Centronuclear myopathies (CNM) are rare congenital myopathies characterized by abnormal centralization of nuclei in muscle fibers. Three main forms of CNM are distinguished: The X-linked recessive CNM (also called X-linked myotubular myopathy, XLMTM) due to mutations in myotubularin (MTM1), the autosomal recessive CNM (AR-CNM) due to mutations in amphiphysin 2 (BIN1), and the autosomal dominant CNM (AD-CNM) due to mutations in dynamin 2 (DNM2). There is no therapies available for patients affected by CNMs. The teams of Marc Bitoun (UMRS974, Myology Institute, Paris) and Belinda Cowling/Jocelyn Laporte (IGBMC, Illkirch) have been involved for many years in the identification and the functional consequences of mutations in CNMs, in the development of animal models and therapeutic strategies for the CNMs. During the last years, common efforts of the two teams supported by the “DynaMuscle” ANR program led to essential breakthrough for the development of innovative therapeutic strategies based on modulation of the DNM2 expression in two forms of CNM. First, proof of concept for allele-specific silencing therapy was achieved in AD-CNM by targeting the most frequent DNM2 mutation in the Knock-in-Dnm2R465W mouse model (KI-Dnm2) and in patient-derived cells. Second, cross-therapy by reduction of DNM2 was established as efficient therapeutic strategy for XLMTM in which DNM2 is over-expressed. DynaTher aims at “converting the try” by pursuing preclinical developments for these two “DNM2 therapies” by tackling the following questions: - What preclinical developments are required for allele-specific therapy for the p.R645W DNM2 mutation in AD-CNM? We will investigate the long-term maintenance of efficacy and benefit of systemic treatment in young KI-Dnm2 mice. We will also optimize the therapeutic benefit in old mice. - Can allele-specific silencing be extended to other AD-CNM DNM2 mutations and is it possible to develop “pan-mutations” tools to avoid a mutation-based strategy? We will screen for allele-specific siRNA able to silence 5 other DNM2 mutations in patient-derived cells. We will also develop “pan-mutations” allele-specific-siRNA against the two versions of frequent heterozygous non-pathological single nucleotide polymorphisms present in the DNM2 mRNA. - Is the cross-therapy strategy also efficient for other forms of CNM, thus increasing the number of patients that can be treated by this approach? Based on our previous proof of principle for XLMTM, we will extend this therapy in mouse models of AR-CNM and AD-CNM. - Do siRNAs against DNM2 have “off-target effects”? That will be answer by associating transcriptome and proteome analyses in human cells from patients affected by the three main forms of CNM allowing also to uncover common and specific altered pathways in CNMs and readouts for future clinical trials. - Can DNM2 therapy be improved by targeting specific DNM2 isoform or by other delivery methods and be extended to other neuromuscular disorders? Therapeutic benefit of reduction of the DNM2 muscle-specific isoform will be determined in Knock-out-Mtm1 and KI-Dnm2 mouse models. Non-viral delivery methods will be also developed. Finally, we will identify novel applications for DNM2 therapy through a screening for elevated DNM2 expression in a panel of neuromuscular disorders. The ambition of DynaTher is to accelerate the preclinical development of these approaches to ultimately provide the most efficient and safe molecular tools targeting DNM2 required for the first gene therapy clinical trial for autosomal CNMs.