published_or_final_version / Zoology / Master / Master of Philosophy

Melanoma is a cancer of the pigment producing cells, melanocytes, and is the most serious type of skin cancer. Cancer is a condition in which one type of cell grows without limit in a disorganized fashion, disrupting and replacing normal tissues and their functions. Normal melanocytes reside in the outer layer of the skin and produce a brown pigment called melanin, which is responsible for skin color. Melanoma occurs when melanocytes become cancerous, grow, and invade other tissues. Pro-opiomelanocortin (POMC) is a precursor polypeptide of 241 amino acids and the prohormone of various neuropeptide, including corticotropin (ACTH), £\-melanocyte-stimulating hormone (£\-MSH), and £]-endorphin (£]-EP). Recently, we demonstrated that systemic POMC overexpression potently suppresses the growth and metastasis of B16-F10 melanoma in vitro and in vivo. However, despite potent inhibition of tumor proliferation and angiogenesis, B16-F10 melanoma still managed to survive after POMC gene therapy. The underlying survival mechanism of B16-F10 melanoma remains unclear. Microphthalmia-associated transcription factor (MITF) is a basic helix-loop-helix transcription factor that plays a key role not only in melanin synthesis, but also in melanocyte development and survival. Besides, MITF binds to the hypoxia-inducible factor-1£\ (HIF-1£\) promoter to stimulate its transcriptional activity. In this study, we investigate the influence of POMC gene delivery on the pro-survival MITF/HIF-1£\ pathway in B16-F10 melanoma cells. Quantitative RT-PCR and western blot analysis revealed that POMC gene delivery increased the MITF mRNA and protein level in B16-F10 melanoma cells. Besides, POMC gene delivery significantly enhanced the HIF-1£\-driven luciferase activities in melanoma cells. By transfection and puromycin selection, we generated and characterized a MITF-knockdown B16-F10 melanoma cells (MITF KD) stably expressing short hairpin RNA against MITF. The growth, invasion, and colonies formation of MITF-KD were similar to those of vector control. However, implantation of MITF-KD cells led to melanoma with significantly reduced tumor size compared with those in mice implanted with vector control cells. Histological analysis revealed a significant reduction of CD31-positive blood vessels in implantation of MITF-KD cells-treated tumors, which was accompanied with a decrease in Ki-67-positive proliferating cells and an increase in TUNEL-positive apoptotic cells. Moreover, POMC-mediated upregulation of MITF and HIF-1 £\ was significantly attenuated in MITF KD-B16-F10 cells. Acetylsalicylic acid (aspirin; ASA) is widely used as an analgesic/antipyretic drug. ASA exhibits a wide range of biological effects, including preventative effects against heart attack, stroke, and the development of some types of cancer. In our study, we found ASA enhanced cell proliferation. However, in invasion test, ASA had no effect on cell migration. POMC gene delivery elevated the mRNA and protein level of hemeoxygenase-1 (HO-1), a downstream effector of HIF-1£\ pathway and an enzyme catalyzing the converting reaction of heme to carbon monoxide, ion and biliverdine. Inhibition of HO-1 activities augmented the inhibitory effect of POMC gene delivery on proliferation, migration and anchorage-independent growth of B16-F10 melanoma cells. These studies indicated that activation of MITF/HIF-1£\/HO-1 indeed contributes to melanoma survival after POMC gene delivery.

