No description available.

The structure and functions of brain show sexual dimorphism in vertebrates. Brain sexual differentiation is resulted from the neural development. The neural development is determined not only by the genetic regulation, but also by the extrinsic environmental influences. Serotonin (5-hydroxytryptamine, 5-HT ) functions as a neurotransmitter or/and neuromodulator in the central nervous system. Serotonin plays a role in the neural development via serotonin receptors. The sexual differentiation of tilapia is influenced by water temperature. The lower temperature induces a higher proportion of female while the elevated temperature induces a higher proportion of male in tilapia. In the present study, the influence of temperature on the proliferation of the neurons was investigated. These results show that the proliferation of neurons are varied with the temperature. The elevated temperature influences the proliferation of neurons via central serotonin system. Serotonin 1A receptor is involved in the serotonin-induced proliferation of neuron.

京都大学 / 0048 / 新制・課程博士 / 博士(生命科学) / 甲第21401号 / 生博第402号 / 新制||生||53(附属図書館) / 京都大学大学院生命科学研究科統合生命科学専攻 / (主査)教授 見学 美根子, 教授 上村 匡, 教授 渡邊 直樹 / 学位規則第4条第1項該当 / Doctor of Philosophy in Life Sciences / Kyoto University / DFAM

Sexual differentiation is divided into gonadal sexual differentiation and brain sexual differentiation in the teleosts. Gonadal sexual differentiation is regulated by brain sexual differentiation. Brain sexual differentiation is resulted from the neural development, which lead to the sexual dimorphism of both structure and functions of brain. The neural development is influenced by the genetic factors and the external environmental factors. The lower temperature induces a higher proportion of female while the elevated temperature induces a higher proportion of male in tilapia. In addition, there is sexual difference in effects of temperature on the activity of brain neurochemicals. Water temperature plays an important role on the development of central neurotransmitter systems and sexual differentiation during the developing period. In the present study, the primary neural culture cloned from the female and male tilapia¡AOreochromis mossambicus was used. The difference of the physiological characteristics between the neural cells derived from the females and males, were investigated. These results show that the elevated temperature has an effect to enhance the proliferation in both primary neural culture of females and males.

No description available.

abstract: Dendrites are the structures of a neuron specialized to receive input signals and to provide the substrate for the formation of synaptic contacts with other cells. The goal of this work is to study the activity-dependent mechanisms underlying dendritic growth in a single-cell model. For this, the individually identifiable adult motoneuron, MN5, in Drosophila melanogaster was used. This dissertation presents the following results. First, the natural variability of morphological parameters of the MN5 dendritic tree in control flies is not larger than 15%, making MN5 a suitable model for quantitative morphological analysis. Second, three-dimensional topological analyses reveals that different parts of the MN5 dendritic tree innervate spatially separated areas (termed "isoneuronal tiling"). Third, genetic manipulation of the MN5 excitability reveals that both increased and decreased activity lead to dendritic overgrowth; whereas decreased excitability promoted branch elongation, increased excitability enhanced dendritic branching. Next, testing the activity-regulated transcription factor AP-1 for its role in MN5 dendritic development reveals that neural activity enhanced AP-1 transcriptional activity, and that AP-1 expression lead to opposite dendrite fates depending on its expression timing during development. Whereas overexpression of AP-1 at early stages results in loss of dendrites, AP-1 overexpression after the expression of acetylcholine receptors and the formation of all primary dendrites in MN5 causes overgrowth. Fourth, MN5 has been used to examine dendritic development resulting from the expression of the human gene MeCP2, a transcriptional regulator involved in the neurodevelopmental disease Rett syndrome. Targeted expression of full-length human MeCP2 in MN5 causes impaired dendritic growth, showing for the first time the cellular consequences of MeCP2 expression in Drosophila neurons. This dendritic phenotype requires the methyl-binding domain of MeCP2 and the chromatin remodeling protein Osa. In summary, this work has fully established MN5 as a single-neuron model to study mechanisms underlying dendrite development, maintenance and degeneration, and to test the behavioral consequences resulting from dendritic growth misregulation. Furthermore, this thesis provides quantitative description of isoneuronal tiling of a central neuron, offers novel insight into activity- and AP-1 dependent developmental plasticity, and finally, it establishes Drosophila MN5 as a model to study some specific aspects of human diseases. / Dissertation/Thesis / Ph.D. Neuroscience 2012

