Background: Acute spinal trauma is followed by a secondary injury that causes additional damage to the tissue. The mouse neuronal hybrid cell line NSC-34 is planned for studies regarding this process, wherefore the cell line needed to be established in the laboratory and a proof-of-concept study needed to be performed. A suitable target gene for this study was Neuronal Nucleus (NeuN), a neuronal marker expressed in nearly all neuronal cells although not yet studied in NSC-34. Aim: The aim of this project was to characterize the expression of NeuN in differentiated and undifferentiated NSC-34 cells and silence gene expression by using siRNA. Methods: RT-qPCR was used to measure NeuN expression during passages 5 to 15 and a comparison was performed between one early and one late passage. Lipofectamine® RNAiMAX was used for siRNA-treatment in different concentrations and several different medium compositions were tested as differentiation media. Results: NeuN was expressed in passages 5 to 15, with decreased expression levels in passage 13 (ΔCt 15.36 ± 0.16) compared to passage 5 (ΔCt 15.09 ± 0.16), p < 0.05. The expression levels did not change after differentiation. siRNA-treatment yielded knockdown when using  high concentrations of the reagent (p < 0.05). Conclusion: NeuN was expressed in a stable, low level throughout passages 5 to 15 with a slightly decreased expression during later passages and no change after differentiation. The siRNA-treatment suppressed gene expression, although further optimization is needed to increase the suppression.

Os gânglios da raiz dorsal (GRD) armazenam neurônios TrkA-positivos. A percepção e transmissão de estímulos por estes neurônios dependem de uma neuritogênese adequada. Miosina (MioVa) é expressa no tecido nervoso e está presente em neuritos, corpo celular e cone de crescimento. Caracterizamos o padrão de expressão de MioVa na neuritogênese de células TrkA-positivas do GRD de galinha in vivo e in vitro. In vivo, MioVa é expressa em células que não começaram a emitir neuritos em HH25, e sua expressão persiste por toda neuritogênese. In vitro, é recrutada para o processo de re-emissão de neuritos de neurônios TrkA positivos na presença de NGF, sendo expressa em neuritos em diferentes estádios de neo-neuritogênese. Nos ensaios funcionais, observamos que a superexpressão do domínio globular de MioVa em culturas de GRD com 10 ou 100ng/ml de NGF reduz a população de células com neuritos longos e aumenta a população de células com neuritos curtos ou sem neuritos. Em conjunto, estes dados sugerem que a MioVa é importante para o estabelecimento de neuritos nociceptores. / The dorsal root ganglia (DRG) harbor the TrkA-positive neurons. The stimuli perception and transmission by these neurons depend on a proper neuritogenesis. Myosin (MyoVa) is widely expressed in nervous tissue and is present in neurites, cell body and growth cone. Here, we characterized the MyoVa expression pattern in chicken DRG TrkA-positive cells neuritogenesis, in vivo and in vitro. In vivo, at stage HH25, MyoVa was present both in cells with and without neurites and its expression persists throughout neuritogenesis. In vitro, it is recruited for the regeneration process and TrkA-positive neurons neurites re-emission in the presence of NGF, being expressed in neurites at different stages of neo-neuritogenesis. In functional assays, we observed that MyoVa globular tail overexpression in GRD cultures maintained with 10 or 100ng/ml NGF reduces the number of neurons with long neurites and increased the number of neurons with short neurites or no neurites. Taken together, these results suggest that Myosin Va is important for the establishment of nociceptor neurites.

