Embora a transferência nuclear de células somáticas (TNCS) seja uma ferramenta promissora, seu amplo uso é impedido devido às altas taxas de mortalidade durante o desenvolvimento dos animais clonados. Acredita-se que a reprogramação epigenética anormal seja a principal causa desta baixa eficiência. Nós hipotetizamos que agentes modificadores de cromatina (AMCs) atingindo a acetilação das histonas e a metilação do DNA poderiam alterar a configuração da cromatina e torná-la mais facilmente reprogramável. Deste modo, fibroblastos bovinos foram tratados com 5-aza-2\'-deoxicitidina (AZA) mais tricostatina A (TSA) ou hidralazina (HH) mais ácido valpróico (VPA) enquanto, em outro experimento, zigotos bovinos clonados foram tratados com TSA. O tratamento dos fibroblastos com AZA+TSA ou HH+VPA aumentou a acetilação das histonas, mas não afetou o nível de metilação do DNA. Entretanto, o tratamento com HH+VPA diminuiu a viabilidade/proliferação celular. O uso destas células como doadoras de núcleo não mostrou efeitos positivos sobre o desenvolvimento pré- e pós-implantação. Em relação ao tratamento dos zigotos clonados com TSA, o tratamento destes mostrou um aumento nos padrões de acetilação das histonas, mas não reduziu o nível de metilação do DNA. Além disso, este tratamento não resultou em efeito positivo sobre o desenvolvimento pré- e pósimplantação. Este trabalho fornece evidências de que o tratamento de células doadoras de núcleo ou zigotos clonados com AMCs não tem efeito positive sobre o desenvolvimento pré- e pós-implantação de bovinos clonados. / Although somatic cell nuclear transfer (SCNT) is a promising tool, its potential use is hampered by the high mortality rates during the development to term of cloned offspring. Abnormal epigenetic reprogramming of donor nuclei after SCNT is thought to be the main cause of this low efficiency. We hypothesized that chromatinmodifying agents (CMAs) targeting chromatin acetylation and DNA methylation could alter the chromatin configuration and turn them more amenable to reprogramming. Thus, bovine fibroblasts were treated with 5-aza-2\'-deoxycytidine (AZA) plus trichostatin (TSA) or hydralazine (HH) plus valproic acid (VPA) whereas, in another trial, cloned bovine zygotes were treated with TSA. The treatment of fibroblasts with either AZA+TSA or HH+VPA increased histone acetylation, but did not affect the level of DNA methylation. However, treatment with HH+VPA decreased cellular viability and proliferation. The use of these cells as nuclear donors showed no positive effect on pre- and post-implantation development. Regarding the treatment of cloned zygotes with TSA, treated one-cell embryos showed an increase in the acetylation patterns, but not in the level of DNA methylation. Moreover, this treatment revealed no positive effect on pre- and post-implantation development. This work provides evidence the treatment of either nuclear donor cells or cloned zygotes with CMAs has no positive effect on pre- and post-implantation development of cloned cattle.

