SMN2 and proximal spinal muscular atrophy: It has been also shown that both CMAP and MUNE are related to SMN2 copy number [39]: Although the gene copy number is not predictive of the phenotypic severity of SMA of individual patients, the modifying effect of SMN2 genes has been demonstrated in several clinical studies, and also in murine models as SMA-like mice with higher hSMN2 copy number display milder phenotypes [44].