Research Interests and Main Results

COMPOSITION OF NICE2 TEAM

TEAM MEMBERS (as on January 1st, 2018)

Team Leader
Pierre SZEPETOWSKI (DR1 CNRS)

Team Members (in alphabetical order)
Laurent ANIKSZTEJN (DR2 INSERM)
Sylvian BAUER (CR1 CNRS)
Hélène BECQ (IE INSERM)
Nadine BRUNEAU (CR1 INSERM)
Nail BURNASHEV (DR2 INSERM)
Alexandre PONS-BENNACEUR (PhD Student)
Manal SALMI (PhD Student)
Jean-Christophe VERMOYAL (Master2 Student)

GENERAL OVERVIEW

OVERALL CONTEXT

Human epilepsies represent one of the most frequent neurological disorders, with an overall prevalence of 0.5-1%. This represents 50.106 people worldwide, 6.106 in Europe, and 400,000 people in France. According to the World Health Organization, the annual cost of the epilepsies in Europe is over €20.109. One third of the patients do not respond well to current anti-epileptic drugs.

Overall the epilepsies cause major socio-economical, societal, welfare, medical and scientific issues. This burden is further emphasized by the existence of frequent comorbid relationships with other brain diseases, such as autism spectrum disorders, depression, migraine, movement disorders, dyslexia, and sleep, cognitive, speech and language impairments.

SCIENTIFIC GOALS & OBJECTIVES

We aim at studying and at targeting the early pathophysiological events associated with epilepsies and encephalopathies of genetic or nongenetic origin, using multidisciplinary approaches in vitro and in vivo.

Particularly we are interested in the pathological alterations that occur early in the developing brain and that may have profound and long-term consequences on brain development and functioning.

Our main objectives are:

• to better understand pediatric epilepsies and epileptic encephalopathies of genetic origin, and to design novel rescue strategies in those contexts;

• to investigate on secondary pathophysiological events, such as neuroimmune alterations (e.g. microglia dysfunctioning), that are likely to impact on the severity, the comorbidity, the outcome and the responses to treatments;

• to decipher how nongenetic factors (e.g. viral infections) impact on brain development and ultimately lead to neurodevelopmental disorders.

 

RECENT FINDINGS

In the recent years we have studied pediatric epilepsies in a genetic and developmental perspective.

•• We have made major findings in epilepsy genetics:

• we have identified mutations in the GRIN2A/GluN2A subunit of glutamate-gated NMDA receptors as the first (and so far major) cause for the sleep-related epilepsy-aphasia spectrum of disorders, which comprises childhood focal epilepsies and epileptic encephalopathies with speech and language dysfunction, and the origin of which had been debated for more than 50 years (Carvill et al. Nature Genetics 2013; Lesca et al. Nature Genetics 2013);

• we have shown that mutations in the retinoid related nuclear receptor RORB cause epileptic disorders, notably absence seizures, variably associated with behavioral and cognitive impairments (Rudolf et al. European Journal of Human Genetics 2016);

• in the context of an international consortium, we have also identified mutations in the Proline-Rich Repeat Protein PRRT2 as the major genetic cause for the variable comorbid association of infantile convulsions, paroxysmal dyskinesia and hemiplegic migraine, which had been searched for more than 15 years (Lee et al. Cell Reports 2012; Cloarec et al. Neurology 2012).

•• We have made important and original findings on the pathophysiological mechanisms associated with early-onset epileptic encephalopathies (EOEE):

• thanks to collaborations with neuro-pediatricians, geneticists, molecular biologists and biochemists, we showed that Kv7.2 mutations may have opposite effects on M current, and may act on the redistribution of Kv7 channels from the axon initial segment to the somato-dendritic compartment (Abidi et al. Neurobiology of Disease 2015; Devaux et al. Epilepsia 2016);
• we found that STXBP1//Munc18.1 decreased the physical interaction of syntaxine 1A with Kv7 channels and reduced the inhibitory effect of syntaxine 1A on M current, indicating a potential functional link between STXBP1/Munc18.1 and Kv7.2 – the two major proteins involved in EOEE (Devaux et al. Epilepsia 2017).
• we also demonstrated that the degradation of glutamate by glutamine synthase, which is specifically expressed by astrocytes in the brain, is fundamental to ensure proper function of glial glutamate transporters and to prevent glutamate spillover (Trabelsi et al. Glia 2017);

