Study of the signaling modulated by HDAC4 in skeletal muscle in ALS

BACKGROUND: Histone deacetylase 4 (HDAC4) has been proposed as a target for the treatment of Amyotrophic Lateral Sclerosis (ALS) because it mediates nerve-skeletal muscle interaction and since its expression in skeletal muscle correlates with the severity of the disease. However, our recent studies on the skeletal muscle response upon long-term denervation highlighted the importance of HDAC4 in maintaining muscle integrity. METHODS: To fully identify the yet uncharacterized HDAC4 functions in ALS, we genetically deleted HDAC4 in skeletal muscles of a mouse model of ALS. Body weight, skeletal muscle, innervation and spinal cord were analyzed over time by morphological and molecular analyses. A transcriptome analysis was also performed to delineate the signaling modulated by HDAC4 in skeletal muscle of a mouse model of ALS. FINDINGS: HDAC4 deletion in skeletal muscle caused earlier ALS onset, characterized by body weight loss, muscle denervation and atrophy, and compromised muscle performance in ALS mice, although the main catabolic pathways were not activated. A transcriptome analysis identified the gene networks modulated by HDAC4 in ALS, revealing UCP1 as a top regulator that may be implicated in worsening ALS features. INTERPRETATION: HDAC4 plays an important role in preserving innervations and skeletal muscle in ALS, likely by modulating the UCP1 gene network. Our study highlights a possible risk in considering HDAC inhibitors for the treatment of ALS. Overall design: Total RNA was isolated and purified from 6 SOD and 5 SOD HDAC4mKO GA muscles at 14 weeks of age. Samples were pooled together and libraries were generated from duplicates of SOD or SOD HDAC4mKO samples