SMN1 and proximal spinal muscular atrophy: To determine whether calpeptin treatment regulates Smn in MNs from E12.5 embryos of the severe SMA transgenic mouse model (FVB·Cg-Tg (SMN2)89AhmbSmn1tm1Msd/J), mice were genotyped and the spinal cords of wild-type (WT) and mutant (mutSMA) were dissected.