Tendo seu início no íleo terminal onde se abre a papila ileal, o ceco é a porção inicial do intestino grosso onde ocorre parte da digestão da celulose proveniente da alimentação e a posterior absorção de seus produtos. O ceco de rato é uma estrutura sacciforme que apresenta partes distintas, tanto macroscópica quanto estruturalmente. O presente estudo teve como finalidade avaliar a densidade e a área do perfil celular dos neurônios mioentéricos em diferentes regiões do ceco de ratos adultos com sete meses de idade (384gr), utilizando as técnicas da Acetilcolinesterase, NADH e NADPH-diaforase. Para tanto o ceco foi dividido em quatro regiões: uma, próxima à ampola cecal (PA), uma, apical mesentérica (AM), uma, basal antimesentérica (BA) e outra apical antimesentérica (AA). Observou-se, que, no que diz respeito à densidade neuronal, existe diferença significativa para as regiões estudadas, sendo à região PA a que apresentou maior quantidade de neurônios com todas as técnicas utilizadas. Em média, nos 80 campos (17,92mm2) microscópicos contados, foram encontrados 1479 ± 357 neurônios acetilcolinesterásicos positivos, 717 ± 142 neurônios que se coram pela técnica da NADH-d e 240 ± 26 células nervosas que se coram pela técnica da NADPH-d. Com relação ao perfil celular dos neurônios, o teste de variância mostrou não haver diferença significativa entre as regiões. O menor e o maior perfil celular foi observado junto à região BA, em neurônios corados com as técnicas da AChE e NADPH-d respectivamente, tendo o menor perfil, 77,94µm2 e o maior, 1579,64µm2. Conforme a área do perfil celular, os neurônios foram agrupados em três classes: pequenos, médios e grandes. A classe mais freqüente em todos as regiões estudadas para as três técnicas foi a dos neurônios médios, chegando a 72,4% corados pela técnica da AChE junto à região AA, 68% na região PA para a técnica da NADH-d e 77,6% com a técnica da NADPH-d na região PA. Concluiu-se que, existe diferença regional na distribuição dos neurônios da parede do ceco do rato. / Beginning in the terminal ileum where the ileal papilla opens, the caecum is the initial portion of the large intestine, where part of the digestion of the cellulose coming from the food and the absorption of its products take place. This study had the purpose of evaluating the density and the cell profile area of the myoenteric neurons in different regions of the caecum of adult rats aging seven months (384 g body weight), using the techniques of acetylcholinesterase (AChE), NADH- and NADPH-diaphorase. For that, the caecum was divided into four regions: next to the caecal ampulla (PA), apical mesenteric (AM), basal antimesenteric (BA) and apical antimesenteric (AA). It was observed that, in what concerns the neuronal density, there is a significant difference for the regions studied, the PA region exhibiting the greatest amount of neurons with all the techniques employed. On average, in the 80 microscopic fields (17.92 m2) counted, 1,479 ± 357 neurons were found with AChE, 717 ± 142 with NADH-d and 240 ± 26 with NADPH-d. As for the cell profile of the neurons, the Variance Analysis showed that there is not a significant difference among the regions. The smallest and the largest cellular profiles were observed at the BA region with the techniques of AChE and NADPH-d, respectively, the smallest having 77.94 µm2 and the largest 1,579.64 µm2. According to the area of the cell profile, the neurons were grouped in three classes: small, medium and large. The most frequent class in all the regions studied and techniques employed was that of medium neurons, reaching 72.4% with AChE at the AA region, 68% in the PA region with NADH-d and 77.6% with NADPH-d in the PA region. Therefore, it was verified that there is a regional difference in the distribution of the neurons in the wall of the rat caecum.

