Chemotactic cell movement during development.

Chemotaxis is an important mechanism controlling cell migration over either short or long distances during different developmental processes. Small rapid diffusing chemo-attractants are detected through serpentine, G protein coupled receptors through graded activation of receptors along the length of the cell. Internal amplification results in polarisation of the actin and myosin cytoskeletal dynamics along the gradient and directed movement. The dynamics of these processes can now be studied in individual cells in developing organisms. Slow diffusing chemo-attractants such as growth factors, providing short-range guidance information, often signal through tyrosine kinase receptors. Detection of these signals may involve the active extension of very long cellular process up growth factor gradients, followed by translocation of the cell in the direction of the gradient.