Thesis (Ph.D.) -- University of Texas Southwestern Medical Center at Dallas, 2005. / Embargoed. Vita. Bibliography: 170-172.

Made available in DSpace on 2014-06-11T19:25:36Z (GMT). No. of bitstreams: 0 Previous issue date: 2010-02-25Bitstream added on 2014-06-13T19:32:57Z : No. of bitstreams: 1 lima_arr_me_botfm.pdf: 825853 bytes, checksum: 593e370c7aa688abb20c1b7dda04672a (MD5) / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Estudos clínicos e experimentais têm sugerido que anormalidades da musculatura esquelética podem colaborar para a ocorrência precoce de dispnéia e fadiga em pacientes com insuficiência cardíaca crônica. Em músculos periféricos e respiratórios, frequentemente observa-se modificação na composição das cadeias pesadas da miosina (MyHC) na insuficiência cardíaca. Os mecanismos e vias intracelulares de sinalização responsáveis pela alteração das MyHCs ainda não estão completamente definidos. Na insuficiência cardíaca direita induzida por monocrotalina, foi verificado que a expressão dos fatores de regulação miogênica está associada a alterações no fenótipo das MyHC. Recentemente, foi verificado que o fator de necrose tumoral-alfa (TNF-α) pode modular a expressão de proteínas miofibrilares. Não identificamos estudos que avaliaram o papel dos fatores de regulação miogênica e a influência do TNF-α na composição das MyHCs no músculo diafragma durante a insuficiência cardíaca. O objetivo deste estudo é determinar se modificações nas isoformas das MyHCs são selacionadas a alterações na expressão gênica dos fatores de regulação miogênica no músculo diafragma de ratos com infarto do miocárdio, com e sem insuficiência cardíaca. Adicionalmente, verificamos se as concentrações séricas de TNF-α e de IL-6 estão relacionadas a alterações das MyHCs e da expressão gênica dos fatores de regulação miogênica. Insuficiência cardíaca foi induzida pro infarto do miocárdio. Seis meses após a cirurgia, foram constituídos três grupos de animais: Sham (n=10), IM/IC- (animais infartados com disfunção ventricular e sem insuficiência cardíaca, n=10) e IM/IC+ (animais infartados com insuficiência cardíaca, n=10). As estruturas cardíacas e a função ventricular foram avaliadas por ecocardiograma... / Several clinial and experimental studies have suggested that skeletal muscle abnormalities can contribute to early fatigue and dyspnea in heart failure patients. Changes of myosin heavy chain (MyHC) isoforms have been frequently observed in peripheral and respiratory muscles during heart failure. Pathophysiological mechanisms and intracellular signaling pathways involved on MyHCs alterations are not completely defined. In monocrotaline-induced right heart failure, it was observed that the expression of myogenic regulatory factors is associated with MyHCs phenotype changes. Tumoral necrosis factor-alpha (TNF-α) has been recently described to modulate skeletal myofibril proteins. We did not find studies evaluating the influence of myogenic regulatory factors and TNF-α serum concentration on diaphragm MyHC isoforms during heart failure. In this study we tested the hypothesis that diaphragm MyHC isoforms changes are related to myogenic regulatory factors gene expression in chronic heart failure. Additionally, we measured TNF-α and interleukin-6 serum levels to examine their correlation with both MyHC isoforms and myogenic regulatory factors gene expression. A coronary ligation nodel was employed to induce heart failure. Six months after the surgical procedure, three groups of rats were studied: Sham (n=10), infarcted rats without heart failure (MI/HF-, n=10), and infarcted rats with heart failure (MI/HF+, n=10). Cardiac structures and ventricular function were assessed by transthoracic echocardiogram. MyHC isoforms were analyzed by protein electrophoresis. Muscle fiber cross-sectional area was measured in hematoxilin-eosin stained sections and in sections submitted to NADH-TR reaction. Myogenic regulatory factors miogenin, MyoD, and MRF4 gene expression was evaluated by real time RT-PCR; TNF-α and interleukin-6 serum levels werre quantified by... (Complete abstract click electronic access below)

