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      Natural history study and statistical modeling of disease progression in a preclinical model of myotubular myopathy

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          ABSTRACT

          Generating reliable preclinical data in animal models of disease is essential in therapy development. Here, we performed statistical analysis and joint longitudinal–survival modeling of the progressive phenotype observed in Mtm1 −/y mice, a reliable model for myotubular myopathy. Analysis of historical data was used to generate a model for phenotype progression, which was then confirmed with phenotypic data from a new colony of mice derived via in vitro fertilization in an independent animal house, highlighting the reproducibility of disease phenotype in Mtm1 −/y mice. These combined data were used to refine the phenotypic parameters analyzed in these mice and improve the model generated for expected disease progression. The disease progression model was then used to test the therapeutic efficacy of Dnm2 targeting. Dnm2 reduction by antisense oligonucleotides blocked or postponed disease development, and resulted in a significant dose-dependent improvement outside the expected disease progression in untreated Mtm1 −/y mice. This provides an example of optimizing disease analysis and testing therapeutic efficacy in a preclinical model, which can be applied by scientists testing therapeutic approaches using neuromuscular disease models in different laboratories.

          This article has an associated First Person interview with the joint first authors of the paper.

          Abstract

          Summary: This study optimized disease severity analysis and modeled disease progression in Mtm1 −/y mice, and confirmed this model using therapeutic Dnm2 reduction in a dose–response analysis.

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          Most cited references22

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          A gene mutated in X-linked myotubular myopathy defines a new putative tyrosine phosphatase family conserved in yeast.

          X-linked recessive myotubular myopathy (MTM1) is characterized by severe hypotonia and generalized muscle weakness, with impaired maturation of muscle fibres. We have restricted the candidate region to 280 kb and characterized two candidate genes using positional cloning strategies. The presence of frameshift or missense mutations (of which two are new mutations) in seven patients proved that one of these genes is indeed implicated in MTM1. The protein encoded by the MTM1 gene is highly conserved in yeast, which is surprising for a muscle specific disease. The protein contains the consensus sequence for the active site of tyrosine phosphatases, a wide class of proteins involved in signal transduction. At least three other genes, one located within 100 kb distal from the MTM1 gene, encode proteins with very high sequence similarities and define, together with the MTM1 gene, a new family of putative tyrosine phosphatases in man.
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            Mice lacking microRNA 133a develop dynamin 2–dependent centronuclear myopathy.

            MicroRNAs modulate cellular phenotypes by inhibiting expression of mRNA targets. In this study, we have shown that the muscle-specific microRNAs miR-133a-1 and miR-133a-2 are essential for multiple facets of skeletal muscle function and homeostasis in mice. Mice with genetic deletions of miR-133a-1 and miR-133a-2 developed adult-onset centronuclear myopathy in type II (fast-twitch) myofibers, accompanied by impaired mitochondrial function, fast-to-slow myofiber conversion, and disarray of muscle triads (sites of excitation- contraction coupling). These abnormalities mimicked human centronuclear myopathies and could be ascribed, at least in part, to dysregulation of the miR-133a target mRNA that encodes dynamin 2, a GTPase implicated in human centronuclear myopathy. Our findings reveal an essential role for miR-133a in the maintenance of adult skeletal muscle structure, function, bioenergetics, and myofiber identity; they also identify a potential modulator of centronuclear myopathies.
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              Reducing dynamin 2 expression rescues X-linked centronuclear myopathy.

              Centronuclear myopathies (CNM) are congenital disorders associated with muscle weakness and abnormally located nuclei in skeletal muscle. An autosomal dominant form of CNM results from mutations in the gene encoding dynamin 2 (DNM2), and loss-of-function mutations in the gene encoding myotubularin (MTM1) result in X-linked CNM (XLCNM, also called myotubular myopathy), which promotes severe neonatal hypotonia and early death. Currently, no effective treatments exist for XLCNM. Here, we found increased DNM2 levels in XLCNM patients and a mouse model of XLCNM (Mtm1(-/y)). Generation of Mtm1(-/y) mice that were heterozygous for Dnm2 revealed that reduction of DNM2 in XLCNM mice restored life span, whole-body strength, and diaphragm function and increased muscle strength. Additionally, classic CNM-associated histological features, including fiber atrophy and nuclei mispositioning, were absent or reduced. Ultrastructural analysis revealed improvement of sarcomere organization and triad structures. Skeletal muscle-specific decrease of Dnm2 during embryogenesis or in young mice after disease onset revealed that the rescue associated with downregulation of Dnm2 is cell autonomous and is able to stop and potentially revert XLCNM progression. These data indicate that MTM1 and DNM2 regulate muscle organization and force through a common pathway. Furthermore, despite DNM2 being a key mechanoenzyme, its reduction is beneficial for XLCNM and represents a potential therapeutic approach for patients.
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                Author and article information

                Journal
                Dis Model Mech
                Dis Model Mech
                DMM
                dmm
                Disease Models & Mechanisms
                The Company of Biologists Ltd
                1754-8403
                1754-8411
                1 July 2022
                25 July 2022
                25 July 2022
                : 15
                : 7
                : dmm049284
                Affiliations
                [1 ]Dynacure , Illkirch 67400, France
                [2 ]Pharmalex , Mont-St-Guibert 1435, Belgium
                [3 ]Institut de Génétique et de Biologie Moléculaire et Cellulaire, Institut National de la Santé et de la Recherche Médicale U1258 , Centre National de la Recherche Scientifique UMR7104, Université de Strasbourg, 67404 Illkirch, France
                [4 ]2 Bridge , Zoersel 2980, Belgium
                Author notes
                [*]

                These authors contributed equally to this work

                []Author for correspondence ( belinda.cowling@ 123456dynacure.com )

                Handling Editor: Monkol Lek

                Author information
                http://orcid.org/0000-0001-5694-2249
                http://orcid.org/0000-0001-8256-5862
                http://orcid.org/0000-0003-4651-9302
                http://orcid.org/0000-0001-6915-2596
                Article
                DMM049284
                10.1242/dmm.049284
                9346515
                35642830
                b6308a4f-760f-447e-bfb8-80f7abeee086
                © 2022. Published by The Company of Biologists Ltd

                This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution and reproduction in any medium provided that the original work is properly attributed.

                History
                : 6 September 2021
                : 23 May 2022
                Funding
                Funded by: Dynacure;
                Funded by: Be Est Projets d'Avenir du programme d'Investissement Avenir 3;
                Award ID: coDyn101
                Categories
                Neuromuscular Disease Models
                Research Article

                Molecular medicine
                centronuclear myopathy,myotubular myopathy,preclinical disease model,dynamin,antisense oligonucleotide,therapy,neuromuscular disorder

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