SMN2 and proximal spinal muscular atrophy: In order to mimic the situation of SMN1-deleted individuals, who remain asymptomatic despite carrying only four SMN2 copies, we injected at PND1 a suboptimal low dose of 30 μg of SMN-ASOs into the severely-affected Taiwanese SMA mice that carry only two human SMN2 copies on null murine background, to produce a mildly affected SMA model that resembles the human situation (Figure 1A) [29,30,37].