16.17: Regulating Gene Expression in Cell Development - Cell Migration in Multicellular Organisms
- Describe how cells can migrate within an organism
Cell migration
Cell migration is a central process in the development and maintenance of multicellular organisms. Processes such as tissue formation during embryonic development, wound healing, and immune responses, all require the orchestrated movement of cells in particular directions to specific locations. Errors during this process have serious consequences, including intellectual disability, vascular disease, tumor formation and metastasis. An understanding of the mechanism by which cells migrate may lead to the development of novel therapeutic strategies for controlling, for example, invasive tumor cells.
Cells often migrate in response to specific external signals, including chemical signals and mechanical signals. Due to a highly viscous environment, cells need to permanently produce forces in order to move. Cells achieve active movement by very different mechanisms. Many less complex prokaryotic organisms (and sperm cells) use flagella or cilia to propel themselves. Eukaryotic cell migration typically is far more complex and can consist of combinations of different migration mechanisms. It generally involves drastic changes in cell shape which are driven by the cytoskeleton, for instance a series of contractions and expansions due to cytoplasmic displacement. Two very distinct migration scenarios are crawling motion (most commonly studied) and blebbing motility.
The migration of cultured cells attached to a surface is commonly studied using microscopy. As cell movement is very slow (only a few µm/minute), time-lapse microscopy videos are recorded of the migrating cells to speed up the movement. Such videos reveal that the leading cell front is very active with a characteristic behavior of successive contractions and expansions. It is generally accepted that the leading front is the main motor that pulls the cell forward.
Cell Migration : Phase images of BSC 1 cells migrating in a scratch assay in the absence of serum over a period of 15 hours.
Common features of cell migration
The processes underlying mammalian cell migration are believed to be consistent with those of (non-spermatozoic) locomotion. Observations in common include cytoplasmic displacement at the leading front and laminar removal of dorsally-accumulated debris toward trailing end. The latter feature is most easily observed when aggregates of a surface molecule are cross-linked with a fluorescent antibody or when small beads become artificially bound to the front of the cell. Other eukaryotic cells are observed to migrate similarly. The amoeba Dictyostelium discoideum is useful to researchers because they consistently exhibit chemotaxis in response to cyclic AMP; they move more quickly than cultured mammalian cells; and they have a haploid genome that simplifies the process of connecting a particular gene product with its effect on cellular behavior.
Key Points
- The disruption or dysfunction of cell migration processes can lead to formation of various diseases such as metastasis, tumor formation and vascular disease.
- In prokaryotic organisms, and some eukaryotic cells such as sperm cells, cell migration occurs via the use of a cilia or flagella to propel forward.
- In eukaryotic organisms, cell migration is a much more complex process and can include, but is not excluded to, changes in the cytoskeleton, motor proteins, blebbing, and cytoplasmic displacement; it involves both external and internal signals that mediate these processes.
Key Terms
- bleb : an irregular bulge in the plasma membrane of a cell
- chemotaxis : the movement of a cell or an organism in response to a chemical stimulant
- laminar : of fluid motion, smooth and regular, flowing as though in different layers
- metastasis : the transference of a bodily function or disease to another part of the body; specifically the development of a secondary area of disease remote from the original site, as with some cancers