Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal.

O sistema nervoso central é o mais complexo de todos os sistemas de órgãos dos vertebrados. Células progenitoras neurais ao se diferenciarem em neurônios e outros tipos celulares, desenvolvem um padrão altamente organizado de conexões, criando uma rede neuronal que forma o cérebro e o restante do sistema nervoso. Para que se possa gerar os diferentes tipos de neurônios e glias deste sistema, as células embrionárias proliferam-se e diferenciam-se através de processos altamente controlados. Este estudo visou avaliar a importância do receptor B2BkR durante o desenvolvimento encefálico do camundongo. Como modelo estudo, foram utilizados animais knockout (B2BkR-/-) para o gene do receptor B2BKR como modelo para avaliação do padrão de expressão de proteínas marcadoras neurais e dos sistemas purinérgicos e de cininas durante o desenvolvimento encefálico de camundongos B2BkR-/-. Há evidências que mostram que o sistema nervoso de mamíferos contém todos os componentes do sistema calicreína-cininas e que as cininas podem atuar como neuromediadores. Os transcritos do receptor B2BkR foram encontrados em células localizadas em regiões neurogênicas a partir do dia 9.5 do desenvolvimento, esta expressão ampliou-se para toda a extensão do sistema nervoso a partir do dia 12,5 do desenvolvimento. A deleção do gene que codificado para o receptor B2BkR levou a um aumento na expressão relativa do receptor B1BkR. No animal knockout foi também observado um aumento nos níveis de expressão dos cininogênios 1 e 2, sugerindo a ativação de mecanismos compensatórios devido a falta do gene codificado para o receptor B2BkR. De acordo com resultados obtidos com modelos de diferenciação in vitro, também os padrões de expressão de marcadores neurais foram alterados ao longo do desenvolvimento de animais knockout, nos quais houve a diminuição da expressão dos marcadores β3-tubulina e MAP2, confirmando o papel do receptor B2BkR na neurogênese. O marcador glial GFAP teve sua expressão relativa significativamente aumentada nos animais knockout B2BkR-/-, confirmando que a inibição deste receptor favorece a gliogênese. A deleção do receptor B2BkR alterou o perfil de expressão dos receptores purinérgicos do subtipo P2X. Os subtipos P2X2 e P2X3 apresentaram níveis de expressão maiores nos animais selvagens. As subunidades P2X4, P2X5, P2X6 e P2X7 apresentam uma expressão maior nos animais B2BkR-/-. Efeitos semelhantes a estes já haviam sido observados na expressão gênica durante a diferenciação d e neuroesferas do telencéfalo de ratos tratados com antagonistas do B2BkR. No entanto, este trabalho é o primeiro a demonstrar os efeitos da delação do B2BkR sob a expressão do receptor B1BkR; de marcadores neurais e gliais; dos cininogênios 1 e 2; e receptores purinérgicos do suptipo P2X in vivo. Deste modo, estes resultados servem como incentivo para estudos adicionais visando elucidar a participação do receptor B2BkR e do sistema calicrína-cininas na determinação de fenótipos neurais utilizando modelos in vivo, bem como os mecanismos envolvidos e o papel do receptor B2BkR na terapia de doenças neurodegenerativas. / The central nervous system (CNS) is the most complex one of all vertebrate organs. Neural stem and progenitor cells differentiate into neurons and other neural cell types such as glia, originating a highly coordinated network characterizing the brain and the remaining nervous system in strictly controlled processes. It is known that the mammalian nervous system expresses all components of the kallikrein-kinin system, and several functions in the brain have been attributed to bradykinin including neurotransmission, neuroprotection and also lately neurogenesis. The present work aimed at studying the importance of the kinin-B2 receptor (B2BKR) during mouse brain development. A B2BKR knock-out model was used for characterizing changes in the expression patterns of neural marker protein and of the purinergic and kininergic systems. Transcripts of B2BkR-coding sequences were detected in neurogenic regions from embryonic day 9.5 (E9.5) on. Expression of the receptor augmented to the whole extension of the CNS beginning from E12.5. Deletion of the B2BKR-coding gene resulted in increased B1BkR gene expression together with augmented kininogen-1 and -2 expression levels. In agreement with results obtained with in vitro models, expression patterns of neural marker proteins also suffered alterations during neural development of B2BKR(-/-) mice when compared to wild-type animals. Reduction of neuronal protein β3-tubulina e MAP2 expression was observed in B2BKR(-/-) mice, while at the same time glial GFAP expression was enhanced, indicating that activation of the B2BKR promotes neurogenesis, while its inhibition favors gliogenesis. Deletion of the B2BkR-coding gene also lets to changes in expression patterns of purinergic P2X receptors. P2X2 and P2X3 subunits were higher expressed in wild-type animals, while P2X4, P2X5, P2X6 e P2X7 subunits revealed increased expression patterns in B2BkR-/- animals. These results are in line with previous ones of our group obtained in differentiating neurospheres from embryonic rat telencephalons. In summary, the present work is the first to demonstrate the effects of B2BKR deletion on expression patterns of neural marker proteins, the B1BKR and several purinergic receptor subunits. Additional studies will be incentivized for elucidation of functions and underlying mechanism of B2BKR actions in vivo, with applications in cell therapy of neurodegenerative diseases.

