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京都大学 / 新制・課程博士 / 博士(生命科学) / 甲第24047号 / 生博第473号 / 新制||生||63(附属図書館) / 京都大学大学院生命科学研究科高次生命科学専攻 / (主査)教授 今吉 格, 教授 見学 美根子, 教授 原田 浩 / 学位規則第4条第1項該当 / Doctor of Philosophy in Life Sciences / Kyoto University / DFAM

<p>Amyotrophic Lateral Sclerosis (ALS) is a fatal progressive neurodegenerative disease with no known cause. Despite the efforts of investigators over the past 150 years, there remains no effective cure which substantially prolongs life. Therapeutic strategies have explored all of the proposed underlying pathological pathways of the disease from increased oxidative damage to impaired axonal transport, with little to no success. In the following pages, a novel perspective will be presented outlining the preliminary investigations of a new line of research demonstrating that Sonic hedgehog (Shh) protein and its agonists have cytoprotective effects on motor neurons. To begin these investigations, initial experiments were conducted <em>in vitro</em> utilizing a mouse hippocampal cell-line (HT-22) which served as a model for transient transfection and oxidative challenge assays. The results are reported in Chapter 2. Building upon these introductory findings, further investigations were conducted exploiting the SOD1^G93A mouse model of ALS. Chapter 3 summarizes key observations pertaining to the abundance of a key cellular organelle in the sensing of Shh signalling, the primary cilium, in the spinal cord of SOD1^G93A mice. In Chapter 4, a semi-quantitative analysis of the effects of Shh and Shh agonists pre-treatment <em>in vitro </em>on primary mixed spinal cord cultures are described. Subsequent challenge with an excitotoxic NMDA treatment was also conducted, as well as an <em>in vivo</em> survival study exploring the potential therapeutic effects of chronic Shh administration on SOD1^G93A mice. The cumulative research presented here represents the very first investigation into the unique application of Shh and its agonists as potential therapeutic agents for the treatment of ALS, and our findings indicate that Shh has the potential of becoming a novel therapeutic agent for the treatment of ALS.</p> / Doctor of Philosophy (Medical Science)

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Hedgehog (Hh) morphogens play fundamental roles in development whilst dysregulation of Hh signalling leads to disease. Multiple receptors are involved in the modulation of Hh morphogens at the cell surface. Among these, the interactions of Hh ligands with glycosaminoglycan (GAG) (for example heparan or chondroitin sulphate) chains of proteoglycans in the extracellular matrix play a key role in shaping morphogen gradients and fulfil important functions in signal transduction. Several high resolution crystal structures of Sonic Hh (Shh)-GAG complexes have been determined. The interaction determinants, confirmed by binding studies and mutagenesis reveal a novel Hh site for GAG interactions, which appears to be common to all Hh proteins. This novel site is supported by a wealth of published functional data, and resides in a hot spot region previously found to be crucial for Hh receptor binding. Crystal packing analysis combined with analytical ultracentrifugation on Hh-GAG complexes suggest a potential mechanism for GAG-dependent multimerisation. A key step in the Hh pathway is the transduction of the Hh signal into the receiving cell. The Hh signal transducer, Smoothened, is a key target drug target in the pathway with several modulators in clinical trials, despite an absence of structural data. Smoothened is required to activate all levels of Hh signalling. Recent evidence points to the conserved N-terminal ectodomain (ECD) in regulating Smo activity, from vertebrates to invertebrates. Despite the central importance of the ECD, its precise function remains elusive. A crystal structure of the ECD at 2.2 &Aring; resolution is reported here. Structural analysis and biophysical experiments are discussed with reference to the potential function of this intriguing domain.

This study deals with the process of building up the local congregation and the manner in which missional objectives are achieved. The study is undertaken against the background of the disturbing decline in membership numbers particularly in the two traditional Reformational churches in South Africa, namely the Dutch Reformed Church (DRC) and the Netherdutch Reformed Church of Africa. This decline is in line with similar tendencies in mainstream churches the world over. Collins’s (2006) three questions to the local congregation constitute the point of departure. Firstly: To what degree does the congregation function effectively in line with her mission in the world? Secondly: To what extent does the congregation make a distinct impact on the community? If the congregation were to disappear all of a sudden – will it leave a serious void in the community? The third question deals with sustainability: Is the congregation’s long term impact of such nature that its success is not just attributable to a single leader. The three questions have been adapted according to Collins’s process model (2001) and the key aspects of the theory of building up the local church are discussed in Chapters 2 and 3. The bulk of Chapter 2 deals with the very important matter of the missio Dei and discusses how the congregation should discover and enact her missional calling in the local community. The study furthermore deals with mission in the current South African context, particularly in view of the fact that an entirely new mission field has opened itself up with the influx into the country of so many people from neighboring countries who have come to live in our midst. Chapter 4 deals with the empirical testing associated with the study to establish if the study’s hypothesis, namely whether local churches that have undergone a structured process of building up the local church are missionally more successful than those that have not undergone a structured process, can be verified. The findings in this regard are dealt with in Chapter 5, while certain aspects that characterize the missional congregation in current times are also discussed. / Thesis (PhD)--University of Pretoria, 2010. / Practical Theology / unrestricted

