UBA1 and proximal spinal muscular atrophy: Molecular analysis of AAV9-UBA1–treated SMA mouse hearts showed that the virally delivered human UBA1 gene was functional in mice in vivo, with increased UBA1 levels sufficient to correct downstream UPS perturbations, reducing β-catenin and increasing monoubiquitin and polyubiquitin levels previously identified in SMA mice (14).