Made available in DSpace on 2016-06-02T20:21:22Z (GMT). No. of bitstreams: 1 2665.pdf: 1669132 bytes, checksum: dfe7f18cc9241784c82420b0409bd47e (MD5) Previous issue date: 2009-09-21 / Universidade Federal de Sao Carlos / Disintegrins are toxins commonly found in snake venoms whose biological effects occour upon interaction with surface receptors known as integrins. DisBa-01, an RGD disintegrin isolated from a cDNA library made with mRNAs from the venom gland of Bothrops alternatus, bears anti-metastatic, anti-angiogenic and anti-thrombotic activity in nude mice, partially mediated by interaction with integrin _v_3. Studies with Wistar rats also show that protein has angiogenic activity during regeneration after surgery. The objectives of this study were to evaluate the effects of DisBa-01 on adhesion, deadhesion and proliferation of C2C12 myoblasts and evaluate the electrophoretic profile of secreted proteins of DisBa-01-treated cells. Myoblasts (103 cells/well) were incubated with five concentrations of DisBa-01 under different incubation times and adhesion substracts (plastic, collagen type I or fibronectin). The supernatant was collected for 2DE analysis and the cells were quantified. Also, flow cytometry was used to evaluate the expression of integrins (_2, _4, _5, _v, _v_3, _1 and _4). DisBa-01 inhibited adhesion to fibronectin in high concentration (1000nM) and to collagen type I in all tested concentrations, but did not detach cells from collagen or fibronectina matrix nor affected myoblast proliferation. Flow cytometry showed that integrins _v and _1 were present. 2DE analysis points to an increase of secreted proteins, mainly in higher DisBa- 01 concentration (1000nM). In conclusion, C2C12 myoblasts are sensitive to DisBa-01, suggesting this protein initiates a sinalization cascade mediated by integrins, which modifies protein expression and secretion. / Desintegrinas são toxinas frequentemente encontradas em venenos de serpentes e cujos efeitos biológicos ocorrem devido à interação com receptores de superfície conhecidos como integrinas. A DisBa-01, uma desintegrina RGD isolada de mRNAs da glândula venenífera de Bothrops alternatus, possui atividade anti-metastática, anti-angiogênica e anti-trombótica em camundongos atímicos, parcialmente mediada pela interação com a integrina _v_3. Estudos in vivo com ratos Wistar também indicam que esta proteína pode ter atividade pró-angiogênica durante regeneração pós-cirúrgica. O objetivo deste estudo foi avaliar os efeitos da DisBa-01 na adesão, desadesão e proliferação celular de mioblastos C2C12, além de avaliar o perfil eletroforético das proteínas secretadas por estas células sob condições normais e tratadas. As células (103 células/poço) foram incubadas com diferentes concentrações de DisBa-01 em diferentes tempos e substratos (plástico, colágeno tipo I e fibronectina). O meio de cultura foi recolhido para análise por eletroforese bidimensional (2DE) e as células foram quantificadas. Além disso, foi realizada citometria de fluxo para avaliar a expressão de integrinas (_2, _4, _5, _v, _v_3, _1 e _4). A DisBa-01 inibiu a adesão das células à fibronectina em alta concentração (1000nM), além de inibir a adesão das células ao colágeno em todas as concentrações testadas, mas não promoveu a desadesão de células aderidas a estes dois substratos tampouco afetou significativamente a proliferação de mioblastos. A análise por citometria de fluxo identificou as integrinas _v e _1, corroborando em parte os resultados obtidos. A análise por 2DE do sobrenadante indicou que a DisBa-01 induz a um aumento no número de proteínas secretadas, principalmente na maior concentração testada (1000nM). Em conclusão, os mioblastos C2C12 são sensíveis à DisBa-01, sugerindo que esta proteína inicia uma cascata de sinalização celular mediada por integrinas que modifica a secreção protéica.

