ASCC1 and proximal spinal muscular atrophy: ASCC1 is a compelling candidate for PD because a recessive mutation in this gene has been associated with spinal muscular atrophy with congenital bone fractures-2 (SMABF2)36, and studies in animal models have demonstrated that ASCC1 knockdown is associated with impaired axonal outgrowth of alpha-motor neurons, impaired neuromuscular junction formation and compromised motor functioning36.