Thesis (Ph. D.)--University of Washington, 2008. / Vita. Includes bibliographical references (leaves 137-156).

Thesis (Ph. D.)--University of Washington, 2006. / Vita. Includes bibliographical references (leaves 121-147).

Orientador: Humberto Santo Neto / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-16T20:39:51Z (GMT). No. of bitstreams: 1 Boni_RobsonAparecidodosSantos_M.pdf: 2053465 bytes, checksum: ae91ac2421ee67ae72964df4c510de03 (MD5) Previous issue date: 2010 / Resumo: A distrofina é uma proteína de membrana ligada ao citoesqueleto da matriz extracelular das fibras musculares (esqueléticas e cardíacas) e nervosas. Enquanto que o papel da distrofina e os efeitos de sua ausência são bem conhecidos nos camundongos mdx (modelo animal da distrofia muscular de Duchenne), sabe-se pouco sobre sua função em nervos periféricos. A distrofina parece ser importante para o crescimento axonal, no sistema trigeminal a sua falta leva a defasciculação do sistema olfatório de camundongos. Em casos de ausência de distrofina a eliminação sináptica ocorre precocemente à expressão de moléculas pré-sinapticas é reduzida e a habilidade das células de Schwann terminais de guiarem as fibras para reinervação muscular fica comprometida. Estes achados sugerem que a distrofina possui papel essencial na regeneração nervosa periférica. Para testar esta hipótese nós examinamos a regeneração nervosa em camundongos mdx. Foram utilizados camundongos adultos machos da linhagem mdx e camundongos da linhagem C57BL/10 como controle, eles foram anestesiados com mistura de cloridrato de cetamina e cloridrato de xilazina. O nervo isquiático direito foi exposto e esmagado com uso de uma pinça fina sem ranhuras. Após o evento cirúrgico e cessado o efeito do anestésico os animais foram acondicionados em gaiolas e submetidos a regime hídrico e alimentar "ad libitum" com ciclo fotoperiódico claro/escuro de 12 horas. Destes, um grupo foi tratado com injeções intraperitoneais de L-arginina (6mg/kg) diluído em água bidestilada. Seis e 21 dias após o esmagamento os animais foram anestesiados e perfundidos por via intracardíaca com solução de Karnovsky. O nervo isquiático foi removido e imerso em fixador por 24 horas e pós-fixado em tetróxido de ósmio 1% por 2 horas. Posteriormente foram inclusos em blocos e feitos cortes semifinos que foram corados com azul de toluidina 0,5%. As secções foram analisadas em fotomicroscópio NIKON ECLIPSE E-400 (NIKON, Inc.). A densidade dos axônios com mielina (6dias) e axônios em regeneração (21 dias) foram contados. Nossos resultados demonstraram que a densidade de axônios com mielina foi significantemente maior no mdx em comparação ao C57BL/10 (312±10,2/mm2 versus 213,8±4,6/mm2). A densidade de macrófagos e células de Schwann com restos de mielina foram respectivamente 77,6±5,6/mm2 e 148±2,4/mm2. Após 21 dias, todos os parâmetros (diâmetro do axônio, espessura da bainha de mielina e número de axônios regenerados) foram significantemente menores nos camundongos mdx. Nos camundongos tratados com L-arginina os parâmetros foram semelhantes ao controle não havendo diferença estatística. Os resultados mostraram que o papel da distrofina e do óxido nítrico são de fundamental importância na regeneração nervosa periférica. / Abstract: Dystrophin is a membrane protein that links the cytoskeleton to the extracellular matrix in skeletal and cardiac muscle fibers and in the nervous system. While the role of dystrophin is well established and the effects of dystrophin loss, as it occurs in the mdx mice model of Duchenne muscular dystrophy, have been widely examined in muscle fibers, less is known about dystrophin function in peripheral nerves. It seems to be important for axonal outgrowth in the trigeminal system and the lack of dystrophin leads to nerve defasciculation in the mouse olfactory system. In the absence of dystrophin, synapse elimination occurs earlier, expression of presynaptic molecules is reduced and the ability of terminal Schwann cells to guide reinnervation of muscle fibers is impaired. These findings suggest a potential role of dystrophin in the regeneration of peripheral nerves. To test this hypothesis we examined nerve regeneration in mdx mice. Adult male mdx and control C57Bl/10 mice were anesthetized with a mixture of ketamine hydrochloride and thyazine hydrochloride. Right sciatic nerve was exposed at mid thigh and crushed with a fine forceps. The wound was closed and mice were kept with food and water ad libitum in a light-dark cycle of 12hs. One group was treated with L-arginine (6mg/kg) in drinking water. Six and 21 days after nerve crush mice were anesthetized and perfused intracardiacally with Karnovsky solution. Sciatic nerves were excised and fragments were immersed in the same fixative for 24 hours and post-fixed in 1% osmium tetroxide for 2 hours. They were conventionally processed for electron microscopy. Transverse semithin sections were stained with 0.5% toluidine blue. Sections were viewed under a Nikon Eclipse E-400 (Nikon, Inc.) microscope. The density of axons with myelin breakdown, of Schwann cells/macrophages filled with myelin debris (6 days) and of myelinated regenerating axons (3 weeks) were directly counted. Our results demonstrated that the density of axons displaying myelin breakdown was significantly higher in mdx than in crushed C57Bl/10 (312±10,2/mm2 versus 213,8±4,6/mm2) the density of macrophages and Schwann cells with myelin debris were respectively 77,6±5,6/mm2 and 148±2,4/mm2. After 21 days, all parameters (axonal diameter, myelin sheath thickness, number of regenerating axons) were significantly lower in mdx mice. When mdx was treated with L-arginine such parameters were not significantly different from control. These results demonstrated that dystrophin plays a role on nerve regeneration and that nitric oxide may be an important factor in that. / Mestrado / Anatomia / Mestre em Biologia Celular e Estrutural