As células-tronco (CT) são células que apresentam propriedades de auto-renovação, capazes de gerar diferentes tipos celulares e reconstituir diversos tipos de tecidos, por isso têm sido vistas como uma alternativa terapêutica para o tratamento de muitas doenças cujo tratamento convencional não é eficiente. Além disso, por sua plasticidade, as CT podem ser usadas para produzir modelos in vitro para o estudo de doenças, o que tem sido particularmente interessante para doenças que acometem o sistema nervoso. As células-tronco humanas de dente decíduo esfoliado (Stem cell from Human Esfoliated Deciduous teeth, SHED) são descritas em alguns trabalhos como capazes de se diferenciarem em células neuronais através da transdiferenciação direta, um processo simples que possibilita a diferenciação de um tipo celular em outro por meio da utilização de agentes químicos. No entanto, a diferenciação de SHED em neurônios é contestada como sendo um artefato de cultura devido ação citotóxica destes agentes. Com base nesta premissa, o objetivo deste trabalho foi realizar protocolos para a produção de neurônios a partir das SHED utilizando modificações de métodos descritos na literatura e utilizados na diferenciação neuronal. Durante um dos protocolos utilizados, foi possível verificar a morfologia de células semelhantes à neurônio, porém após alguns dias de manutenção, as células voltavam ao formato fusiforme original. Com este trabalho podemos afirmar que, de acordo com os resultados obtidos, as SHED não geram neurônios funcionais / Stem cells (SC) are cells that present self-renewal properties, capable of generating cells types and reconstitute several tissue types. For this reason, they have been seen as a therapeutic alternative to the treatment of many diseases which conventional treatment is not efficient. Besides, because of its plasticity, SC may be used to produce in vitro models in order to study diseases, what is interesting to diseases that affect the nervous system. Human SC from SHED (Stem cell from Human Exfoliated Deciduous teeth, SHED) are described in some papers as being capable of self-differentiation in neuronal cells through the direct transdifferentiation, a simple process that makes possible the differentiation of a cell type in another through the use of chemical agents. Nevertheless, SHED differentiation is refuted as being a artifact of culture due to cytotoxic action of these agents. Based on this premise, the aim of this study was to carry out protocols in order to produce neurons from SHED, using modifications and methods of neuronal differentiation described in the literature and used in the neuronal differentiation. During one of the protocols used, it was possible to verify the morphology of the cells as neuron-like, however, after some days of maintenance, they turn back to their original fusiform format. In this study, we can state, according to the obtained results, that SHED do not generate functional neurons

Os objetivos do presente trabalho foram determinar a morfologia do plexo cardíaco e verificar se o coração de camundongos é alterado pela exposição à poluição atmosférica em relação ao peso, ao número de neurônios e gânglios. Camundongos foram mantidos em câmaras situadas próximas a vias de trafego intenso em São Paulo. Os animais foram divididos em 4 grupos (n=5) segundo a exposição à poluição atmosférica no período gestacional e/ou pós natal: ar filtrado (F-F), ar não filtrado (NF-NF), ar filtrado e ar não filtrado (F-NF) e ar não filtrado e ar filtrado (NF-F). Ao atingirem 120 dias de vida, os animais foram eutanasiados e seus corações removidos. O número de neurônios cardíacos assim como seu volume, volume do gânglio, área do neurônio, perímetro e o diâmetro de Feret máximo (FMax) e mínimo (FMin) foram estimados por meio de avaliações morfométricas e estereológicas. Os neurônios e gânglios cardíacos foram corados pelo método de Giemsa. As fibras colágenas foram identificadas pelo método de Picro-sirius sob luz polarizada. Verificou-se que as fibras colágenas tipo III são predominantes na cápsula do gânglio nos grupos NF-F e NF-NF. O peso corpóreo foi significativamente menor nos animais que foram expostos no período pós natal (F-NF, NF-NF) quando comparados aos grupos F-F e NF-F. A média do perímetro neuronal foi maior no grupo F-F que nos grupos expostos no período gestacional e pós natal (F-NF, NF-F e NF-NF). O FMax foi estatisticamente diferente entre o grupos expostos no período pós natal (F-NF e NF-NF) (p<0,05). Houve uma redução significativa no volume dos neurônios nos grupos F-NF e NF-NF. Os resultados permitem especular que a mudanças no controle autonômico do coração resultante da exposição à poluição atmosférica, pode ser relacionado a alterações no desenvolvimento do plexo cardíaco / The aims of the present study were to determine the cardiac plexus morphology and to test whether or not the heart of the mice alters in weight, neuronal and ganglia number with air pollution exposure. Mice were maintained in exposure chambers situated close to a busy crossroads in São Paulo. Animals were grouped in to four groups (n=5) according to prenatal and/or postnatal exposure to air pollution: filtered air (F-F); non-filtered air (NFNF); filtered and non-filtered air (F-NF); non-filtered and filtered air (NF-F). Reaching 120 days of life, the animals were euthanized for obtaining their hearts. The number of cardiac neurons as well as their volume, ganglion volume, neuron sectional area, perimeter and maximum (FMax) and minimum (FMin) Ferrets diameter were estimated under the stereological and morphometric aspects. The cardiac neurons and ganglia were stained employing the Giemsa method. Collagen fibers were identified by Picro-sirius under polarized light. Type III collagen fibers predominate in the ganglion capsule of the NF-F and NF-NF groups. Body weight was significantly reduced in those animals exposed to air pollution postnatally (F-NF, NF-NF) when compared to groups F-F and NF-F. The average of the neuronal perimeter was larger in F-F group than in those groups with gestational and postnatal exposure (F-NF, NF-F and NF-NF). The volume, volume do gânglio, área do neurônio, perímetro e o diâmetro de Feret máximo FMax was statistically different among the groups exposed to air pollution postnatally (F-NF and NF-NF) (p<0.05). A decrease in the total neuronal volume was significantly detected in F-NF and NF-F groups. The mean neuron volume was significant in the F-NF and NF-NF. Our results, allow us to speculate that changes in autonomic control of heart resulting from exposure to air pollution may be linked to alterations in the development of the cardiac plexus

A Esclerose Lateral Amiotrófica (ELA) é uma doença progressiva caracterizada pela perda de neurônios motores levando rapidamente os pacientes à morte. Os mecanismos da morte neuronal são desconhecidos e estudos recentes indicam que a microglia pode participar deste processo. Para investigar o papel da microglia na ELA, camundongos transgênicos SOD1G93A foram utilizados na avaliação da morte e do trofismo neuronal em sistemas de co-culturas neurônio/microglia e do efeito do meio condicionado microglial sob os neurônios motores. Ambas as células foram extraídas da medula espinal de camundongos transgênicos (TG) e wild type (WT). A microglia foi obtida dos animais neonatos e adultos na fase pré-clínica da doença. Os neurônios extraídos de neonatos foram marcados com reagente específico para morte neuronal e seus prolongamentos foram quantificados em contraste de fase por métodos estereológicos específicos. A expressão gênica de moléculas candidatas à participação do processo neurodegenerativo relacionadas com a microglia foi quantificada pelo PCR em tempo real, assim como a quantidade de moléculas secretadas no meio condicionado das culturas microgliais dosada pelo ELISA sanduíche. O meio condicionado da microglia TG neonatal não foi capaz de acentuar a morte neuronal, entretanto a neurodegeneração foi potenciada nas análises das co-culturas. Interessantemente, o meio condicionado das microglias WT provenientes de animais adultos foram capazes de aumentar os prolongamentos neuronais feito não observado em relação às microglias TG. Quantidades aumentadas do fator de necrose tumoral ?, interleucina-6 e fator de crescimento derivado do nervo foram quantificadas no meio condicionado das microglias TG. A microglia TG neonatal apresentou