To generate a more comparable situation as found in discordant SMA families (where 3–4 SMN2 copies are present, but never only 2 copies as in the severe SMA mouse model), an intermediate-like SMA mouse phenotype has been generated by subcutaneous injection of a low dose of SMN-ASOs (Nusinersen, 30 μg at P2 and P3) [61]. Here, SMN1 is linked to proximal spinal muscular atrophy.