Le médulloblastome est une des tumeurs les plus fréquentes du système nerveux central chez l’enfant. Son impact clinique, ainsi que les effets secondaires engendrés par les traitements actuels, sont significatifs en matière de morbidité et de mortalité. La caractérisation moléculaire des tumeurs du système nerveux central a grandement évolué, et ce, particulièrement en ce qui concerne le médulloblastome. Des travaux antérieurs ont permis d’établir qu’un des sous-groupes de médulloblastome est caractérisé par l’activation de la voie sonic hedgehog. La mutation la plus fréquente menant à ce sous-type de médulloblastome est la mutation du gène suppresseur de tumeur PTCH1. Grâce au modèle de souris Ptch1+/-, des données issues de notre laboratoire ont permis de caractériser le développement de cette tumeur comme étant en deux étapes. Ce travail porte sur la caractérisation du mécanisme par lequel cette première étape, soit la perte d’hétérozygotie de Ptch1, survient. Tout d’abord, nous revisitons le rôle in vivo du corécepteur Boc dans la tumorigenèse. Selon nos résultats, la modulation de Boc ne semble pas avoir un impact significatif sur le développement tumoral dans des expériences de transplantation orthotopiques. Ensuite, nous démontrons que le ligand Shh augmente le dommage à l’ADN, ce qui mène à une hausse des évènements de recombinaisons qui peuvent causer une perte d’hétérozygotie. Nous tentons de moduler l’activité de Rad51 en observant une tendance non statistiquement significative des évènements de recombinaison avec des inhibiteurs de Rad51. Nous démontrons ensuite qu’un inhibiteur de Cdc7 permet la diminution des évènements de recombinaisons ainsi qu’une diminution du stress réplicatif de l’ADN. En intervenant sur le gène Mcm2 grâce à un modèle de souris transgénique, nous parvenons à prouver qu’une diminution de l’action de Mcm2 permet une diminution du stress réplicatif de l’ADN. En somme, la première étape du développement du médulloblastome sonic hedgehog-activé est la perte d’hétérozygotie de Ptch1. Celle-ci est caractérisée par une augmentation du dommage à l’ADN engendrant une hausse des évènements de recombinaison. Plusieurs cibles potentielles de modulation s’avèrent prometteuses pour un éventuel traitement ciblé. / Medulloblastoma is one of the most common central nervous system tumors of the child. Its clinical impact, as well as the adverse effects caused by current treatments, are significant in terms of morbidity and mortality. The molecular characterization of tumors of the central nervous system has greatly evolved, particularly in the case of medulloblastoma. Previous work has established that one of the medulloblastoma sub-groups is characterized by the activation of the sonic hedgehog (Shh) pathway. The most common mutation leading to this medulloblastoma subtype is the PTCH1 tumor suppressor gene mutation. Working with the Ptch1+/- mouse model, data from our la-boratory characterized the medulloblastoma tumorigenesis as a two-step process. This work focuses on the characterization of the mechanism by which this first step, the loss of heterozygosity of Ptch1, occurs. First, we revisit the in vivo role of the Boc coreceptor in the medulloblastoma tumor-igenesis. According to our results, Boc modulation does not seem to have a significant impact on tumor development. Next, we show that the Shh ligand increases DNA dam-age. This leads to an increase in recombination events which predispose to loss of het-erozygosity. We attempt to modulate Rad51 activity and observe a non-statistically sig-nificant trend to decrease recombination events with Rad51 inhibitors. We then demonstrate that Cdc7 inhibition reduces recombination events as well as DNA replica-tive stress. Using an Mcm2 transgenic mouse model, we demonstrate that a reduction in the action of Mcm2 reduces DNA replicative stress. To conclude, the first step in the development of Shh-activated medulloblastoma is the loss of heterozygosity of Ptch1. This is characterized by an increase in DNA damage leading to an increase in recombination events. Several potential modulation targets hold promise for possible targeted therapy.

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