La fasciculation des axones joue un rôle essentiel dans le développement des réseaux neuronaux. Cependant, la dynamique de la fasciculation axonale, ainsi que les mécanismes biophysiques à l’œuvre dans ce processus, demeurent encore très mal compris. En vue d'étudier les mécanismes de fasciculation d'axones ex vivo, nous avons développé un système modèle simple, constitué par des explants d'épithélium olfactif de souris embryonnaires en culture, à partir desquels poussent les axones des neurones sensoriels olfactifs. Grâce à une étude en vidéomicroscopie, nous avons observé que ces axones interagissent de façon dynamique par leur fibre, à la manière de fermetures éclair pouvant se fermer ("zippering") ou s'ouvrir ("unzippering"), ce qui conduit respectivement à la fasciculation ou à la défasciculation des axones. Mettant à profit cette nouvelle préparation expérimentale pour l'étude des interactions dynamiques entre axones, nous avons développé une analyse biophysique détaillée des processus de zippering/unzippering.Nous mettons en évidence dans notre travail l'existence d'un mécanisme biophysique cohérent de contrôle des interactions locales entre fibres axonales. Ce mécanisme local est à mettre en relation avec les changements de la structure globale du réseau axonal (degré de fasciculation) qui s'opèrent sur une échelle temporelle plus longue. Enfin, nous discutons la signification fonctionnelle de nos observations et analyses, et proposons un nouveau rôles de la tension mécanique dans le développement du système nerveux : la régulation de la fasciculation des axones et, en conséquence, de la formation des cartes topologiques au sein des réseaux neuronaux. / While axon fasciculation plays a key role in the development of neural networks, very little is known about its dynamics and the underlying biophysical mechanisms. In a model system composed of neurons grown ex vivo from explants of embryonic mouse olfactory epithelia, we observed that axons dynamically interact with each other through their shafts, leading to zippering and unzippering behaviour that regulates their fasciculation. Taking advantage of this new preparation suitable for studying such interactions, we carried out a detailed biophysical analysis of zippering, occurring either spontaneously or induced by micromanipulations and pharmacological treatments.We show that there is a consistent mechanism which governs local interactions between axon shafts, supported by broad experimental evidence. This mechanism can be reconciled with changes in global structure of axonal network developing on slower time scale, analogically to well-studied relation between local relaxations, and topological changes and coarsening in two-dimensional liquid foams. We assess our observations and analysis in light of possible in vivo functional significance and propose a new role of mechanical tension in neural development: the regulation of axon fasciculation and consequently formation of neuronal topographic maps.

Orientador: Jorg Kobarg / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-14T01:48:42Z (GMT). No. of bitstreams: 1 Lanza_DanielCarlosFerreira_D.pdf: 39179290 bytes, checksum: cbd84a5b7ba74e985bc1fc48595debd6 (MD5) Previous issue date: 2009 / Resumo: A proteína FEZ1 foi caracterizada inicialmente como um ortólogo da proteína UNC76 de C. elegans, responsável pelo desenvolvimento e fasciculação neuronal nesse verme. Estudos subsequentes demonstraram sua atuação em processos de desenvolvimento neuronal, polarização celular, mecanismos de transporte associado à kinesinas e transporte de vesículas e mitocôndrias. Outros trabalhos demonstraram que a superexpressão de FEZ1 interfere no ciclo de vida de alguns tipos de vírus como HIV e JCV. FEZ1 é capaz de interagir com mais de 51 proteínas diferentes, e participa em muitos processos celulares. Observamos que FEZ1 apresenta ausência de estrutura molecular rígida, sendo pertencente à classe das natively unfolded proteins, e é capaz de formar dímeros em solução. Essa observação condiz com sua extrema capacidade de interagir com muitas proteínas diferentes. A capacidade de FEZ1 interagir com outras proteínas é influenciada pela fosforilação da sua região C-terminal por diferentes isoformas de PKC. FEZ1 interage e colocaliza com NEK1 e com CLASP2 em células de mamífero, em uma região candidata ao centrossomo. Essas interações são dependentes da região coiled-coil presente na parte C-terminal de FEZ1, e ocorrem em regiões coiled-coil de CLASP2 e NEK1. A interação com CLASP2 é rompida quando FEZ1 é fosforilada por PKC. A superexpressão de FEZ1 causa o fenótipo flower like observado em células de alguns tipos de leucemia. Nós observamos que FEZ1 interage e colocaliza com a e ?