Transcriptional adaptation upregulates utrophin in Duchenne muscular dystrophy

Abstract

Abstract Duchenne muscular dystrophy (DMD) is a muscle-degenerating disease caused by mutations in the DMD gene, which encodes the dystrophin protein 1,2 . Utrophin ( UTRN ), the genetic and functional paralogue of DMD , is upregulated in some DMD patients 3–5 . To further investigate this UTRN upregulation, we first developed an inducible messenger RNA (mRNA) degradation system for DMD by introducing a premature termination codon (PTC) in one of its alternatively spliced exons. Inclusion of the PTC-containing exon triggers DMD mutant mRNA decay and UTRN upregulation. Notably, blocking nonsense-mediated mRNA decay results in the reversal of UTRN upregulation, whereas overexpressing DMD does not. Furthermore, overexpressing DMD PTC minigenes in wild-type cells causes UTRN upregulation, as does a wild-type DMD minigene containing a self-cleaving ribozyme. To place these findings in a therapeutic context, we used splice-switching antisense oligonucleotides (ASOs) to induce the skipping of out-of-frame exons of DMD , aiming to introduce PTCs. We found that these ASOs cause UTRN upregulation. In addition, when using an ASO to restore the DMD reading frame in myotubes derived from a DMD patient, an actual DMD treatment, UTRN upregulation was reduced. Altogether, these results indicate that an mRNA decay-based mechanism called transcriptional adaptation 6–8 plays a key role in UTRN upregulation in DMD patients, and they highlight an unexplored therapeutic application of ASOs, as well as ribozymes, in inducing genetic compensation via transcriptional adaptation.