Imaging-based evaluation of pathogenicity by novel DNM2 variants associated with centronuclear myopathy

Centronuclear myopathy (CNM) is characterized clinically by muscle weakness and pathologically by the presence of centralized nuclei and disarrangement of T-tubules in muscle fibers. DNM2 which encodes a large GTPase dynamin 2 have been identified as a causative gene for CNM. Nevertheless, the identification of DNM2 variants may not always lead to the definitive diagnosis as their pathogenicity is often unknown. In this study, by imaging T-tubule-like structures reconstituted in cellulo, we demonstrated that aberrant membrane remodeling by mutant dynamin 2 is tightly associated with gain-of-function features of DNM2 variants. This simple in cellulo assay provided quantitative data required for accurately evaluating pathogenicity of reported and novel DNM2 variants identified from CNM patients in our cohort. Our approaches combining the in cellulo assay with clinical information of the patients enabled to explain the course of a disease progression by pathogenesis of each variant in DNM2-associated CNM.