SMN1 and proximal spinal muscular atrophy: As expected, Smn protein level was significantly reduced in total cell lysates of cultured MNs from both SMA models (mutSMA, 0.39 ± 0.04, p < 0.0001; SMNdelta7, 0.16 ± 0.03, p < 0.0001), compared to the WT controls (Fig. 1).