A epigenética é uma subárea da Genética, na qual são estudados mecanismos que são essenciais para o adequado desenvolvimento dos mamíferos, sendo que, alterações neste estágio podem levar a vários distúrbios metabólicos, como a obesidade. Atualmente a obesidade é um grave problema de saúde pública mundial, tem origem multifatorial envolvendo tanto fatores ambientais quanto genéticos. Existem alguns genes que estão envolvidos com a obesidade, como por exemplo, o gene da pró-opiomelanocortina (POMC). O objetivo do presente projeto de pesquisa é investigar os padrões de expressão e metilação do gene Pomc na prole de ratas submetidas às dietas deficiente e suplementada com ácido fólico. Os animais utilizados foram ratos Wistar. O estudo envolveu filhotes (n=24) machos e fêmeas que foram desmamados com a mesma dieta de suas respectivas mães, sendo três grupos de tratamento, o grupo controle (2,0 mg de ácido fólico/kg de ração), o grupo deficiente (0,5 mg de ácido fólico/kg de ração) e o grupo suplementado (8 mg de ácido fólico/kg de ração). Foram coletadas amostras do núcleo arqueado do hipotálamo, a partir das quais foram extraídos DNA, RNA e proteínas utilizando kits comerciais seguindo o protocolo do fabricante. Com o DNA foi realizada a análise do padrão de metilação. O mRNA foi utilizado para a análise da expressão gênica, por PCR em tempo real, pelo sistema TaqMan® (Life Technologies(TM)). O estudo de proteômica foi realizado por Western blotting. De modo geral, observou-se que o peso corpóreo dos filhotes machos não apresentou diferença estatística entre os grupos. O consumo de ração do grupo deficiente em ácido fólico foi estatisticamente (p = 0,03) maior do que o grupo controle. Em relação aos filhotes fêmeas observou-se que o peso corpóreo do grupo suplementado foi estatisticamente (p = 0,01) maior do que o grupo controle, e referente ao consumo de ração, não houve diferença estatística significativa entre os grupos de tratamento. As análises de peso cerebral, expressão gênica, metilação e expressão proteica de Pomc não apresentaram diferenças estatísticas significativas entre os grupos de tratamento de ambos os sexos. Conclui-se que a intervenção com dietas com diferentes concentrações de ácido fólico não ocasionou alterações significativas na prole, em relação ao estudo de proteômica e aos padrões de metilação e expressão do gene Pomc. Quanto ao peso corpóreo e consumo de ração dos animais mostrou-se que a suplementação com ácido fólico durante a gestação e no pós desmame foi capaz de alterar estes dois parâmetros, com resposta divergente entre os machos e fêmeas na prole adulta. / Epigenetic mechanisms are essential for proper development in mammals, and that changes at this stage may lead to various metabolic disorders such as obesity. Currently obesity is a serious problem of public health worldwide, has a multifactorial origin involving both environmental and genetic factors. There are some genes that are involved with obesity, such as the proopiomelanocortin gene (POMC). The aim of this research project is to investigate the expression and methylation patterns of the Pomc gene in the offspring of rats subjected to deficient and supplemented diets with folic acid. Animals used were Wistar rats. The study involved males and females pups (n = 24) that were weaned at the same diet their mothers, three treatment groups, control group (2,0 mg/kg of folic acid), deficient group (0,5 mg/kg of folic acid) and the supplemented group (8,0 mg/kg of folic acid). The arcuate nucleus of the hypothalamus tissue were collected, from which was extracted DNA, RNA and proteins using commercially available kits following the manufacturer\'s protocol. The DNA methylation pattern analysis was performed. The mRNA was used for the analysis of gene expression by real time PCR, the TaqMan (Life Technologies (TM)) system. The proteomic study was carried out by Western blotting. In general, we found that the body weight of the male offspring showed no statistical difference between the groups. The feed intake of folic acid deficient group was statistically (p = 0.03) higher than the control group. In relation to female offspring was observed that the body weight of the supplemented group was statistically (p = 0.01) higher than the control group, and related to feed intake, there was no statistically significant difference between the treatment groups. The analysis of brain weight, gene expression, methylation and protein expression of Pomc no significant statistical differences among treatment groups of both sexes. Concluded that the intervention diets with different folic acid concentrations did not cause significant changes in the offspring compared to the study of proteomics and methylation and expression patterns of the Pomc gene. As for the body weight and feed consumption of animals it showed that supplementation with folic acid during pregnancy and post weaning was able to alter these two parameters with differing response between males and females in the adult offspring.

