RAC1 and amyotrophic lateral sclerosis: Moreover, other Rho GTPases such as RhoA and Rac1 have also been demonstrated to be involved in motoneuron survival, and mutations of ALS2, which encodes alsin, a GEF with dual specificity for Rac1 and Rab GTPases, cause a form of juvenile-onset of the degenerative disorder of motor function Amyotrophic Lateral Sclerosis (reviewed in [17]).