The accumulation of NF proteins and poor arborization in distal axons and motor nerve terminals are considered to be specific features of SMA model mice, although their significance in the pathogenesis of human SMA is unknown (Cifuentes-Diaz et al., 2002; Kariya et al., 2008; Kong et al., 2009). The gene discussed is NFASC; the disease is proximal spinal muscular atrophy.