A epigenética é uma subárea da Genética, na qual são estudados mecanismos que são essenciais para o adequado desenvolvimento dos mamíferos, sendo que, alterações neste estágio podem levar a vários distúrbios metabólicos, como a obesidade. Atualmente a obesidade é um grave problema de saúde pública mundial, tem origem multifatorial envolvendo tanto fatores ambientais quanto genéticos. Existem alguns genes que estão envolvidos com a obesidade, como por exemplo, o gene da pró-opiomelanocortina (POMC). O objetivo do presente projeto de pesquisa é investigar os padrões de expressão e metilação do gene Pomc na prole de ratas submetidas às dietas deficiente e suplementada com ácido fólico. Os animais utilizados foram ratos Wistar. O estudo envolveu filhotes (n=24) machos e fêmeas que foram desmamados com a mesma dieta de suas respectivas mães, sendo três grupos de tratamento, o grupo controle (2,0 mg de ácido fólico/kg de ração), o grupo deficiente (0,5 mg de ácido fólico/kg de ração) e o grupo suplementado (8 mg de ácido fólico/kg de ração). Foram coletadas amostras do núcleo arqueado do hipotálamo, a partir das quais foram extraídos DNA, RNA e proteínas utilizando kits comerciais seguindo o protocolo do fabricante. Com o DNA foi realizada a análise do padrão de metilação. O mRNA foi utilizado para a análise da expressão gênica, por PCR em tempo real, pelo sistema TaqMan® (Life Technologies(TM)). O estudo de proteômica foi realizado por Western blotting. De modo geral, observou-se que o peso corpóreo dos filhotes machos não apresentou diferença estatística entre os grupos. O consumo de ração do grupo deficiente em ácido fólico foi estatisticamente (p = 0,03) maior do que o grupo controle. Em relação aos filhotes fêmeas observou-se que o peso corpóreo do grupo suplementado foi estatisticamente (p = 0,01) maior do que o grupo controle, e referente ao consumo de ração, não houve diferença estatística significativa entre os grupos de tratamento. As análises de peso cerebral, expressão gênica, metilação e expressão proteica de Pomc não apresentaram diferenças estatísticas significativas entre os grupos de tratamento de ambos os sexos. Conclui-se que a intervenção com dietas com diferentes concentrações de ácido fólico não ocasionou alterações significativas na prole, em relação ao estudo de proteômica e aos padrões de metilação e expressão do gene Pomc. Quanto ao peso corpóreo e consumo de ração dos animais mostrou-se que a suplementação com ácido fólico durante a gestação e no pós desmame foi capaz de alterar estes dois parâmetros, com resposta divergente entre os machos e fêmeas na prole adulta. / Epigenetic mechanisms are essential for proper development in mammals, and that changes at this stage may lead to various metabolic disorders such as obesity. Currently obesity is a serious problem of public health worldwide, has a multifactorial origin involving both environmental and genetic factors. There are some genes that are involved with obesity, such as the proopiomelanocortin gene (POMC). The aim of this research project is to investigate the expression and methylation patterns of the Pomc gene in the offspring of rats subjected to deficient and supplemented diets with folic acid. Animals used were Wistar rats. The study involved males and females pups (n = 24) that were weaned at the same diet their mothers, three treatment groups, control group (2,0 mg/kg of folic acid), deficient group (0,5 mg/kg of folic acid) and the supplemented group (8,0 mg/kg of folic acid). The arcuate nucleus of the hypothalamus tissue were collected, from which was extracted DNA, RNA and proteins using commercially available kits following the manufacturer\'s protocol. The DNA methylation pattern analysis was performed. The mRNA was used for the analysis of gene expression by real time PCR, the TaqMan (Life Technologies (TM)) system. The proteomic study was carried out by Western blotting. In general, we found that the body weight of the male offspring showed no statistical difference between the groups. The feed intake of folic acid deficient group was statistically (p = 0.03) higher than the control group. In relation to female offspring was observed that the body weight of the supplemented group was statistically (p = 0.01) higher than the control group, and related to feed intake, there was no statistically significant difference between the treatment groups. The analysis of brain weight, gene expression, methylation and protein expression of Pomc no significant statistical differences among treatment groups of both sexes. Concluded that the intervention diets with different folic acid concentrations did not cause significant changes in the offspring compared to the study of proteomics and methylation and expression patterns of the Pomc gene. As for the body weight and feed consumption of animals it showed that supplementation with folic acid during pregnancy and post weaning was able to alter these two parameters with differing response between males and females in the adult offspring.

