Caspase cleavage of several intermediate filament (IF) proteins generates proteolytic fragments that characterize apoptosis as shown for lamins and vimentin. These fragments affect IF assembly in a way that promotes filament aggregation. The hypothesis is that disease-causing mutations in IF proteins and subsequent characteristic histopathological aggregates could involve caspase cleavage of IF proteins. Desmin is a type III IF protein that is expressed mainly in the muscle cells. Heterozygous missense mutations in the desmin gene cause desmin-related myopathy (DRM), a progressive muscle wasting disease. The pathological hallmark of DRM is cytoplasmic desmin-containing aggregates in skeletal and cardiac muscles. The expression of mutant desmin induced filament aggregation and mitochondrial clumping. Accompanied with these changes were caspase activation and desmin proteolysis. In this study, I have demonstrated that desmin is cleaved specifically by caspase-6 at VEMD263 and produces two major cleavage products. While the C-terminal desmin (C-desmin) is unable to assemble into filaments, the N-terminal desmin (N-desmin) forms aggregates and interfere with normal IF assembly. When transiently expressed into a range of cultured cell lines, N-desmin formed cytoplasmic aggregates that also disrupted the endogenous IF networks of desmin, consistent with its effect in vitro. In addition, I have generated a neo-epitope antibody that recognized caspase-cleaved but not the intact desmin. This antibody revealed the presence of the N-desmin in a subset of transfected cells expressing myopathic desmin mutants. Furthermore, expression of mutants induces a cellular stress response and alters mitochondrial morphology. Taken together, these data suggest that the integrity of IF is a key sensor for cell homeostasis and their functional interaction with mitochondria and cell death signaling pathway are central to the progressive muscle degeneration seen in human desminopathies.