Etude des mécanismes moléculaires de la Dystrophie Myotonique de Type 1 à l'aide de cellules souches embryonnaires humaines porteuses de la mutation causale

Les cellules souches embryonnaires humaines (hESC) représentent un nouvel outilbiologique au potentiel prometteur pour l amélioration de la compréhension des mécanismes moléculaires et cellulaires impliqués dans le développement de maladies monogéniques. Cette application est dans un premier temps devenue possible grâce à l utilisation de lignées de cellules souches embryonnaires humaines porteuses de mutation causale de pathologie, obtenues au cours d un diagnostique pré-implantatoire. Mon travail de thèse s est inscrit dans la validation de ce nouveau concept en utilisant des lignées de cellules souches embryonnaires humaines porteuses de la mutation causale de la Dystrophie Myotonique de type 1 (DM1). Ces cellules, ainsi que leurs progenies neurales et mésenchymateuses représentent un modèle pertinent pour l étude des conséquences physiopathologiques de la mutation DM1 dans la mesure où elles reproduisent certaines caractéristiques moléculaires connues de la pathologie. Mon projet a eu pour objectif de caractériser d un point de vue moléculaire et physiopathologique deux nouvelles altérations géniques identifiées par transcriptome différentiel entre les cellules contrôles et DM1. Ainsi, ce travail nous a permis d identifier un nouveau marqueur, le facteur de transcription ZNF37A, dont l expression est diminuée en association avec la mutation DM1 et qui serait impliqué dans les défauts myogéniques caractérisant cette pathologie. Parallèlement nous avons identifié un nouveau défaut d épissage alternatif d un gène impliqué dans la guidance axonale, l EphA5 qui pourrait être impliqué dans les défauts cognitifs des patients DM1.Abstract not availableEVRY-Bib. électronique (912289901) / SudocSudocFranceF

Etude des mécanismes moléculaires et cellulaires impliqués dans le développement de la dystrophie myotonique de type 1 à l'aide de cellules souches embryonnaires humaines porteuses de la mutation causale

Parmi leurs applications prometteuses, les cellules souches pluripotentes humaines présentent un potentiel inestimable pour améliorer la compréhension des mécanismes moléculaires et cellulaires impliqués dans le développement de maladies monogéniques. Cette application est dans un premier temps devenue possible grâce à l utilisation de lignées de cellules souches embryonnaires humaines (CSEh) porteuses de mutation causale de maladie monogénique, obtenues au cours d un diagnostique pré-implantatoire, puis dans un second temps par la reprogrammation des cellules somatiques en cellules souches pluripotentes (iPS). Dans le cadre de la validation de ce concept, nous avons démontré que des lignées de CSEh porteuses de la mutation causale de la dystrophie myotonique de type 1 (DM1), ainsi que leursprogénies neurales et mésodermiques, exprimaient des défauts moléculaires caractéristiques de la pathologie. Par l intermédiaire d une étude transcriptomique comparative, nous avons identifié une liste de biomarqueurs pouvant être considérés comme une nouvelle signature moléculaire de la DM1. Parmi ces derniers, nous avons montré que l anomalie d expression de certains gènes de la famille SLITRK était à l origine des défauts d arborisation neuritique mis en évidence dans des cellules motoneuronales dérivées des CSEh mutées, et que ces cellules peuvent interagir avec leur ciblemusculaire. Parallèlement, nous avons identifié un facteur de transcription à domaine Krab dont l expression est fortement altérée dans la DM1 et qui semble être impliqué dans les défauts de régénération musculaire associé à des fins thérapeutiques en définissant leur capacité à modéliser une maladie génétique de façon suffisamment précise pour permettre d élaborer des biothérapies spécifiquement liées aux mécanismes moléculaires mis en jeu.Human pluripotent stem cells present far reaching implication not only for their therapeutic potential but also for the understanding of the molecular and cellular mechanisms of monogenic diseases. This application became at first possible by using human embryonic stem cells lines (hES) carrying the causal mutation of the monogenic disease, obtained during pre-implantation genetic diagnosis, thereafter through the development of somatic cells reprogramming into pluripotent stem cells (iPS). In line with this concept, we provided evidence that hES lines carrying the causal mutation of myotonic dystrophy type 1 (DM1), as well as their neural and mesodermal progenitors, expressed characteristic molecular defects of the pathology. Through a comparative study of their transcriptome profile, we identified a list of biomarkers which can be considered as new molecular signature of DM1. Among these genes, we showed that abnormal expression of some genes of the SLITRK family was responsible for the defective neuritic outgrowth observed in motor neuron cells derived from mutated hES, but that these cells could nonetheless interact with their muscular target. In parallel, we identified a Krab domain transcription factor which expression is strongly altered in DM1 and which seems to be involved in muscular regeneration defects associated with DM1. In conclusion, the aim of this work was to extend the spectrum of hES cells use for therapeutic purposes by accurately defining their capacity to model a genetic disease, enabling the elaboration of biotherapies targeted to disease specific molecular mechanisms.EVRY-Bib. électronique (912289901) / SudocSudocFranceF

