The superiority of the 25 mer PMO (−10, −34) to the shorter 20 or 18 mer PMOs, on augmenting SMN2 exon 7 splicing in cellular assay and tissues as well as on improving survivals in SMA mouse models has been confirmed in three independent studies from different laboratories [29,30,107,108]. Here, SMN2 is linked to proximal spinal muscular atrophy.