Le but de ce projet était d'identifier de manière méthodique et standardisée les partenaires interagissant avec la protéine dystrophine dans les cellules musculaires squelettiques humaines différenciées et découvrir de nouveaux rôles de la dystrophine. Des cellules immortalisées ont été obtenue en sur-exprimant de manière stable hTERT / CDK4. Nous avons réalisé une analyse transcriptomique comparant des lignées immortalisées avec leurs populations primaires correspondantes, à l’état de prolifération et de différentiation. Nous avons constaté que l'immortalisation n'a pas d'effet mesurable sur le programme myogénique ou sur tout autre processus cellulaires, et qu'elle avait un effet protecteur contre le processus de sénescence. Les lignées de cellules musculaires humaines constituent donc de bon model in vitro pour l’étude de l’interactome de la dystrophine. Nous avons déterminé l’interactome de la dystrophine en utilisant l’approche proteomique ‘QUICK’. Nous avons identifié 18 nouveaux partenaires directs de la dystrophine, partenaires étant impliqués dans le transport vésiculaire ou étant des protéines d'adhésion. Ces résultats renforcent les données précédemment publiées suggérant un lien entre la dystrophine et le trafic vésiculaire, ainsi que dystrophine et adhesion cellulaire. Ces nouveaux partenaires ont été ajoutés à l’interactome de la dystrophine, interactome accessible sur le Web: sys-myo.rhcloud.com/dystrophin-interactome. Ce site web est dédié à être un outil facile d’utilisation permettant d’explorer et de visualiser l’interactome de la dystrophine du muscle squelettique. / The aim of this project was to systematically identify new interaction partners of the dystrophin protein within differentiated human skeletal muscle cells in order to uncover new roles in which dystrophin is involved, and to better understand how the global interactome is affected by the absence of dystrophin. hTERT/cdk4 immortalized myogenic human cell lines represent an important tool for skeletal muscle research however, disruption of the cell cycle has the potential to affect many other cellular processes to which it also linked. A transcriptome-wide analysis of healthy and diseased lines comparing immortalized lines with their parent primary populations in both differentiated and undifferentiated states testing their myogenic character by comparison with non-myogenic cells found that immortalization has no measurable effect on the myogenic cascade or on any other cellular processes, and that it was protective against the senescence. In this context the human muscle cell lines are a good in vitro model to study the dystrophin interactome. We investigated dystrophin’s interactors using the high-sensitivity proteomics ‘QUICK’ approach. We identified 18 new physical interactors of dystrophin which displayed a high proportion of vesicle transport related proteins and adhesion proteins, strengthening the link between dystrophin and these roles. The proteins determined through previously published data together with the newly identified interactors were incorporated into a web-based data exploration tool: sys-myo.rhcloud.com/dystrophin-interactome, intended to provide an easily accessible and informative view of dystrophins interactions in skeletal muscle.