dimuição na expressão gênica de AKAP13, HIPK3, UBE2I E NTF5. Esses achados precoces sugerem perda de migração microglial, perda de resistência à apoptose, desbalanço entre proliferação e morte celular e diminuição do suporte trófico neuronal. Em conjunto, os resultados evidenciam a participação da microglia nos mecanismos da ELA / Amyotrophic Lateral Sclerosis (ALS) is a progressive degenerative disorder affecting motoneurons and leading the patient to death.The cause of motor neurons degeneration in ALS is uncertain and there is any treatment able to prolong the patient life. Recent studies show that microglia could participate of the process of ALS degeneration. Its activation is linked to the disbalance of neuroprotective and neurotoxic action. To investigate the microglia role in ALS, SOD1G93A transgenic mice that develop symptoms similar to the clinical disease were used. We evaluated the neuronal death and trophism in microglia/neuron co-cultures system and in microglial conditioned medium effect under the neurons. Neurons and microglia were extracted from transgenicor wild type mice spinal cord. Microglia was obtained from 1 day pos natal pups and adult onset of disease mice. Cells were stained with a specific marker to neuronal death. Neuronal extensions area and neuronal death was quantified by stereological method. The genic expression of candidate molecules related to degeneration in ALS was quantified by real time PCR and the release of some molecules were quantified by ELISA sandwich. Results showed that maybe transgenic neonatal microglia is not able to increase the neuronal death through releasing molecules in its conditionated medium, on the other hand when transgenic microglia was co-cultured with any kind of neuron, neuronal death was observed. Microglia from adult transgenic mice was not able to promote a neuroprotection compared to wild type in co-culture and conditionated medium experiments. In addition to this, was observed increased tumor necrosis factor alpha, interleukin 6 and nerve growth factor secretion by transgenic microglia. Neonatal transgenic microglia also exhibited reduced genic expression of AKAP13, HIPK3, UBE2I and NTF5. These findings at an early stage suggest a lost of migration potential, lost of apoptosis resistance, disbalance of proliferation and cell death and reduction of neuronal trophic support. So together, these data indicate the involvement of microglia in ALS mechanisms

"The objective of this thesis project was to begin identifying which regulatory transcription factors are involved in the up-regulation of the gene promoter for the Ą6 subunit of the gamma-alpha-butyric acid (GABAA-Ą6) receptor in cerebellar granule cell neurons (GCNs). Although a 150 base pair sequence proximal to the GABAA-Ą6 gene promoter had been characterized previously using electrophoretic mobility shift assays (EMSAs), the specific transcription factor(s) needed to express the GABAA-Ą6 gene had not been examined. This project utilized EMSAs to investigate this 150 base pair sequence further. It was found that when this sequence proximal to the gene promoter was divided into two overlapping halves, both shortened sequences were able to compete for binding with nuclear extracts. The full-length sequence was further divided into six sub-regions, and double-stranded competitors were generated from synthetic oligonucleotides. The only oligonucleotide to compete was the one that corresponded to the region of overlap between the left and right halves. This overlap region contains consensus sites for OCT-1, STAT, and the regulatory transcription factor NF-1. An NF-1 consensus sequence was able to compete DNA-protein complexes. Supershift assays showed that a xenopus NF-1 antibody, previously shown to compete in gel shift assays, caused a mobility shift of the DNA-probe complex. Analysis of extracts from granule cell neurons, cultured from 0 to 6 days in vitro (DIV) indicated NF-1 to be present all time points. Northern analyses were performed using probes for NF-1A, NF-1B, NF-1C and NF-1X. NF-1A transcripts were observed from 0 to 6 DIV, while NF-1B and NF-1X transcripts were present at 2 and 4 DIV. NF-1C RNA was barely detectable at any time point."