-tubulinas e que a formação desse fenótipo em células HEK293 ocorre devido a uma alteração na organização dos microtúbulos causada pelo excesso de FEZ1. A formação do fenótipo flower like é influenciada por ativação das vias de PKC e PI3K. Os dados obtidos durante o nosso trabalho indicam que FEZ1 é uma proteína intrinsecamente desenovelada, que atua em processos celulares associados ao citoesqueleto e centrossomo em conjunto com NEK1 e CLASP2, e que defeitos em sua regulação, possivelmente pelas vias de PKC ou PI3K, causam alteração da organização dos microtúbulos originando núcleos flower like. / Abstract: FEZ1 was identified first as a orthologue of C elegans UNC-76 protein, that plays functions related to neuronal development in this worm. Subsequent studies, shows FEZ1 functions in neuronal development process, cell polarization, transport mechanisms associated to kinesins and vesicular and mitochondrial transports. Other works showed that FEZ1 superexpression interfere in the life cycle of some viral types such as HIV and JCV. FEZ1 is able to interact with more than 51 different proteins and participates in several cellular processes. We observed that FEZ1 has a mobile molecular structure, is a member of the natively unfolded protein class, and can form dimers in solution. This observation is in agreement with its capacity to interact with a large number of different proteins. The capacity of FEZ1 to interact with other proteins is influenced by different PKC isoforms phosphorylation in its C-terminal region. FEZ1 interacts and co-localizes with NEK1 and CLASP2 in a centrossomal candidate region of mammalian cells. These interactions are dependent of a coiled coil inside the C-terminal region of FEZ1, and occur in dependence of coiled coil regions of NEK1 and CLASP2. The interaction between FEZ1 and CLASP2 is abolished after FEZ1 phosphorylation by PKC. The FEZ1 overexpression causes the flower like phenotype observed in cells of some leukemias. We observed that FEZ1 interacts and co-localizes with _ and _-tubulins and that the phenotype formation in HEK293 cells is mediated by an atypical organization of microtubule spindles, caused by overexpression of FEZ1. The flower like phenotype formation is influenced by activation of PKC and PI3K pathways. The data generated by our work indicate that FEZ1 is an intrinsically unfolded protein, that works in cellular processes associated to the cytoskeleton in conjunct with NEK1 and CLASP2, and that defects in its regulation, maybe via the PKC or PI3K pathways, causes alterations in microtubule organization and formation of the "flower like" nuclei. / Doutorado / Bioquimica / Doutor em Biologia Funcional e Molecular

Hintergrund: Der genaue Pathomechanismus zur Entstehung des benignen Faszikulations- Crampus-Syndrom ist nicht bekannt, und es wurde noch nie eine größere Anzahl dieser Patienten mittles des threshold trackings untersucht. Material und Methoden: 18 Patienten mit einem BFCS und 15 gesunde Probanden wurden mithilfe des threshold trackings, welches eine Methode zur Messung von Exzitabilitätsparametern von peripheren Nerven in vivo ist, untersucht und die Ergebnisse verglichen. Ergebnisse: Die stärksten Unterschiede zeigten sich im threshold electrotonus, der current/threshold relationship und der stimulus-response-curve. Im threshold electrotonus war insbesondere die Schwellenwertzunahme auf hyperpolarisierende Reize signifikant geringer bei einer Reizstärke von -40%, -70% und -100% des Kontrollimpulses (p < 0,01). Die current/threshold relationship war in hyperpolasierender Richtung bei den BFCS Patienten steiler als bei der gesunden Kontrollgruppe (p < 0,05). Außerdem benötigten sie eine deutlich geringere Reizintensität, um 50% des maximalen Summenaktionspotentials des Muskels auszulösen (p < 0,05). Schlussfolgerung: Die Ergebnisse weisen auf eine veränderte Expression oder Kinetik der HCN-Kanäle an peripheren Nerven der Patienten mit einem BFCS hin und geben folglich neue Hinweise auf die Entstehung dieser Erkrankung. Da zum ersten Mal ein Zusammenhang zwischen der Veränderung der HCN-Kanäle und dem BFCS gezeigt werden konnte, sollten sich zukünftige Studien darauf konzentrieren, genauere Informationen über diese Pathologie zu erlangen.