Resumo: Estudos clínicos e experimentais têm sugerido que anormalidades da musculatura esquelética podem colaborar para a ocorrência precoce de dispnéia e fadiga em pacientes com insuficiência cardíaca crônica. Em músculos periféricos e respiratórios, frequentemente observa-se modificação na composição das cadeias pesadas da miosina (MyHC) na insuficiência cardíaca. Os mecanismos e vias intracelulares de sinalização responsáveis pela alteração das MyHCs ainda não estão completamente definidos. Na insuficiência cardíaca direita induzida por monocrotalina, foi verificado que a expressão dos fatores de regulação miogênica está associada a alterações no fenótipo das MyHC. Recentemente, foi verificado que o fator de necrose tumoral-alfa (TNF-α) pode modular a expressão de proteínas miofibrilares. Não identificamos estudos que avaliaram o papel dos fatores de regulação miogênica e a influência do TNF-α na composição das MyHCs no músculo diafragma durante a insuficiência cardíaca. O objetivo deste estudo é determinar se modificações nas isoformas das MyHCs são selacionadas a alterações na expressão gênica dos fatores de regulação miogênica no músculo diafragma de ratos com infarto do miocárdio, com e sem insuficiência cardíaca. Adicionalmente, verificamos se as concentrações séricas de TNF-α e de IL-6 estão relacionadas a alterações das MyHCs e da expressão gênica dos fatores de regulação miogênica. Insuficiência cardíaca foi induzida pro infarto do miocárdio. Seis meses após a cirurgia, foram constituídos três grupos de animais: Sham (n=10), IM/IC- (animais infartados com disfunção ventricular e sem insuficiência cardíaca, n=10) e IM/IC+ (animais infartados com insuficiência cardíaca, n=10). As estruturas cardíacas e a função ventricular foram avaliadas por ecocardiograma... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: Several clinial and experimental studies have suggested that skeletal muscle abnormalities can contribute to early fatigue and dyspnea in heart failure patients. Changes of myosin heavy chain (MyHC) isoforms have been frequently observed in peripheral and respiratory muscles during heart failure. Pathophysiological mechanisms and intracellular signaling pathways involved on MyHCs alterations are not completely defined. In monocrotaline-induced right heart failure, it was observed that the expression of myogenic regulatory factors is associated with MyHCs phenotype changes. Tumoral necrosis factor-alpha (TNF-α) has been recently described to modulate skeletal myofibril proteins. We did not find studies evaluating the influence of myogenic regulatory factors and TNF-α serum concentration on diaphragm MyHC isoforms during heart failure. In this study we tested the hypothesis that diaphragm MyHC isoforms changes are related to myogenic regulatory factors gene expression in chronic heart failure. Additionally, we measured TNF-α and interleukin-6 serum levels to examine their correlation with both MyHC isoforms and myogenic regulatory factors gene expression. A coronary ligation nodel was employed to induce heart failure. Six months after the surgical procedure, three groups of rats were studied: Sham (n=10), infarcted rats without heart failure (MI/HF-, n=10), and infarcted rats with heart failure (MI/HF+, n=10). Cardiac structures and ventricular function were assessed by transthoracic echocardiogram. MyHC isoforms were analyzed by protein electrophoresis. Muscle fiber cross-sectional area was measured in hematoxilin-eosin stained sections and in sections submitted to NADH-TR reaction. Myogenic regulatory factors miogenin, MyoD, and MRF4 gene expression was evaluated by real time RT-PCR; TNF-α and interleukin-6 serum levels werre quantified by... (Complete abstract click electronic access below) / Orientador: Marina Politi Okoshi / Coorientador: Katashi Okoshi / Banca: Márcia Koike / Banca: Paula Schmidt Azevedo Gaiolla / Mestre

Orientador: Maeli Dal Pai Silva / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-05T10:23:42Z (GMT). No. of bitstreams: 1 Lopes_FrancisdaSilva_M.pdf: 7866898 bytes, checksum: ade20c607baab16a33f7564ca3630b10 (MD5) Previous issue date: 2005 / Resumo: A insuficiência cardíaca (IC) é caracterizada pela intolerância ao exercício físico, devido à fadiga precoce e à dispnéia. Entre as alterações que podem contribuir para a dispnéia nesta síndrome, tem sido descrita a miopatia diafragmática com atrofia e mudanças na miosina de cadeia pesada (MHC) do tipo II "rápida" para a do tipo I "lenta". Entretanto, os mecanismos regulatórios músculos específicos que alteram a expressão das isoformas de miosinas no diafragma durante a IC não são conhecidos. O objetivo do presente