Reducing dynamin 2 (DNM2) rescues DNM2 -related dominant centronuclear myopathy

Abstract

Centronuclear myopathies (CNM) are a group of severe muscle diseases for which no effective therapy is currently available. We have previously shown that reduction of the large GTPase DNM2 in a mouse model of the X-linked form, due to loss of myotubularin phosphatase MTM1, prevents the development of the skeletal muscle pathophysiology. As DNM2 is mutated in autosomal dominant forms, here we tested whether DNM2 reduction can rescue DNM2-related CNM in a knock-in mouse harboring the p.R465W mutation (Dnm2RW/+) and displaying a mild CNM phenotype similar to patients with the same mutation. A single intramuscular injection of adeno-associated virus-shRNA targeting Dnm2 resulted in reduction in protein levels 5 wk post injection, with a corresponding improvement in muscle mass and fiber size distribution, as well as an improvement in histopathological CNM features. To establish a systemic treatment, weekly i.p. injections of antisense oligonucleotides targeting Dnm2 were administered to Dnm2RW/+mice for 5 wk. While muscle mass, histopathology, and muscle ultrastructure were perturbed in Dnm2RW/+mice compared with wild-type mice, these features were indistinguishable from wild-type mice after reducing DNM2. Therefore, DNM2 knockdown via two different strategies can efficiently correct the myopathy due to DNM2 mutations, and it provides a common therapeutic strategy for several forms of centronuclear myopathy. Furthermore, we provide an example of treating a dominant disease by targeting both alleles, suggesting that this strategy may be applied to other dominant diseases.

Physiological impact and disease reversion for the severe form of centronuclear myopathy linked to dynamin

“…Reduction of DNM2 upon injection of ASO-1 was shown to prevent and revert the phenotypes of the X-linked CNM model, the Mtm1 y/mouse (32). This strategy was also applied to the Dnm2 RW/+ mouse and appeared to ameliorate the mild muscle phenotypes of this model (22). In this last study, ASO injections were done before disease onset, preventing a full reversion study.…”

“…First proof-of-concept results with prospective technologies such as RNA trans-splicing and RNA inhibition were recently reported. RNA trans-splicing was only tested in WT mice (20), while RNA inhibition with allele-specific shRNA silencing (21) or antisense oligonucleotides (ASO) targeting the total pool of Dnm2 both prevented the progression of the phenotypes of the Dnm2 RW/+ mouse (22,23) DNM2 mutations in ADCNM are proposed to be gain-of-function mutations. The functions of DNM2 depend on its ability to hydrolyze GTP, oligomerize, and bind lipids (24).…”

New Therapeutics Options for Pediatric Neuromuscular Disorders

“…Mutations in DNM2 encoding dynamin-2 cause autosomal dominant centronuclear myopathy, which is associated with variable muscle weakness and wasting (87). In DNM2-mutated mice, weekly intrapleural injections of ASOs targeting DNM2 for 5 weeks corrected muscle mass, histopathology, and muscle ultrastructure (88). These findings prompted an ongoing phase 1/2 study with DYN101, a synthetically manufactured constrained ethyl gapmer ASO directed against DNM2 pre-mRNA in 18 adolescents and young adults (NCT04033159).…”

The expanding spectrum of neurological disorders of phosphoinositide metabolism

“…Of note, the field is currently hindered by the lack of a pre-clinical model of DNM2-related CNM that phenocopies the clinical aspects of the human disease and thus could be used to develop and test potential therapies. Other models exist, including a mouse Dnm2 knock-in with a mild phenotype (Buono et al, 2018; Fongy et al, 2019), a zebrafish morphant (Bragato et al, 2016) and a transient dominant dnm2 zebrafish model (Gibbs et al, 2014), but additional models are clearly needed.…”