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Last update 2011-03-25 15:22:13.778

Florence Molinari Pathophysiological mechanisms involved in early epileptic encephalopathy: study of the SLC25A22 gene

Course and current status

Qualification

Since 2009           Researcher, permanent position (CR1 INSERM), in Alfonso Represa’s Laboratory: “Neonatal epileptic encephalopathies and glutamate transporters”

INMED-INSERM U901, Parc Scientifique de Luminy (Marseille, France)

2006-2008            Researcher, permanent position (CR2 INSERM), in Arnold Munnich’s Laboratory: “Identification and functional analysis of genes involved in autosomal recessive form of mental retardation”

INSERM U781, Hôpital Necker-Enfants Malades (Paris, France).

2005                   Post-doctoral position in Peter Sonderegger’s Laboratory, “Behavioural Studies of Prss12 KO Mice”.

Institute of Biochemistry, Zürich University (Switzerland).                         

2001-2004          Ph. D in Genetics, defended November 25th 2004: “Identification and functional analysis of genes involved in autosomal recessive form of mental retardation”, headed by Laurence Colleaux.

INSERM U393, Hôpital Necker-Enfants Malades (Paris, France).

2000-2001             Master of Molecular genetics, development and oncogenesis.

Université Paris 5 - René Descartes

Scientific background

CR1 INSERM            Since 2009, I work on the mechanisms involved in neonatal epileptic encephalopathy, more precisely on the consequences of SLC25A22 gene mutations. I gained experience in glial cells culture and transfection and electrophysiology techniques such as patch clamp and field recordings.

CR2 INSERM            The aim of my first position was to identify genes involved in autosomal recessive form of mental retardation. I succeed to identify mutations in two genes, TUSC3 (11p15.5) and IAP (Xq22), which are involved in the same pathway: the N-glycosylation. I gained experience in quantitative RT-PCR and RNA interference.

Post-doctorate      The aim of my post-doctorate is to characterized Prss12 mice using cognitive tests. I perform these tests in collaboration with David P. Wolfer and Hans P. Lipp. I gain experiments in cognitive tests such as Water Maze, Open Field, Radial Maze, Object Intrusion, Light-Dark Box, Puzzle Box, Rotarod, and Startle. I also learned neuronal (low and high density) and glial cells cultures for immunolocalization.

Ph D                          The aim of my thesis was to identify new genes involved in autosomal recessive form of mental retardation using homozygosity mapping and inbred families. This work resulted in the identification and the functional analysis of two genes: PRSS12 involved in an autosomal recessive nonsyndromic mental retardation, and SLC25A22 involved in a mental retardation associated with a severe neonatal epileptic encephalopathy. I gained experience in a number of techniques such as PCR, RT-PCR, genotyping, sequencing, Northern hybridization, in-situ Hybridization, mutation detection with DHPLC and computer aided gene database analysis.

Academic and Professional Awards

2008           Isabelle Oberlé Award, European Society of Human Genetics meeting

2005            Fellowship from Fondation de la Recherche Médicale

2002           Isabelle Oberlé Award, European Society of Human Genetics meeting

2001-2004 Fellowship from the French Ministry of Research

Scientific summary

     Neonatal epileptic encephalopathy with suppression burst (NEESB) is a rare condition characterized by the onset of seizure in the first months of life and interictal “suppression burst” (SB) electroencephalogram (EEG) pattern. This specific pattern is described as generalized and multifocal, high voltage, spikes and sharp wave complexes alternating with silent period. Among these conditions, we could find two very severe syndromes: early myoclonic encephalopathy (EME) and early infantile epileptic encephalopathy (EIEE). A number of etiological factors have been associated with these syndromes as cortical malformations, metabolic disorders or mutations in genes involved in different pathways (SLC25A22, PNPO, ARX, and STXBP1). However, the pathophysiology bases of severe neonatal encephalopathies with SB are still unknown and the outcome remains very poor; most of the patients either die within the first few years of life or survive in a vegetative state.

     Recently, genetic analyses of two consanguineous families, with children presenting NEESB, allowed us to identify homozygous mutations in SLC25A22 gene which encodes a mitochondrial glutamate carrier. These patients presented seizures few hours after birth characterized by an EEG with SB, neonatal hypotonia, microcephaly, abnormal electroretinogram with weak visual evoked potential signal. The mutations identified, p.Pro206Leu and p.Gly236Trp, changed highly conserved amino-acids that are crucial for SLC25A22 activity as demonstrated by the complete loss of transport and uniport activity of mutated proteins in vitro. Interestingly, this protein seems to be mainly expressed in astrocytes, regulator of the extrasynaptic glutamate. Moreover, Laurent Aniksztejn’s team shows that TBOA, an inhibitor of the cellular glutamate carriers (GLAST and GLT-1), could induce slow network oscillations (SNOs) in vitro and in vivo. This activity pattern is very similar to SB observed in patients with NEESB. All these results suggest that glutamate concentration regulation is crucial in the generation of SB pattern.

     The aim of this project is to: (i) Generate and validate an in vitro model to study SLC25A22 inactivation; (ii) Study the molecular and electrophysiological consequences of SLC25A22 inactivation in cells ; and (iii) Analyse the consequences on the cortical network activity. More generally, we would like to investigate the role of glutamate transport in the generation of the SB pattern in order to understand how these activities occur and propagate and we would also concentrate on the particular role of the astrocytic cells which seem to play a critical role in these conditions.

     We hope that this project would lead us to characterize the bases of NEESB which is essential to guide us for improvement or development of new therapeutic strategies. These results would certainly help clinicians to anticipate the disease evolution and adapt the patients treatment.

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