SMA has been modeled in mice (Hsieh-Li et al., 2000), Drosophila (Spring et al., 2019), zebrafish (McWhorter et al., 2003) and C. elegans (Briese et al., 2009) by deleting the endogenous Smn gene and overexpressing the human SMN2 gene. Here, SMN2 is linked to proximal spinal muscular atrophy.