A Amiotrofia Espinhal Progressiva (AEP) é uma doença autossômica recessiva que afeta os motoneurônios do corno anterior da medula espinhal, acarretando hipotonia e fraqueza muscular. A partir do conhecimento do mecanismo molecular da AEP, abriu-se um campo para testes clínicos com agentes farmacológicos que possam aumentar o nível da proteína SMN2. Diversas drogas com esta ação estão sendo testadas na tentativa de encontrar um possível tratamento para esta trágica doença. O ácido valpróico (AV), droga muito utilizada para o tratamento da epilepsia mostrou ter a propriedade de ativar o promotor do gene da proteína SMN2, aumentando a sua produção. Tendo em vista que não há uniformização do sistema de avaliação clínica dos resultados do tratamento em diferentes países, foi elaborado um protocolo selecionando métodos de avaliação fáceis, rápidos e já validados a fim de verificar se o AV é eficaz para manter ou melhorar a força muscular dos pacientes com AEP. Os métodos selecionados foram: escala Medical Research Council (MRC) para força muscular; Hammersmith motor ability score para habilidade motora; goniometria das principais articulações; cronometragem de tempo despendido para deambular, quando possível; índice de Barthel para atividades da vida diária e, por fim, um questionário para verificar as modalidades de fisioterapia e hidroterapia em uso. Vinte e dois pacientes com AEP tipo II e III, com idades variando de 2 a 18 anos, medicados com AV, foram avaliados a cada três meses durante um ano, totalizando cinco visitas, das quais a primeira ocorreu nos dias anteriores ao início do tratamento. Os resultados dos testes demonstraram que, durante o seguimento de um ano, os pacientes obtiveram melhora na habilidade motora, porém não na força muscular, o que é um resultado extremamente positivo. Crianças com idade menor ou igual a 6 anos mostraram melhores ganhos quanto à habilidade motora. / Spinal Muscular Atrophy (SMA) is an autosomal recessive disorder that affects the spinal motoneurons, resulting in hypotonia and muscle weakness. The knowledge of the molecular mechanism of SMA has originated new researches including clinical trials with pharmacological agents that increase SMN2 protein level. Many drugs with this action are being tested with the aim of finding a possible treatment for this severe disease. The valproic acid (VA), a well-known drug used to treat epilepsy has the property of activating the SMN2 gene promoter and then to increase SMN2 protein level. Since there isnt an uniform system for the clinical evaluation of the treatment results, we selected a set of easy, fast and already validated methods to evaluate if the VA is effective to stabilize or improve the motor function in patients with SMA. The selected methods were: Medical Research Council scale (MRC) to muscular strength; Hammersmith motor ability score to motor ability; goniometry of the main joints; time to walk when possible; Barthel índex for daily activities, and a questionnaire to verify the types of physiotherapy and hydrotherapy in use. Twenty two patients with SMA II and III, aged between 2 and 19 years, and treated with VA were evaluated every three months during the period of one year; the first evaluation occurred immediately before the onset of the treatment. The results of the tests demonstrated that along the period of 12 months the patients didnt gain muscle strength but improved their motor ability, that can be considered a positive result. Children aged six years or younger had a higher gain in motor ability along the period of the study.

Dans le cadre du programme commun d’études pharmaco-épidémiologiques de la caisse nationale de l'assurance maladie et de l’agence nationale de sécurité du médicament, visant à évaluer l'impact sanitaire en France de l'exposition in utero à l’acide valproïque à partir des bases de données médico-administratives (BDMA) françaises, l’objectif de cette thèse était d’étudier l’utilisation des antiépileptiques pendant la grossesse et les risques de malformations congénitales et de troubles neuro-développementaux associés chez l’enfant. Le premier volet de cette thèse a consisté à formaliser et publier un algorithme d’identification des grossesses spécifiquement adapté aux BDMA françaises. L’application de cet algorithme à la description de l’utilisation des antiépileptiques pendant la grossesse a permis d’estimer à 6,7‰ la prévalence de l’utilisation des antiépileptiques pendant la grossesse et de montrer une baisse de l’utilisation des antiépileptiques de première génération, en particulier de l’acide valproïque, au bénéfice des antiépileptiques de deuxième génération entre 2007 et 2014. Dans le deuxième volet de cette thèse, l’exposition in utero à l’acide valproïque a été retrouvée associée à une augmentation du risque d’un grand nombre des malformations congénitales majeures (MCM) étudiées, avec une relation dose-effet pour les MCM les plus fréquentes, et l’exposition in utero au topiramate à une augmentation du risque de fentes oro-faciales. Des signaux relatifs à la prégabaline, au clonazépam et au phénobarbital ont aussi été identifiés. Dans le troisième volet de cette thèse, l’exposition in utero à l’acide valproïque a été retrouvée associée à une augmentation du risque de chacun des événements neuro-développementaux précoces étudiés versus lamotrigine, avec une relation dose-effet, à l’inverse des autres antiépileptiques. La réalisation d’études pharmaco-épidémiologiques à partir des BDMA françaises a permis aux autorités sanitaires de fournir rapidement des données sur l’utilisation des antiépileptiques pendant la grossesse en France. La réalisation de ces études a aussi permis de participer à l’enrichissement de la littérature observationnelle internationale sur les conséquences de l’exposition in utero aux antiépileptiques pour l’enfant à naitre. / The works of this thesis have been carried out within a