STMN1 and proximal spinal muscular atrophy: A recent study demonstrated that skeletal muscle-specific depletion of Smn (one copy of SMN2 still present to resemble severe SMA genotype) in mice is sufficient to recapitulate the muscular fibers abnormalities typical of SMA, and, more importantly, to cause NMJ defects, despite normal SMN expression in neuronal cells [134].