Team:
Cécile Martinat : Chargée de recherche CR1 (Inserm)
Sandrine Baghdoyan: Research engineer (Inserm)
Jacqueline Gide: Engineer (CECS)
Florine Roussange : Engineer (Inserm)
Juliette Duchesne de Lamotte : PhD Student
Julie Tahraoui : PhD Student
Antoine Merien : PhD Student
Camille Januel : PhD Student
Vincent Mouilleau: PhD Student
Aims and background:
Modeling neuromuscular disorders
The lack of pertinent models for neuromuscular disorders has rendered many important questions in disease pathogenesis inaccessible. Current drugs provide only limited benefit by alleviating certain symptoms. Clearly, the development of efficacious preventive or protective therapies is impeded by our limited knowledge of the neurobiology of these severe conditions and the lack of more faithful assay systems.
Human embryonic stem cells derived from affected embryos during a pre-implantation diagnostic (PGD), as well as the conversion of somatic cells, such as skin fibroblasts, into induced pluripotent stem cells by genetic manipulation, offer the unique opportunity to have access to a large spectrum of disease-specific cell models.
This project aims to the elaboration of new therapeutic strategies for neuromuscular diseases. Indeed, human pluripotent stem cell lines and derivatives, which express a disease-related mutated gene, represent a relevant and pertinent disease cell model to analyse pathological mechanisms through large-scale drug screenings. Consequently we highlight and investigate new therapeutic strategies.
Validating this original concept, we previously demonstrated that PGD-derived hES cells and their derivatives, which express the causal mutation implicated in the Myotonic Dystrophy type 1 (DM1), offer pertinent disease-cell models, applicable for a wide systemic mechanistic analysis ranging from functional studies at the cellular level to a large-scale drug screening. Our goal is, through the greater understanding of pathological mechanisms implicated in this disease, to identify new therapeutic strategies for this neuromuscular disease and to extend this experimental approach to other neuromuscular diseases.
Strategy, means and methods:
Identification of new biomarkers by using a differential transcriptomic approach between mutated and control cells, our goal is to identify new biomarkers for DM1. The identification of new biomarkers and of the molecular pathway of the DM1 may lead to possible therapeutic applications and the development of new diagnostic tools for DM1.
Drug screening Identification of compounds with therapeutic potential for DM1 will be performed through the implementation of large-scale technological resources. One of the main pathological feature is the nuclear aggregation of the mutant mRNA. hES-derived progenies present this pathological sigma. A high-content screening has been developed in order to identify any compound that is able to disintegrate these nuclear aggregation of mutant mRNA by using DM1 hES progenies.
Functional pathological modeling the functional defect between nerve and muscle, which leads to one of the most important symptom associated with DM1: myotonia, will be analyzed. We will use nerve-muscle in vitro system that we previously developed, which is based on hES-derived motoneurons and muscular cells. Functional abnormalities will be identified and potential therapeutic compounds will be tested for their ability to revert these dysfunctions.
Detection of neuromusuclar junction using hES-derived motoneurons maintained on top of human muscular cells. Neurons were detected using the pan neuronal marker TuJI (red) and the synaptic contact by alpha-Bungarotoxin (green).
Results and future prospects:
As a proof of principle, we demonstrated that PGD-derived hES cells and derivatives which, express the causal mutation implicated in the Myotonic Dystrophy type 1 (DM1), may mimic molecular defects associated to the pathology.
Taking advantage of this relevant cell model, we provided, by using a whole-genome transcriptional analysis, a list of DM1 specific biomarkers that could be considered as a robust DM1 signature. In order to use these DM1-specific biomarkers to develop new therapeutic treatments, we successfully developed technical assessments of miniaturization to realize high content screenings based on detection of the nuclear aggregation of the mutant mRNA. Combining DM1-specific biomarkers with a large-scale screening should provide more insights into the development of new therapeutic strategies for DM1.
By combining the transcriptomic analysis to a functional approach, we have revealed a yet unknown neuropathological mechanism of DM1 that links gene defects in cells of the neural lineage to dysfunction in neuritic outgrowth and synaptogenesis.
At longer extend, based on our technical and scientific expertises, this project aims to extend pathological modelling to others neuro-muscular diseases, such as Spinal Muscular Atrophy (SMA) for which, human pluripotent stem cells carrying the causal mutation have been derived.
Detection of the nuclear aggregation of mutant mRNA by in situ hybridization. CTG repeats were detected with a CAG probe (red) in colocalization with the RNA-binding protein MBNL (green). Left : DM1 derived Neural Precursors Cells (NPC); Right:DM1 derived Mese,chymal Precursors Cells (MPC)
Collaborations:
- Dr. Gourdon and Dr. Gomez-Pereira, Inserm U781, Paris, France, (DM1 consortium)
- Dr. Furling , Institut de Myologie, UMR 787, Paris, France, (DM1 consortium)
- Dr. Charlet, IGBMC, Strasbourg, France, (DM1 consortium)
- Dr. Bassez, Hopital Henri Mondor, Paris, France, (DM1 consortium)
- Dr. Scharfman, Inserm U845, Paris, France (DM1 associated insulin resistance analysis)
- Dr. Rachdi, Inserm U845, Paris, France (DM1 associated insulin resistance analysis)
- Dr.Lefebvre, UMR 7592 CNRS, Paris, France, (SMA project)
- Dr. Yates, Inserm UMR 935, Villejuif, France, (SMA project)
- Dr. Barkats, Inserm-UPMC-CNRS UMRS_974, Paris, France, (SMA project)
- Dr. Nicolas Pollet, CNRS UPS3201-Université d’Evry Val d’Essone, France, (SMA project)