La maladie de Cushing résulte du développement de tumeurs hypophysaires corticotropes d’agressivité variable. Cette forme d'hypercorticisme dépendante de l’ACTH se distingue des formes indépendantes de l’ACTH, souvent consécutives à une tumeur surrénalienne. Les outils de distinction entre ces deux formes ainsi que les marqueurs d’agressivité des tumeurs hypophysaires ont été peu documentés ; ils seraient pourtant précieux pour les cliniciens. Un premier objectif, atteint, de notre travail a visé à identifier sur des cohortes cliniquement caractérisées de chiens atteints de syndrome de Cushing, des marqueurs sanguins et morphologiques qui soient distinctifs des deux formes de syndromes de Cushing (concentration plasmatique en ACTH, échographie et examen tomodensitométrique des glandes surrénales). Un second objectif de notre travail a visé à identifier des paramètres cliniques et biologiques susceptibles de refléter l'agressivité des tumeurs corticotropes. Nous avons ainsi montré chez le chien qu'une hypothermie ou une bradycardie peut signer une tumeur de grande taille. Chez le chat, atteint d'adénomes corticotropes généralement agressifs, nous avons démontré que le dosage de la POMC plasmatique est pertinent pour diagnostiquer la maladie de Cushing. La valeur élevée de la concentration plasmatique en POMC chez l'homme, le chien et le chat, a suggéré que ces tumeurs induisent un défaut de maturation de la POMC. L'analyse par western-blot des acteurs protéiques de cette maturation chez le chien a en effet révélé une diminution de la quantité d'enzyme pro-convertase 1/3 au sein des tumeurs corticotropes de grande taille. / Cushing’s disease or hyperadrenocorticism (HAC) is one of the most frequent endocrine diseases in dogs. Most cases are ACTH-dependent HAC and are associated with pituitary tumors of variable aggressiveness. The other form of HAC is known as ACTH-independent. The present work was carried out on cohort of dogs and cats presented with HAC. The first objective of this work was to assess the accuracy of diagnostic investigations (such as adrenal glands ultrasonography, computed tomodensitometry scan of adrenal glands and pituitary gland and basal ACTH measurement) in a large cohort of dogs with HAC and to identify the best thresholds that allow a correct classification of HAC (ACTH dependent vs ACTH independent). The second objective was to demonstrate that clinical information such as bradycardia or hypothermia reflect the aggressiveness of the pituitary tumor. We also demonstrated that plasma proopiomelanocortin (POMC) concentration was elevated in cats with Cushing’s disease. This observation, previously reported in dogs and humans, suggests a physiopathological implication of ACTH loss of maturation in aggressive pituitary tumour. We investigated if proconvertase 1/3 (PC1/3) could be involved in this alteration through western blot detection of POMC, pro-ACTH, ACTH and PC1/3 in corticotropic tumors. This work showed a difference in PC1/3 protein levels between large and small corticotroph tumours, PC1/3 signal being weak to undetectable in large pituitary tumours.

Hypothalamic pro-opiomelanocortin (POMC) neurons are canonically recognized as key anorexigenic neurons in the melanocortin circuit with a role in satiety and energy homeostasis. However, optogenetic stimulation does not decrease feeding behavior during ad-lib fed animals in a physiologically relevant manner. This suggests that there are possible nuances in their activity dynamics such as timing (when a neuron is active in relation to a specific behavior), direction (inhibition or excitation), or specificity (if only certain subgroups of POMC neurons are active). POMC neurons in the hypothalamus are a molecularly diverse population, which suggests that they would display diverse neuronal activity responses during various ingestive behaviors. Currently, single-cell recordings of hypothalamic POMC neurons has never been investigated in behaving animals. Using one-photon microendoscopic calcium imaging, we characterized the neuronal activity dynamics of individual hypothalamic neurons during a broad range of feeding behaviors prior to, during, and after ingestion, during different metabolic states in mice. We show that hypothalamic POMC neurons are highly engaged during food-seeking, consumption of different nutrients, and post-ingestive responses related to circulating molecules relaying metabolic information. Individual hypothalamic POMC neurons show diverging responses in terms of valence, duration, magnitude, and timing to different feeding behaviors that are responsive to intercurrent metabolic status. Our results suggest that hypothalamic POMC neurons may integrate moment-to-moment metabolic status with feeding and food-seeking actions at short- and long-term scales to implement behaviors and autonomic responses to coordinate complex components of energy homeostasis.

Proopiomelanocortin (POMC) is a 241 amino acids precursor protein, which encodes various neuropeptides including corticotropin (ACTH), a-melanocyte-stimulating hormone (a-MSH), and b-endorphin (b-EP). POMC plays an important role in stress response, metabolism, energy homeostasis and anti-inflammation. Recent studies demonstrated that systemic POMC gene delivery potently suppresses the tumor growth and metastasis of B16-F10 melanoma in vitro and in vivo via inhibition of NF-£eB/COX2 pathway. However, systemic POMC expression also led to elevated urine excretion and water intake in mice. This was attributed to enhanced steroidgenesis as evidence by elevated plasma corticosteroids levels in animals and increased cortisol production in adrenal H295R cells after POMC gene delivery. Since corticosteroids are also potent anti-inflammatory agents, it remains unclear whether the ACTH-mediated cortisol synthesis also contributed to the POMC-induced tumor suppression. To address this issue, we generated a series of adenovirus vectors encoding POMC genes with mutation or deletion in ACTH domain including ACTH (K15A/R17A). Unlike the wild type POMC, gene delivery of ACTH (K15A/R17A) resulted in significantly lower cortisol production, CYP11B1 mRNA level, and glucocorticoid responsive element (GRE)-driven luciferase activities in H295R cells. ACTH (K15A/R17A) gene delivery did not affect the urination and water intake in mice. Above all, ACTH (K15A/R17A) gene delivery remained capable of inhibiting the colonies formation and invasiveness of B16-F10 melanoma cells. In summary, steroidgenesis is not essential to POMC-mediated melanoma suppression. In addition, ACTH (K15A/R17A) gene delivery may provide a better alternative for melanoma control.