programme of pharmacoepidemiological studies initiated by the National Agency of Medicine and Health Product Safety (ANSM) and the National Health Insurance fund (Cnam) in order to evaluate the public health situation in relation to prenatal exposure to valproic acid in France on the basis of the French health care databases. The objective of this thesis was to study antiepileptic drug (AED) use during pregnancy and the risks of congenital malformations and neurodevelopmental disorders associated with prenatal exposure to these drugs. In a first study, we developed an algorithm to identify pregnancy episodes and related outcomes using the French health care claims databases and applied it to study AED use during pregnancy between 2007 and 2014. Over the study period, 6.7 per 1000 pregnancies were exposed to an AED. The use of newer AEDs increased concomitantly with the decreased use of valproic acid and the other older AEDs. In a second study, prenatal exposure to valproic acid was found to be associated with a wide range of malformations among those investigated, with a dose-response relationship for half of them, and prenatal exposure to topiramate with an increased risk of cleft lip with or without cleft palate. Signals concerning pregabalin, clonazepam and phenobarbital have also been identified. In a third study, prenatal exposure to valproic acid was found to be associated with increased risks of all early neurodevelopmental outcomes investigated compared with lamotrigine, with a dose-response relationship. Prenatal exposure to the other AEDs was not associated with an increased risk of any of these neurodevelopmental outcomes versus lamotrigine. Conducting pharmacoepidemiological studies based on the French health care databases enabled the health authorities to rapidly provide data on the use of AED during pregnancy in France. It also brought additional evidence to the international observational literature on the consequences of prenatal exposure to AEDs for the unborn child.

A amiotrofia espinal (AEP) é a mais freqüente das doenças neuromusculares (DNM) responsáveis pela Síndrome da Criança Hipotônica (SCH), causada pela degeneração das células do corno anterior da medula espinhal. O comprometimento neurológico se estabelece de forma rápida e intensa nos primeiros meses de vida de tal maneira que, em pouco tempo, a única atividade motora voluntária persistente pode ser a motricidade ocular. O Ácido Valpróico é um medicamento de fácil aquisição e administração, demonstrou-se eficaz em evitar a deleção do exon 7, o que prolongaria ainda mais a sobrevivência dos neurônios. Com base nesta nova perspectiva terapêutica para esta drástica doença e por não existir nenhuma forma de avaliação motora validada e de fácil reprodutibilidade, foi desenvolvido um protocolo de avaliação física-funcional para acompanhamento deste grupo de pacientes e de outros com a SCH, com o objetivo de avaliar quantitativamente e qualitativamente a evolução de aquisição motora nos pacientes, selecionando provas funcionais e criando uma nova forma de avaliação utilizando o recurso da filmagem para posterior examinação, de fácil aplicação em consultório, que permitam uniformizar a interpretação dos resultados em diferentes pesquisas ou individualmente ao longo de um acompanhamento clínico. Cinco pacientes com AEP-I, com idades variando de 04 a 18 meses, sem a necessidade de auxílio respiratórios, e submetidos à intervenção medicamentosa com o Ácido Valpróico, foram avaliados em 05 visitas, totalizando um acompanhamento de 2 meses e meio. A análise das aquisições motoras obedeceu a um roteiro de movimentação utilizando a filmagem e posteriormente atribuindo uma pontuação. Os resultados demonstraram que todas as crianças participantes do estudo não apresentaram piora do quadro motor, o que seria esperado pela evolução natural da doença. Consideramos assim que: os pacientes submetidos à intervenção medicamentosa com o Ácido Valpróico apresentaram uma tendência à melhora das aquisições motoras, em relação ao descrito na evolução natural da doença e a utilização da filmagem como método de análise de aquisição motora se mostrou ser um recurso eficaz no acompanhamento da evolução motora dos pacientes. / The spinal muscle atrophy (SMA) is the most frequent neuromuscular disease responsible for Hypotonic Children Syndrome (HCS). SMA is caused by anterior horn cells degeneration in the narrow. The neurological impairment is quickly and strongly established in the first months of life, so, after few months, the only movement that the children can do is moving the eyes. The Valproic acid is a drug easy to buy and to manage, and seems to avoid exon 7 deletion, which could prolong the neurons life. By this new therapeutic knowledge, and for don\'t exist a validate and easy to reproduce way to evaluate the motor function, there were made a functional evaluation protocol to follow the group of patients with SMA and other patients with HCS, with the purpose to qualify and to quantify the motor gain in these patients, creating a new form to evaluate, using film to exam in the end. It\'s easy to apply in the office and can became the only way to evaluate the results in different trials. There were evaluate five patients with SMA type 1, ages from 04 to 18 months, without respiratory assistance use, underwent to Valproic acid intervention. They were evaluated in five visits, in a total 2 years and a half of following. The motor acquisitions were made from the film and scores. The results showed that no one off al children presented a motor loss, which would be expected for the natural evolution of SMA type 1. Consequently, the patients that underwent to valproic acid trial presented a tendency to gain motor abilities when compared to the natural evolution of the disease and the film as an analyze method seem to be an efficient way to follow the motor evolution of these patients.