La dystrophine est une très grande protéine codée le gène DMD et située sous la membrane plasmique des fibres musculaires. Elle joue un rôle essentiel dans le maintien de l’intégrité de la cellule musculaire lors des cycles de contraction/relaxation. Cette protéine filamenteuse est composée de quatre domaines structuraux dont le domaine central composé de 24 répétitions homologues à la spectrine. Chaque répétition est organisée en faisceau de trois α-hélices appelé « coiled-coil ». Des mutations du gène DMD sont à l’origine des myopathies de Duchenne (DMD) et de Becker (BMD) qui s’accompagnent d’un déficit total ou d’une dystrophine mutée et induisent de ruptures fréquentes de la membrane des cellules musculaires. La connaissance de la structure de la dystrophine est nécessaire au développement de thérapies à ce jour inexistantes pour les myopathies. Au laboratoire, des données structurales du domaine central de la dystrophine ont été acquises par diffusion des rayons X aux petits angles (SAXS, Small Angles X-ray Scattering). Cette thèse présente le développement d’une approche multi-échelle combinant des données expérimentales SAXS et des données in silico pour la reconstruction de modèles haute-résolution des fragments du domaine central de la dystrophine et d’un fragment muté observé dans une mutation BMD fréquente. Nous avons également cartographié l’interaction de ce domaine central avec deux de ses partenaires fonctionnels importants, l’actine filamenteuse et avec la nitroxyde synthase neuronale (nNOS) et proposé les premiers modèles atomiques des complexes macromoléculaires correspondants. L’ensemble de ces résultats permettra à terme l’optimisation de thérapies pour le traitement des dystrophies musculaires. / Dystrophin is a large protein encoded by DMD gene and located under the plasma membrane of muscle fibers. It plays an essential role in maintaining the integrity of muscle cells during contraction/relaxation cycles. This filamentous protein is composed of four structural domains including the central domain consisting of 24 spectrin-like repeats and four hinges. Each repetition is folded in three α-helices in a ‘coiled-coil’ assembly. Mutations in the DMD gene leads to Duchenne muscular dystrophy (DMD) and Becker (MDBs), which are accompanied by frequent plasma membrane ruptures, due to the loss or modification of dystrophin protein. There are very few structural data available concerning the central domain of dystrophin, which is subject to many mutations involved in DMD and BMD diseases. However, the description and the understanding to an atomic level of dystrophin structure and its interaction is essential for optimization of therapies. Given the impossibility to solve its structure by X-ray crystallography or NMR, structural data of the dystrophin central domain were acquired by small angles X-rays scattering (SAXS, Small Angles X-ray Scattering). This thesis presents the development of an innovative multi-scale approach combining experimental SAXS and in silico derived data, allowing the reconstruction of high-resolution models of dystrophin central domain fragments. Structural data were also obtained on a mutated dystrophin frequently observed in BMDs. Furthermore, we also mapped the interactions of the central domain with two of its majors functional partners, Filamentous actin and neuronal nitroxyde synthase (nNOS) and proposed models of the related macromolecular complexes. At long-term, all of these results will allow optimization of therapies for the treatment of muscular dystrophies.

