P.264 - Satellite cell alteration in DNM2-related centronuclear myopathy

Abstract

Autosomal dominant centronuclear myopathy (AD-CNM) is due to mutations in dynamin 2 gene (DNM2). The main histological feature is fibers with centrally positioned nuclei. The knock-in murine model KI-Dnm2R465W (HTZ) bears the most frequent mutation found in AD-CNM patients and develops a myopathy including force reduction, muscle atrophy and histopathological abnormalities. Moreover, this animal model presents few centronucleated fibers and lack of an evident degeneration. Recently, alterations in satellite cell (SC) quantity and behavior were observed in the mouse model for X-linked CNM. Thus, we hypothesized that regeneration in other CNM types could also be compromised. Here we studied the regeneration process within the muscle affected by CNM with DNM2 mutations. For this purpose, we induced muscle lesion by electroporation and analyzed gastrocnemius muscles after 3, 5, 10 and 15 days post injury. Histological analysis showed a similar pattern of degeneration and regeneration both in WT and HTZ mice in all time points. Nevertheless, the number of regenerating dMyHC positive fibers was variable, but reduced in HTZ mice after 5 days post-injury. Regeneration was completed after 15 days, in both strains, however, in HTZ muscles there was more collagen deposition than in WT. The analysis of the expression of genes important for satellite cell function and the regenerative process, such as Myf5, Myod and Myog showed lower expression in HTZ mice before injury, and a significant activation after lesion in both WT and HTZ mice, but with lower levels in the HTZ. Interestingly, the SC marker Pax7 had a reduced expression in HTZ mice even before injury; and after lesion, its expression continued lower than in WT animals. Spry1 is a regulator of SC quiescence and showed a higher expression in HTZ mice before injury. Taken together, these results point to alterations in satellite cell population in DNM2-related CNM.