Astroglial expression of the P-glycoprotein is controlled by intracellular CNTF

BACKGROUND: The P-glycoprotein (P-gp), an ATP binding cassette transmembrane transporter, is expressed by astrocytes in the adult brain, and is positively modulated during astrogliosis. In a search for factors involved in this modulation, P-gp overexpression was studied in long-term in vitro astroglial cultures. RESULTS: Surprisingly, most factors that are known to induce astroglial activation in astroglial cultures failed to increase P-gp expression. The only effective proteins were IFNγ and those belonging to the IL-6 family of cytokines (IL-6, LIF, CT-1 and CNTF). As well as P-gp expression, the IL-6 type cytokines - but not IFNγ - stimulated the expression of endogenous CNTF in astrocytes. In order to see whether an increased intracellular level of CNTF was necessary for induction of P-gp overexpression by IL-6 type cytokines, by the same cytokines analysis was carried out on astrocytes obtained from CNTF knockout mice. In these conditions, IFNγ produced increased P-gp expression, but no overexpression of P-gp was observed with either IL-6, LIF or CT-1, pointing to a role of CNTF in the intracellular signalling pathway leading to P-gp overexpression. In agreement with this suggestion, application of exogenous CNTF -which is internalised with its receptor - produced an overexpression of P-gp in CNTF-deficient astrocytes. CONCLUSIONS: These results reveal two different pathways regulating P-gp expression and activity in reactive astrocytes, one of which depends upon the intracellular concentration of CNTF. This regulation of P-gp may be one of the long searched for physiological roles of CNTF

Contribution of gap junctional communication between tumor cells and astroglia to the invasion of the brain parenchyma by human glioblastomas

BACKGROUND: Gliomas are "intraparenchymally metastatic" tumors, invading the brain in a non-destructive way that suggests cooperation between glioma cells and their environment. Recent studies using an engineered rodent C6 tumor cell line have pointed to mechanisms of invasion that involved gap junctional communication (GJC), with connexin 43 as a substrate. We explored whether this concept may have clinical relevance by analyzing the participation of GJC in human glioblastoma invasion. RESULTS: Three complementary in vitro assays were used: (i) seeding on collagen IV, to analyze homocellular interactions between tumor cells (ii) co-cultures with astrocytes, to study glioblastoma/astrocytes relationships and (iii) implantation into organotypic brain slice cultures, that mimic the three-dimensional parenchymal environment. Carbenoxolone, a potent blocker of GJC, inhibited cell migration in the two latter models. It paradoxically increased it in the first one. These results showed that homocellular interaction between tumor cells supports intercellular adhesion, whereas heterocellular glioblastoma/astrocytes interactions through functional GJC conversely support tumor cell migration. As demonstrated for the rodent cell line, connexin 43 may be responsible for this heterocellular functional coupling. Its levels of expression, high in astrocytes, correlated positively with invasiveness in biopsied tumors. CONCLUSIONS: our results underscore the potential clinical relevance of the concept put forward by other authors based on experiments with a rodent cell line, that glioblastoma cells use astrocytes as a substrate for their migration by subverting communication through connexin 43-dependent gap junctions

