Thesis (doctoral)--Lund University, 1992. / Added t.p. with thesis statement inserted.

Thesis (doctoral)--Lund University, 1992. / Added t.p. with thesis statement inserted.

M.A. (Psychology) / Sudden Infant Death Syndrome is the most prevalent cause of death in infants between one and twelve months of age. Most deaths attributed to Sudden Infant Death Syndrome occur between 1 and 4 months of age. There is a marked decrease after this age in the number of deaths classified as Sudden Infant Death Syndrome. It is usually defined as the sudden death of any infant usually during sleep which is unexpected by history and in which a thorough postmortem examination tails to demonstrate an adequate cause tor death (Foundation for the Study of Infant Deaths, 1989) • Epidemiologic, pathologic and physiologic data suggest the mechanism ot Sudden Infant Death Syndrome is complex, characterized by interaction at many levels ot the neural axis, between the organism and the environment and spanning both pre- and post-natal lite. Observations suggest that the Sudden Infant Death Syndrome infant has experienced adverse influences prenatally Which may make him peculiarly vulnerable to postnatal environmental stress (Valdes Dapena, 1988). However, the specific nature and cause of this condition continues to elude both scientists and practitioners. In the last few years research has shed some light on various epidemiologic aspects of the problem, on pathologic anatomy and on clinical issues such as the relative importance of spontaneous, prolonged, idiopathic apnea. Some Sudden Infant Death Syndrome victims showed evidence of neonatal brain dysfunction, including abnormalities in respiration, feeding and temperature regulation and have been shown to have pathologic abnormalities consistent with chronic hypoxia (Kelly' Shannon, 1982). Once again, however, the research appears not to be conclusive, leaving many unanswered questions...

L’étude des inositols hautement phosphorylés est un domaine en pleine expansion. Leurs essors ne datent que d’une dizaine d’années, mais de nombreuses fonctions y sont déjà associées bien qu’ils en restent sans doute encore à découvrir. Les inositols phosphates (incluant les inositols hautement phosphorylés) s’inscrivent dans un cycle dont le représentant le plus connu est inositol 1,4,5-trisphosphate (Ins(1,4,5)P3). De ce fait, chaque inositol phosphate influence directement ou indirectement les autres membres de ce cycle.<p>Au cours de la thèse, nous avons pu éclaircir une controverse de la littérature sur la voie de synthèse des inositols hautement phosphorylés. Grâce à un modèle de cellules MEF (mouse embryonic fibroblast) n’exprimant aucune des trois isoformes de l’inositol 1,4,5-trisphosphate 3-kinase (ITPK) et à l’aide des cellules souches déficientes pour l’inositol polyphosphate multikinase (IPMK), nous avons pu révéler le rôle majeur de cette dernière dans la génération de l’InsP5 et l’InsP6.<p>Dans un second temps, nous avons comparé la neurogenèse de ces cellules souches IPMK+/+ et IPMK-/- mises dans un milieu de différenciation par défaut (DDM). Les cellules dépourvues de l’IPMK entrent en apoptose et se différencient très difficilement en progéniteurs neuronaux et en neurones. Afin de comprendre le mécanisme sous-jacent pouvant expliquer ce phénomène, nous avons réalisé des PCRs quantitatives qui ont montré une sous expression des gènes du neuroectoderme ainsi qu’une augmentation de l’expression de gènes du mésoderme dans les cellules IPMK-/- par rapport aux cellules IPMK+/+. De plus, nous avons découvert que le phénomène d’apoptose observé au cours de la différenciation en DDM était spécifique à ce milieu. En effet, nous n’avons pas pu mettre en évidence un tel phénomène au cours de la différenciation en corps embryoïdes.<p>Durant la thèse, nous avons également développé des anticorps dirigés contre l’isoforme B de l’inositol 1,4,5-trisphosphate 3-kinase et contre la forme native de l’IPMK. Ceci nous a permis de mener à bien nos expériences et d’ouvrir de futures perspectives de recherche.<p>En conclusion, nous avons démontré le rôle majeur de l’IPMK dans la voie de synthèse des inositols hautement phosphorylés. Nous avons également découvert que l’IPMK est très importante pour la survie de ces cellules souches en cours de différenciation et nous avons également introduit une nouvelle fonction pour l’IPMK dans la neurogenèse.<p> / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished

