WAS translates into the WASP protein, which is mainly expressed in white blood cells and platelets affecting their numbers and function. WASP, expressed in all hematopoietic stem cell–derived lineages is located predominantly in the cytoplasm. It promotes the white blood cells to change their shape to move towards an area in the body where it is needed.
Defects in the WASP are the cause of Wiskott-Aldrich syndrome, X-linked thrombocytopenia, and severe congenital neutropenia. Mutations in the first 4 exons have been associated with milder phenotypes, whereas the ones between exons 5 and 12 cause more severe phenotypes.