SMN2 and proximal spinal muscular atrophy: Insufficient levels of Survival Motor Neuron (SMN) protein, primarily arising from mutations or deletions in the SMN1 gene, are the root cause of spinal muscular atrophy (SMA), a hereditary neuromuscular disorder widely acknowledged as one of the leading genetic causes of infant mortality (Lefebvre et al., 1995; Lefebvre et al., 1997; Crawford and Pardo, 1996).