Fig. 1. Typical confocal sections through a chick embryo show the dense streams of cranial neural crest cells and various features of cell shapes and extensions within the migratory streams. (A) This typical embryo was co-injected with Gap43-tagged EGFP (green) and MRFP (red) to label the cell plasma membranes and nuclei, respectively, and re-incubated for 15 hours. Neural crest cells are seen along the migratory routes in dense streams emanating from r4 and r6, and individual cells leaving from r7. Many of the cells have nearly reached the destination branchial arches (ba2-ba4). The individual boxes highlight regions that are magnified in the remainder of the figure. (B) Cells within the r4 stream are relatively densely packed. Some of the individual Gap43-labeled cells reveal filopodial extensions, which overlap with neighboring MRFP-labeled cells. The Gap43-labeled cells also show the difference in potential extent to which an individual cell has contacts with other neural crest cells in the stream. (C) Interestingly, some neural crest cells from r5 travel laterally to the edge of r5 and then move in the anteroposterior direction toward a neighboring migratory stream along the edge of the otic vesicle. (D) Neural crest cells that have nearly reached the branchial arch destinations are very closely packed within the migratory stream. The protruding extensions of the cells appear to stretch out from the cell body such that an individual cell may contact a cell that is not within its local neighborhood. (E) A closer look at individual cells within the stream reveals that an individual cell may extend many thin filopodial protrusions. Scale bars: 50 µm in D; 10 µm in E. ov, otic vesicle.