Orientador: Jorg Kobarg / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-21T03:42:39Z (GMT). No. of bitstreams: 1 Migueleti_DeividLucasdosSantos_M.pdf: 8057948 bytes, checksum: ef239a4533686a90e511e97afd0f97ba (MD5) Previous issue date: 2012 / Resumo: A proteína UNC-76 foi identificada como necessária para a fasciculação e elongação de axônios do verme Caenorhabditis elegans durante o desenvolvimento do sistema nervoso. A homóloga de mamíferos FEZ1 apresenta altos níveis de expressão em tecidos neuronais e camundongos knockout para o gene FEZ1 apresentam desvios de comportamento que remetem a desordens neurológicas. O papel de FEZ1 no desenvolvimento do sistema nervoso parece residir na sua associação com elementos do citoesqueleto e vias de sinalização (e.g., PKC?, E4B, DISC1) que conduzem o crescimento axonal e a polarização celular. Trabalhos do grupo mostram que FEZ1 é uma proteína multifuncional (hub), capaz de interagir com mais de 50 parceiros através de seus domínios coiled-coil. Além disso, a superexpressão de FEZ1 em células HEK293 provoca o aparecimento de núcleos multilobulados, um fenótipo comum em alguns tipos de leucemia. Nesse trabalho foi investigado o papel de FEZ1 nos mecanismos causadores dos núcleos multilobulados e as consequências funcionais de sua superexpressão na viabilidade celular, tentando extrapolar esse modelo para leucemias. Análises in silico de diversas leucemias mostraram que FEZ1 está superexpressa em LMAs e que isso pode se relacionar à ocorrência da fusão 11q23/MLL. A expressão de FEZ1 na linhagem leucêmica THP-1 foi detectada por Western blotting, mas, a expressão em PBMCs de pacientes ainda permanece sem provas empíricas. Para avaliar as consequências funcionais da superexpressão, uma linhagem com expressão estável e indutível foi obtida e utilizada em ensaios de proliferação e resistência a quimioterápicos. Porém, não foram observadas diferenças entre as linhagens expressando a fusão FLAG-FEZ1 e as que expressavam o FLAG tag apenas. Em um ensaio de IP-MS utilizando tais linhagens, foram identificadas proteínas cuja interação com FEZ1 pode ser modulada pela atividade de PKCs. Finalmente, a cotransfecção de FEZ1 inteira com coiled-coils C-terminais diminui a formação de núcleos multilobulados em quase 40%. A transfecção com o mutante FEZ1 nocys contendo 5 cisteínas mutadas não teve o mesmo efeito, mas, novos experimentos são necessários para determinar o potencial de sinergismo que esses dois componentes podem ter sobre a ocorrência desse fenômeno / Abstract: The protein UNC-76 was identified as necessary for fasciculation and elongation of axons of the worm Caenorhabditis elegans during development of the nervous system. The mammalian homologue FEZ1 is mostly expressed in neuronal tissues and FEZ1 knockout mice present behavior abnormalities that resemble neurological disorders. The role of FEZ1 in the development of the nervous system seems to lie in its association with cytoskeletal elements and signaling pathways (e.g., PKC?, E4B, DISC1) regulating axon outgrowth and cell polarization. The studies of our group have shown that FEZ1 is a hub, able to interact with more than 50 partners through its coiled-coil domains. Furthermore, overexpression of FEZ1 in HEK293 cells causes the appearance of flower-like nuclei, a common phenotype to certain types of leukemia. In this work the role of FEZ1 in the mechanisms of flower-like nuclei formation and functional consequences of its overexpression on cell viability were investigated, attempting to extrapolate this model for leukemias. In silico analysis of several leukemias showed that FEZ1 is overexpressed in AML patients and that this may relate to the occurrence of 11q23/MLL genetic fusion. FEZ1 expression in leukemic THP-1 cells was detected by Western blotting, but the expression in PBMCs of