La dystrophine est une grande protéine membranaire périphérique qui assure un rôle de soutien du sarcolemme permettant aux cellules musculaires de résister aux stress mécaniques engendrés lors des processus de contraction/élongation. Des mutations génétiques conduisent à sa production sous forme tronquée voire à un déficit total en protéine engendrant de sévères myopathies actuellement incurables. Concevoir des thérapies adaptées passe par une meilleure compréhension du rôle biologique de la dystrophine. Par une approche structure/fonction, notre objectif est de déterminer les bases moléculaires impliquées dans les interactions de la dystrophine avec les lipides membranaires du sarcolemme. Grâce à une approche de diffusion aux petits angles (SAXS et SANS) combinée à de la modélisation moléculaire, nous montrons dans un premier temps que les bicelles constituent un modèle expérimental particulièrement adapté aux analyses de structures de protéines qui y sont associées. Ce développement méthodologique original a été exploité dans un deuxième temps pour caractériser les modifications structurales subies par la dystrophine lorsqu’elle interagit avec les lipides. Nous montrons particulièrement que la liaison aux lipides induit l’ouverture significative de la structure en triple hélice « coiled-coil » de la répétiton 1 du domaine central, et proposons en conclusion un modèle tout atome de la protéine en présence de bicelles. Ces travaux de thèse (i) constituent un apport méthodologique significatif pour l’étude de protéines membranaires, (ii) contribuent à une meilleure compréhension du rôle biologique de la dystrophine en vue de thérapies dédiées aux patients atteints de myopathies. / Dystrophin is a large peripheral membrane protein that provides a supporting role for sarcolemma allowing muscle cells to withstand the mechanical stresses generated during contraction / elongation processes. Genetic mutations lead to dystrophin production in truncated form or even to a total deficit in the protein leading to severe myopathies currently incurable. Designing adapted therapies requires a huge knowledge of the biological role of dystrophin. Using a structure / function approach, our aim is to determine the molecular bases involved in the interactions of dystrophin with the membrane lipids of the sarcolemma. Using a small-angle scattering approach (SAXS and SANS) combined with molecular modeling, we show that bicelles constitute a versatile membrane mimic that is particularly adapted to analyze the structure of membrane proteins. This original methodological development was exploited to characterize the structural changes undergone by dystrophin upon lipid binding. We highlight in particular that the lipid binding induces a significant opening of the coiled-coil structure of the repeat 1 of the central domain and, in conclusion, we propose an all-atom model of the protein bound to a bicelle. These thesis works (i) constitute a significant methodological contribution for the study of membrane proteins, (ii) contribute to a better understanding of the biological role of dystrophin for therapies dedicated to patients with myopathies.

The CRISPR-Cas9 gene editing system gives researchers the ability to manipulate and edit DNA with unprecedented ease and precision. It was discovered in bacteria as part of their adaptive immune system, but has been reengineered to target any double stranded DNA. This burgeoning molecular tool has created great excitement as scientists are rapidly adopting it to study fields including human gene therapy, disease modeling, agriculture, gene drive in mosquitos, and many others. This paper will explore the potential impact of CRISPR-Cas9 in human therapeutics. Specifically, the potential of CRISPR-Cas9 to treat Duchenne Muscular Dystrophy will be examined. In several ways, this debilitating degenerative disease is an ideal candidate for gene-editing with CRISPR-Cas9. Recent progress in the lab has demonstrated the gene editing system’s ability to rescue dystrophin protein levels in vivo. Although CRISPR-Cas9 holds great promise for previously incurable diseases, there are still many limitations that must be overcome before the gene editing system can be used in patients. This paper will discuss these barriers as well as recent advancements to overcome them.

京都大学 / 0048 / 新制・課程博士 / 博士(医学) / 甲第18870号 / 医博第3981号 / 新制||医||1008(附属図書館) / 31821 / 京都大学大学院医学研究科医学専攻 / (主査)教授 萩原 正敏, 教授 瀬原 淳子, 教授 中畑 龍俊 / 学位規則第4条第1項該当 / Doctor of Medical Science / Kyoto University / DFAM

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