Historically, the role of immune cells in the nervous system was predominantly examined throughthe lens of disease. In recent years, studies have shown that the complex, orchestrated events of immune activity throughout embryonic and postnatal critical periods are crucial for proper nervous system development. While previous studies have suggested limited immune heterogeneity in the adult brain, the diverse roles of the hippocampus in cognition and pathological development would suggest variation of immune cells in this region. Specifically, the hippocampus is known to be a site of adult neurogenesis. However, fundamental traits of immune cells in this region have not been well characterized. In chapter one, I present a summary of literature that discusses what was previously known of immune regulation of adult neurogenesis during health and disease. In chapter two, I compare different reporter lines and marker genes to evaluate responses in various cell types in the neurogenic niche and in other regions of the brain in the context of injury and pharmacological modulation. I discuss preliminary evidence suggesting microglial depletion may result in phenotypic changes in astrocytes throughout the hippocampus. In chapter three, I provide evidence of heterogeneity in myeloid-lineage cells in the hippocampus. I leveraged the highthroughput nature of cell suspension based single cell RNA-sequencing to collect transcriptomes of over 20,000 myeloid lineage cells from murine hippocampi. Using a series of bioinformatic techniques, I was able to computationally dissect different populations within this system and found spatial mapping of one distinct subset specifically localized to the neurogenic niche of the hippocampus. The transcriptomic signature of these cells alongside immunoreactivity to candidate genes, and morphological properties of this population resemble those of reactive microglia associated with the restriction of neurodegenerative diseases. In chapter four, I discuss how the immune landscape of the hippocampus responds to perturbation using a model of Focused Ultrasound mediated Blood-Brain Barrier opening. Subtypes of myeloid lineage cells change in composition and in transcriptomic response. We find distinct, temporally defined transcriptional responses in microglial and macrophage populations, indicating discrete roles for microglia and macrophages in immune activity during the transition from acute to chronic response. Together, these findings point towards diverse properties of microglia in the adult hippocampus.

Primary cilia are sensory organelles that are important for initiating cell division in the brain, especially through sonic hedgehog (Shh) signaling. Several lines of evidence suggest that the mitogenic effect of Shh requires primary cilia. Proliferation initiated by Shh signaling plays key roles in brain development, in neurogenesis in the adult hippocampus, and in the generation of glial cells in response to cortical injury. In spite of the likely involvement of cilia in these events, little is known about their characteristics. Centrosomes, which are associated with primary cilia, also have multiple influences on the cell cycle, and they are important in assembling microtubules for the maintenance of the cell’s cytoskeleton and cilia. The cilia of terminally differentiated neurons have been previously examined with respect to length, incidence, and receptors present. However, almost nothing is known about primary cilia in stem cells, progenitors, or differentiated glial cells. Moreover, it is not known how the properties of cilia and centrosomes may vary with cell cycle or proliferative potential, in brain or other tissues. This dissertation focuses first on neurogenesis in the hippocampal subgranular zone (SGZ). The SGZ is one of the few brain regions in mammals that gives rise to a substantial number of new neurons throughout adulthood. The neuron lineage contains a progression of identifiable precursor cell types with different proliferation rates. This present study found that primary cilia were present in every cell type in the neuronal lineage in SGZ. Cilium length and incidence were positively correlated among these cell types. Ciliary levels of adenylyl cyclase type III (ACIII) levels relative to ADP-ribosylation factor-like protein 13b (Arl13b) was higher in neurons than in precursor cells and glia, and also changed with the cell cycle. G-protein coupled receptors, SstR3, MCHR1, and Gpr161 receptors were only found in neuronal cilia. The levels and distribution of three centrosomal proteins, γ-tubulin, pericentrin and cenexin in neurons was different from the distributions in precursors and glia. The second focus of study is glial responses to injury in the neocortex, which has been widely studied as an injury model. This study found that in the normal adult somatosensory cortex, primary cilia were present in astrocytes and polydendrocytes but not in microglia. Following injury, the incidence of primary cilia decreased in astrocytes. Also, a new cell type expressing GFAP, NG2 and Olig2 was seen 3 days following injury, but was not present in normal mice. The characteristics of primary cilia and centrosome described here suggest that in stem cells and progenitors their characteristics may be well suited for proliferation, whereas in neurons, the cilia and centrosomes are important for other sensory functions.