A Amiotrofia Espinhal Progressiva (AEP) é uma doença autossômica recessiva que afeta os motoneurônios do corno anterior da medula espinhal, acarretando hipotonia e fraqueza muscular. A partir do conhecimento do mecanismo molecular da AEP, abriu-se um campo para testes clínicos com agentes farmacológicos que possam aumentar o nível da proteína SMN2. Diversas drogas com esta ação estão sendo testadas na tentativa de encontrar um possível tratamento para esta trágica doença. O ácido valpróico (AV), droga muito utilizada para o tratamento da epilepsia mostrou ter a propriedade de ativar o promotor do gene da proteína SMN2, aumentando a sua produção. Tendo em vista que não há uniformização do sistema de avaliação clínica dos resultados do tratamento em diferentes países, foi elaborado um protocolo selecionando métodos de avaliação fáceis, rápidos e já validados a fim de verificar se o AV é eficaz para manter ou melhorar a força muscular dos pacientes com AEP. Os métodos selecionados foram: escala Medical Research Council (MRC) para força muscular; Hammersmith motor ability score para habilidade motora; goniometria das principais articulações; cronometragem de tempo despendido para deambular, quando possível; índice de Barthel para atividades da vida diária e, por fim, um questionário para verificar as modalidades de fisioterapia e hidroterapia em uso. Vinte e dois pacientes com AEP tipo II e III, com idades variando de 2 a 18 anos, medicados com AV, foram avaliados a cada três meses durante um ano, totalizando cinco visitas, das quais a primeira ocorreu nos dias anteriores ao início do tratamento. Os resultados dos testes demonstraram que, durante o seguimento de um ano, os pacientes obtiveram melhora na habilidade motora, porém não na força muscular, o que é um resultado extremamente positivo. Crianças com idade menor ou igual a 6 anos mostraram melhores ganhos quanto à habilidade motora. / Spinal Muscular Atrophy (SMA) is an autosomal recessive disorder that affects the spinal motoneurons, resulting in hypotonia and muscle weakness. The knowledge of the molecular mechanism of SMA has originated new researches including clinical trials with pharmacological agents that increase SMN2 protein level. Many drugs with this action are being tested with the aim of finding a possible treatment for this severe disease. The valproic acid (VA), a well-known drug used to treat epilepsy has the property of activating the SMN2 gene promoter and then to increase SMN2 protein level. Since there isnt an uniform system for the clinical evaluation of the treatment results, we selected a set of easy, fast and already validated methods to evaluate if the VA is effective to stabilize or improve the motor function in patients with SMA. The selected methods were: Medical Research Council scale (MRC) to muscular strength; Hammersmith motor ability score to motor ability; goniometry of the main joints; time to walk when possible; Barthel índex for daily activities, and a questionnaire to verify the types of physiotherapy and hydrotherapy in use. Twenty two patients with SMA II and III, aged between 2 and 19 years, and treated with VA were evaluated every three months during the period of one year; the first evaluation occurred immediately before the onset of the treatment. The results of the tests demonstrated that along the period of 12 months the patients didnt gain muscle strength but improved their motor ability, that can be considered a positive result. Children aged six years or younger had a higher gain in motor ability along the period of the study.