leukemic patients still lacks empirical evidence. To assess the functional consequences of overexpression, cell lineage with stable and inducible expression of FEZ1 was obtained and used in proliferative assays. However, it was not observed any differences between lineages expressing FLAG-FEZ1 fusion protein or FLAG tag alone. IP-MS assay using these lineages identified proteins whose interaction with FEZ1 could be modulated by the activity of PKCs. Finally, cotransfection of C-terminal coiled-coils and FEZ1 full-length decreases flower-like nuclei formation to nearly 40%. Transfection with FEZ1nocys mutant containing five substituted cysteines did not play the same, but further experiments are needed to determine the potential synergism these two components may have on this phenomenon / Mestrado / Genetica Animal e Evolução / Mestre em Genética e Biologia Molecular

The anatomy of the cranial peripheral nervous system has been studied for over a century, yet surprisingly little is known about how the nerves are guided to their targets. The study of the development of these nerves has important implications for our understanding of craniofacial anomalies and possible treatments for both injury and genetic disorders of nerve development such as Goldenhar-Gorlin syndrome. We have discovered that retinoic acid (RA) may play a role in the development of the trigeminal nerve. Inhibition of retinoic acid receptors (RAR) results in trigeminal nerves that become unbundled or defasciculated in the eye region. To further understand how RA is affecting trigeminal development we searched for genes downregulated in response to RAR inhibition by the inhibitor BMS-453 and have identified neurotrophin-3 (NT-3), activated leukocyte cell adhesion molecule (ALCAM) and Semaphorin 4B (Sema4B). We have analyzed the expression patterns of Sema4B and NT-3 by in situ hybridization and have found NT-3 expression in the eye and Sema4B in the embryonic target of the trigeminal nerve, lens of the eye and in the pharyngeal arches. ALCAM has been analyzed via qRT-PCR and its transcription is downregulated just prior to the observed defasciculation phenotype. The pattern of expression of these genes combined with known expression of NT-3 receptors allows us to suggest a model whereby RA signaling regulates Sema4B, ALCAM and NT-3, which support the survival, guidance and fasciculation of the trigeminal nerve. This work has the potential to better understanding of the complex nature of cranial nervous system development.

in English While axon fasciculation plays a key role in the development of neural networks, very lit- tle is known about its dynamics and the underlying biophysical mechanisms. In a model system composed of neurons grown ex vivo from explants of embryonic mouse olfactory epithelia, we observed that axons dynamically interact with each other through their shafts, leading to zippering and unzippering behaviour that regulates their fasciculation. Taking advantage of this new preparation suitable for studying such interactions, we carried out a detailed biophysical analysis of zippering, occurring either spontaneously or induced by micromanipulations and pharmacological treatments. We show that zippering arises from the competition of axon-axon adhesion and me- chanical tension in the axons. This is upheld on quantitative level by conforming change of network global structure in response to various pharmacological treatments, without active involvement of growth cones. The calibrated manipulations of interacting shafts provide qualitative support for the hypothesis, and also allow us to quantify the mechan- ical tension of axons in our system. Furthermore, we introduce a biophysical model of the zippering dynamics, which efficiently serves the purpose of estimating the magnitude of remaining involved...