Cell migration is accomplished by chemoattractant receptors signaling the spatially-restricted activation of rho gtpases. specifically, chemoattractant receptors signal via gai and downstream guanine nucleotide exchange factors (gefs), p-rex and pixa, to activate rac and cdc42 at the leading edge and ultimately leads to cellular protrusion. In contrast, chemoattractant receptor signaling by ga12/13 activate rhoa at the trailing edge and promote cytoskeletal contraction. however, the gef(s) that activate rhoa downstream of chemoattractant receptor and ga12/13 have not been identified. here...