Cette thèse vise à faire émerger de nouvelles descriptions de la variabilité des plissements du cortex humain en s’appuyant sur des techniques de fouilles de données. L’objectif principal est la conception d’algorithmes permettant de découvrir des motifs de plissement spécifiques à une sous-population d’individus. Le but final est de réaliser un dictionnaire de ces motifs et de les associer à des particularités cognitives ou architecturales, voire à des pathologies. Deux stratégies de « clustering » sont proposées pour mettre en évidence de tels motifs. La première repose sur des descripteurs de formes globaux correspondant aux invariants de moment 3D, la seconde repose sur l’estimation d’une matrice de distances entre chaque paire d’individus. Un algorithme de clustering dédié est conçu pour détecter les motifs les plus fréquents de manière robuste. Une technique de réduction de dimension est utilisée pour mettre en évidence les transitions entre motifs au sein de la population. Les méthodes algorithmiques proposées sont utilisées pour étudier la forme du cortex sensori-moteur d’une population de gauchers contrariés. Des résultats originaux sur le lien entre la forme du sillon central et la latéralité manuelle sont mis en évidence. Les méthodes développées sont ensuite utilisées pour construire le premier dictionnaire des motifs observés dans les plissements corticaux issu d’une approche algorithmique. / This thesis aims at proposing new descriptions of the variability of the folding of the human cortex using data mining. The main objective is the design of algorithms detecting folding patterns specific to a sub-population. The long term goal is the constitution of an exhaustive dictionary of all the folding patterns enriched with links to cognitive or architectural specificities, or to pathologies. Two clustering strategies are proposed to detect such patterns. The first one is based on global shape descriptors called the 3D moment invariants, the second one implies the computation of a pairwise distance matrix. A dedicated clustering algorithm is designed for robust detection of the most frequent patterns. A dimension reduction strategy is proposed to study the transition from one pattern to another across the population. The proposed framework is applied to the study of the shape of the sensori-motor cortex of a population of left-handers forced to write with the right hand. Original discoveries relating the shape of the central sulcus to handedness are achieved. The framework is finally used to build the first computerized dictionary of the cortical folding patterns.

