SMN1 and proximal spinal muscular atrophy: Similarly, elevated SMN protein levels in prenatal post-mortem tissues were observed in both SMA patients with 2 SMN2 copies (type 1 and 2 patients) and healthy individuals, with a confirmed decline after birth in healthy new-borns in different disease-related tissues (spinal cord, brain cortex, diaphragm), suggesting the necessity of SMN protein for prenatal development (67, 68).