Glutamatergic synaptic currents of nigral dopaminergic neurons follow a postnatal developmental sequence

International audienceThe spontaneous activity pattern of adult dopaminergic (DA) neurons of the substantia nigra pars compacta (SNc) results from interactions between intrinsic membrane conductances and afferent inputs. In adult SNc DA neurons, low-frequency tonic background activity is generated by intrinsic pacemaker mechanisms, whereas burst generation depends on intact synaptic inputs in particular the glutamatergic ones. Tonic DA release in the striatum during pacemaking is required to maintain motor activity, and burst firing evokes phasic DA release, necessary for cue-dependent learning tasks. However, it is still unknown how the firing properties of SNc DA neurons mature during postnatal development before reaching the adult state. We studied the postnatal developmental profile of spontaneous and evoked AMPA and NMDA (N-Methyl-D-aspartic acid) receptor-mediated excitatory postsynaptic currents (EPSCs) in SNc DA neurons in brain slices from immature (postnatal days P4-P10) and young adult (P30-P50) tyrosine hydroxylase (TH)-green fluorescent protein mice. We found that somato-dendritic fields of SNc DA neurons are already mature at P4-P10. In contrast, spontaneous glutamatergic EPSCs show a developmental sequence. Spontaneous NMDA EPSCs in particular are larger and more frequent in immature SNc DA neurons than in young adult ones and have a bursty pattern. They are mediated by GluN2B and GluN2D subunit-containing NMDA receptors. The latter generate long-lasting, DQP 1105-sensitive, spontaneous EPSCs, which are transiently recorded during this early period. Due to high NMDA activity, immature SNc DA neurons generate large and long lasting NMDA receptor-dependent (APV-sensitive) bursts in response to the stimulation of the subthalamic nucleus. We conclude that the transient high NMDA activity allows calcium influx into the dendrites of developing SNc DA neurons

PRRT2 links infantile convulsions and paroxysmal dyskinesia with migraine.

OBJECTIVE: Whole genome sequencing and the screening of 103 families recently led us to identify PRRT2 (proline-rich-transmembrane protein) as the gene causing infantile convulsions (IC) with paroxysmal kinesigenic dyskinesia (PKD) (PKD/IC syndrome, formerly ICCA). There is interfamilial and intrafamilial variability and the patients may have IC or PKD. Association of IC with hemiplegic migraine (HM) has also been reported. In order to explore the mutational and clinical spectra, we analyzed 34 additional families with either typical PKD/IC or PKD/IC with migraine. METHODS: We performed Sanger sequencing of all PRRT2 coding exons and of exon-intron boundaries in the probands and in their relatives whenever appropriate. RESULTS: Two known and 2 novel PRRT2 mutations were detected in 18 families. The p.R217Pfs*8 recurrent mutation was found in ≈50% of typical PKD/IC, and the unreported p.R145Gfs*31 in one more typical family. PRRT2 mutations were also found in PKD/IC with migraine: p.R217Pfs*8 cosegregated with PKD associated with HM in one family, and was also detected in one IC patient having migraine with aura, in related PKD/IC familial patients having migraine without aura, and in one sporadic migraineur with abnormal MRI. Previously reported p.R240X was found in one patient with PKD with migraine without aura. The novel frameshift p.S248Afs*65 was identified in a PKD/IC family member with IC and migraine with aura. CONCLUSIONS: We extend the spectrum of PRRT2 mutations and phenotypes to HM and to other types of migraine in the context of PKD/IC, and emphasize the phenotypic pleiotropy seen in patients with PRRT2 mutationsjournal articleresearch support, non-u.s. gov't2012 Nov 202012 10 17importedComment in : Paroxysmal disorders associated with PRRT2 mutations shake up expectations on ion channel genes. [Neurology. 2012

Caractérisation d'un modèle d'infection cérébrale in utero par le cytomégalovirus chez le rat : conséquences post-natales et rôle de l'activation microgliale

