Control of pre-T cell proliferation and differentiation by the GTPase Rac-I

The GTPase Rac-1 has the potential for pleiotropic functions due to its abi lity to interact with multiple effecters, Here, activation of Rac-1 is show n to potently regulate pre-T cell differentiation and proliferation at the point of T cell antigen receptor (TCR) beta selection. An activated Rac-1 e ffector domain mutant that restricts signaling to particular actions on act in dynamics can drive prei cell differentiation. Rac-1 activation cannot fu lly substitute for the pre-TCR complex but can fully correct defects in pre -T cell development in mice lacking the adapter molecule Vav-1. The present study identifies the subset of Rac-1 responses that mediate Vav-1 action a s critical regulators of TCR beta selection.