Neurons are generated from unspecialized neural precursor cells (NPCs) in a process termed neurogenesis. This neuronal development continues throughout life in the ventricular zone (VZ) of the lateral ventricles, and the subgranular zone (SGZ) of the dentate gyrus in the hippocampus. NPCs undergo a complex and highly regulated set of behaviours in order to ultimately integrate into the existing brain circuitry as fully functional neurons. Recently the pannexin (Panx) large-pore channel proteins were discovered. One family member, Panx1 is expressed in the nervous system in mature neurons, and acts as an ATP release channel in various cell types throughout the body. Post-natal NPCs are responsive to ATP via activation of purinergic receptors, which modulate a variety of NPC behaviours. I therefore investigated the hypothesis that Panx1 was expressed in post-natal VZ NPCs, where it functioned as an ATP release channel and regulated neuronal development. In the course of my studies, I found that Panx1 positively regulated NPC proliferation and migration, and negatively regulated neurite outgrowth in vitro. Using an NPC-specific Panx1 knock-out strategy, I showed that Panx1 expression was required for maintenance of a consistent population of VZ NPCs in vivo in both healthy and injured brain. Together these data indicated that Panx1 directed NPC behaviours associated with neuronal development both in vitro and in vivo. To further understand the molecular underpinnings of this regulation, I examined the Panx1 interactome, and uncovered a novel association with collapsin response mediator protein 2 (Crmp2). Functional studies suggested that this interaction likely was at least in part responsible for Panx1’s negative impact on neurite outgrowth. Overall, my results represent important novel findings that contribute to our understanding of post-natal neuronal development and the molecular function of Panx1 within the brain. / Graduate / 0317 / 0379 / leighws@uvic.ca

The mammalian neocortex is an exquisite, highly organized brain structure composed of hundreds of subpopulations of neurons and glia, precisely connected to enable motor control, sensory perception, information integration, and planning. Unique molecular, structural, and anatomical neuronal properties underlie diverse functionality, endowing much of the neocortex’s complex processing power. Neocortical size correlates with information processing capacity, suggesting that increased neuronal number and diversity begets increased sophistication. One excitatory projection neuron type, callosal projection neurons (CPN), has disproportionately expanded with cortical size increase. CPN directly connect homotypic regions of the two neocortical hemispheres by sending axons via the largest white matter fiber tract in the brain, the corpus callosum (CC), allowing quick relay, integration, and comparison of information. In humans, the CC contains over 300,000 axons, CPN have been centrally implicated in autism spectrum disorders, and absence or surgical disruption of CPN connectivity in humans is associated with defects in abstract reasoning, problem solving, and generalization. Therefore, CPN are critical to complex brain functions, and their diversity likely contributes to these roles. Work presented in this dissertation addresses molecular controls over CPN development, specifically genes that are expressed by, and function in, particular subpopulations of CPN. While much progress has been made in identifying molecular controls over neocortical arealization, lamination, and broad subtype specification, CPN diversity has remained largely unaddressed. Therefore, this work begins by identifying genes more highly expressed in CPN than other closely related projection neuron populations, and uncovers molecular diversity within CPN. From this molecular diversity, functional analysis of three candidate molecular controls over CPN subtype diversity follows. Cited2 acts broadly in neocortical progenitor development and postnatally in refining somatosensory CPN identity. Caveolin1 identifies a population of CPN with dual axonal projections. Tmtc4 is mutated in human CC disease and can function in CPN axonal development. These analyses of CPN molecular diversity in mouse then expand to an investigation of which molecular subpopulations are conserved, expanded, or uncommon between rodent and primate, allowing both for comparative evolutionary theories of CPN function, and indicating which CPN populations critical for human brain function can be best studied in rodent models.