Tesis por compendio / [ES] El sistema de melanocortina es una estructura clave en la regulación de una amplia gama de funciones fisiológicas que incluyen la melanogénesis, la respuesta al estrés y el equilibrio energético, mediante la unión a una familia de receptores acoplados a la proteína G específicos (MC1R-MC5R). La sobreexpresión de agonistas inversos, la proteína de señalización agutí (Asip) y la proteína relacionada con agutí (Agrp) da como resultado un aumento de la ingesta de alimentos, de crecimiento lineal y de peso corporal. Asip regula la polaridad de pigmentación dorsoventral a través del MC1R, y la sobreexpresión induce obesidad en ratones al unirse al Mc4r central. La sobreexpresión de asip1 en el pez cebra transgénico (asip1-Tg) mejora el crecimiento, sin afectar la acumulación lipídica (obesidad), incluso cuando se alimentan bajo regímenes inductores severos. Los peces asip1-Tg no necesitan comer más para crecer más y más rápido, lo que sugiere una mayor eficiencia alimentaria. Además, los peces asip1-Tg criados en alta densidad son capaces de crecer mucho más que los peces de tipo salvaje (WT) criados en baja densidad, aunque los peces asip1-Tg parecen ser más sensibles al estrés por hacinamiento que los peces WT. El análisis transcriptómico comparativo del intestino de asip1-Tg refleja una expresión diferencial de transportadores aminoácidicos, monocarboxilatos, transportadores iónicos y de vitaminas. La sobreexpresión reduce la integridad del epitelio intestinal aumentando su permeabilidad paracelular y potencia el transporte electrogénico de aminoácidos. Así, los peces transgénicos poseen mayor capacidad para la absorción de nutrientes y, por extensión una mejora en la eficiencia alimenticia que podría explicar, en parte, ese crecimiento diferencial bajo tasas de ingesta similares. Esta tesis tuvo también como objetivo investigar si los asip1-Tg mantienen un fenotipo dominante asociado con una mayor tasa de alimentación. Los resultados muestran, por el contrario, un carácter reactivo/subordinado en los asip1-Tg que aboga por una participación del sistema de melanocortinas en la regulación del comportamiento de peces. El perfil subordinado de los animales asip1-Tg, junto con una activación del eje del estrés, sugiere que estos animales pueden mostrar un comportamiento de ansiedad. Los resultados indicaron que los peces asip1-Tg muestran un comportamiento de ansiedad que además relacionado con una severa disminución de los niveles centrales de serotonina (5HT) y dopamina y elevación de su recaptación neuronal y degradación. La administración de un inhibidor de la recaptación de 5HT, recupera el fenotipo comportamental salvaje, mitigando el comportamiento de ansiedad en los peces transgénicos y rescatando los niveles de 5HT. Esta ansiedad podría repercutir en una alteración del comportamiento locomotor de los animales, por ello estudiamos los ritmos circadianos de actividad locomotora. Los resultados muestran que los animales asip1-Tg exhiben una disrupción completa del ritmo de actividad, con una actividad muy elevada, especialmente durante la noche. Esta disrupción es concomitante con una desaparición del ritmo diario de serotonina y melatonina. Además, los resultados muestran una pérdida de ritmos de expresión de genes reloj (per1a y clock1a). La incubación, in vitro, de glándulas pineales con Asip1 produjo una inhibición de la secreción de melatonina replicando los resultados obtenidos in vivo y demostrando un efecto directo de Asip1, sobre la fisiología de la pineal. En esta tesis, se utilizó el pez cebra como modelo para investigar los efectos de la obesidad sobre la ansiedad y la memoria. La obesidad no tuvo ningún efecto sobre la ansiedad, pero produjo una disminución de la memoria a corto plazo, estudiada mediante test de condicionamiento aversivo. Este estudio proporciona, un protocolo fiable para evaluar el efecto de las enfermedades metabólica en la función cognitiva y conductual. / [CA] El sistema de melanocortina és una estructura clau en la regulació d'una ampla gamma de funcions fisiològiques que inclouen la melanogènesi, la resposta a l'estrès i l'equilibri energètic, mitjançant la unió a una família de receptors acoblats a la proteïna G específics (MC1R-MC5R). La sobreexpressió d'agonistes inversos, la proteïna de senyalització agutí (Asip) y la proteïna relacionada con agutí (Agrp) dona com a resultat un augment de la ingesta d'aliments, de creixement lineal i de pes corporal. Asip regula la polaritat de pigmentació dors-ventral a través del MC1R, y la sobreexpressió indueix obesitat en ratolins en