Team 1

Transversal projects

PI : Michael Schumacher

Teams of our research unit are not separated from one another, but collaborate on common projects. Team 1 is a converging point for transversal projects, sharing expertise in steroid neuroendocrinology and providing precise, sensitive and robust steroid profiling by gas chromatography-tandem mass spectrometry (GC-MS/MS).

Teams 1 and 2 bring together their expertise in the use of steroids and other neuroactive signaling molecules, as well as of adeno-associated virus (AVV) carriers, to promote the regeneration of myelin. To improve the safety and efficacy of steroids for treating diseases and lesions of the nervous system, and for preferentially administering them to the brain and spinal cord, the intranasal delivery route is explored. The identication of the intracellular progesterone receptors as major players in actions of progesterone in neural cells has important therapeutic implications, opening the way for the use in neuroprotective and myelin repair strategies of synthetic progestins, developed for hormonal contraception and the treatment of endocrine disorders.

Team 2, a member of the LabEX « NanoSaclay », explores the therapeutic usefulness of squalenoyl small molecule nanoparticles for promoting neuroprotection and neuroregeneration. We also share a research program with team 2 with the aim to promote peripheral nerve regeneration by combining new neurosurgical procedures with small molecule therapies (TSPO ligands and steroids) and with viral vector-mediated neurotrophin gene transfer.

New therapeutic approaches of myelin disorders and

inflammation in the central nervous system

PI : Elisabeth Traiffort

Elisabeth Traiffort is neurobiologist. Her scientific carrier started after 4 years as pharmacist in AP-HP (Assistance Publique-Hôpitaux de Paris). After a first interest in the field of histaminergic or serotoninergic neurotransmission and G-protein coupled receptors (1988-1996), she moved to the investigation of the first signaling pathway that was identified in the genetic control of early embryo development, the Hedgehog signaling. From 1998, her collaborators and herself revealed the persistence of Hedgehog pathway in the postnatal and adult central nervous system. They notably showed the transport of Hedgehog proteins in axons, their ability to control electrophysiological properties of neurons and the role of the pathway in the cell division mode of the adult neural stem cells. In 2013, while she had just revisited the involvement of the Hedgehog signaling pathway during myelin regeneration, she joined Kremlin-Bicêtre Hospital, where she was proposed as the leader of the team ‘Myelination and Myelin Repair’ that became in 2018 the team ‘Glial Cells, Regeneration and Plasticity’.

The present project is aimed at delineating the molecular and cellular mechanisms implicated in the process of developmental and repairing myelination. The two signaling pathways that are currently studied include the pathways triggered respectively by the secreted proteins Hedgehog and the steroid hormone testosterone. The project relies on the genetic and pharmacological manipulation of these pathways during development and in various murine models of demyelination. The group is also focalized on local inflammation associated with myelin pathologies and other CNS diseases. Ultimately, the objective is the finding of new therapeutic targets in the field of myelin diseases and inflammatory CNS pathologies.

Grants : Since 2013, the work is funded by ANR, ARSEP, ARSLA

Roles of androgens and progestagens on myelin

PI : Abdel Ghoumari

My research topic is to investigate the role of natural and synthetic small molecules such as steroids, progestagens, and androgens in myelin development and myelin regeneration, using in vitro, ex vivo, and in vivo models of multiple sclerosis (MS). Also, we are studying the importance of these steroids in the setting up of myelin dimorphism. This makes sense as the MS is a sexually dimorphic disease, whose evolution is influenced by the endocrine profile of SEP patients. Our previous work has shown that progesterone and testosterone, via their respective nuclear receptors, are very important for the regeneration of myelin in the demyelination model of mouse spinal cord and organotypic cultures of rodent cerebellum. Similarly, the effect of testosterone via its nuclear receptor (AR) is permanent on sexual dimorphism of myelin (figure below). To understand how steroids influence myelination and remyelination, we are studying in detail their mechanism (s) of actions by the determination of the signaling pathways and the target genes. For this, we use a molecular approach based on the analysis of transcriptomes between male and female mice and between intact and demyelinated mice, treated or not with steroids. The functionality of each of these target genes is studied in mice after confirmation in vitro and / or ex vivo culture.

Cerebroprotective effects of steroid hormones and neurosteroids

PI : Rachida Guennoun

The project aims to better understand
1) the role of neurosteroid synthesis in cerebroprotection after ischemic stroke;
2) the mechanisms by which steroids exert their cerebroprotective effects at the molecular and cellular level;
3) The optimization of intranasal administration of natural or synthetic steroids as a potential route of cerebroprotection in ischemic stroke.