No description available.

The purpose of the study was to investigate the role of metabotropic glutamate receptors (mGluR) in the ontogeny of amphetamine-induced behavioral sensitization. Eleven-day-old rat pups were given five daily bilateral infusions of the mGluR antagonist, (RS)-methyl-4-carboxyphenylglycine (MCPG) followed by a systemic injection of amphetamine and locomotor activity was measured. It was hypothesized that rats receving amphetamine pretreatment and an amphetamine challenge would exhibit a significant increase in activity, indicating short-term behavioral sensitization. As predicted, repeated amphetamine administration during the pretreatment phase produced progressively enhanced locomotor activity, indicating the development of behavioral sensitization. The effect of MCPG on locomotor activity appears to be independent from the effects of amphetamine-induced locomotor activity and MCPG pretreatment failed to consistently block the expression of behavioral sensitization in rats pretreated with amphetamine and challenged with amphetamine. This study demonstrated that contrary to previous studies on adult rats, the mGluR system does not appear to consistently mediate the development of amphetamine-induced sensitization in neonatal rats.

Les circuits neuronaux peuvent générer une panoplie de rythmes. Nous pouvons séparer les mécanismes de création de ces rythmes en deux grands types. Le premier consiste de circuits contrôlés par des cellules « pacemakers », ayant une activité rythmique intrinsèque, comme dans le ganglion stomatogastique des crustacés. Le deuxième consiste de circuits multi-neuronaux connectés par un réseau synaptique qui permet une activité rythmique sans la présence de neurones pacemakers, tel que démontré pour les circuits de la nage chez plusieurs vertébrés. Malgré nos connaissances des mécanismes de rhythmogénèse chez les vertébrés adultes, les mécanismes de la création et la maturation de ces circuits locomoteurs chez les embryons restent encore inconnus. Nous avons étudié cette question à l’aide du poisson-zébré où les embryons débutent leur activité motrice par des contractions spontanées alternantes à 17 heures post-fertilisation (hpf). Des études ont démontré que cette activité spontanée n’est pas sensible aux antagonistes de la transmission synaptique chimique et ne requiert pas le rhombencéphale. Après 28 hpf, les embryons commencent à nager et se propulser en réponse au toucher. Des études antérieures on démontré que l’apparition de la nage nécessite le rhombencéphale et la transmission synaptique chimique. Cette thèse explore la possibilité que ces changements comportementaux représentent la progression d’un circuit contrôle par un pacemaker à un circuit ou le rythme provient d’un circuit distribué. En mesurant le groupement des contractions de l’activité spontanée, plutôt que la fréquence moyenne, nous avons découvert une nouvelle forme d’activité spontanée qui débute à 22 hpf. Cette activité consiste de deux contractions alternantes à succession très rapide. Contrairement à l’activité spontanée présente dès 17 hpf cette nouvelle forme d’activité requiert le rhombencéphale et la transmission synaptique chimique, comme démontré pour la nage qui apparait à 28 hpf. Cette forme de comportement intermédiaire représente potentiellement une étape transitoire lors de la maturation des circuits moteurs. / Neuronal circuits are capable of generating diverse forms of rhythmic activity. Mechanisms underlying rhythmogenesis can be separated into two main groups. First, pacemaker central pattern generators (CPGs) are composed of neurons that have intrinsic oscillatory properties, such as the lobster stomatogastric ganglion. Second, CPGs driven by network-based dynamics rely on synapse-mediated cell properties, such as locomotion in aquatic vertebrates. Despite an existing wealth of knowledge obtained through studying frog and lamprey swimming CPGs, the means by which a locomotor CPG develops remains elusive. Here, we propose to address this question using the zebrafish embryo, for its rapid development, optical transparency and stereotyped behaviour. Motor activity in zebrafish embryos begins with spontaneous activity around 17 hours post-fertilization (hpf). Studies have shown that this activity is not sensitive to antagonists of chemical neurotransmission, and does not require the hindbrain. By 28 hpf, they become able to swim, and generate low-amplitude alternating contractions at a rate of 30 Hz. This study explores the developmental window between the onset of motility and the onset of a mature locomotor output, such as swimming, with the objective of uncovering key steps in motor network maturation. By measuring the grouping of contractions rather than overall frequency of spontaneous activity, we uncovered a novel form of spontaneous activity, starting around 22 hpf. This activity consists of two alternating contractions in rapid succession. In contrast to early spontaneous activity, this motor activity requires glutamatergic neurotransmission and input from the hindbrain, as previously shown for swimming at 28 hpf. This intermediate behavior may reveal an important step in the maturation of the motor network.

