Cells have an internal skeleton that maintains their structure and also drives their movement. Known as the cytoskeleton, this scaffold is composed of a network of dynamic filaments made of a protein called actin.

Given how important these structures are, alterations in the proteins that work together to build and control the actin cytoskeleton are often lethal or cause severe effects. For example, children born with mutations in the ARPC5 protein, which is part of the Arp2/3 complex, experience immunodeficiency and a high risk of fatal sepsis in early life.

“This is a rare and devastating condition, and until recently, it wasn’t clear how these mutations lead to such severe illness,” says Michael Way, who runs the Cellular Signaling and Cytoskeletal Function Laboratory at the Crick. “The only known effective treatment would involve early bone marrow transplantation to replace the faulty immune cells with ones which have a healthy actin cytoskeleton.”