Stathmin, a microtubule-destabilizing protein, is dysregulated in spinal muscular atrophy

Spinal muscular atrophy (SMA), a motor neuron degeneration disorder, is caused by either mutations or deletions of survival motor neuron 1 (SMN1) gene which result in insufficient SMN protein. Here, we describe a potential link between stathmin and microtubule defects in SMA. Stathmin was identified by screening Smnknockdown NSC34 cells through proteomics analysis. We found that stathmin was aberrantly upregulated in vitro and in vivo, leading to a decreased level of polymerized tubulin, which was correlated with disease severity. Reduced microtubule densities and β_III-tubulin levels in distal axons of affected SMA-like mice and an impaired microtubule network in Smn-deficient cells were observed, suggesting an involvement of stathmin in those microtubule defects. Furthermore, knockdown of stathmin restored the microtubule network defects of Smn-deficient cells, promoted axon outgrowth and reduced the defect in mitochondria transport in SMA-like motor neurons. We conclude that aberrant stathmin levels may play a detrimental role in SMA; this finding suggests a novel approach to treating SMA by enhancing microtubule stability.