La leucémie lymphoïde chronique (LLC) est la plus fréquente des leucémies qui touchent le monde occidental. Cette pathologie est toujours incurable et se caractérise par une hétérogénéité d’évolution clinique marquée par une survie globale oscillant de quelques mois à des dizaines d’années. Il est donc primordial de savoir à quel type d’évolution le patient sera confronté afin d’adapter au mieux le suivi de la maladie et la précocité ou non du traitement.<p><p>\ / Doctorat en Sciences biomédicales et pharmaceutiques / info:eu-repo/semantics/nonPublished

<p>Valproic acid (<em>2-propylpentanoicacid</em>) has long been in use as an anticonvulsant and mood-stabilizer. Recently, VPA has been shown to inhibit the activity of histone deacetylases (HDACs), resulting in chromatin remodelling and changes in gene expression<em>.</em> Although the molecular mechanism for VPA action in the central nervous is not well understood, many signalling pathways have been suggested as targets for this HDAC inhibitor. For instance, VPA was found to induce differentiation in adult hippocampal neural progenitor cells via the β-catenin-Ras-ERK pathway. Also, VPA up regulated Bcl-2, a neurotrophic/neuroprotective protein, with association of extracellular signal-regulated kinase (ERK-1) and phosphatidylinositol 3- kinase (PI3) pathway activation. In this study, C17.2 neural stem cells were used to examine the effects of VPA on the expression of several neurotrophic factors including; cerebral dopamine neurotrophic factor (CDNF) and mesencephalic astrocyte-derived neurotrophic factor (MANF), glial cell-derived neurotrophic factor (GDNF), <em>brain-derived neurotrophic factor</em><em> (</em>BDNF). Other genes including; the orphan nuclear receptor-related factor1 (Nurr-1), the early growth response protein 1(Egr-1), and the sex determining region Y-box-2 (Sox-2) were examined. Histone H3 acetylation and the ERK1/2 pathway were examined as possible targets for VPA action. Treatment with clinically relevant concentrations of VPA (1mM, and 3 mM) induced a significant increase of CDNF protein concentrations. Also, increases in the mRNA expression of GDNF, Nurr-1, and Egr-1 were detected following 24 hours VPA treatment at clinically relevant concentrations. Moreover, an increase of histone H3 acetylation was noticed in C17.2 NSCs. These findings might support the role of VPA in neuronal differentiation and neuroprotection.</p> / Master of Science (MSc)

This research delves into idiopathic autism spectrum disorder (ASD), investigating the role of TrkB signaling pathways and BDNF regulation in the cortex. Additionally, it explores offering insights into maternal influences on mouse models. / Autism spectrum disorder (ASD) is a neurodevelopmental disorder characterized by challenges in social interactions and repetitive behaviors. Prevalence of ASD is estimated to be 1 in 54 globally and is rising recently in many countries including Canada. ASD affects individuals differently, making diagnosis challenging. At present, no molecular diagnosis of ASD is available. Further, available medications only manage some symptoms of the disease and have adverse side effects in children. Therefore, there is a need for accurate molecular diagnostic tools to aid in molecular detection and treatment of ASD. To this end, a better understanding of the underlying molecular mechanisms that link ASD etiology to ASD-related behavior is crucial. While genetic factors contribute to syndromic ASD, most cases of ASD are idiopathic with unknown causes, influenced by a combination of epigenetic and environmental factors. TrkB and its downstream signaling pathways, such as Akt and Erk, are hyper-activated in syndromic ASD and hypo-activated in idiopathic cases. Therefore, drugs like rapamycin that inhibit the mTOR pathway downstream of TrkB are beneficial for syndromic ASD but not idiopathic cases. Additionally, insulin-like growth factor 1 (IGF-1), which mitigates ASD-related synaptic disruptions via Akt and Erk signaling, shows unchanged mRNA and protein levels along with its receptor in the idiopathic ASD fusiform gyrus. In ASD with either genetic or epigenetic/environmental causes, disruptions in synaptic connectivity are observed. Synaptic function is regulated by signaling pathways involving brain-derived neurotrophic factor (BDNF) and its receptor, tropomyosin-related kinase B (TrkB), as well as their downstream signaling cascades such as MAPK and Akt. The existing literature suggests that there is an association between BDNF and TrkB signaling pathways and ASD. However, a serious