•• We have also made a series of important and original findings regarding the pathophysiological pathways of developmental epileptic disorders and on their possible therapeutic targeting:

• we have demonstrated that a short administration of a tubulin deacetylase inhibitor to pregnant rats was sufficient to prevent the long-term epileptiform consequences of a neuronal migration disorder in the embryos (Salmi et al. Brain 2013);

• in a model of tuberous sclerosis complex (TSC), we have shown that tuberless heterozygote Tsc1+/- mice show functional upregulation of cortical GluN2C-containing NMDA receptors in an mTOR-dependent manner and exhibit recurrent, unprovoked seizures during early postnatal life. Accordingly, specific GluN2C/D antagonists block seizures in Tsc1+/- mice in vivo and in vitro. Likewise, GluN2C expression is upregulated in TSC human surgical resections, and a GluN2C/D antagonist reduces paroxysmal hyperexcitability (Lozovaya et al. Nature Communications 2014).

Current research projects

ONGOING PROJECTS & EXPERIMENTAL APPROACHES

 

Genetic and nongenetic (viruses, drugs…) factors may cause or influence a broad range of neurodevelopmental disorders, including severe epilepsies and encephalopathies, which can be associated with comorbid manifestations (e.g. cognitive or behavioral impairment).

Despite the recent identification of various genes participating in such disorders, the underlying pathogenic mechanisms and rationale for treatment still remain poorly understood. In these conditions, identifying the early events likely altered during brain development and deciphering the underlying pathophysiological processes is mandatory.

Notably, what sustains i/ the variable degree of severity, ii/ the association with different comorbid conditions such as autism manifestations or cognitive and language impairments, iii/ the somehow unpredictable outcome, and iv/ the unsatisfactory response to treatment, that are all frequently seen in such disorders, remains poorly known.

Obviously both genetic factors such as the genetic background or the existence of somatic mutations, and nongenetic factors such as environmental insults or the reaction of the neuroimmune system, might play a role in such a diversity.

We use multidisciplinary approaches and tools that non exhaustively include molecular genetics, cell biology, flow cytometry, protein analysis, electrophysiological recordings in vitro and in vivo, intracerebroventicular electroporation and infection of the embryonic brain in utero, behavioral analyses, rescue strategies in vivo, 2-photon microscopy, etc.

We study four rodent models of different neurodevelopmental disorders where both specific and non-specific determinants are likely involved, albeit at different levels, in the emergence and in the variable evolution of the phenotypes.

•• KCNQ2-related early-onset epileptic encephalopathies: we study the impact of KCNQ2 pathogenic defects on the biophysical properties of Kv7 channels and analyze their consequences on cortical network activities, notably using a mouse model bearing a selective pathogenic Kv7.2 variant.

•• GRIN2A-related disorders: in humans, mutations in the corresponding NMDA receptor subunit GLUN2A cause quite benign to severe disorders of the epilepsy-aphasia spectrum. We study GRIN2A variants in order to investigate for altered functioning of NMDA receptors, and the corresponding Grin2a KO murine model in search of early structural and functional alterations.

•• TSC1-related disorders: in humans, mutations in the hamartin protein (TSC1 gene) cause variably-expressed tuberous sclerosis complex and epilepsy associated with cognitive impairment and autism manifestations. We study the corresponding murine model to decipher the underlying pathophysiological mechanisms of epileptic activity, and to address the possible involvement of early immune events as possible second hits.

