Diss. (sammanfattning) Stockholm : Karolinska institutet, 2007. / Härtill 4 uppsatser.

Complex I (NADH:ubiquinone oxidoreductase), located in the mitochondrial inner membrane, is a major electron entry point to the respiratory chain. It couples the energy released from electron transfer (from NADH to ubiquinone) to the concomitant pumping of protons across the membrane, to generate an electrochemical proton motive force. Mammalian complex I is composed of 45 subunits, 14 of which comprise its simpler bacterial homologues. It is encoded by both the mitochondrial and nuclear genomes, and pathological mutations in both sets of subunits result in severe neuromuscular disorders such as Leigh syndrome. Several structures of mammalian complex I from various organisms have been determined, but the limited resolutions of the structures, which typically refer to poorly characterised enzyme states, has hampered detailed analyses of mechanistic features. The first part of this thesis describes development of a method for purifying complex I from the genetically amenable and medically relevant model organism Mus musculus (mouse), in a pure, stable and active state. The enzyme from mouse heart mitochondria was then comprehensively characterised, to ensure the presence of all the expected subunits and co-factors, and to define its kinetic properties. The second part of this thesis describes structural studies by single particle electron cryomicroscopy (cryo-EM) on the purified mouse enzyme in two distinct states, the 'active' and 'de-active' states. The active state was determined to 3.3 Å resolution, the highest resolution structure of a eukaryotic complex I so far. Subsequently, comparison of the two mouse structures, together with previously determined mammalian and bacterial structures, revealed variations in key structural elements in the membrane domain, which may be crucial for the catalytic mechanism. Moreover, in the high-resolution active mouse complex I structure a nucleotide co-factor was observed bound to the nucleoside kinase subunit NDUFA10. Finally, complex I from the Ndufs4 knockout mouse model, which recapitulates the effects of a human mutation that causes Leigh syndrome, was purified and subjected to kinetic and proteomic analyses. Following cross-linking and preliminary structural studies, it was concluded that the detrimental effects of deleting NDUFS4 are due to lack of stability of the mature complex.

Diss. (sammanfattning) Stockholm : Karolinska institutet, 2005. / Härtill 3 uppsatser.

Thesis (M.Sc.). / Written for the Dept. of Human Genetics. Title from title page of PDF (viewed 2008/07/30). Includes bibliographical references.

No description available.

Diss. (sammanfattning) Stockholm : Karol. inst., 2005. / Härtill 4 uppsatser.