Made available in DSpace on 2017-07-21T19:26:04Z (GMT). No. of bitstreams: 1 Kelly Cristiane Iarosz.pdf: 12762091 bytes, checksum: 098f86a58a73585913aa53aff950b6e2 (MD5) Previous issue date: 2013-02-22 / Fundação Araucária de Apoio ao Desenvolvimento Científico e Tecnológico do Paraná / In this thesis we considered cellular automaton model with time delay. Time delay included in this model reflects the delay between the time in which the site is affected and the time in which its variable is updated. Firstly, we studied the growth of cancer considering the infiltration of cancer cells in normal tissues. It was used a simple cellular automaton that models a biological system, which is classified in spatio-temporal classes using the Hamming distance as a form of diagnosis. With this diagnosis it was possible to observe the suppression of cancerous cells, varying the system parameters. We also studied the relation between the time delay in the cell cycle and the time to start the metastasis, using suitable numerical diagnostics. Moreover, we study the firing rate properties of a cellular automaton model for a neuronal network with chemical synapses. We propose a simple mechanism in which the nonlocal connections are included, through electrical and chemical synapses. In the latter case, we introduce a time delay which produces selfsustained activity. Nonlocal connections, or shortcuts, are randomly introduced according to a specified connection probability. There is a range of connection probabilities for which neuron firing occurs, as well as a critical probability for which the firing ceases in the absence of time delay. The critical probability for nonlocal shortcuts depends on the network size according to a power-law. We also compute the firing rate amplification factor by varying both the connection probability and the time delay for different network sizes. A issue that would be interesting to explore in future works is the influence of cancerous cells on the firing rate in a neuronal network considering cellular automaton. / Nesta tese apresenta-se um modelo de autômato celular onde insere-se um tempo de atraso, representado pelo intervalo entre o momento em que a célula é afetada e o tempo em que sua variável de estado é atualizada. Estudou-se a Proliferação de células canceríıgenas, considerando-se sua metástase para tecidos normais. Com um autômato celular simples modelou-se o sistema biológico, atribuindo a esses classes espaço temporais utilizando-se a distância de Hamming como forma de diagnóstico. Por meio do diagnóstico observou-se a supressão de células cancerígenas quando os parâmetros do sistema são variados. Posteriormente, estudou-se a relação existente entre o tempo de atraso no ciclo celular e o tempo para que a met´astase ocorra. Além dos pontos citados acima, ainda apresenta-se nesta tese o estudo da taxa de disparos de uma rede neuronal com sinapses elétricas equímicas, modeladas por um autômato celular. Propõe-se um mecanismo simples, onde conexões não-locais são inclusas na rede aleatóriamente com probabilidade especificada no modelo. Um tempo de atraso ´e inserido no modelo, desta forma, produz-se a atividade autosustentável, verifica-se uma gama de probabilidades de conexão com as quais os disparos neuronais podem ocorrer, bem como uma probabilidade crítica de conexões não locais para que os disparos venham cessar na ausência do tempo de atraso. Essa probabilidade crítica depende do tamanho da rede e segue uma lei de potência. Calculou-se também o fator de amplificação da taxa de disparos, variando a probabilidade de conexões e o tempo de atraso para tamanhos diferentes de rede. Por fim apresenta-se alguns pontos sobre a influência de células cancerígenas na taxa de disparos em uma rede neuronal.

In hippocampal CA1 and CA3 regions, various properties of neuronal activity follow skewed, lognormal-like distributions, including average firing rates, rate and magnitude of spike bursts, magnitude of population synchrony, and correlations between pre- and postsynaptic spikes. In recent studies, the lognormal features of hippocampal activities were well replicated by a multi-timescale adaptive threshold (MAT) neuron network of lognormally distributed excitatory-to-excitatory synaptic weights, though it remains unknown whether and how other neuronal and network properties can be replicated in this model. Here we implement two additional studies of the same network: first, we further analyze its burstiness properties by identifying and clustering neurons with exceptionally bursty features, once again demonstrating the importance of the lognormal synaptic weight distribution. Second, we characterize dynamical patterns of activity termed neuronal avalanches in in vivo CA3 recordings of behaving rats and in the model network, revealing the similarities and differences between experimental and model avalanche size distributions across the sleep-wake cycle. These results show the comparison between the MAT neuron network and hippocampal readings in a different approach than shown before, providing more insight into the mechanisms behind activity in hippocampal subregions. / Nas regiões CA1 e CA3 do hipocampo, várias propriedades da atividade neuronal seguem distribuições assimétricas com características lognormais, incluindo frequência de disparo média, frequência e magnitude de rajadas de disparo (bursts), magnitude da sincronia populacional e correlações entre disparos pré- e pós-sinápticos. Em estudos recentes, as características lognormais das atividades hipocampais foram bem reproduzidas por uma rede de neurônios de limiar adaptativo (multi-timescale adaptive threshold, MAT) com pesos sinápticos entre neurônios excitatórios seguindo uma distribuição lognormal, embora ainda não se saiba se e como outras propriedades neuronais e da rede podem ser replicadas nesse modelo. Nesse trabalho implementamos dois estudos adicionais da mesma rede: primeiramente, analisamos mais a fundo as propriedades dos bursts identificando e agrupando neurônios com capacidade de burst excepcional, mostrando mais uma vez a importância da distribuição lognormal de pesos sinápticos. Em seguida, caracterizamos padrões dinâmicos de atividade chamados avalanches neuronais no modelo e em aquisições in vivo do CA3 de roedores em atividades comportamentais, revelando as semelhanças e diferenças entre as distribuições de tamanho de avalanche através do ciclo sono-vigília. Esses resultados mostram a comparação entre a rede de neurônios MAT e medições hipocampais em uma abordagem diferente da apresentada anteriormente, fornecendo mais percepção acerca dos mecanismos por trás da atividade em subregiões hipocampais.

