Neural crest migration methods in the chicken embryo.

Neural crest cells emerge from the neural tube early in development. They migrate extensively throughout the embryo and form most of the head and peripheral nervous system, giving rise to sensory and sympathetic ganglia, heart regions, adrenal cells, head bones, teeth, muscle cells, sensory organs, melanocytes, and other cell types. The neural crest is interesting because of its unique origin, development and differentiation. These cells are initially part of the dorsal neural tube, with a clear epithelial character; later, they transform into actively motile mesenchymal cells. Little is known about the underlying mechanism directing this process. It remains unknown why neural crest cells target particular derivatives (neurons, heart muscle and glia) and body regions (peripheral nerves, heart, skin, head and gut). Neural crest migration can be divided into three stages: 1) emigration from the neural tube; 2) migration along defined pathways; and 3) cessation of migration. At the onset of migration, neural crest cells lose their epithelial nature within the neural tube and transform into a migratory, mesenchymal cell type. Neural crest development has been best studied in avian embryos, which are amenable to surgical manipulation, cell marking techniques, cell culture and transgenesis by electroporation and retrovirally mediate gene transfer. The methods outlined below are those typically used to study and understand the different factors and signals necessary for the neural crest development before and during their migration.