryonic axis and the position of removal affected regulation to a greater extent than did stage of removal. Defects in development and/or pigmentation occurred if large regions of premigratory TNC were removed, or if neural crest was removed from the cardiac region or the posterior trunk. Otherwise, pigmentation was remarkably normal. Altered cell migration and increased cell division were investigated as mechanisms of regulation. Coincident with epidermal regeneration, neural crest cells consistently migrated into extirpated regions from the posterior edges over a period of 24 hours. Also, more cells were dividing adjacent to the surgery site relative to controls, including TNC migrating along medial and lateral pathways. | en_US |
