SMN1 and proximal spinal muscular atrophy: In a Drosophila model of SMA, the mutant phenotype can onlybe reversed after SMN is restored in both proprioceptive and central cholinergicneurons (90); thus, some defects ofspinal cholinergic interneurons induced by SMN insufficiency may contribute tothe neural circuit dysfunction that underscores the post-SMA motor impairment.Indeed, in the mouse spinal cholinergic interneurons that modulate locomotormotoneuronal activity have been identified (97).