trabalho foi determinar, no músculo diafragma (DIA) de ratos Wistar com IC induzida por monocrotalina, se a transição da expressão protéica das MHCs está associada com alterações na expressão do RNAm dos fatores de regulação miogênicos (MRF). A região costal do diafragma de ratos Wistar machos (3-4 semanas de idade; 80-100g) dos grupos IC (n= 09) e Controle (CT; n= 06) foi estudada quando os sinais de IC estavam evidentes, aproximadamente 22 dias após a administração da monocrotalina nos animais IC. A expressão de MyoD e miogenina foi determinada através da técnica de RT-PCR enquanto que a expressão das MHCs foi estudada através de eletroforese por gel de poliacrilamida. Os animais com IC apresentaram diminuição tanto na expressão protéica da MHC Ila/llx quanto na expressão gênica de MyoD, sem alterar a expressão das MHCs I e IIb e da miogenina. Em conclusão, na IC, a alteração na expressão do RNAm da MyoD pode, em parte, explicar a alteração na expressão protéica da MHC Ilalllx / Abstract: Heart failure (HF) is characterized bya reduced tolerance to exercise due to early fatigue and dyspnea. Alterations that may contribute to dyspnea in this syndrome are diaphragmatic myopathy with atrophy and shift from type 11 "fast" to type I "slow" myosin heavy chain (MHC). However, the skeletal muscle-specific molecular regulatory mechanisms that alter MHC expression in the diaphragm during heart failure have not been defined. The purpose of this investigation was to determine whether myosin heavy chain expression during heart failure is associated with changes in myogenic regulatory factors (MRFs) mRNA expression in Wistar rat diaphragm with heart failure (HF) induced by monocrotaline. Costal diaphragm (DIA) muscle from HF (n=09) and control (n=06) 3-4 week old, 80-100g male Wistar rats was studied when overt HF had developed in the HF animais 22 days after monocrotaline administration. MyoD and myogenin expression were determined by RT-PCR, MHC isoform expression was determined by polyacrylamide gel electrophoresis. HF animais presented decreased myosin heavy chain lIa/llx protein isoform and MyoD gene expression content, without altering MHC I & IIb and myogenin expression. In summary, our results show that in HF, alterations in MyoD mRNA expression may, in part, explain alterations in MHC lIalllx content / Mestrado / Biologia Celular / Mestre em Biologia Celular e Estrutural

La myogénèse est un processus multi-étapes hautement régulé impliquant la prolifération et la différenciation de myoblastes. Bien que la myogenèse ait été largement décrite, les mécanismes de régulation qui régissent ce processus complexe sont encore mal connus, notamment les réseaux de gènes et les interactions potentielles entre les voies de signalisation impliquées. Afin d'identifier de nouveaux gènes jouant un rôle dans la différenciation myogénique, j’ai mis en place un nouveau protocole in vitro, basé sur la lignée myoblastique C2C12, l’utilisation de l’ARN interférence et l'analyse quantitative d'images d'une grande quantité de myoblastes différenciés. J’ai pu inactiver une centaine de gènes et par une analyse quantitative de la densité cellulaire, de la quantité de myotubes, de la morphologie du myotube et de l'indice de fusion, j’ai pu montrer que six gènes parmi les 100 sont impliqués à la fois dans la prolifération et la différenciation des cellules C2C12 et 13 gènes jouant un rôle uniquement dans l’étape de différenciation. Nos résultats montrent que notre crible peut être un outil efficace pour détecter aussi bien les phénotypes subtils permettant l'identification de nouveaux régulateurs myogéniques chez les mammifères. / Myogenesis is a highly regulated multi-step process involving myoblast proliferation and differentiation. Although studies over the last decades have identified several factors governing these distinct major phases, many of them are not yet known. In order to identify novel genes, we took advantage of the C2C12 myoblastic line to establish a functional siRNA screen combined with quantitative-imaging analysis of a large amount of differentiated myoblasts. We knocked down 100 mouse-preselected genes without a previously characterized role in muscle. Using image analysis, we tracked gene-silencing phenotypes by quantitative assessment of cellular density, myotube quantity, myotube morphology and fusion index. Our results have revealed six genes involved in both stages of C1C12 myogenesis and 13 genes specific to the differentiation stage. These findings prove that our RNAi-based screen could be an efficient tool to detect clear and subtle phenotypes allowing the identification of new myogenic regulators in Mammals.

