One of the first identified mechanisms to be related to HSP was the disruption of the axonal transport, which was supported by the identification of several HSP genes that encode kinesin chains (KIF5A and later, KIF1A, KIF1C), essential members of the anterograde microtubule-dependent axonal transport (Crosby and Proukakis, 2002; Reid et al., 2002). The gene discussed is KIF5A; the disease is hereditary spastic paraplegia.