unir-se al MC4R central. La sobreexpressió de asip1 en el peix zebra transgènic (asip1-Tg) millora el creixement, sense afectar l'acumulació lipídica (obesitat), inclús quan s'alimenten sota règims inductors severs. Los peces asip1-Tg no necessiten menjar més per a créixer més i més ràpid, lo qual suggereix una major eficiència alimentària. A més a més, els peixos asip1-Tg criats en alta densitat són capaces de créixer molt més que els peixos de tipus salvatge (WT) criats en baixa densitat, malgrat que els peixos asip1-Tg semblen ser més sensibles a l'estrès per amuntegament que els peixos WT. L'anàlisi transcriptòmic comparatiu de l'intestí de asip1-Tg reflecteix una expressió diferencial de transportadors aminoacídics, monocarboxilats, transportadors iònics i de vitamines. La sobreexpressió redueix la integritat de l'epiteli intestinal augmentant la seua permeabilitat paracel·lular i potencia el transport electrogènic d'aminoàcids. Per tant, els peixos transgènics posseeixen major capacitat per l'absorció de nutrients i, per extensió una millora en la eficiència alimentària que podria explicar, en part, eixe creixement diferencial sota taxes d'ingesta similars. Aquesta tesi tingué també com a objectiu investigar si els asip1-Tg mantenien un fenotip dominant associat amb una major taxa d'alimentació. Els resultats mostren, pel contrari, un caràcter reactiu/subordinat en los asip1-Tg que advoca per una participació del sistema de melanocortines en la regulació del comportament de peixos. El perfil subordinat dels animals asip1-Tg, junt amb una activació de l'eix de l'estrès, suggereix que aquests animals poden mostrar un comportament d'ansietat. Els resultats indicaren que els peixos asip1-Tg mostren un comportament d'ansietat relacionat amb una severa disminució dels nivells centrals de serotonina (5HT) i dopamina i elevació de la seua recaptació neuronal i degradació. L'administració de un inhibidor de la recaptació de 5HT recupera el fenotip comportamental salvatge, mitigant el comportament d'ansietat en els peixos transgènics i rescatant els nivells centrals de 5HT. Esta ansietat podria repercutir en una alteració del comportament locomotor dels animals, per la qual cosa vam estudiar els ritmes circadians d'activitat locomotora. Els resultats mostren que els animals asip1-Tg exhibeixen una disrupció completa del ritme d'activitat, amb una activitat molt elevada durant tot el cicle diari, especialment durant la nit. Esta disrupció es concomitant amb una desaparició del ritme diari de serotonina i melatonina. A més a més, els resultats mostren una pèrdua de ritmes de expressió de gens rellotge (per1a y clock1a). La incubació, in vitro, de glàndules pineals con Asip1 va produir una inhibició de la secreció de melatonina replicant els resultats obtinguts in vivo y demostrant un efecte directe de Asip1 sobre la fisiologia de la pineal. En esta tesi, se va utilitzar el peix zebra com a model per investigar els efectes de la obesitat sobre la ansietat i la memoria. L'obesitat no va tindre cap efecte sobre l'ansietat, però va produir una disminució de la memòria a curt termini, estudiada mitjançant tests de condicionament aversiu. Aquest estudi proporciona, un protocol fiable per a avaluar l'efecte de les malalties metabòliques en la funció cognitiva i conductual. / [EN] The melanocortin system plays a key role in the regulation of a wide range of physiological functions including melanogenesis, stress response and energy balance, through binding to a family of specific G protein-coupled receptors (MC1R-MC5R). Overexpression of inverse agonists, agouti-signalling protein (Asip) and agouti-related protein (Agrp) results in increased food intake, linear growth and body weight. Asip regulates dorso-ventral pigmentation polarity through MC1R, and over-expression induces obesity in mice by binding to the central MC4R. Overexpression of asip1 in transgenic zebrafish (asip1-Tg) enhances growth, without affecting lipid accumulation (obesity), even when fed under severe inducing regimens. The asip1-Tg fish do not need to eat more to grow bigger and faster, suggesting increased feed efficiency. In addition, asip1-Tg fish reared at high density are able to grow much larger than wild-type (WT) fish reared at low density, although asip1-Tg fish appear to be more sensitive to overcrowding stress than WT fish. Comparative transcriptomic analysis of asip1-Tg gut reflects differential expression of amino acid, monocarboxylate, ionic and vitamin transporters. Overexpression reduces the integrity of the intestinal epithelium by increasing its paracellular permeability