This is different from the gene dysregulation we previously noted in spinal muscular atrophy (SMA), in which resilient CN3/4 MNs elicited a large early gene response compared with vulnerable spinal and facial (CN7) MNs, which only responded to the loss of the Smn1 gene (survival MN 1) later in disease. This evidence concerns the gene SMN1 and proximal spinal muscular atrophy.