Projet de thèse en Biologie moléculaire et cellulaire
Sous la direction de Helge Amthor.
Thèses en préparation à université Paris-Saclay , dans le cadre de École doctorale Structure et Dynamique des Systèmes Vivants , en partenariat avec Handicap Neuromusculaire: Physiopathologie, Biotechnologies et Pharmacologie appliquées (laboratoire) et de Université de Versailles-Saint-Quentin-en-Yvelines (référent) depuis le 01-10-2018 .
Déterminer dans un modèle de souris DMD mdx, les effets thérapeutique de la restauration de la dystrophine dans les cellules souches.
THE ROLE OF DYSTROPHIN IN MUSCLE STEM CELLS AND ITS CONSEQUENCE FOR THE THERAPY OF DUCHENNE MUSCULAR DYSTROPHY
Duchenne muscular dystrophy is caused by mutations in gene DMD, which encodes a protein called dystrophin. Absence of dystrophin causes cycles of degeneration and regeneration of muscles ﬁbers. However, regeneration fails in time and muscle ﬁbers become replaced by fatty ﬁbrosis, and patients, in consequence, become completely paralyzed. Satellite cells (SCs) are stem cells of skeletal muscle, which can regenerate muscle ﬁbers following damage, such as in DMD. It has recently shown that dystrophin is required for asymmetric cell division of SCs, however, the exact role of dystrophin in SCs in vivo and the pathophysiological consequences in DMD remains to be elucidated. This PhD project aims to determine, in the DMD mouse model mdx, the role of dystrophin in SCs and whether restoration of dystrophin in SCs bears therapeutic value for DMD. In a ﬁrst step, transcriptome signature of SCs with and without DMD mutation will be compared at diﬀerent disease stages. Next, the diﬀerences in SCs behavior will be determined during regeneration of wildtype mice compared to mdx mice. In a second step, satellite cells will be characterized that bear the potential to regenerate so-called revertant ﬁbres that spontaneously restore dystrophin expression. It is assumed that these satellite cells restore dystrophin expression following a yet unknown molecular event that restores the open reading frame and which is either based on alternative splicing or on second mutation DMD. The identiﬁcation of such revertant SCs bears the potential of developing a novel therapeutic strategy for DMD by their ampliﬁcation and subsequent regeneration of muscle capable of re-expressing dystrophin. The host laboratories currently investigate the underlying mechanism of the revertant event. The PhD student will integrate in these eﬀorts and speciﬁcally determine whether these revertant SCs regain wildtype behavior. He will analyze of why these revertant SCs have a selection advantage over non-revertant SCs during repetitive rounds of degeneration and regeneration and why they are able, in time, to form increasing number of revertant muscle ﬁbers. The student will explore, of whether revertant SCs can be used as a stem cell therapy approach for DMD by grafting them into mdx muscle and monitoring their ability to form revertant muscle ﬁbers. Finally, two other therapeutic strategies for DMD will be applied that previously have been shown to restore dystrophin expression in muscle ﬁbers: i) the use of antisense oligonucleotides for correcting the DMD mutation at RNA level, and ii) the use of CRISPR/Cas9 technology for correcting the DMD mutation at DNA level. It will be determined whether these approaches can also restore dystrophin expression in SCs and whether this normalize the molecular signature of SCs and SC function.