gap in knowledge about the precise molecular role of TrkB in ASD pathology is that our current understanding is correlational in nature and based on observational studies that lack causal experiments. This underscores the importance of further research to understand the causative role of TrkB and its related molecular events in idiopathic ASD. The present work aims to provide a deeper understanding about the causative role of molecular mechanisms underlying TrkB signaling in ASD. ASD mouse models exhibit behaviors and molecular features resembling those observed in human ASD. Therefore, these mouse models are helpful tools for studying ASD. However, understudied physiological confounding factors, such as maternal age and parity, can introduce biases and add to data variability, thus negatively impacting the reproducibility and translational value of ASD mouse models. To achieve a reliable mouse model of ASD, we conducted our first study that examines the impact of maternal age and parity on pregnancy complications, neurodevelopment, and social behavior in mice. Results demonstrate that older maternal age and prior motherhood interact to ensure a normal, steady developmental rate and provide protective effects against anxiety, social impairment, and olfactory deficits. Given the current lack of clarity regarding the causative impact of TrkB on ASD pathology, our subsequent investigation sought to establish a causal relationship between TrkB signaling and ASD. We used the TrkB agonist, LM22A-4 treatment in a validated ASD mouse model. Our results demonstrate that treatment with LM22A-4 effectively rescues the core symptoms associated with ASD (social impairment and repetitive behavior). These findings indicate that impaired TrkB signaling is responsible for ASD-like behavior of valproic acid (VPA)-exposed mice. However, unlike TrkB-related molecular events occurring in the fusiform gyrus of idiopathic ASD, TrkB isoform protein levels, BDNF species, Akt, and Erk total protein levels and activation remained unchanged in VPA-exposed cortices compared to healthy control mice. Since our VPA mouse model does not replicate human idiopathic ASD, our study cannot draw a conclusion on how disruptions in these signaling pathways may contribute to the development and manifestation of ASD symptoms. Cortex is responsible for various aspects of social behavior that are impaired in ASD. However, regulatory mechanisms that are involved in ASD upstream of cortical TrkB and BDNF are not well known. BDNF expression is highly cell-and tissue-specific and is regulated by different sets of transcription factors in specific tissues. While NURR1, the BDNF regulator in midbrain neurons, is associated with ASD pathology, its specific role in regulation of cortical BDNF is not yet well-established. Our third study aimed to understand the role of NURR1 in regulating BDNF specifically in the cortex. We showed that in resting and depolarized neurons, when NURR1 is knocked down, BDNF mRNA levels remained unchanged, suggesting that NURR1 does not regulate BDNF in cortical neurons and highlighting the tissue-specificity of BDNF regulation. In summary, we address the understudied effects of maternal factors on mouse models, which enhances the reliability of ASD research. Further, our studies significantly enhance the understanding of ASD by elucidating the role of TrkB and its downstream signaling pathways in the behavioral aspects of the disorder. We also contribute to the knowledge of BDNF regulation in the cortex, a brain tissue with crucial roles in various aspects of social behavior. In a forward-looking approach, the results of our studies provide valuable insights into mouse modeling of idiopathic ASD and the potential role of TrkB in ASD behavioral symptoms. / Thesis / Candidate in Philosophy / Autism spectrum disorder (ASD) is a condition that is accompanied by challenges in social interaction and repetitive behaviors. ASD is a complicated condition because we do not fully understand all the details of how it works in the body. Studying ASD is important as it is the most challenging condition in children and it is becoming more common, especially in the last two decades. While scientists are developing molecular tools to improve ASD diagnosis and understand its biology, these tools are not widely used in clinics for ASD diagnosis yet. Also, the approved medications available can only help with managing some of the behavioral symptoms like self-harming behavior. Despite the pressing need to find a solution, our recent advancements have not yet brought us