SMN1 and spinal muscular atrophy: Spinal muscular atrophy (SMA) is a rare neuromuscular disorder characterized by loss of α-motor neurons in the anterior horn of the spinal cord and progressive muscle wasting, often leading to early death.125 The cause of the disease is a mutation in the Survival Motor Neurons 1 (SMN1) gene that results in reduced expression of the full-length SMN protein, which is necessary for survival of motor neurons.126 The first evidence of a possible involvement of ZPR1 (C4-type, not transcription factor) in SMA came from the experimental observation that the SMN protein interacts with ZPR1.