Spastin, a microtubule-cutting protein in the “ATPases associated with diverse cellular activities” (AAA) protein family (Sharp and Ross, 2012), was first discovered in hereditary spastic paraplegia (HSP; Hazan et al., 1999), a neurodegenerative disease involving the degeneration of axons in the bilateral corticospinal tract of the spinal cord (McDermott et al., 2000). The gene discussed is SPAST; the disease is hereditary spastic paraplegia.