Sous le terme de maladies mitochondriales, on désigne des maladies multi-systémiques ou à expression tissu-spécifique dues à un déficit de la phosphorylation oxydative qui est assurée par le fonctionnement de 5 complexes protéiques enzymatiques (chaîne respiratoire) parmi lesquelles 13 sous-unités sont codées par le génome mitochondrial, les autres par le génome nucléaire. Ces pathologies recouvrent donc en pratique des maladies génétiques par mutation de l’ADN mitochondrial (ADNmt) mais aussi des maladies génétiques à hérédité mendélienne classique. Dans les cytopathies mitochondriales liées à des mutations de gènes nucléaires, il existe deux sortes de gènes (i) à effet direct correspondant à des gènes codant pour les sous-unités protéiques de la chaîne respiratoire ou leur assemblage, et (ii) à effet indirect correspondant à des gènes codant pour des protéines impliquées dans le maintien et la réplication de l'ADN mitochondrial. Des mutations dans cette dernière classe de gènes peuvent s'accompagner d'anomalies quantitatives ou qualitatives de l'ADNmt : déplétion de l'ADNmt (réduction majeure du nombre de molécules d'ADNmt) et délétions multiples.Après des dosages enzymatiques de l’activité des complexes respiratoires mitochondriaux chez les patients, le ou les types de complexes altérés sont connus. Un grand nombre de gènes mutés responsables de pathologies mitochondriales ont été identifiés, tous codant des constituants des différents complexes de la chaîne respiratoire. Ces dernières années, le groupe d’Agnès Rötig (Hôpital Necker, Paris) a identifié de nouveaux gènes grâce à une approche gènes candidats ou grâce à des tours de génome de familles consanguines de patients qui permettent de délimiter une région chromosomique portant la mutation à l’état homozygote. La validation de l’effet délétère de la mutation identifiée se fait en général en utilisant des organismes modèles d’étude comme les cellules humaines en culture ou bien la levure. Cependant, il reste un grand nombre de cas où la mutation n’a pas pu être identifiée, soit parce que le déficit de tel ou tel complexe ne met pas en jeu un des composants connus de ce complexe ou bien plusieurs complexes de la chaîne respiratoire sont déficitaires mettant en jeu, dans un grand nombre de cas, le maintien de l’ADN mitochondrial pour lequel peu de gènes sont connus.Au laboratoire d’Orsay, nous disposons de deux organismes modèles d’étude, la levure S. cerevisiae et le nématode C. elegans. La levure S. cerevisiae est l’organisme modèle de choix pour étudier les fonctions mitochondriales grâce à ses caractéristiques comme la respiration facultative, mais aussi et surtout par la puissance de sa génétique et le fait que les mitochondries peuvent être transformées. Cependant de par sa respiration facultative et sa division clonale, elle ne se prête pas facilement à des études sur la stabilité de l’ADNmt. En effet, S. cerevisiae perd très facilement son ADNmt après inactivation d’un grand nombre de gènes impliqués dans pratiquement toutes les voies de la biogenèse mitochondriale. Cette levure ne peut donc pas être utilisée de façon simple pour l’étude de la transmission de l’ADN mitochondrial. C’est pourquoi nous nous sommes alors intéressés à l’autre organisme modèle développé au laboratoire, le nématode C. elegans dont ses caractéristiques en font un excellent modèle complémentaire à la levure. / Mitochondrial respiratory chain diseases of nuclear origin represent one of the major causes of metabolic disorders. These diseases are characterized by a huge clinical and genetic heterogeneity which is a major problem in identifying the disease causing gene. Although several gene mutations have already been found in some patients or families, the disease causing gene of the majority is yet to be determined. The overall structure and gene content of the mitochondrial genome and the proteins required for mtDNA transactions are largely conserved from yeast to human offering the opportunity to use animal models to understand the molecular basis of mitochondrial dysfunctions. To expand the number of human candidate genes of mitochondrial diseases involved in mtDNA maintenance, we have developed in this study, the nematode Caenorhabditis elegans as a model organism to identify new proteins involved in mtDNA maintenance by combining RNAi and ethidium bromide exposure. We have developed a large-scale screening method of genes required for mtDNA maintenance in the worm and initially indentified four new C. elegans genes (atad-3, dnj-10, polrmt, phi-37 and immt-1) involved in mtDNA stability. The human homologs of these genes (ATAD3, DNAJA3, POLRMT and ATP5A1) can be now considered as candidate genes for patients with quantitative mtDNA deficiencies. Using our screening design we have begun to screen all the C. elegans genes encoding mitochondrial proteins. Of the 721 estimated C. elegans mitochondrial genes homologous to human genes, we have tested 185 genes and found that 41 genes are required for the maintenance of the mitochondrial genome in post mitotic cells. These genes fall into three main functional categories of metabolism, protein synthesis and oxidative phosphorylation. Finally, in this study, we investigated the reversibility of mtDNA depletion with drugs to counteract POLG dificiency. Three molecules, Chlorhexidine, Resveratrol and Bezafibrate, have been tested to restore normal mtDNA content and worm life cycle. These experiments hold promise for future work using C. elegans as a pharmacological model for mitochondrial diseases.Altogether, the data generated in this work is a starting point for promising advances in the mitochondrial field, showing the relevance of the nematode as a model organism to study fundamental processes as well as human health research.

