RHO and Huntington disease: One such promising target is inhibition of the Rho kinase pathway, which reduces mtHtt aggregation, enhances huntingtin clearance, and improves motor function in the R6/2 transgenic model of HD [3, 4], perhaps by modulating p21-activated kinase1 (Pak1), a downstream target protein of the Rho family that enhances mtHtt aggregation in cell culture and colocalizes with mtHtt in postmortem HD brain [5].