As lesões dos nervos periféricos, que inervam os músculos esqueléticos, evoluem para perdas da propriocepção e alterações na morfologia e função das fibras musculares, causando um impacto negativo na qualidade de vidas dos indivíduos. Tais lesões implicam em alteração na expressão de genes específicos do músculo, como por exemplo, na MyoD e Miogenina, atuantes na ativação de células satélites e reguladores da massa muscular A técnica cirúrgica de tubulização é um recurso empregado na prática clínica para tratamento de músculos que sofreram desnervação. O objetivo do presente estudo foi analisar se a técnica de tubulização com o preenchimento de gordura altera a expressão de Myod e Miogenina, a morfometria do músculo sóleo de ratos e localização da Myod e Miogenina. Para isso, 57 ratos Wistar foram separados em grupos: controle inicial (GCI); final 45 (GCF45), final 150 (GCF150), desnervado 45 dias (GD45), desnervado 150 dias (GCD150) e grupos experimentais com veia vazia 45 dias (GESP45) e 150 dias (GESP150) e com veia preenchida de gordura 45 dias (GEG45) e 150 dias (GEG150). Para os procedimentos cirúrgicos de desnervação e reinervação e coleta do músculo os animais foram profundamente anestesiados. Após os devidos tempos experimentais, os animais foram sacrificados, o músculo sóleo foi dissecado, envolvido em meio de criopreservação e estocado a -80°C. A quantificação de mRNA do MyoD e Miogenina foi realizada por amplificação por reação em cadeia de polimerase (PCR) em tempo real (RealTimePCR) e a localização da produção de Myod e Miogenina foi realizada por microscopia confocal a laser e imunofluorescência. A morfometria foi realizada em lâminas coradas com HE, observadas em microscópio ótico e calculadas pelo software Image Pro-Plus 6.2. Os resultados do presente estudo mostraram que houve aumento da expressão do Myod e Miogenina nos grupos experimentais 45 dias quando comparados ao grupo controle inicial e um decréscimo da expressão de Myod e Miogenina para os grupos experimentais com 150 dias. A área da secção transversa nos grupos experimentais com 45 dias (GESP45 e GEG45) não apresentaram diferença estatística, quando comparado com grupo desnervado 45 dias (GCD45), enquanto que o grupo experimental com preenchimento de gordura 150 dias (GEG150) obteve os melhores resultados na medida da área da secção transversal do músculo sóleo. As lâminas observadas no microscópio confocal mostram a MyoD e Miogen localizadas no mionúcleo. Concluiu-se que o uso da gordura na técnica de tubulização do nervo ciático de ratos, interfere na regeneração do músculo sóleo. / Peripheral nerve injuries can result in the loss of propioception, morphological and functional alterations of muscle fibers which causes a negative impact on the quality of life. These injuries elicit an alteration on the expression of muscle specific genes, like MyoD and Myogenin, involved in the satellite cell activation and muscle mass regulation. The vein graft tubulization is a well known technique for treatment of denervated muscle. The aim of this work was to investigate if vein graf tubulization filled with fat tissue changes the expression and localization of MyoD and Myogenin and to study if it can modify the morphometry of soleus muscle. Fifty seven Wistar rats were divided in initial control group (ICG), final control group 45 days and 150 days (FCG45; FCG150), denervated 45 days and 150 days (D45; D150) and experimental groups with vein graft 45 days and 150 days (VG45; VG150). and vein graft filled with fat tissue 45 days and 150 days (VF45; VF150). For denervation and reinervation procedures and muscle biopsy the animals were submitted to anaesthesia and after the experimental time they were euthanized. Soleus muscle was dissected, involved in criopreservation medium and stored at -80oC. It was performed RealTime polymerase chain reaction (RealTimePCR) for MyoD and Myogenin mRNA quantification. The localization of its production was analysed by laser confocal microscopy and immunofluorescence staining. The morphometric analysis were done by Hematoxilin-Eosin staining and examined at optical microscopy using the Image ProPlus 6.2 software. There was an upregulation on the expression of MyoD and Myogenin for the experimental groups at 45 days when compared to the initial control group. On the other hand, we found a downregulation on the MyoD and Myogenin expression in the same groups with 150 days. The area of transversal section in the 45 days experimental groups (VF45, VG45) did not show statistical difference compared with denervated group with 45 days (D45). Moreover, the group filled with fat tissue at 150 days (VF150) presented the best results in the transversal section area of soleus muscle. In addition, the slides analysed under confocal microscopy showed the localization of MyoD and Myogenin in the mionuclei. In conclusion, the application of vein graft filled fat tissue improves the soleus muscle regeneration.

