SMN1 and proximal spinal muscular atrophy: We recently provided evidence for EAAT1 protein downregulation in the spinal cord of late-onset SMA mice and cultured SMA-like astrocytes generated by small interfering ribonucleic acid (siRNA) transfection [41], proposing a role for glutamate excitotoxicity as a potential mechanism for MN loss in the mild form of SMA.