New tools in molecular genetics, such as genetic interaction screens and co
nditional gene targeting, have advanced the study of actin dynamics in a nu
mber of model systems. Yeast, Dictyostelium, Caenorhabditis elegans, Drosop
hila, and mice have contributed much in recent years to a better understand
ing of both the numerous functions and modes of regulation of the actin cyt
oskeleton.