Objective: The aim of this study was to compare cervical and ocular vestibular evoked myogenic potentials (cVEMP and oVEMP) in young gender- and age-matched black African and Caucasian male and female adults. Design: A quasi-experimental between-subjects research design was utilised. This study was comparative in nature, thus data was collected in a cross-sectional manner from two age- and gender-matched racial groups, namely black African and Caucasian, and compared. Furthermore, interactions of gender and race were also examined in this research study. Methods: Sixty healthy age- and gender-matched participants (30 black African, 30 Caucasian) between the ages of 18 25 years participated in this study. Fifteen males and fifteen females, within one year of the age of their racial participant counterparts, were included in each racial group. Latencies, peak-to-peak amplitudes and asymmetry ratios were analysed for both groups in these tests. Furthermore, auditory brainstem response (ABR) and electromyography (EMG) testing were conducted to investigate whether possible racial differences in VEMP tests could be attributed to differences in neural or muscular function. Results: Black African participants demonstrated significantly shorter latencies of the n23 component of the cVEMP and the p15 component of the oVEMP, as well as larger peakto- peak amplitude of the oVEMP response. Highly significant differences were found in all EMG measurements between the two racial groups, suggesting that these racial VEMP differences are primarily based on differences in muscular function between black Africans and Caucasians. Significant gender differences were observed in all tests conducted, with females predominantly displaying shorter latencies, while males had larger amplitudes. Conclusions: Young black African adults demonstrated significant differences in both cVEMP and oVEMP responses, namely shorter latencies and larger amplitudes, in comparison to young Caucasian adults. Correlations with differences in EMG measurements suggest that these differences are primarily due to differences in muscular function as opposed to neural function. Future research is required to confirm and expand on these findings. / Dissertation (MCommunication Pathology)--University of Pretoria, 2016. / Speech-Language Pathology and Audiology / MCommunication Pathology / Unrestricted

La phospholipase D (PLD) hydrolyse la phosphatidylcholine des membranes cellulaires, libérant le messager acide phosphatidique. La capacité de la PLD à influer sur la voie de signalisation de mTOR, acteur central dans le contrôle du tissu musculaire, nous a incités à étudier son rôle dans ce tissu. Mes travaux de thèse ont pour but d'étudier les mécanismes par lesquels la PLD intervient dans la différenciation myogénique et dans la régulation de la masse musculaire. Dans un premier temps, nous avons montré que le contrôle de la différenciation des myoblastes L6 par la PLD met en jeu l'activation des deux complexes de mTOR (mTORC1 et mTORC2). mTORC2 active la différenciation, probablement via son effecteur PKCalpha, alors que mTORC1 la réprime via son effecteur S6K1, en induisant la phosphorylation de rictor, un composant de mTORC2, et l'inhibition de ce complexe. Nous avons par ailleurs montré que l'extinction de PLD par interférence de I'ARN induit l'atrophie de myotubes L6 en culture, ainsi qu'une baisse de la phosphorylation de S6K1 et 4E-BP1, effecteurs de mTORC1. Inversement, la surexpression de PLD à l'aide de vecteurs adénoviraux induit une hypertrophie des myotubes, associée à une activation de la voie mTORC1, et de Akt, effecteur de mTORC2. De plus, la surexpression de PLD atténue l'atrophie induite par la dexaméthasone. Ces résultats mettent en évidence un rôle hypertrophique et anti-atrophique de la PLD, qui pourrait s'exercer par stimulation de la voie mTOR. Nos résultats suggèrent que la PLD est susceptible de jouer un rôle clé dans le muscle squelettique, en agissant tant au niveau de la régénération du tissu qu'au niveau de la régulation de sa masse. / Phospholipase D (PLD) hydrolyzes phosphatidylcholine of cell membranes, releasing the lipid messenger phosphatidic acid. The ability of PLD to affect mTOR signaling pathway, a central actor in the control of muscle tissue, prompted us to study its role in this tissue. My thesis aims at investigating how PLD is involved in myogenic differentiation, and how it regulates muscle mass. We first showed that the mechanism by which PLD controls differentiation of L6 myoblasts involves the activation of the two mTOR complexes (mTORC1 and mTORC2). mTORC2 activates differentiation, probably via its effector PKCalpha, whereas mTORC1 represses differentiation via its effector S6K1, by inducing the phosphorylation of Rictor, a component of mTORC2, and the inhibition of this complex. Besides, we showed that extinction of PLD by RNA interference induces the atrophy of L6 myotubes, and decreases the phosphorylation of the mTORC1 effectors S6K1 and 4E-BP1. Conversely, overexpression of PLD using adenoviral vectors induces the hypertrophy of myotubes and the activation of both mTORC1 pathway and the mTORC2 effector Akt. Furthermore, PLD overexpression attenuates atrophy induced by dexamethasone. These results highlight a hypertrophic and anti-atrophic role of PLD, which could be achieved through stimulation of the mTOR pathway. Our results suggest that PLD is likely to play a key role in skeletal muscle homeostasis, by acting at both the tissue regeneration and mass regulation levels.

No description available.