SMN2 and proximal spinal muscular atrophy: Additionally, given that humans can have multiple copies of SMN2, which impacts the clinical phenotypes manifested by SMA patients, an interesting challenge would be the possibility and consequence of efficiently editing more than one copy of SMN2. Overall, this study marks an important advance toward a one-time treatment for SMA and may break ground in the therapeutic application of base editing technologies in diseases with potential positive modifiers.