La diferenciació dels precursors neuronals en cèl·lules especialitzades implica una restricció de la seva capacitat proliferativa i la sortida definitiva del cicle cel·lular. Entre les proteïnes HLH activadores de la diferenciació hi ha les proteïnes E (E47, E12, HEB, E2-2), les quals s’expressen a la majoria de teixits. Al nostre laboratori es va descriure que la proteïna E47 forma heterodímers amb la proteïna HLH específica de teixit NeuroD, i activa l’expressió del receptor del BDNF (TrkB) i l’inhibidor de cicle p21CIP en resposta a la senyal diferenciadora d’àcid retinoic (RA). La correcta expressió del receptor TrkB juga un paper clau en el desenvolupament del sistema nerviós en vertebrats i la seva alteració s’ha relacionat amb diferents malalties humanes importants. En aquest treball s’ha demostrat que la quinasa MLK2 interacciona amb la bHLH E47 en cèl·lules de neuroblastoma SHSY-5Y. Es proposa que la MLK2 controla l’activitat del factor bHLH E47 a través de la seva fosforilació, la qual redueix l’activació del promotor de trkB. A més, la inhibició de la MLK2 augmenta l’expressió de l’mRNA de trkB in vivo explicant perquè aquesta inhibició no només prevé l’activació dels processos de mort cel·lular sinó que també ajuda a les vies de supervivència. D’altra banda, estudis molt recents revelen la importància dels processos de localització d’mRNAs als axons i a les dendrites i la seva traducció localitzada. Conèixer com es regula la localització dels mRNAs i la seva traducció localitzada a nivell molecular ajuda a entendre aspectes fonamentals de la plasticitat i la diferenciació neuronal. Durant el transport dels mRNAs, la seva traducció està reprimida i aquesta s’activa a llocs concrets com a resposta a senyals sinàptics, i en conseqüència, s’activa la plasticitat neuronal. Prèviament, al nostre laboratori, es va demostrar que la proteïna KIS pot estimular la traducció localitzada d’mRNAs, afavorir el creixement neurític i la supervivència neuronal. En aquest treball demostrem que la KIS interacciona amb proteïnes i mRNAs implicats en activitat sinàptica, els quals són transportats a través de partícules mRNP. La nostra hipòtesi és que quan el grànul transportat per KIF3A arriba al seu destí, diversos estímuls sinàptics possiblement indueixin l’activació de la quinasa Src, la qual fosforila la KIS, activant la traducció dels mRNAs transportats. / La diferenciación de precursores neuronales en células especializadas implica la restricción de su capacidad proliferativa y la salida definitiva del ciclo celular. Entre las proteínas HLH activadoras de la diferenciación están las proteínas E (E47, E12, HEB, E2-2) las cuales se expresan en la mayoría de los tejidos. En nuestro laboratorio se describió que la proteína E47 forma heterodímeros con la proteína HLH especifica de tejido, NeuroD, y activa la expresión del receptor de BDNF (TrkB) y el inhibidor de ciclo p21CIP en respuesta a la señal diferenciadora del ácido retinoico (RA). La correcta expresión del receptor TrkB juega un papel clave en el desarrollo del sistema nervioso en vertebrados y su alteración se ha relacionado con diferentes enfermedades humanas importantes. En este trabajo se ha demostrado que la quinasa MLK2 interacciona con la bHLH E47 en células de neuroblastoma SHSY-5Y. Se propone que MLK2 controla la actividad del factor bHLH E47 a través de su fosforilación, la cual reduce la activación del promotor de trkB. Además la inhibición de MLK2 aumenta la expresión del mRNA de trkB in vivo explicando por qué esta inhibición