Personlig integritet är av stor vikt för en sund utveckling av en individs identitet, psykiska hälsa och välbefinnande och påverkas av omgivningen. Personlig integritet är därför en viktig parameter i en psykologs terapeutiska arbete. Syftet med föreliggande kvalitativa studie var att undersöka hur psykologstuderande ser på personlig integritet i dagens individcentrerade samhälle med internet och sociala medier. Sju psykologstuderande på Stockholms universitet intervjuades. Resultatet av en tematisk analys visade att deltagarna ansåg att den personliga integriteten betyder olika mycket för olika individer, men uppfattas påverkas negativt. Möjligheten att behålla en hög integritet upplevs bli allt svårare. Internet tenderar också att påverka identitetsskapandet, särskilt hos unga. Kunskap och dialog framstår som vägen till ett sundare användande av internet. Framtidens psykologer kommer sannolikt att påverkas i sin yrkesutövning av den sänkta integriteten. Studien indikerar flera viktiga framtida forskningsområden och lyfter behovet av att belysa problematiken på psykologutbildningen. / Personal integrity is of great importance for the healthy development of an individual's identity, mental health and well-being and is influenced by the environment. Personal integrity is therefore an important parameter in a psychologist's therapeutic work. The purpose of the present qualitative study was to investigate how psychological students look at personal integrity in today's individual-centered society with internet and social media. Seven psychologist students at Stockholm University were interviewed. The result of a thematic analysis showed that the participants considered that the personal integrity means different things to different individuals, but is perceived to be adversely affected. The ability to maintain high integrity is perceived to be increasingly difficult. The Internet also tends to affect identity creation, especially among young people. Knowledge and dialogue are the way to a healthier use of the internet. The psychologists of the future are likely to be affected by their reduced integrity in their professional practice. The study indicates several important future research areas and highlights the need to highlight the problems during psychology education

Les récepteurs NMDA (NMDARs) sont des canaux cationiques activés par le glutamate. Les NMDARs participent au développement cérébral, à la plasticité synaptique, à l'apprentissage, à la mémoire et aux fonctions cognitives supérieures. Des variants pathogènes de GRIN2A, codant pour la sous-unité GluN2A des NMDARs, peuvent causer des épilepsies focales et encéphalopathies épileptiques de l'enfance avec troubles du langage et de la parole, connue sous le nom de spectre des épilepsies-aphasies (EAS). Les caractéristiques communes de l'EAS comprennent une activité épileptiforme âge-dépendante activée pendant le sommeil lent associées à des troubles de la parole, de la cognition et du comportement qui peuvent persister à l'âge adulte. Afin de commencer à identifier les événements précoces possiblement associés aux altérations de GluN2A, nous avons exploré le modèle correspondant de souris knock-out (KO) du gène Grin2a. Nous avons notamment recherché des altérations précoces de la communication vocale, de la (micro)structure cérébrale, et de l'activité électrique néocorticale. Nos données démontrent l'existence de plusieurs altérations à ces différents niveaux, parfois transitoirement à des stades spécifiques. De plus, les enregistrements néocorticaux mettent en évidence des anomalies de divers types liées au sommeil lent. Nos résultats indiquent également un rôle de GluN2A dans la communication vocale, dans l'organisation de la microstructure cérébrale, et dans la maturation des activités d’ondes lentes. Ces données suggèrent que les souris KO Grin2a représentent un modèle fiable pour appréhender les mécanismes physiopathologiques associés à l’EAS et leur séquence temporelle. / NMDA receptors (NMDARs) are cation channels that are gated by glutamate - the major excitatory neurotransmitter of the central nervous system. NMDARs participate in brain development, synaptic plasticity, learning, memory and high cognitive functions. Pathogenic variants in the GRIN2A gene, which encodes the GluN2A subunit of the NMDARs, can cause a group of childhood focal epilepsies and epileptic encephalopathies with speech and language dysfunction, known as the epilepsy-aphasia spectrum (EAS). Features shared in common by EAS disorders include age-dependent epileptiform activity activated in sleep associated with speech, neuropsychological and behavioral deficits that may persist in adulthood. In order to start in deciphering the early events possibly associated with the dysfunctioning of GluN2A-containing NMDARs, we have explored the corresponding Grin2a knock-out (KO) mouse model. That consisted in looking for early alterations of vocal communication, of brain (micro)structure, and of neocortical electrical activity. Our data demonstrated the existence of several alterations at those various levels. Some alterations were transient only, being detected at selective stages; also, neocortical recordings pointed for sleep-related anomalies of various types. Our data also indicated a role for GluN2A-containing NMDA receptors in vocal communication, fine organization of brain microstructure, and proper maturation of slow wave activity in sleep. Altogether, our data suggest that the Grin2a KO mice represent a reliable model to further elucidate the pathophysiological mechanisms associated with the disorders of EAS and their temporal sequences.

