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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Duchenne Muscular Dystrophy
Exons
Dystrophin
Phenotype
Muscular Dystrophies
Frameshift Mutation
Proteins
Clinical Trials
Reading Frames
Messenger RNA
Pediatric Hospitals
Antisense Oligonucleotides

Cite this

Anthony, Karen ; Arechavala-Gomeza, Virginia ; Ricotti, Valeria ; Torelli, Silvia ; Feng, Lucy ; Janghra, Narinder ; Tasca, Giorgio ; Guglieri, Michela ; Barresi, Rita ; Armaroli, Annarita ; Ferlini, Alessandra ; Bushby, Katherine ; Straub, Volker ; Ricci, Enzo ; Sewry, Caroline ; Morgan, Jennifer ; Muntoni, Francesco. / Biochemical characterization of patients with in-frame or out-of-frame DMD deletions pertinent to Exon 44 or 45 skipping. In: JAMA Neurology. 2014 ; Vol. 71, No. 1. pp. 32-40.
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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.",
author = "Karen Anthony and Virginia Arechavala-Gomeza and Valeria Ricotti and Silvia Torelli and Lucy Feng and Narinder Janghra and Giorgio Tasca and Michela Guglieri and Rita Barresi and Annarita Armaroli and Alessandra Ferlini and Katherine Bushby and Volker Straub and Enzo Ricci and Caroline Sewry and Jennifer Morgan and Francesco Muntoni",
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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, vol. 71, no. 1, pp. 32-40. https://doi.org/10.1001/jamaneurol.2013.4908

Biochemical characterization of patients with in-frame or out-of-frame DMD deletions pertinent to Exon 44 or 45 skipping. / Anthony, Karen; Arechavala-Gomeza, Virginia; Ricotti, Valeria; Torelli, Silvia; Feng, Lucy; Janghra, Narinder; Tasca, Giorgio; Guglieri, Michela; Barresi, Rita; Armaroli, Annarita; Ferlini, Alessandra; Bushby, Katherine; Straub, Volker; Ricci, Enzo; Sewry, Caroline; Morgan, Jennifer; Muntoni, Francesco.

In: JAMA Neurology, Vol. 71, No. 1, 01.01.2014, p. 32-40.

Research output: Contribution to JournalArticle

TY - JOUR

T1 - Biochemical characterization of patients with in-frame or out-of-frame DMD deletions pertinent to Exon 44 or 45 skipping

AU - Anthony, Karen

AU - Arechavala-Gomeza, Virginia

AU - Ricotti, Valeria

AU - Torelli, Silvia

AU - Feng, Lucy

AU - Janghra, Narinder

AU - Tasca, Giorgio

AU - Guglieri, Michela

AU - Barresi, Rita

AU - Armaroli, Annarita

AU - Ferlini, Alessandra

AU - Bushby, Katherine

AU - Straub, Volker

AU - Ricci, Enzo

AU - Sewry, Caroline

AU - Morgan, Jennifer

AU - Muntoni, Francesco

PY - 2014/1/1

Y1 - 2014/1/1

N2 - 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.

AB - 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.

U2 - 10.1001/jamaneurol.2013.4908

DO - 10.1001/jamaneurol.2013.4908

M3 - Article

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SP - 32

EP - 40

JO - JAMA Neurology

JF - JAMA Neurology

SN - 2168-6149

IS - 1

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