Out of the 72 targets identified by arginine methyl proteome profiling of human cells (Fong et al, 2019), MS023 changed the methylation pattern of other splicing factors implicated in the regulation of SMN2 splicing (i.e. HNRNPU, HNRNPA2B1, ELAVL1, RBM10, KHDRBS1, SRSF9, TRA2B, and U2AF1; Singh & Singh, 2018), and the individual contribution of such proteins to the overall effect of this small molecule in SMA models remains to be established. Here, U2AF1 is linked to proximal spinal muscular atrophy.