Biochemical characterization of patients with in-frame or out-of-frame DMD deletions pertinent to Exon 44 or 45 skipping

Karen Anthony, Virginia Arechavala-Gomeza, Valeria Ricotti, Silvia Torelli, Lucy Feng, Narinder Janghra, Giorgio Tasca, Michela Guglieri, Rita Barresi, Annarita Armaroli, Alessandra Ferlini, Katherine Bushby, Volker Straub, Enzo Ricci, Caroline Sewry, Jennifer Morgan, Francesco Muntoni

Research output: Contribution to JournalArticle

Abstract

Importance: In Duchenne muscular dystrophy (DMD), the reading frame of an out-of-frame DMD deletion can be repaired by antisense oligonucleotide (AO)–mediated exon skipping. This creates a shorter dystrophin protein, similar to those expressed in the milder Becker muscular dystrophy (BMD). The skipping of some exons may be more efficacious than others. Patients with exon 44 or 45 skippable deletions (AOs in clinical development) have a less predictable phenotype than those skippable for exon 51, a group in advanced clinical trials. A way to predict the potential of AOs is the study of patients with BMD who have deletions that naturally mimic those that would be achieved by exon skipping. Objective: To quantify dystrophin messenger RNA (mRNA) and protein expression in patients with DMD deletions treatable by, or mimicking, exon 44 or 45 skipping. Design, Setting, and Participants: Retrospective study of nondystrophic controls (n = 2), patients with DMD (n = 5), patients with intermediate muscular dystrophy (n = 3), and patients with BMD (n = 13) at 4 university-based academic centers and pediatric hospitals. Biochemical analysis of existing muscle biopsies was correlated with the severity of the skeletal muscle phenotype. Main Outcomes and Measures: Dystrophin mRNA and protein expression. Results: Patients with DMD who have out-of-frame deletions skippable for exon 44 or 45 had an elevated number of revertant and trace dystrophin expression (approximately 19% of control, using quantitative immunohistochemistry) with 4 of 9 patients presenting with an intermediate muscular dystrophy phenotype (3 patients) or a BMD-like phenotype (1 patient). Corresponding in-frame deletions presented with predominantly mild BMD phenotypes and lower dystrophin levels (approximately 42% of control) than patients with BMD modeling exon 51 skipping (approximately 80% of control). All 12 patients with in-frame deletions had a stable transcript compared with 2 of 9 patients with out-of-frame deletions (who had intermediate muscular dystrophy and BMD phenotypes). Conclusions and Relevance: Exon 44 or 45 skipping will likely yield lower levels of dystrophin than exon 51 skipping, although the resulting protein is functional enough to often maintain a mild BMD phenotype. Dystrophin transcript stability is an important indicator of dystrophin expression, and transcript instability in DMD compared with BMD should be explored as a potential biomarker of response to AOs. This study is beneficial for the planning, execution, and analysis of clinical trials for exon.
Original languageEnglish
Pages (from-to)32-40
Number of pages9
JournalJAMA Neurology
Volume71
Issue number1
Early online date13 Nov 2013
DOIs
Publication statusPublished - 1 Jan 2014

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  • Impacts

    FDA approves first drug to treat Duchenne muscular dystrophy (DMD)

    Karen Anthony (Co-Investigator)

    Impact: Public policy impacts, Health and Well-Being impacts, Quality of life impacts, 03: Good Health and Well-Being (UN SDG)

    Activities

    • 1 Participating in a conference or workshop

    Final COST Action meeting

    Karen Anthony (Participant)

    22 Mar 2017

    Activity: Participating in or organising a conference or workshopParticipating in a conference or workshopResearch

    Cite this

    Anthony, K., Arechavala-Gomeza, V., Ricotti, V., Torelli, S., Feng, L., Janghra, N., Tasca, G., Guglieri, M., Barresi, R., Armaroli, A., Ferlini, A., Bushby, K., Straub, V., Ricci, E., Sewry, C., Morgan, J., & Muntoni, F. (2014). Biochemical characterization of patients with in-frame or out-of-frame DMD deletions pertinent to Exon 44 or 45 skipping. JAMA Neurology, 71(1), 32-40. https://doi.org/10.1001/jamaneurol.2013.4908