Orientadora: Profª Dra Alexandre Hiroaki Kihara / Dissertação (mestrado) - Universidade Federal do ABC, Programa de Pós-Graduação em Neurociência e Cognição, 2014. / No desenvolvimento pós-natal do Sistema Nervoso Central (SNC), a formação do bulbo olfatório ocorre a partir da zona subventricular (ZSV) próxima ao ventrículo lateral, por meio da proliferação e migração dos neurônios formados nestas regiões em idade pós-natal. As atividades das células das ZSV são moduladas pela variação da concentração de cálcio intracelular, que por sua vez é dependente do cálcio externo e de estoques intracelulares deste íon localizados em organelas como o retículo endoplasmático e mitocôndria. Estas organelas expressam receptores de rianodina (RyRs) que controlam a liberação do cálcio para o citosol. O objetivo deste projeto foi verificar a expressão destes receptores e, consequentemente, a participação do cálcio intracelular no desenvolvimento das células da ZSV de ratos da cepa Wistar. Para este fim, primeiramente foi realizada análise da expressão gênica dos RyRs na ZSV de ratos neonatos no dia do nascimento (P0) e animais adultos (P60), além da distribuição proteica dos RyRs em ratos P0; posteriormente, foi realizado o bloqueio in vitro dos RyRs em células da ZSV, extraídas de animais P0, com dantrolene por um período de 4 horas. Após o bloqueio, foram avaliadas possíveis alterações i) na morfologia das células; ii) desenvolvimento de neuritos. Para isto, foram utilizadas técnicas combinadas como imuno-histoquímica, PCR em tempo real, além de avaliações morfológicas. Na parte descritiva, verificamos menor expressão gênica em neonatos em relação aos animais adultos e acumulo proteico das três isoformas de RyRs na ZSV de neonatos, enquanto que o bloqueio das células em meio de cultura inibiu a formação de neuritos assim como as células mantiveram-se com morfologia circular, diferentemente de células controle, que apresentaram morfologia diferencial e maior arborização dendrítica. Assim, podemos concluir que os RyRs participam do processo de desenvolvimento das células da ZSV, as quais migram e formam as circuitarias do bulbo olfatório. / During the development of the central nervous system (CNS), the formation of the olfactory bulb occurs through the proliferation and migration of postnatal differentiated neurons from the subventricular zone (SVZ) close to the lateral ventricle. The activity of SVZ cells is modulated by the variation of intracellular calcium concentration, which in turn depends on external calcium and intracellular stores, localized in organelles such as mitochondria and endoplasmic reticulum. These organelles accumulate ryanodine receptors (RyRs) that control the release of calcium into the cytosol. The aim of this project was to verify the role of these receptors and, consequently, the participation of intracellular calcium in the development of the SVZ cells from Wistar rats. To this end, we first analyzed gene expression of these receptors in neonates animals (P0) and adult animals (P60) and also descriptive analysis related to the protein distribution in the SVZ of neonate animals in the day of birth (P0). Then we performed in vitro blockade of RyRs in SVZ cells, isolated from P0 animals with dantrolene during 4 hours. After the blockade, possible alterations were evaluated i) cell morphology; ii) neurite growth. For this, combined techniques such as immunohistochemistry and real time PCR were used, besides morphological evaluations. We observed gene expression of the three isoforms of RyRs in neonates lower than in adults, and protein accumulation of these proteins in all SVZ from neonates. In vitro blockade of RyRs in primary cell culture from SVZ inhibited the neurite growth, as well as preserved the circular morphology of the treated cells, contrary to the observed in control cells, which showed differentiated shape and increased dendritic branching. Thus, we are able to disclose that RyRs participate in the development of the cells from SVZ, which migrate and participate the olfactory bulb circuitries.