BACKGROUND: Mitochondrial complex I deficiency often leads to a devastating neurodegenerative disorder of childhood. In most cases, the underlying genetic defect is unknown. Recessive nuclear gene mutations, rather than mitochondrial DNA mutations, account for the majority of cases. AIM: Our aim was to identify the genetic basis of complex I deficiency in 34 patients with isolated complex I deficiency, by studying six of the 39 nuclear encoded complex I subunit genes (NDUFV1, NDUFS1, NDUFS2, NDUFS4, NDUFS7 and NDUFS8). These genes have been conserved throughout evolution and carry out essential aspects of complex I function. METHODS: RNA was extracted from patient fibroblasts and cDNA made by reverse transcription. Overlapping amplicons that together spanned the entire coding area of each gene were amplified by PCR. The genes were screened for mutations using denaturing High Performance Liquid Chromatography (dHPLC). Patient samples with abnormal dHPLC profiles underwent direct DNA sequencing. RESULTS: Novel mutations were identified in six of 34 (18%) patients with isolated complex I deficiency. Five patients had two mutations identified and one patient had a single mutation in NDUFS4 identified. All patients with mutations had a progressive encephalopathy and five out of six had Leigh syndrome or Leigh like syndrome. Mutations were found in three nuclear encoded subunit genes, NDUFV1, NDUFS2 and NDUFS4. Three novel NDUFV1 mutations were identified (R386H, K111E and P252R). The R386H mutation was found in two apparently unrelated patients. Four novel NDUFS2 mutations were identified (R221X, M292T, R333Q and IVS9+4A&ltG). The novel NDUFS4 mutation c.221delC was found in two patients - one in homozygous form and the other heterozygous. Specific genotype and phenotype correlations were not identified. CONCLUSIONS: Nuclear encoded complex I subunit gene mutations are an important contributor to the aetiology of isolated complex I deficiency in childhood. Screening of these genes is an essential part of the investigation of complex I deficiency.

Orientador: Gabriel Forato Anhê / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Ciências Médicas / Made available in DSpace on 2018-08-21T11:57:04Z (GMT). No. of bitstreams: 1 Silva_CarolinaSolonda_M.pdf: 587503 bytes, checksum: cd74a1063d709369d29c9a998e1cc9a4 (MD5) Previous issue date: 2012 / Resumo: A prevalência de esteato hepatite não alcólica (NASH) aumenta de 20% em indivíduos magros para 80% em pacientes obesos com inflamação hepática caracterizada por elevados níveis de TNF-alfa. Um dos eventos que caracteriza a evolução para NASH é a marcante morte de hepatóciotos resultante da ação do excesso de ácidos graxos livres circulantes. O mecanismo pelo qual o palmitato induz a apoptose é dependente, entre outros parâmetros, do aumento dos níveis de espécies reativas de oxigenio (EROS). O objetivo do presente trabalho foi avaliar se a apoptose de hepatócitos induzida pelo palmitato é dependente do aumento da produção de TNF-alfa. Para testar tal hipótese, utilizamos o Infliximabe, um anticorpo monoclonal específico anti-TNF-alfa, como ferramenta farmacológica para reverter as injúrias provocadas pelo palmitato. Foi observado que após 6 horas de tratamento com o palmitato houve um aumento de expressão de mRNA de TNF-alfa levando a um aumento de apoptose 24 horas após à exposição com o ácido graxo. Este fenômeno concordou temporalmente com um aumento na fosforilação das proteínas IkK, IKbeta e JNK, indicativo de ativação da via de sinalização do TNF-alfa. A apoptose induzida pelo palmitato foi revertida pela adição de um inibidor geral de síntese proteica (Ciclohexamida) ou de um anticorpo neutralizante para o TNF-alfa circulante. Além disso, a produção de EROs e a disfunção mitocondrial induzidas pelo palmitato também foram revertidos por estas estratégias farmacológicas. Com base em tais resultados, concluímos que a apoptose, o acúmulo de EROs e da disfunção mitocondrial induzidas pelo palmitato em células HepG2 são dependentes da produção de TNF-alfa / Abstract: In the last three decades, the prevalence of overweight and obesity has been continuously increasing. Obesity is a risk factor for developing a series of diseases such as whole-body insulin resistance and type 2 diabetes mellitus. Adipose tissue, originally considered merely energy storage, today is recognized as an endocrine organ able of secreting a variety of cytokines, hormones and other substances with specific biological activities, such as saturated fatty acids. Both long chain saturated fatty acids, like palmitate, and the proinflammatory cytokines, as TNF-alfa, are known to activate signaling pathways that promote apoptosis. The mechanism by which the palmitate induces apoptosis is dependent on cell type, for example, human hepatocellular carcinoma line (HepG2) treated with palmitate led lipotoxicity and to increased levels of reactive oxygen species (ROS). Thus, the objective of this study was to evaluate whether apoptosis in HepG2 cells is dependent on increased production of TNF-alfa induced by treatment with palmitate. To test this hypothesis, we used the Infliximab, a monoclonal antibody anti-TNF-alfa, as a pharmacological tool to reverse injuries caused by palmitate. We observed that palmitate increased the mRNA for TNF-alfa and phosphorylation of IkK, Ikbeta and JNK, all indicative of activation of inflammatory signaling pathways. Apoptosis induced by palmitate was suppressed by simultaneous treatment with cycloheximide or infliximab. Furthermore, the production of ROS and mitochondrial dysfunction induced by palmitate were also suppressed by these two pharmacological strategies. Based on these results, we conclude that apoptosis and related events such as increased ROS production and mitochondrial dysfunction induced by palmitate in HepG2 cells are dependent on autocrine action of TNF--alfa / Mestrado / Farmacologia / Mestra em Farmacologia

