Fig. 1. Expression of TrkC and C-Kit during neural crest development in vitro. (A,B) A subset of live cells present in a population of cells 4 hours after the initiation of segregation from neural tube explants. Two cells (arrows) were expressing TrkC as revealed by immunolabeling (A) while the rest of the cells (B) are TrkC^-. (C,D) A C-Kit-expressing neural crest cell (C, arrowhead) in a field of C-Kit^- (D) cells present in a live 13-16 hour population. (E,F) A double immunolabeled 13-16 hour population of neural crest cells shown after fixation, stained with Hoechst nuclear dye (E) and by phase contrast (F). TrkC-expressing cells (arrows, red) and C-Kit-expressing cells (arrowheads, green) are present in distinct subpopulations of neural crest cells. (G,H) A differentiated (108 hour) culture immunolabeled live with TrkC antiserum (red), fixed and labeled with 16A11 to reveal neurons (green). TrkC is expressed by a subpopulation of neurons (G, yellow) and is not expressed by non-neuronal cells (G,H). (I,J) A region of a live differentiated culture immunolabeled with anti-C-Kit (I, green). A phase-contrast image of the same field shows that the immunolabeled cells are melanocytes (J), whereas unpigmented cells are C-Kit^-. Scale bar: 8 µm.