Cell migration is essential for a number of important cellular processes, and migration defects can contribute to the pathogenesis of different diseases including cancer. Cell migration involves the assembly and disassembly of cell-matrix adhesions sites, as well as associated changes in the actin cytoskeleton. Cell contractility is controlled by the actin motor protein myosin II (Myo II) and the Rho family of GTPases, but the role of other GTPases such as Rac in the process is not well understood. On page 5585, Donna Webb and co-workers set out to investigate the role of Asef2 (also known as SPATA13), a recently identified Rac guanine nucleotide exchange factor, in the modulation of cell migration. They find that activation of Rac by Asef2 inhibits cell migration on type I collagen through a mechanism that is dependent on Myo II and that enhances contractility. This is interesting because, thus far, Myo II contractility has been thought to be mediated by Rho. Furthermore, the authors show that Asef2 slows down adhesion turnover and induces large, mature adhesions sites. When they knocked down Rac or inhibited its activity, they observe reduced levels of active Myo II together with an increase in cell migration. Moreover, inhibition of Myo II by using blebbistatin abolishes the effect of Asef2 on cell migration. Taken together, these data point to a so far unknown role of Rac1 – mediated by Asef2 – in regulating actomyosin contractility and, thus, cell migration.