SMN2 and proximal spinal muscular atrophy: Notably, a small portion of full-length SMN2 mRNA, including exon 7, may play a role in improving SMA symptoms [1], although it has been reported that the protein product of △7 SMN2 mRNA (i.e., △7 SMN2 protein) may increase the amount of functional SMN complex that is present in the motor neurons of SMA model animals [7].