Les homéoprotéines sont des facteurs de transcription qui en plus de leur rôle important durant le développement des métazoaires, bénéficient de fonctions autonome et non autonome-cellulaire dans le cerveau adulte. Parmi ces homéoprotéines, Engrailed1/2 (collectivement Engrailed) est exprimée dans les neurones dopaminergiques mésencéphaliques adulte, ceux-là même qui dégénèrent dans la maladie de Parkinson. Chez les souris délétées d’une copie du gène (En1+/-), une dégénérescence progressive des neurones dopaminergiques s’accompagne de symptômes moteurs et non moteurs rappelant la maladie de Parkinson, ce qui pourrait faire de ces souris un modèle nouveau et intéressant de cette maladie neurodégénérative. Des expériences de transduction de la protéine En1 dans les cellules du mésencéphale de souris démontrent son effet neuroprotecteur dans des modèles toxicologiques de la maladie de Parkinson et chez les souris En1+/-, menant à l’hypothèse qu’Engrailed est important dans la physiopathologie de cette maladie. L’essentiel de ce travail de thèse s’inscrit dans la compréhension des mécanismes d’action de l’homéoprotéine Engrailed dans les neurones dopaminergiques mésencéphaliques. L’activité physiologique importante de ces neurones et le stress métabolique oxydant qui est généré touche plusieurs compartiments cellulaires, dont le noyau. La stabilité du génome semble être un aspect majeur de l’action d’Engrailed dans ces neurones. D’abord contre les effets délétères du stress oxydatif sur l’intégrité de l’ADN et la structure de la chromatine, ensuite, contre l’activité génotoxique des éléments transposables LINE-1. / Homeoproteins are a major class of transcription factors that exert some of their functions through non-cell autonomous activity, due to their ability to transfer between cells. Two of these homeoproteins, En1 and En2 (collectively Engrailed) are responsible for midbrain dopaminergic (mDA) neuron development, and maintenance during adulthood. En1+/- mice display a selective and progressive degeneration of the mDA neurons, reminiscent of Parkinson disease (PD). Engrailed infusion confers neurotection against cell death in several mouse models of PD, leading to the hypothesis that Engrailed could be implicated in the physiopathology of the disease. To dissect the mechanisms underlying Engrailed-mediated protection, the transcriptome of mDA neurons in En1+/- was analyzed. It was found that the loss of one En1 allele leads to severe alterations in the expression of DNA damage response and chromatin remodeling genes. The same alterations were detected and amplified in an acute mouse model of oxidative stress, suggesting that mDA neurons from En1+/- mice are less resistant to oxidative stress and, conversely, that Engrailed may protect them against oxidative stress. Indeed, Engrailed transduction into mDA neurons saves them from cell death and restores all DNA damage and epigenetic marks. A second mechanism neuroprotection by Engrailed concerns LINE-1 elements. These retrotransposons have the ability to create genomic instability through their endonuclease activity. Their direct repression by Engrailed could be part of a general protective activity against genomic instability.