Histone deacetylase inhibition suppresses myogenin-dependent atrogene activation in spinal muscular atrophy mice

Spinal muscular atrophy (SMA) is an autosomal recessive neuromuscular disease caused by mutations in the survival of motor neuron 1 (SMN1) gene and deficient expression of the ubiquitously expressed SMN protein. Pathologically, SMA is characterized by motor neuron loss and severe muscle atrophy. During muscle atrophy, the E3 ligase atrogenes, atrogin-1 and muscle ring finger 1 (MuRF1), mediate muscle protein breakdown through the ubiquitin proteasome system. Atrogene expression can be induced by various upstream regulators. During acute denervation, they are activated by myogenin, which is in turn regulated by histone deacetylases 4 and 5. Here we show that atrogenes are induced in SMA model mice and in SMA patient muscle in association with increased myogenin and histone deacetylase-4 (HDAC4) expression. This activation during both acute denervation and SMA disease progression is suppressed by treatment with a histone deacetylase inhibitor; however, this treatment has no effect when atrogene induction occurs independently of myogenin. These results indicate that myogenin-dependent atrogene induction is amenable to pharmacological intervention with histone deacetylase inhibitors and help to explain the beneficial effects of these agents on SMA and other denervating diseases.