Functional properties and epigenetic signature of quiescent and early activated human muscle reserve cells

Dr. Thomas Laumonier, University of Geneva


In the last decades, muscle stem cells (MuSC) emerged as a promising therapeutic target for muscle diseases and turn to be the most efficient cell type for muscle cell therapy. However, the strategy still needs to be optimized as the culture conditions are known to decrease the regenerative capacities of amplified MuSC. We demonstrated previously that human myogenic reserve cells (MuRC) are quiescent Pax7+ MuSC arrested in a G0 reversible cell cycle state with increased regenerative potential as compared to proliferating human myoblasts1. Human MuRC also display the advantage to be generated in vitro in a quiescent state without the need of in situ fixation techniques prior to isolation.

Recently, we demonstrated that human MuRC are heterogenous for Pax7 expression, with a Pax7High and a Pax7Low subpopulation. Using RNA-seq, we showed that Pax7High human MuRC are in a deeper quiescent state, less primed to myogenic differentiation and with a lower metabolism2. Moreover, we recently observed that intracellular autofluorescence allows the isolation of functional human MuRC subpopulations with distinct stem cell states (AFHigh MuRC enriched in Pax7High cells).

In this proposal, we aim to perform chromatin accessibility profiling (ATAC-seq) and gene expression analysis (RNA- seq) in quiescent and early reactivation state of human MuRC subpopulations. The proposed project will bring new information on the functional properties of freshly isolated human MuRC subpopulations and on epigenetic modifications in human MuRC subpopulations, in quiescent versus early reactivated state. Through gene expression characterization and identification of possible regulatory regions, notably potential Pax7 target, we should be able to identify molecular mechanisms which are crucial for the maintenance of human MuRC deep quiescence. The outcome of this project is of crucial importance for future stem cell-based therapies.