Orientador: Edi Lúcia Sartorato / Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-25T22:58:29Z (GMT). No. of bitstreams: 1 Miranda_PauloMauriciodoAmorDivino_D.pdf: 3949549 bytes, checksum: 8cd1e0647087ac34cd2bc0ed5d096d0b (MD5) Previous issue date: 2014 / Resumo: A Neuropatia Óptica Hereditária de Leber (LHON) e a Atrofia Óptica Autossômica Dominante (ADOA ou OPA1) são doenças caracterizadas pela perda da visão bilateral, devido a uma degeneração do nervo óptico. Ambas as doenças apresentam também acuidade visual reduzida, discromatopsia, palidez do nervo óptico e escotoma central ou centrocecal. A LHON é causada por mutações no DNA mitocondrial (mtDNA), onde três dessas mutações representam 95% dos casos (mutações primárias principais G11778A, T14484C e G3460A) e as mutações subsequentes representam apenas 5% do total (mutações raras). A ADOA é causada por mutações (mais de 300) no gene nuclear OPA1. Embora os mecanismos moleculares precisos envolvidos no desenvolvimento das duas doenças ainda não são bem compreendidos, foi demonstrado que LHON e ADOA possuem um defeito comum de acoplamento da fosforilação oxidativa. Nesses dois casos, a hipótese é de que as mutações no mtDNA e no gene OPA1 afetariam a integridade mitocondrial, resultando em uma diminuição do fornecimento de energia para os neurônios do nervo óptico. É possível que no Brasil a presença e frequência das alterações da relacionadas à LHON e ADOA sejam diferentes das encontradas em outras partes do mundo. Por isso, o presente estudo teve como principais objetivos rastrear mutações e haplogrupos associadas à LHON e detectar mutações no gene OPA1 em pacientes brasileiros com hipótese diagnóstica de LHON e com Neuropatia Óptica de etiologia a esclarecer. Também foi objetivo otimizar o método de PCR Multiplex Alelo-Específico e padronizar as plataformas de alto rendimento TaqMan® OpenArray® e Iplex Gold/Maldi TOF MS para o rastreamento da LHON. Foram avaliados 101 pacientes, sendo 67 com hipótese diagnóstica de LHON e 34 com neuropatia óptica de etiologia a esclarecer. As mutações da LHON foram detectadas por meio de PCR-RFLP e PCR Multiplex Alelo-Específico. As mutações raras da LHON e do gene nuclear OPA1 (10 principais éxons) foram rastreadas por sequenciamento direto. Foram encontradas mutações da LHON em 36 casos (83.3% com a mutação G11778A e 16.7% com a mutação T14484C). Não foi encontrada a mutação G3460A. Também não foram encontradas mutações raras da LHON e nem mutações relacionadas à ADOA. Haplogrupos de origem africana (L1/L2 e L3) foram mais frequentes no estudo. Foi otimizado o método de PCR Multiplex Alelo-Específico e padronizadas as plataformas TaqMan® OpenArray® e Iplex Gold/Maldi TOF, os quais se mostraram reprodutivos, eficientes e eficazes. A análise molecular das mutações da LHON e do OPA1 foi importante para a confirmação do diagnóstico de 35% dos casos clínicos típicos