Desmin involvement in mechanical properties of skeletal muscle cell – DESMECA

The cytoskeleton is composed of three networks (microtubules, microfilaments and intermediate filaments), which interact directly or indirectly via associated proteins and plays a central role in the generation and transmission of mechanical forces through the cell. In muscle, it is well established that desmin intermediate filaments (I.F.) are essential for maintaining cellular integrity in response to mechanical stress. In particular, P. Vicart’s team has identified mutations in desmin causing desminopathy, a skeletal and cardiac myopathy leading to slowly progressive muscular weakness and cardiac disorders, associated with the formation of aggregates containing desmin. Mechanical stimulation probably plays a role in the appearance of the disease, since sportive patients show more accute symptoms at younger age. The different desmin mutants have been previously studied in cell lines for their ability to form or not a network with or without aggregate formation. However, contribution of the I.F. network to the behavior of muscle cells in the presence of mechanical stress remains largely unknown. In this context our project aims at determining whether the mechanical properties of muscle cells (myoblasts, myotubes and myofibers) and their response to mechanical stimulations are impaired by desmin mutations related to desminopathies. We will develop two complementary aspects: i) characterizing the mechanical properties of living muscle cells, in normal and pathological contexts; ii) evaluating the effects of mechanical stress on desmin filaments and associated signaling. This approach requires close collaboration between biologists (P. Vicart’s team) and biophysicists (S. Hénon’s team, F. Briki’s team). We will use tools dedicated to micromechanics, and to the generation of stress either on a cell population, or on single cells (myoblasts, myotubes or myofibers): on the one hand, S. Hénon’s team has developed experimental set-ups which allow to quantify cell deformability under stress (rheology) and to measure the forces developed by the cell (cell contractility), by applying a controlled mechanical stress to a cell either locally (optical and magnetic tweezers set-ups) or globally (single cell rheometer) ; on the other hand, the tensile apparatus developed by F. Briki’s team permits to apply periodic or incremental stretches to a cell population. Using these devices, we will characterize cell mechanical properties, cell morphology alteration under mechanical stimulation, aggregate formation and signaling pathways activation, for cells expressing wild-type desmin or pathogenic mutants, developed in the team of P. Vicart. Moreover, we could envisage to test potential anti-aggregative effect of various interesting molecule in response to mechanical stress.
Our project aims to highlight desmin function in the response of muscle cell to mechanical stresses, and will provide us with a better understanding of the molecular and cellular events leading to myofibrillar myopathy.