SMN1 and proximal spinal muscular atrophy: Although SMA is not a splicing disease per se, SMN2 is an optimum candidate for a splicing therapy, because all SMA-affected individuals retain at least two copies of SMN2. Correction of E7 missplicing can be obtained through antisense masking of an hnRNPA1-dependent intronic splicing silencer N1 (ISS-N1) located downstream of the E7 donor splice site via chemically modified antisense oligonucleotides (AONs) or modified U7 snRNAs.17,29 In addition, a compound has been recently described that selectively enhances SMN transcripts.30