de LHON e para a elucidação 35% casos de neuropatia óptica de etiologia a esclarecer / Abstract: The Leber Hereditary Optic Neuropathy (LHON) and Autosomal Dominant Optic Atrophy (ADOA) are diseases characterized by loss of vision in both eyes due a degeneration of the optic nerve. Both diseases also exhibit reduced visual acuity, dyschromatopsia, optic nerve and central scotoma or centrocecal. The LHON is caused by mutations in mitochondrial DNA (mtDNA), where three of these mutations account for 95% of cases (major primary mutations G11778A, T14484C and G3460A) and subsequent mutations account for only 5% of the total (rare mutations). The ADOA is caused by mutations (more than 300) in the nuclear gene OPA1. Although the precise molecular mechanisms involved in the development of the two diseases are not well understood, it was shown that LHON and ADOA have a common defect coupling of oxidative phosphorylation. In both cases, the hypothesis is that mutations in mtDNA and OPA1 gene affect mitochondrial integrity, resulting in a decrease in the supply of energy to the neurons of the optic nerve. It is possible that in Brazil the presence and frequency of changes related to LHON and ADOA be different from those found in other parts of the world. Therefore, the present study had two main objectives track haplogroups and mutations associated with LHON and detect mutations in the OPA1 gene in Brazilian patients with a diagnosis of LHON and optic neuropathy of unknown etiology. Another objective was to optimize the method of PCR Multiplex allele-specific and standardize platforms high throughput TaqMan® OpenArray® and Iplex Gold/Maldi TOF MS for screening of LHON. 101 patients were evaluated, 67 with a diagnosis of LHON and 34 with optic neuropathy of unknown etiology. LHON mutations were detected by PCR-RFLP and allele-specific multiplex PCR. Rare mutations of LHON and nuclear gene OPA1 (top 10 éxons) were screened by direct sequencing. LHON mutations were found in 36 cases (83.3% with the G11778A mutation and 16.7% with the T14484C mutation). Not the G3460A mutation. Nor rare mutations of LHON and ADOA or related mutations were found. Haplogroups of African origin (L1/L2 and L3) were more frequent in the study. The method of allele-specific multiplex PCR was optimized and standardized the TaqMan® OpenArray® and iPLEX Gold/Maldi TOF platforms which are shown reproductive, efficient and effective. Molecular analysis of mutations of LHON and ADOA was important to confirm the diagnosis of 35% of the typical clinical cases of LHON and to elucidate 35% cases of optic neuropathy of unknown etiology. Besides being useful also in the prognosis of each patient, for the phenotypic expression of the LHON and ADOA may vary with different genetic background in our population of individuals / Doutorado / Genetica Animal e Evolução / Doutor em Genetica e Biologia Molecular