L’infection par le cytomégalovirus (CMV) au cours de la grossesse est fréquente et représente la première cause de pathologie neurodéveloppementale. En dépit de cette importance médicale, il n’existe à ce jour aucun traitement préventif ou curatif satisfaisant, et les mécanismes physiopathologiques mis en jeu, en particulier au niveau du cerveau foetal, restent mal connus. Des découvertes récentes sur les modèles murins d’infection cérébrale par le CMV, principalement réalisées pendant la période néonatale, ont apporté des données convergentes sur la physiopathologie de ces infections cérébrales ; notamment, le rôle joué par les cellules immunitaires périphériques dans la résolution de l’infection, et l’implication du système immunitaire cérébral (SIC) au cours du processus infectieux. Afin de compléter et préciser les résultats précédemment obtenus dans différents modèles murins, et de comprendre le rôle joué par le SIC, le premier objectif de ma thèse a consisté à mettre au point et à caractériser un nouveau modèle d’infection cérébrale par le CMV au cours du développement in utero chez le rat. Dans l'ensemble, nos résultats confirment l'altération du SIC au cours de l'infection par le CMV du cerveau en développement, et suggèrent fortement, dans ce modèle, un rôle majeur joué par le système microglie/macrophage dans l'émergence de troubles neurologiques semblables à ceux observés dans la pathologie humaine correspondante.Cytomegalovirus (CMV) infection during pregnancy is the leading cause of neurodevelopmental disorders (polymicrogyria, microcephaly) and may lead to severe sensorineural consequences (deafness, epilepsy, cerebral palsy and hearing loss). Despite this medical importance, no preventive or curative treatment is satisfactory to date, and the pathophysiological mechanisms, notably in the fetal brain, remain poorly understood. Recent findings in murine brain CMV infection, mostly in neonatal models, have brought converging insights into the pathogenesis of these infections; the possible role played by peripheral immune cells against infection and the involvement of the brain immune system (BIS) have been proposed. The actual roles of BIS during in utero infection, and more specifically that of microglial cells and macrophages, remain unclear. In order to expand and precise the data previously obtained in the murine models, and to clarify the role of BIS, the first objective of my thesis was to design and to characterize a novel model of CMV infection during the fetal development of the rat brain. Overall, our datas confirm the altered state of BIS as a consequence of CMV infection of the developing brain, and strongly suggest, in the rat model studied here, that the microglia/macrophages system plays critical role in the pathogenesis of neurological manifestations similar to those classically seen after human congenital CMV infection

Tridimensional micro-nano structuration & functionalisation of substrates for sensitive & fast DEP/SPRI biochip system

International audienc

Towards miniaturized pH sensor based on carbon nanotubes assembled by DEP on titanium electrodes?

International audienceIn this paper, the pH response of a chemiresistor based on single walled carbon nanotubes (SWNT) was studied. SWNT functionalized with carboxylic groups (COOH-SWNT) were assembled by dielectrophoresis (DEP) between titanium electrodes. Current-voltage I (V) characteristics show that the device conductance decreases as the solution pH increases. DEP enabled to fabricate micronic size structures with low amounts of carbon nanotubes by comparison with SWNT dense films. These structures yielded responses to pH variations

A study of optimal electrode design for electric field driven target capture in SPR biosensors

International audienc

In Utero Administration of Drugs Targeting Microglia Improves the Neurodevelopmental Outcome Following Cytomegalovirus Infection of the Rat Fetal Brain

Congenital cytomegalovirus (CMV) infections represent one leading cause of neurodevelopmental disorders. Recently, we reported on a rat model of CMV infection of the developing brain in utero, characterized by early and prominent infection and alteration of microglia—the brain-resident mononuclear phagocytes. Besides their canonical function against pathogens, microglia are also pivotal to brain development. Here we show that CMV infection of the rat fetal brain recapitulated key postnatal phenotypes of human congenital CMV including increased mortality, sensorimotor impairment reminiscent of cerebral palsy, hearing defects, and epileptic seizures. The possible influence of early microglia alteration on those phenotypes was then questioned by pharmacological targeting of microglia during pregnancy. One single administration of clodronate liposomes in the embryonic brains at the time of CMV injection to deplete microglia, and maternal feeding with doxycyxline throughout pregnancy to modify microglia in the litters' brains, were both associated with dramatic improvements of survival, body weight gain, sensorimotor development and with decreased risk of epileptic seizures. Improvement of microglia activation status did not persist postnatally after doxycycline discontinuation; also, active brain infection remained unchanged by doxycycline. Altogether our data indicate that early microglia alteration, rather than brain CMV load per se, is instrumental in influencing survival and the neurological outcomes of CMV-infected rats, and suggest that microglia might participate in the neurological outcome of congenital CMV in humans. Furthermore this study represents a first proof-of-principle for the design of microglia-targeted preventive strategies in the context of congenital CMV infection of the brain

Early events in cytomegalovirus infection of the developing rat brain: a pathophysiological role for viral chemokine r129?

International audienc