Ratchetaxis: a new way how cells move
Scheme of in vitro experiments showing that the movement of the cells can be directed through a locally repeated asymmetry (here an asymmetry of the substrate)
Trends Cell Biol Dec 2015
Nov. 24, 2015
Directed migration of cells in the body is often explained by long-range physical or chemical gradients. However, in collaboration with Matthieu Piel’s team at the Institut Curie and Raphaël Voituriez, a researcher in theoretical physics at UPMC, Daniel Riveline's team has shown that other types of more local signals can influence cell migration. Their work is published on November 24th in the Journal Trends in Cell Biology.
Cell movement in the body
Within an organism, cell movements are very diverse: collective or individual, random or directed. For instance some cells follow specific paths during various stages of development. This phenomenon is usually linked automatically to long-range chemical gradients, even when these latter are unknown. Such directed orientation of cells under the influence of external chemical substances is called chemotaxis.
Researchers conducted and compiled several in vitro studies that investigate the movement of individual cells in the absence of long range chemical gradients. They were inspired by the theory proposed by the physicist Richard Feynman* in the 60’s, which is based on the generation of a directed movement of a ratchet wheel, using a simple temperature difference and local fluctuations. They have implemented this principle experimentally for cells. The question was then as follows: can a local broken symmetry at the scale of a cell induce a directed motion of the cell whose shape fluctuates over time ? The researchers demonstrated that the repetition of a slight asymmetry in the immediate environment of cells can direct cell migration over long distances. These cell movements led by such local cues were coined "ratchetaxis", in reference to the Feynman mechanism. The teams showed that nucleus or cell protrusions are cellular sensors for local asymmetries.
These studies established ratchetaxis in vitro. Future studies will probe its relevance in living organisms with new types of measures. Furthermore, molecular mechanisms involved in these directed movements are still to be discovered. Cell migration is essential in embryogenesis as well as in cancer and tissue invasion by metastasis, and these results open a new path for understanding cell motions and open potential future applications.
* Ratchet and Pawl, R. P. Feynman, R.B. Leighton, and M. Sands, The Feynman Lectures on Physics, vol. 1 (Addison, Wesley, Reading, Massachusetts, 1963), p 46.1.