no sólo previene la activación de los procesos de muerte celular sino que también ayuda a las vías de supervivencia. Por otro lado, estudios muy recientes revelan la importancia de los procesos de localización de mRNAs en axones y dendritas y de su traducción localizada. Conocer cómo se regula la localización de los mRNAs y su traducción localizada a nivel molecular ayuda a entender aspectos fundamentales de la plasticidad y la diferenciación neuronal. Durante el transporte de los mRNAs su traducción está reprimida y ésta se activa en lugares concretos en respuesta a señales sinápticas resultando en la activación de la plasticidad neuronal. Previamente, en nuestro laboratorio, se demostró que la proteína KIS puede estimular la traducción localizada de mRNAs, favorecer el crecimiento neurítico y la supervivencia neuronal. En este trabajo demostramos que KIS interacciona con proteínas y mRNAs implicados en actividad sináptica, los cuales son transportados a través de partículas mRNPs. Nuestra hipótesis es que cuando el gránulo transportado por KIF3A llega a su destino, varios estímulos sinápticos posiblemente induzcan la activación de la quinasa Src la cual fosforila KIS, activando la traducción de los mRNAs transportados. / The differentiation of neuronal precursors in specialized cells induces an increase of a restriction of their proliferative capacity and a complete exit of the cell cycle. Among the HLH protein activators of differentiation the E protein family (E47, E12, HEB, E2-2) is expressed in most of the tissues. In our laboratory it has been described that in response to the differentiating signal of retinoic acid (RA), E47 heterodimerizes with the HLH protein tissue specific NeuroD which activates the expression of the receptor BDNF (TrkB) and the cell cycle p21CIP inhibitor. TrkB expression plays a key role in the nervous system development in vertebrates, and its alteration has been related with different types of important human diseases. In the present work we identified the kinase MLK2 as an E47-interaction protein in SHSY-5Y human neuroblastoma cells. We propose MLK2 as a controller of the BDNF receptor TrkB through the phosphorylation of bHLH transcription factor E47 which reduces the activation of trkB promoter. Furthermore, MLK2 inhibition increases trkB mRNA expression in vivo. These results could explain the reason why the inhibition of MLKs avoid the activation of cell death program and also increase the cell survival pathway being a key component of their neuroprotector potential. In the other hand, recent studies some recent work reveal the importance of mRNA localization in axons and dendrites and its local translation. Unraveling how mRNA localization and its translation are regulated at molecular level will help to understand basic processes of neuronal differentiation and plasticity. Translation is inhibited during mRNA transport, and is activated in specific synapses in response to synapse signals resulting from activation of neuronal plasticity. Previous work from our laboratory demonstrated that protein kinase KIS can stimulate the local translation of mRNAs, increase the neuritic outgrowth and the neural survival. In the present work we demonstrate that KIS can interact with transported granular proteins and mRNAs importants for the synaptic activity. Our hypothesis is that when the granule reaches his fate through KIF3A, some synaptic stimuli induce the activation of the kinase Src, which phosphorylates KIS, therefore activating the transported transcript.