Sensory, cognitive, and emotional processing are rooted in the cerebral cortex. The cerebral cortex is comprised of six layers defined by the neurons within them that have distinctive connection, both within cortex itself and with other subcortical structures. Although still far from solving the mysteries of the mind, it is clear that networks form by neurons in the cerebral cortex provide the computational substrate for a remarkable range of behaviours. This neuron to neuron activation is mediated through dendritic spines, the postsynaptic target of most excitatory synapses in the cerebral cortex. Dendritic spines are small protrusions found along dendrites of neurons, and their number, as well as structural changes, accompany the development of synapses and establishment of neuronal networks. In fact, dendritic spines undergo rapid structural and functional changes guided by neuronal activity. This marriage between structural and functional plasticity, makes dendritic spines crucial in fine-tuning of networks in the brain; not surprisingly, dendritic spine aberrations are a hallmark of multiple neurodevelopmental, neuropsychiatric, and neurodegenerative disorders. With this in mind, I considered Pannexin 1 (Panx1) an interesting novel candidate for a regulatory role on cortical neuronal network and dendritic spine development, for the following reasons. First, Panx1 transcripts are enriched in the brain and in the cortex are most abundant during the embryonic and early postnatal period. . This timing roughly corresponds to a period of synaptogenesis in the postnatal brain. Second, Panx1 localizes to postsynaptic compartments in neurons and its disruption leads to enhance excitability and potentiation of neuron-to neuron communication. Third, disruption of Panx1 (either knockdown or pharmacological blockade) leads to neurite outgrowth in neuron-like cells. Lastly, genetic variants in PANX1 have been associated with neurodevelopmental disorders. This dissertation explores the role of Panx1 in the development of dendritic spines and neuronal networks, furthering our understanding on cortical development and placing Panx1 as a novel regulator of structural and functional plasticity in the brain. Chapter 1 discusses core concepts on cortical development, with an emphasis on pyramidal neuron, the most abundant and only known projection neurons in the cerebral cortex. Here, I review the embryonic origin of pyramidal neurons, their postnasal development, and how cortical circuits are assembled. I finish this chapter with a brief review on Panx1 and its known expression and involvement in neuronal function. In Chapter 2 I explore the functional properties of neuronal networks and synaptic composition of cortical neurons in the absence of Panx1. Using live cell imaging and analysis of Ca2+ transients in dense primary cortical cultures, revealed that Panx1 knock-out (KO) cultures exhibit more and larger groups of significantly co-activated neurons, known as network ensembles. These network properties were not explained by differences in cell viability or cell-type composition. Examination of protein expression from cortical synaptosome preparations revealed that Panx1 is enriched in synaptic compartments, while also confirming a developmental downregulation. This analysis also revealed increased levels of the postsynaptic scaffolding protein PSD-95, along with the postsynaptic glutamate receptors GluA1 and GluN2A. Lastly, ex vivo tracing of dendritic spines on apical dendrites of Layer 5 pyramidal neurons in global and glutamatergic-specific Panx1 KO brain slices revealed higher spine densities in early and late postnatal development, with no differences in spine length. Analysis of dendritic spine densities in fixed cultured cortical neurons revealed an increase associated with Panx1 KO. Altogether, this work presents for the first time a connection between Panx1 and structural development of dendritic spines and suggest that Panx1 regulates cortical neuronal networks through changes in spine density. Chapter 3 examines the influence of Panx1 on spiny protrusions growth and movement. Spiny protrusion are long, thin, highly dynamic spine precursors. Taking advantage of a fluorescent signal localized to the plasma membrane, I visualized spiny protrusions and quantified their dynamics in wildtype (WT) and Panx1 KO developing cortical neurons, both under fixed and live conditions. I found that transient Panx1 expression is associated with decreased spiny protrusion density both in WT and Panx1 KO neurons. Using live cell imaging, I found that spiny protrusions are more stable and less motile in Panx1 KO neurons, while its transient expression reversed both of these phenotypes. These results suggest that Panx1 regulation of dendritic spines development is rooted partly in the regulation of spiny protrusion dynamics. Overall, this dissertation demonstrates that Panx1 negatively regulates dendritic spines in part by influencing spiny protrusion dynamics. It is reasonable to speculate that Panx1 regulation of dendritic spines underlies its newly discovered role in the formation network ensembles, providing a putative mechanism for previously described roles of Panx1 in synaptic plasticity. Likewise, this body of work furthers our understanding of Panx1 by filling some of the gaps attached to its developmental expression and association with neurodevelopmental disease. / Graduate / 2021-04-16