In an effort to obtain animal models with longer survival and slower disease progression, which could better mimic type III human SMA, a novel SMN-KO (Smn−/−) mouse model was generated featuring a human SMN1 mutation (SMN1A2G), along with human SMN2 (Monani et al. 2003). The gene discussed is SMN2; the disease is proximal spinal muscular atrophy.