closer to a cure for ASD, mainly because of the complexity of the disorder. Therefore, identifying the specific ASD-related mechanisms at the molecular level that contribute to ASD-related behaviors is crucial for gaining a deeper understanding of the disease. In ASD, there are problems with how brain cells communicate with each other. This communication is controlled by certain molecules in the brain, such as brain-derived neurotrophic factor (BDNF) and its receptor, tropomyosin-related kinase B (TrkB), along with other molecules. There is evidence suggesting a link between these molecules and ASD, but we have not fully understood their precise roles because most of the current knowledge is based on observations and correlations, rather than on establishing cause-and-effect relationships. To bridge this gap, our research focused on understanding TrkB's role in ASD. We required reliable mouse models. Since we aimed to induce ASD-like behaviors in mice using an ASD-causing chemical, it was crucial to ensure they were healthy beforehand. We needed to confirm that any social deficits or repetitive behaviors were not due to other factors, such as adverse infancy experiences or impaired interactions between mother and infant. We discovered that sexually mature dams aged between 3 to 6 months, with a history of previous pregnancies and motherhood, give birth to healthier litters. These litters can serve as a more dependable source for our animal behavioral studies. Many cases of ASD in humans are caused by non-genetic factors such as environmental influences like pesticides, air pollution, and the use of certain drugs during pregnancy. In cases of human ASD triggered by non-genetic factors, there is an increase in proBDNF, the precursor of BDNF. However, this proBDNF does not efficiently convert to BDNF. With insufficient BDNF and TrkB receptors, molecules like Akt (protein kinase B, also PKB) and Erk (Extracellular Signal-Regulated Kinase), which are crucial for neuron communication, are also less active downstream. This imbalance disrupts neuron connections, leading to ASD behaviors. In our research, the ASD-causing chemical which we used is valproic acid. It is originally an anti-seizure medication. When pregnant women took valproic acid, the chance of their child having ASD increased. Scientists used this information to inject pregnant mice with valproic acid, and as a result, all the offspring showed ASD-like behaviors. We anticipated that by isolating the brains of these offspring and measuring protein levels of BDNF, TrkB, Akt, and Erk, we would observe a similar pattern to that seen in humans with non-genetic ASD cases. We focused on studying the cortex, a region of the brain responsible for regulating social behaviors in both mice and humans. Since ASD is associated with challenges in social behaviors, we isolated the cortex from mouse brains to analyze protein levels. A chemical known as LM22A-4 with a structure resembling BDNF can bind to TrkB and activate it. We expected that the offspring of pregnant dams injected with valproic acid, which led to reduced TrkB axis activation in their brains, would show improvement in ASD behavior. This anticipation stems from the understanding that LM22A-4 activates the TrkB axis, thus compensating for its reduction, which is thought to be causing ASD-like behaviors. The offspring of mothers injected with valproic acid exhibited ASD-like behaviors, unlike the control mice. Control mice were offspring of pregnant dams injected with a solution containing only the substances used to dissolve valproic acid, typically water and salt (saline). Mice prenatally exposed to valproic acid (VPA) exhibited ASD-like behaviors, but treatment with LM22A-4 helped alleviate these behaviors, promoting more typical behavior patterns. LM22A-4, by activating TrkB receptors, helped to protect the brain from harm caused by exposure to valproic acid before birth. This could mean that valproic acid-induced changes in TrkB-related molecular mechanisms are involved in social behavior difficulties and increased repetitive behaviors seen in autism. Nevertheless, the levels of TrkB, BDNF, proBDNF, Akt, and Erk in the cortex of offspring from mothers injected with valproic acid were like those in the offspring from mothers injected with the saline solution. Therefore, the BDNF and TrkB signaling pathways remained unchanged in the cortex of our valproic acid model in this study, and they differ from those observed in human idiopathic ASD. We also speculated that a protein, called NURR1 acting upstream of BDNF and TrkB might