Cells are not static blobs. They can move and change shape by pushing and pulling on an internal web of specialised proteins. Actin proteins form the delicate ‘bones’ of the cell skeleton in temporary ‘limbs’ called lamellipodia used to crawl. In this migrating mouse cell, actin is visible as wire-like filaments (stained red) that give structure to a lamellipodium (on the left). As it extends and then withdraws back towards the body of the cell, the protein bones that support this short-lived limb grow and are later destroyed. Another protein, cofilin (here shown fluorescing green) disassembles actin filaments. At higher magnification, the scientists could see cofilin at the tips of tiny fingers or filopodia used to sense the environment. Insights into the shape-shifting nature of cells are helping us understand more about movement, which may help explain how cancer cells spread from one part of the body to another.
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