and enhances electrogenic amino acid transport. Thus, transgenic fish possess a greater capacity for nutrient absorption and, by extension, an improvement in feed efficiency that could explain, in part, this differential growth under similar intake rates. This thesis also aimed to investigate whether asip1-Tg maintain a dominant phenotype associated with a higher feeding rate. Experimental results show, on the contrary, a reactive/subordinate character in asip1-Tg which argues for an involvement of the melanocortin system in the regulation of fish behaviour. Improving feeding motivation without promoting aggression in fish, thus avoiding the threat to native populations in case of an escape, makes the inhibition of the melanocortin system, through the overexpression of asip1, a feasible target for the development of genetically modified lines. The subordinate profile of the asip1-Tg animals, together with an activation of the stress axis, suggests that these animals may exhibit anxiety-like behaviour. The results indicated that asip1-Tg fish show a behaviour similar to our concept of anxiety related to a severe decrease in central serotonin (5HT) and dopamine levels as well as the elevation of their neuronal reuptake and degradation. The administration of fluoxetine, a serotonin reuptake inhibitor, recovers the wild-type behavioural phenotype, mitigating anxiety behaviour in transgenic fish and restoring central 5HT levels. This anxiety could have repercussions on the locomotor behaviour of the animals, so we studied circadian rhythms of locomotor activity. The results show that asip1-Tg animals exhibit a complete disruption of the activity rhythm, with very high activity levels throughout the daily cycle, especially during the night. This disruption is concomitant with a disappearance of the daily rhythm of serotonin and melatonin. In addition, the results show a loss of clock gene expression rhythms (per1a and clock1a). Incubation, in vitro, of pineal glands with Asip1 produced an inhibition of melatonin secretion replicating the results obtained in vivo and demonstrating a direct effect of Asip1 on pineal physiology. In this PhD thesis, zebrafish was used as a model to investigate the effects of overfeeding-induced obesity on anxiety-like behaviour and memory. Obesity had no effect on anxiety, but produced a decrease in short-term memory, studied by means of aversive conditioning tests. This study also provides a reliable protocol for assessing the effect of metabolic diseases on cognitive and behavioural function, supporting zebrafish as a model for cognitive and behavioural neuroscience. / Esta tesis ha sido realizada a través del programa de ‘Ayudas para la formación de personal investigador’ (FPI) BES‐2017‐082424 de la Agencia Estatal de Investigación, en Instituto de Acuicultura Torre de la Sal (IATS) del Consejo Superior de Investigaciones Científicas (CSIC) en el Grupo de investigación de Control de la Ingesta en Peces dirigido por José Miguel Cerdá Reverter, director de esta tesis. Los trabajos llevados a cabo en esta tesis han sido financiados por Ministerio de Ciencia, Innovación y Universidades (MICIU) a través de los siguientes proyectos: MELANOCONDUCT: Implicación del sistema de melanocortinas en la regulación de los mecanismos temporales y conductuales de peces AGL2016-74857-C3-3-R; Cronopeces: Red temática de cronobiología de peces y sus aplicaciones en acuicultura RED2018-102487-T; MacForFish: Nuevos aspectos homeostáticos y comportamentales de la regulación de la ingesta en peces PID2019-103969RB-C33; FISHTASTE: Implicación de los mecanismos sensoriales del gusto en la regulación de la ingesta de peces - Involvement of taste sensing mechanisms in the regulation of feed intake of fish PID2022-136288OB-C33 / Godino Gimeno, A. (2024). Involvement of the Melanocortin System in the Regulation of Circadian and Behavioural Mechanisms in Zebrafish [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/203148 / Compendio