be involved in the process. NURR1 acts as a regulatory protein that binds to the BDNF, increasing the production of copies from the BDNF. We also used a small RNA that targets a specific region in the Nurr1 and inhibits its protein production We anticipated a reduction in Nurr1 levels. As NURR1 acts as an upregulator of BDNF, lower levels of Nurr1 would result in decreased BDNF production. Activating NURR1 resulted in increased BDNF mRNA levels. However, when NURR1 was reduced, BDNF mRNA levels remained unaffected. This led us to conclude that if NURR1 levels decrease, other proteins may step in to maintain BDNF mRNA levels. Therefore, in the cortex, unlike in some other brain regions, the presence of NURR1 is not essential for regulating Bdnf. In summary, before inducing ASD-like behavior in mice using valproic acid, it is crucial to ensure the health of the mice. We used sexually mature mothers with prior pregnancy experience to provide a healthy baseline. We showed valproic acid induced ASD-like behaviors in mice offspring. We also observed that LM22A-4 treatment alleviated ASD-like behaviors of offspring. In our study, we demonstrated that the levels of BDNF, TrkB, Erk, and Akt proteins in the cortex of mice exposed to valproic acid were not affected. For this reason, our mouse model does not resemble human non-genetic ASD. Finally, NURR1's role in BDNF regulation varies by brain region. Lowering NURR1 did not affect BDNF mRNA levels, suggesting compensatory mechanisms. Our findings suggest new directions for further research to better understand the roles of TrkB and BDNF in non-genetic ASD. Overall, this study provides valuable knowledge that can contribute to advancing our understanding of idiopathic ASD-related molecular mechanisms.

L’acétylation est une modification post-traductionnelle des protéines essentielles. Elle est impliquée dans bon nombre de processus cellulaires importants comme la régulation de la structure de la chromatine et le recrutement de protéines. Deux groupes d’enzymes, soient les lysines acétyltransférases et les lysines désacétylases, régulent cette modification, autant sur les histones que sur les autres protéines. Au cours des dernières années, de petites molécules inhibitrices des désacétylases ont été découvertes. Certaines d’entre elles semblent prometteuses contre diverses maladies telles le cancer. L’acide valproïque, un inhibiteur de deux des trois classes des désacétylases, a un effet antiprolifératif chez plusieurs organismes modèles. Toutefois, les mécanismes cellulaires sous-jacents à cet effet restent encore méconnus. Ce mémoire met en lumière l’effet pH dépendant de l’acide valproïque sur différentes voies cellulaires importantes chez la levure Saccharomyces cerevisiae. Il démontre que ce composé a la capacité d’inhiber la transition entre les phases G1 et S par son action sur l’expression des cyclines de la phase G1. De plus, il inhibe l’activation de la kinase principale de la voie activée suite à un stress à la paroi cellulaire. L’acide valproïque occasionne également un arrêt dans la réplication de l’ADN sans y causer de dommage. Il s’agit là d’un effet unique qui, à notre connaissance, n’est pas observable avec d’autres agents qui inhibent la progression en phase S. / Acetylation is an essential post-translational modification involved in many important cellular processes such as regulation of chromatin structure and proteins interactions. Two enzyme families, lysine acetyltransferases and lysine deacetylases, allow proper regulation of this modification both on histones and non-histones proteins. In recent years, the discovery of small deacetylase inhibitors has led to promising novel therapy in the treatment against various diseases such as cancer. Valproic acid, a class I and II deacetylase inhibitor, has been shown to have antiproliferative effects in various models. However, the cellular mechanisms underlying this effect remain unknown. This thesis highlights the pH-dependent effects of VPA on numerous important cellular pathways in the yeast Saccharomyces cerevisiae. Our results demonstrate that VPA inhibits the transition from G1 to S phase of the cell cycle by its action on the expression of G1 cyclins. Moreover, VPA inhibits the activation of the main kinase involved in the cell wall integrity pathway. Furthermore, VPA exposure also leads to DNA replication arrest in a DNA damage-independent manner. This is a unique effect that, to our knowledge, is not observable with other agents that inhibit S phase progression.

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