TP53 and proximal spinal muscular atrophy: Using an Smn inducible mouse model of SMA, we show that at P4 [a time point where treatment with tamoxifen causes > 50% of mice to live over 200 days (11)], there are already high levels of NMJ pathology, including denervation, presynaptic swelling and an increase in transcripts associated with the P53 signalling pathway.