SMN1 and myopathy: The time course of MN loss led us to establish two postnatal evolutive stages in SMN∆7 mouse myopathy: (i) the preneurodegenerative stage (PND, from P0 to P7), characterized by muscle SMN deficiency but with the absence of overt MN loss and myofiber denervation [38], and (ii) the neurodegenerative stage (ND, from P8 to P14), characterized by both SMN deficiency and denervation-dependent (neurogenic) atrophic myofibers (Figure S1C).