Adipositas ist eine polymorphe chronische Erkrankung mit epidemischer Prävalenz. Im katabolen Leptin-Melanocortin-Signalweg ist das Proopiomelanocortin Gen (POMC) ein zentrales Element, das bei Dysfunktion massive Adipositas bewirken kann. Auch eine kürzlich identifizierte intragenische Methylierungsvariante des POMC wurde mit Adipositas assoziiert und deutet somit auf eine mögliche epigenetische Modulation des Gewichtsphänotyps hin. Zur Aufklärung der Relevanz, Stabilität und Entwicklung dieser epigenetischen Modifikation wurden die Funktionalität, Ontogenese und Phylogenese der POMC DNA-Methylierung untersucht. In vitro Analysen zeigten DNA-Methylierungsabhängige Promoteraktivität beider CpG-Inseln (CGIs) des POMC. Diese hier erstmals beschriebene Transkriptionsaktivität der intragenischen CGI weist auf einen alternativen Promoter des POMC hin. Hinsichtlich der Ontogenese konnten in Mensch und Maus postnatal stabile DNA-Methylierungsmuster mit interindividueller Konservierung für beide CGIs des POMC identifiziert werden. Zusätzlich erwiesen sich Gewebeunabhängigkeit der DNA-Methylierungsmuster und ihre pränatale Ausbildung zwischen dem Blastocystenstadium und der frühen Organogenese in der Maus. Die POMC DNA-Methylierungsmuster upstream des Exon3 unterscheiden sich in Mensch und Maus. Der mögliche Einfluss von primatenspezifischen Alu-Elementen im Intron2 des POMC hierauf wurde in verschiedenen Primatenfamilien analysiert. Die Ergebnisse zeigen eine bedingte Assoziation der Alu-Elemente mit der DNA-Methylierung in der entsprechenden Region, lassen jedoch auch weitere Einflussfaktoren vermuten. Insgesamt zeigt diese Arbeit, dass die POMC DNA-Methylierung artspezifisch konserviert ist und in der frühen Embryogenese, vermutlich Alu-abhängig, ausgebildet wird. Dabei könnten stochastische Variationen der DNA-Methylierung die POMC-Aktivität beeinflussen und somit das Risiko für Adipositas erhöhen. / Obesity is a polymorphic chronic disease with epidemic prevalence. Within the catabolic leptin-melanocortin signaling pathway pre-proopiomelanocortin (POMC) is a pivotal element. Dysfunction of POMC, e.g. due to mutations, can cause severe obesity. Moreover, a recently identified intragenic methylation variant of POMC was found to be associated with obesity. Therefore, this indicates potential epigenetic modulation of the weight phenotype. To gain further insight into the relevance, stability, and origin of this epigenetic modification, the functionality, ontogenesis, and phylogenesis of the POMC DNA methylation patterns were analyzed. In vitro analyses revealed DNA methylation-dependent promoter activity of both CpG islands (CGIs) of POMC. Thereby, the intragenic CGI was identified as a potential alternative promoter of POMC, which has not been described before. Regarding the ontogenesis, postnatally stable POMC DNA methylation patterns with interindividual conservation were detected for both CGIs in humans and mice. In addition, it was observed that the POMC DNA methylation patterns are non-tissue-specific, stable upon long time administration of a high fat diet, and develop prenatally between the blastocystal stage and the early organogenesis. The POMC DNA methylation pattern upstream of exon3 differs in humans and mice. A possible influence of primate-specific Alu elements within the intron2 region of POMC was analyzed in various primate families. Results evince a partial association of the Alu elements with the DNA methylation pattern in this particular region, but also suggest an influence of additional factors. Overall, this work demonstrates that DNA methylation of the POMC locus is species-specific highly conserved, and that it is established during early embryogenesis, possibly Alu-triggered. In the course of this, stochastic variances of the POMC DNA methylation might influence the POMC activity and consequently alter the risk to develop obesity.

Secondary sexual traits play an irreplaceable role in the reproduction of a range of animals and are used as quality and fitness sensors during pairing of individuals. Expression of these traits, ornamentes, can correlated with an individual's personal and behavioral strategies. In the case of melanin ornaments, not only the relationships with personal individuals are considered, but there is the possible connections with stress resistance and the level of stress responses too. This hypothesis is based on the pleiotropic effect of the melanocortin system, which can be used during melanogenesis but also in the production of hormones that contribute to range of stress responses. The aim of this work was to clarify the relationship between an individual's ornaments, his stress response and individuality in the barn swallows (Hirundo rustica rustica). In this work the relationship between selected ornaments and the stress reaction of the organism, stressed glucose levels measured 15 minutes after a stress stimulus, was tested. Both sexes showed a correlation between area of white tail spots and stress response. Only for males a relationship with the length of outermost tail feathers was found and a correlation with the color saturation of feathers on the throat was shown for females. The second part of...