SMN1 and proximal spinal muscular atrophy: Recent findings have suggested that altered ubiquitin homeostasis is a core molecular feature of SMN1-dependent SMA, with reduced UBA1 expression central to this disruption in a range of animal models and in SMA patient-derived iPSC motor neurons (Aghamaleky Sarvestany et al., 2014; Wishart et al., 2014; Fuller et al., 2015; Powis et al., 2016).