Neural crest cells are migratory cells responsible for the formation of many different anatomical structures located throughout the body. They are formed during the development of an embryo from the ectoderm of the neural tube along the neural plate. These cells are specific to organisms with vertebrae. Neural crest cells are divided into four different types: cranial, cardiac, trunk, and vagal neural crest cells.
During embryonic development, the neural crest is formed shortly before the neural tube — the beginning of the central nervous system — pinches off and closes shut. This signals the cells to undergo an epithelial-mesenchymal transitionary phase, separating from the ectoderm of the neural plate before migrating throughout the vertebrate's body. Eventually, the transitory cells begin to form pigment cells, cartilage, smooth muscle, nerves, and bone. Migration of these cells halts when they encounter a barrier, such as blood vessels or cell clusters. The position of the neural crest cell within the body after its migration has ended helps determine the eventual differentiation of the cell into specific anatomical structures.
After moving from the stationary ectoderm cell layer to the mobile mesoderm layer, the neural crest cells migrate through the cranium and settle into the pharyngeal arches. Now called cranial neural crest cells, they will contribute to the formation of the connective tissues, cartilage, and skeletal structures of the head and facial features. Nerves and some pigment cells are also created by the cranial neural crest cells.
Some of the neural crest cells will continue to travel to other parts of the body. Ganglia within the digestive system are largely formed by the vagal neural crest cells. An integral part of the heart, called the aorticopulmonary septum, is formed by cardiac neural crest cells.
Trunk neural crest cells form a portion of the sensory nerves and ganglia of the sympathetic nervous system. Other trunk cells migrate to the skin, where they form pigment-producing cells called melanocytes. The pigment melanin made by the melanocytes is further divided into two types, eumelanin and pheomelanin. The presence of eumelanin results in varied shades of brown and black pigments. Pheomelanin causes yellow and red pigments to develop.
Malformed neural crest cells can result in the craniofacial deformaties commonly associated with congenital conditions like Treacher-Collins Syndrome. Neural tube defects occur before the eighth week of gestation when many women may not be aware of the pregnancy. Most women are advised to begin a daily supplement of folic acid and prenatal vitamins several months before trying to become pregnant to help prevent neural tube defects from occurring.