An Ultrastructural and Proteomic Analysis in DM1 Young Adults' Myoblasts: Stressed RER and Mitochondrial Dysfunction Involvement.

Myotonic dystrophy type 1 (DM1) is a progressive muscular disorder caused by the expansion of CTG repeats in the 3' UTR of the DMPK gene. Although the pathogenic mechanisms remain unclear, recent evidence suggests that activation of innate immune responses may contribute to disease progression. In this study, we examined the ultrastructure and proteomic data of myoblasts from young adult DM1 patients carrying approximately 800 and 1300 CTG repeats in order to investigate a link between cellular stress and immune activation. We observed activation of the type I interferon (IFN-I) pathway associated with rough endoplasmic reticulum stress (sRER). The sRER response is likely triggered by the accumulation of toxic RNA species generated from the expanded DMPK allele. Our data suggest that this inappropriate activation of the IFN-I pathway contributes to muscle pathology, not by blocking differentiation directly, but through chronic stress signalling. These findings support a model in which innate immune dysregulation plays a central role in DM1 muscle degeneration and highlight the IFN1 pathway as a potential therapeutic target for restoring normal muscle function.