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Thèse numérisée par la Division de la gestion de documents et des archives de l'Université de Montréal

Background: Children born very preterm are at an elevated risk of behavioural adjustment problems, particularly Attention-Deficit/Hyperactivity Disorder (ADHD) or inattention/hyperactivity difficulties. Importantly, these risks remain even after controlling for the effects of social risk factors correlated with very preterm birth. Behavioural outcomes in follow-up studies of children born very preterm are typically assessed using parent reports only. However, the extent to which behavioural problems are evident across multiple contexts (i.e., parent or teacher report) is not well known. Furthermore, the neonatal neuropathology underlying these behavioural difficulties in this population remains poorly understood. Aims: Three research studies are undertaken primarily to examine: (1) the degree of agreement between parent and teacher reports of child behaviour adjustment, and the extent of situational (parent- or teacher-identified) and pervasive (parent- and teacher-identified) inattention/hyperactivity problems at ages 4, 6, and 9 years among children born very preterm and full-term; (2) to cross-validate the classification of children with situational and pervasive inattention/hyperactivity problems across the ages of 4 to 9, for a clinical diagnosis of ADHD at age 9 years; (3) to document risk of persistent ADHD symptoms between ages 4 and 9 years in children born very preterm, and to examine associations between qualitative measures of neonatal cerebral white matter injury/abnormality and quantitative volumetric measures of cerebral structural development, identified using magnetic resonance imaging (MRI) at term equivalent age, and children’s later risks of persistent symptoms. Persistent ADHD symptoms were defined as behavioural inattention/hyperactivity problems shown at ages 4, 6, and 9, along with meeting the criteria for an ADHD clinical diagnosis at age 9 years. Methods: As part of a prospective longitudinal study, a regional cohort of 110 very preterm (≤ 33 weeks of gestation) and 113 full-term children born between 1998 and 2000 were studied from birth to age 9 years. At term equivalent age, all children born very preterm and 10 children born full-term underwent an MRI scan that was analysed using qualitative measures for cerebral white matter injury/abnormality, and quantitative volumetric techniques with tissue segmentation and regional parcellation for cortical and subcortical grey matter, myelinated and unmyelinated white matter, and cerebrospinal fluid. At ages 4, 6 (corrected for the extent of prematurity), and 9 years (uncorrected), children were screened for behavioural adjustment problems including inattention/hyperactivity symptoms using the parent and teacher rated Strengths and Difficulties Questionnaire (SDQ). At age 9, the Development and Well-Being Assessment (DAWBA) structured psychiatric interview was also completed with primary caregiver and an independent clinical diagnosis of ADHD determined by a child psychiatrist blinded to child’s perinatal history and group status. Results: Agreement between parent and teacher reports regarding child behaviour adjustment was lower for children born very preterm than full-term (mean alternative chance-correlated coefficient, AC₁ = 0.63 vs. 0.80). Across all assessment time-points, very preterm birth was associated with on average a 2-fold increased risk of behavioural inattention/hyperactivity problems. These elevated risks largely reflected high rates of situational symptoms (very preterm = 22.3% − 31.7%; full-term = 10.9% − 16.7%). In contrast, rates of pervasive symptoms were relatively modest (very preterm = 6.8% − 11.5%; full-term = 4.7% − 7.3%). Examination of the predictive validity of inattention/hyperactivity problems identified using parent and teacher reports showed that children exhibiting situational symptoms at ages 4 and 6 were much less likely than those exhibiting pervasive symptoms, for a subsequent clinical diagnosis of ADHD at age 9 years (very preterm = 29% − 47.8% vs. 66.7% − 75%; full-term = 13.3% − 22.2% vs. 33.3% − 40%). Furthermore, receiver operating characteristic curves fitted to the data showed that children born very preterm exhibiting inattention/hyperactivity problems at two or three time-points (area under curve, AUC = .909) have better predictive validity for later ADHD diagnosis, compared to those exhibiting symptoms at age 4 (AUC = .794) or 6 years (AUC = .813) only. Children born very preterm were also at an elevated risk of persistent ADHD symptoms across the ages of 4 to 9 years, with the risk being 5-fold higher than their full-term peers (13.1% vs. 