State of the Art
Skeletal muscle has an extraordinary regenerative capacity thanks to the presence of adult muscle stem cells named Satellite Cells (MuSC). Despite the ability of the MuSC to regenerate the muscle after damage, skeletal muscle regeneration is functionally successful only when the newly formed myo¿bres become innervated through the establishment of new Neuro-Muscular Junctions (NMJs). The mechanisms that regulate the growth or extension of neurites toward regenerating fibers and the timing of functional synaptic reestablishment on a regenerating ¿ber remain unclear and unexplored. Moreover, loss of NMJ in the intact muscle tissue leads to muscle atrophy consistent with the vital role of NMJ in muscle maintenance and homeostasis.
General interest of the project
Recently we demonstrate that not only muscle fibers are sensitive to muscle innervation. Indeed, alteration of the neuromuscular integrity - due to either traumatic or genetic disease - activate a specific gene expression program in muscle resident cell populations. In this proposal we aim to explore the cellular and molecular network that coordinate NMJ integrity.
Objectives and Methodology
We will, for the first time, dissect the role of glial cells in skeletal muscle regeneration and their cross talk with muscle resident cell populations. We will use a lineage tracing mouse models to better analyze the involvement of this population in muscle maintenance and regeneration. Finally, we will couple in-vivo study with next-generation sequencing approach and in-vitro culture system to tackle this unexplored faced of muscle biology.
Conclusions
This study will pave the way to the discovery of new cellular and molecular targets in neuromuscular disease or in pathologies characterized by nerve degeneration and muscle fibers regeneration.
Skeletal muscle has an extraordinary regenerative capacity thanks to the presence of adult muscle stem cells named Satellite Cells (MuSC). Despite the ability of the MuSC to regenerate the muscle after damage, skeletal muscle regeneration is functionally successful only when the newly formed myo¿bres become innervated through the establishment of new Neuro-Muscular Junctions (NMJs). The mechanisms that regulate the growth or extension of neurites toward regenerating fibers and the timing of functional synaptic reestablishment on a regenerating ¿ber remain unclear and unexplored. Moreover, loss of NMJ in the intact muscle tissue leads to muscle atrophy consistent with the vital role of NMJ in muscle maintenance and homeostasis. Beside this, the primary role of skeletal muscle in neurological disorder such as Amyotrophic Lateral Sclerosis (ALS) progression is still controversial, different studies promote the hypothesis that skeletal muscle directly influences NMJ stability and nerve degeneration (Wong and Martin, 2010). Indeed, it has been shown that muscle-specific expression of mutated SOD1 in mice leads to muscle atrophy and skeletal muscle functional impairment (Dobrowolny et al., 2008). Finally, it has been shown that preserving the NMJ ¿ increasing activity of the Agrin tyrosine kinase (MuSK), required for the formation and maintenance of the neuromuscular junction - is sufficient to delay neuron degeneration, improving motor function and delaying the onset of the disease in a mouse model of ALS (Perez-Garcia and Burden, 2012). For this reason, understanding the crosstalk between neuron, glial cells and skeletal muscle strongly contribute to the knowledge of this devasting disease.
We will, for the first time, dissect the role of glial cells in skeletal muscle regeneration and their cross talk with muscle resident cell populations. To this aim we will use a lineage tracing mouse models for glial cells to better analyze the involvement of this population in muscle maintenance and regeneration. Furthermore, we will generate transcriptome profile of muscle derived glial cell during different stages of nerve and muscle regeneration.
In conclusion, this study will pave the way to the discovery of new cellular and molecular targets in neuromuscular disease or in pathologies characterized by muscle fibers regeneration.
Bibliography
-Brack, A.S., and Rando, T.A. (2012). Tissue-specific stem cells: lessons from the skeletal muscle satellite cell. Cell Stem Cell 10, 504¿514.
-Dobrowolny, G., Aucello, M., Rizzuto, E., Beccafico, S., Mammucari, C., Boncompagni, S., Belia, S., Wannenes, F., Nicoletti, C., Del Prete, Z., et al. (2008). Skeletal muscle is a primary target of SOD1G93A-mediated toxicity. Cell Metab 8, 425¿436.
-Perez-Garcia, M.J., and Burden, S.J. (2012). Increasing MuSK activity delays denervation and improves motor function in ALS mice. Cell Rep 2, 497¿502.
-Wong, M., and Martin, L.J. (2010). Skeletal muscle-restricted expression of human SOD1 causes motor neuron degeneration in transgenic mice. Hum Mol Genet 19, 2284¿2302.
-Yin, H., Price, F., and Rudnicki, M.A. (2013). Satellite Cells and the Muscle Stem Cell Niche. Physiol. Rev. 93, 23¿67.