SMN2 and proximal spinal muscular atrophy: Most of SMA cases are linked to downregulation of the SMN1 gene and the aberrant splicing of exon 7 of the SMN2 gene, a nearly identical copy of SMN1. ASOs are being used to correct the aberrant splicing of exon 7 of SMN2 and promote its inclusion by binding to the unique GC-rich sequence located within the downstream intron, as illustrated in Fig. 9a (Singh et al. 2009; Osman et al. 2016).