2.8%). Results also revealed possible associations between neonatal neuropathology and later risk of persistent ADHD symptoms. There were no significant linear associations between increasing severity of qualitative neonatal MRI measures of white matter injury/abnormality and very preterm children’s later risk of persistent ADHD symptoms. However, reduction in total cerebral tissue volumes and corresponding increase of cerebrospinal fluid (adjusted for intracranial volume) were significantly associated with increased risk of persistent symptoms in children born very preterm (p = .001). In terms of regional tissue volumes, total cerebral tissues in the dorsal prefrontal region showed the largest volumetric reductions among all the subregions in children born very preterm exhibiting persistent ADHD symptoms, with 3.2 ml (7%) and 8.2 ml (16%) lower tissue volumes than children born very preterm and full-term without persistent symptoms, respectively. Conclusions: Reliance on a single informant to examine child behaviour outcomes at a single time-point may lead to an under- or over-estimation of later ADHD risks. Combining reports from multiple informants and repeated assessments over time may provide better clinical prognostic validity. Children born very preterm are at an increased risk of behavioural inattention/hyperactivity problems during their early school years; although risks of more severe, pervasive problems are relatively modest compared with situational problems. Behavioural adjustment difficulties recognised as early as during preschool age using standardised behaviour screening tools can be a reliable indicator for identifying children born very preterm at risk of subsequent ADHD diagnosis. Finally, study findings suggest that increased risk of ADHD symptoms in children born very preterm can at least in part be accounted for by disturbances to neonatal cerebral growth and maturation.

The developing brain goes through a number of developmental periods during which it displays an increased sensitivity to exogenous disturbances. On such period is the so called “Brain growth spurt” (BGS) which in humans takes place starting from the third trimester of pregnancy and throughout the first few years of life. The corresponding period in rats and mice is the first postnatal weeks. Exposure to relatively modest concentrations of the brominated flame retardant PBDE-99 during the second week of life in mice causes a more or less permanent impairment in the ability of the animals to adjust properly to environmental changes at adulthood. This “late response on early exposure” reflects the long-term consequences of disrupting the developing brain during a sensitive time period. The cellular mechanisms underlying the behavioral effects are far from clear. To address the initial damage occurring around the time of exposure, the approach used in this thesis is to use proteomics to analyze the effects of PBDE-99 on protein expression soon (24 hours) after exposure of the neonatal mouse on postnatal day (PND) 10.The thesis comprises the effects on the proteome in three distinct brain parts: cerebral cortex, striatum and the hippocampus. In addition, an in vitro model was developed and used to evaluate the PBDE-99 effects on cultured cerebral cortex cells from embryonic rat brains. Gel-based proteomics (2D-DIGE) coupled to MALDI- or ESI-MS has been used throughout for the proteomics experiments, but other techniques aimed at analyzing both proteins and mRNA have also been used to better characterize the effects. Even if the protein complements expressed by the different brain parts and separated with 2D-DIGE are seemingly similar, the effects are apparently specific for the different brain regions. In hippocampus, PBDE induces effects on proteins involved in metabolism and energy production, while the effects in striatum point towards effects on neuroplasticity. PBDE-99 changes the expression of cytoskeletal proteins in the cerebral cortex 24 hours after exposure. Interestingly, in vitro exposure of cerebral cortex cells to a PBDE-99 concentration in the same order of magnitude as in the in vivo neonatal brain also induces cytoskeletal effects, in the absence of cytotoxicity. This may suggest effects on regulatory aspects of cytoskeletal dynamics such as those involved in neurite sprouting. This thesis also addresses the problems involved in presenting proteomics data. Many of the available methods and approaches for presenting transcriptomics data are not suitable for isoform rich protein data. Modifications of existing methods and the development of a new approach (DEPPS) is also presented. Most importantly, the thesis presents the application and usefulness of proteomics as hypothesis generating techniques in neurotoxicology.