Every moment, millions of a body's cells flawlessly divvy up their genes and pinch perfectly in half to form two identical progeny for the replenishment of tissues and organs - even as they collide, get stuck, and squeeze through infinitesimally small spaces that distort their shapes.
Now Johns Hopkins scientists, working with the simplest of organisms, have discovered the molecular sensor that lets cells not only "feel" changes to their neat shapes, but also to remodel themselves back into ready-to-split symmetry. In a study published September 15 in Current Biology, the researchers show that two force-sensitive proteins accumulate at the sites of cell-shape disturbances and cooperate first to sense the changes and then to resculpt the cells. The proteins - myosin II and cortexillin I - monitor and correct shape changes in order to ensure smooth division.
"What we found is an exquisitely tuned mechanosensory system that keeps the cells shipshape so they can divide properly," says Douglas N. Robinson, Ph.D., an associate professor of Cell Biology, Pharmacology and Molecular Sciences, Johns Hopkins University School of Medicine.
Faulty cell division can put organisms, including people, on the pathway to diseases such as cancer, Robinson notes, and a better understanding of how cells respond to mechanical stress on their shapes could present new targets for both diagnosing and treating such diseases.
Working with hardy, single-celled protozoa that move and divide similarly to human cells, the scientists watched through microscopes while they deformed the cells' shapes with a tiny instrument that, like a soda straw, sucks in on the cell surface and creates distorted shapes.
"This particular method, based on a very old principle that dates back to Archimedes, enables us to deform cells without killing them, much in the same way that natural processes in the body constantly assault them, Robinson says."