A defective Krab-domain zinc-finger transcription factor contributes to altered myogenesis in myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is an RNA-mediated disorder caused by a non-coding CTG repeat expansion that, in particular, provokes functional alteration of CUG-binding proteins. As a consequence, several genes with misregulated alternative splicing have been linked to clinical symptoms. In our search for additional molecular mechanisms that would trigger functional defects in DM1, we took advantage of mutant gene-carrying human embryonic stem cell lines to identify differentially expressed genes. Among the different genes found to be misregulated by DM1 mutation, one strongly downregulated gene encodes a transcription factor, ZNF37A. In this paper, we show that this defect in expression, which derives from a loss of RNA stability, is controlled by the RNA-binding protein, CUGBP1, and is associated with impaired myogenesis—a functional defect reminiscent of that observed in DM1. Loss of the ZNF37A protein results in changes in the expression of the subunit α1 of the receptor for the interleukin 13. This suggests that the pathological molecular mechanisms linking ZNF37A and myogenesis may involve the signaling pathway that is known to promote myoblast recruitment during development and regeneratio

Alloimmunisation to Donor Antigens and Immune Rejection Following Foetal Neural Grafts to the Brain in Patients with Huntington's Disease

BACKGROUND: The brain is deemed “immunologically privileged” due to sparse professional antigen-presenting cells and lymphatic drainage, and to the blood-brain barrier. Although the actual extent of this privilege is controversial, there is general consensus about the limited need in intracerebral neural grafts for immunosuppressive regimens comparable to those used in other cases of allotransplantation. This has led over the past fifteen years to the use of either short-term or even no immunosuppression in most clinical trials with foetal neural transplant in patients with Parkinson's and Huntington's disease. METHODOLOGY/PRINCIPAL FINDINGS: We report biological demonstration of alloimmunisation without signs of rejection in four grafted patients out of 13 studied during the course of a clinical trial involving fetal neural transplantation in patients with Huntington's Disease. Biological, radiological and clinical demonstration of an ongoing rejection process was observed in a fifth transplanted patient. The rejection process was, however, fully reversible under immunosuppressive treatment and graft activity recovered within six months. CONCLUSIONS/SIGNIFICANCE: There had been, up to date, no report of documented cases that could have cast a doubt on those procedures. Our results underline the need for a reconsideration of the extent of the so-called immune privilege of the brain and of the follow-up protocols of patients with intracerebral grafts. It also suggests that some of the results obtained in past studies with foetal neural transplants may have been biased by an unrecognized immune response to donor cells

The Time to Offer Treatments for COVID-19

Introduction: COVID-19 has several overlapping phases. Treatment has focused on the late stage of the disease in hospital. Yet, the continuation of the pandemic is by propagation of the disease in outpatients. The current public health strategy relies solely on vaccines to prevent disease. Areas Covered: We searched the major national registries, pubmed.org, and the preprint servers for all ongoing, completed and published trial results with subject numbers of 100 or more on, and used a targeted search to find announcements of unpublished trial results. As of 2/15/2021, we found 111 publications reporting findings in human studies on 14 classes of agents, and on 9 vaccines. There were 62 randomized controlled studies, the rest retrospective observational analyses. Only 21 publications dealt with outpatient care, the rest all in hospitalized patients. Remdesivir and convalescent plasma have emergency use authorization for hospitalized patients in the U.S.A. There is also support for glucocorticoid treatment of the COVID-19 respiratory distress syndrome. Monoclonal antibodies are authorized for outpatients, but the supply is inadequate to treat all at time of diagnosis. Favipiravir, ivermectin, and interferons are approved in certain countries Expert Opinion: Worldwide vaccination is now underway. Vaccines and antibodies are highly antigen specific and new variants are appearing. There is a need for treatment of outpatients who contract the disease, in addition to mass immunization. We call on public health authorities to authorize treatments with known low risk and potential benefit for use in parallel with mass immunization

[Stem cells, time for scale-up.]

International audienc