•• Cytomegalovirus (CMV)-related disorders: in human, congenital cytomegalovirus (CMV) infections of the brain is a major cause of neurodevelopmental disorders and may have various consequences with highly variable degrees of severity. We have designed a rat model of cytomegalovirus infection into the developing brain in utero. In this model, early neuroimmune alterations (microglia, chemokines) were observed. We study the possible involvement of such early alterations in the pathophysiology and in the emergence of neurological and other postnatal outcome.

Key words

Epilepsy / Encephalopathies /Brain development / NMDA Receptors / GRIN2A / Kv7.2 / Tuberous sclerosis complex /Congenital cytomegalovirus / Microglia / Rodent models

Experimental approaches

We use multidisciplinary approaches and tools that non exhaustively include molecular genetics, cell biology, flow cytometry, protein analysis, electrophysiological recordings in vitro and in vivo, intracerebroventicular electroporation and infection of the embryonic brain in utero, behavioral analyses, rescue strategies in vivo, 2-photon microscopy, cellular and rodent models, etc.

Recent and/or Ongoing Collaborations

Locally, the team has got long-term collaborations with several INMED teams (C Cardoso/A Represa, R Khazipov, J Epsztein) and INMED platforms (PPGI, PBMC, InMAGIC, animal facility) as well as with pediatric epileptology (M Milh, Marseille University Hospital), CRN2M centre (J Devaux), Marseille Medical Genetics lab (L Villard) and the CIPHE/CIML immunology centre (H Luche, M Malissen). We further integrated within the local epileptology community in the context of the university hospital foundation (FHU) EPINEXT that brings together a large number of teams having well-recognized activity in epileptology, from the clinical aspects to more fundamental views, and located at several research centres in Marseille.

Other collaborations have been established elsewhere in France and abroad: non exhaustively, these include the Rothschild Foundation (O Delalande, Paris), INSERM unit U1141 (P Gressens, Paris), the CERMEP neuroimaging centre (R Bolbos, Lyon), the INSERM/CNRS CPTP Physiopathology Center (S Chavanas, Toulouse), the University of Heidelberg (A Rozov, Germany), UCSF (LJ Ptacek, USA), Yale University (A Bordey, USA), Washington University (HC Mefford, USA), University of Melbourne (IE Scheffer & SF Berkovic, Australia), Nuremberg-Erlangen University, (T Stamminger, Germany), Oregon University (DN Streblow, USA), Eastern Finland University (R Giniatullin, Finland), Verona University (G Bertini, Italy).

Funding / Labels

SUBVENTIONS (as from 2010)

Acronym/Name/Number: CERVIR
Topic: Cytomegalovirus and Brain Development
Funded by: Sud PACA Regional Council
Period: 2011-13

Acronym/Name/Number: EPIPHOT
Topic: Epilepsy
Funded by: UCB-Pharma France
Period: 2012-14

Acronym/Name/Number: EPILAND
Topic: Epilepsy, Brain Development and Comorbidity
Funded by: ANR
Period: 2010-14

Acronym/Name/Number: -
Topic: Tuberous Sclerosis Complex
Funded by: ANR
Period: 2013-15

Acronym/Name/Number: -
Topic: Tuberous Sclerosis Complex
Funded by: Aix-Marseille University (AMIDEX)
Period: 2014-16

Acronym/Name/Number: Early Behavioral Signatures
Topic: Equipement for Behavioral Analyzes
Funded by: FRC
Period: 2015-16

Acronym/Name/Number: -
Topic: Tuberous Sclerosis Complex
Funded by: ANR
Period: 2014-17

Acronym/Name/Number: Behavior impairment in disorders of the epilepsy-aphasia spectrum
Topic: Behavior and Epilepsy
Funded by: FRC
Period: 2015-17

Acronym/Name/Number: EPI’K
Topic: Early Onset Epileptic Encephalopathies
Funded by: ANR
Period: 2015-18

Acronym/Name/Number: DESIRE
Topic: Epilepsy
Funded by: European Community FP7
Period: 2013-18

Join our team

Applications at various levels are welcome: Engineer schools, Master1, Master2, PhD, post-Doc, permanent researchers. Applications to be sent by email to :pierre.szepetowski@inserm.fr

Publications

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