We have a multidisplinary approach combining generation of mice with selective invalidation of steroid receptors or enzymes of steroidogenesis using the Cre/Lox strategy, surgery (experimental cerebral ischemia), behavioral tests to evaluate functional recovery (neurological deficits, motor coordination), histological analysis, gene and protein expression analysis (Transcriptomic analysis, RT-qPCR, Western blot, immunofluorescence, Confocal microscopy) and steroid measurement by Gas Chromatography-tandem mass spectrometry.

Thanks to the interaction between basic scientists and clinicians we aim to generate preclinical data for the development of a neuroprotective therapy based on treatment with natural or synthetic steroids or on stimulation of endogenous synthesis of neurosteroids in stroke patients of both sexes.

Unnatural amino acids highlight specificity of signaling transduction

PI : Shixin Ye-Lehmann

We are developing synthetic biology tools to address fundamental problems associated with signaling transduction mechanisms in neuronal diseases. Synthetic biology is an interdisciplinary branch of biology and engineering, which enables to dissect the biological complexity by the precise synthesis of biomolecules in vivo. We have developed efficient methods to genetically encode unnatural amino acids (UAA) into membrane proteins (including G protein-coupled receptors, ligand-gated ion channels) to study their structure-function relationships. We demonstrated the feasibility to expand the genetic code in mammalian cells, Xenopus laevis oocytes, primary neurons, and recently two animal models (mice and zebrafish). The incorporation of light-sensitive UAA has elucidated a novel molecular mechanism that explains functional differences between N-methyl-D-aspartate (NMDA) receptor subtypes, which play key roles in the excitatory synaptic transmission associated with learning and memory. In the course of these studies, we have identified series of light-sensitive NMDA receptors whose activities can be modulated by light. Currently we are developing new optical methods to regulate neuronal signaling processes with light, and we are engineering light-responsive neuronal receptors for optogenetic studies.

Cerebroprotection in Alzheimer’s disease

PI : Yvette Akwa

Our research is part of innovative strategies to protect and repair the brain in Alzheimer’s disease. There is currently no cure for this neurodegenerative disease. One of the causes of these failures could lie in the extreme specificity of the tested drugs targeting only one component of this multifactorial pathology. Neuropathological aspects include a progressive accumulation of protein aggregates consisting of -amyloid peptides or tau protein, early synaptic dysfunction and neuroinflammation. We believe that multi-target strategies against these pathogenic elements could be more effective in protecting neurons and improving symptoms.

Our research focuses on:

1- The evaluation of the effects of direct administration of natural steroids or their synthetic enantiomers, particularly excitatory compounds stimulating neurotransmission (Leader: Yvette Akwa, PhD, in collaboration with Davide Tampellini, PhD and Anne Boiret, IE)

2- The study of the efficacy of molecules that stimulate the endogenous production of steroids or neurosteroids with cerebroprotective properties and the understanding of the role of the TSPO protein as a therapeutic target (Leaders: Yvette Akwa, PhD, Michael Schumacher, PhD)

3- The study of the effects of deep brain stimulation and synaptic activation (Leader: Davide Tampellini, in collaboration with Yvette Akwa)

Analysis and profiling of steroids by gas chromatography/tandem

mass spectrometry

PI : Philippe Liere

We analyse steroid metabolomes in plasma and small nervous tissue samples by gas chromatography-tandem mass spectrometry (GC-MS/MS). This technology represents the gold standard for accurate, sensitive and extensive steroid profiling.The GC-MS/MS analysis of steroids is an evolutive technology, and our group is engaged in further development. So far, GC-MS/MS allows us the profiling of up to 70 different steroids, in the femtomole range, in a robust and precise manner in small tissue and biological fluids samples.

However, this technology only provides accurate reference values when combined with upstream very careful samples purification and fractionation methods in order to obtain a reliable steroid profiling without cross-contamination The combination between validated sample preparation and a reference analytical technology is a prerequisite for steroid analysis in biological samples, and in particular in complex matrices such as fatty nervous tissues. Radioimmunoassays and enzyme-linked immunosorbent assays, even with prepurification steps, do not provide the required specificity. The major strength of GC-MS/MS is its capacity to separate a large number of structurally similar steroids such as stereoisomers and enantiomers, thus permitting to obtain key informations on the neuroendocrine physiopathological processes in injuried nervous system, in neurodegenerative diseases.

We provide steroid analysis for academic, preclinical and clinical research projects as well as for pharmaceutical companies.

PIs : Catherine Le Stunff, Pierre Bougnères

We use postnatal and prenatal AAV gene transfer to transduce brain and spinal cord oligodendrocytes in mouse disease models and in non human primates as preclinical models for the gene therapy of X-adrenoleukodystrophy, adrenomyeloneuropathy, Krabbe’s disease, and more generally demyelinating diseases or axonopathies. We also develop a program of AAV mediated gene therapy directed at mitofusin deficiency (Charcot-Marie Tooth 2). We design and build plasmids with specific CNS expressing promoters and use all techniques allowing gene expression to be quantified in these animal models.