In spinal muscular atrophy (SMA), neuron-specific IAP family members NAIP and XIAP effectively block the enzymatic activity of group II caspases (3 and 7) and reduce the expression levels of cleaved-caspase-3, thereby protecting spinal motor neurons (MNs) and preventing severe SMA [366,367]. This evidence concerns the gene NAIP and proximal spinal muscular atrophy.