The FSHD effector protein Dux promotes myopathy via Myostatin-Smad signaling

Facioscapulohumeral muscular dystrophy (FSHD) is an autosomal-dominant condition that is characterised by a progressive degeneration and weakness of skeletal muscle fibers. The underlying cause of FSHD has been attributed to inappropriate expression of the transcription factor double homeobox (Dux); however, the mechanisms leading to myopathy in response to Dux expression remain incompletely understood. To study the acute effects of Dux activation in mammalian skeletal muscle fibers, we generated a recombinant adeno-associated viral vector allowing tunable Dux expression. Consistent with previous findings, we confirmed that the ectopic expression of Dux in mouse skeletal muscle results in a degenerative myopathy. Building on these findings, we observed that the acute expression of Dux in muscle fibers causes profound transcriptome changes prior to the onset of pathology. Furthermore, muscles expressing Dux display elevated levels of the TGF-beta superfamily member, Myostatin and increased Smad2/3 activity. Notably, inhibition of Myostatin is sufficient to prevent Dux-induced myopathy. Collectively, these findings support further investigation of interventions targeting the Myostatin-Smad2/3 pathway as prospective approaches to treating myopathy associated with Dux mis-expression. Overall design: RNA-seq was performed to understand gene expression changes in skeletal muscle caused by overexpression of Dux from a doxycycline inducible transgene.