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Recent molecular evidence suggests staurozoans are medusozoans that diverged from Medusozoa before the medusa stage emerged. Morphological studies are needed to determine whether this framework can provide insight into medusa evolution. I studied the neuromuscular morphology of two staurozoans, Haliclystus ‘sanjuanensis’ and Manania handi using FMRFamide and α-tubulin antibodies to label neurons, and phalloidin to label muscles. Results indicate that similar to polyps, staurozoans possess one regionally differentiated FMRFamide and α-tubulin immunoreactive (IR) nerve net, and smooth muscles only. Comparisons with other cnidarians indicate that ancestral medusozoans had a marginal circular muscle and muscular manubrium, but lacked the parallel conducting nerve nets, striated muscle, and pacemaker required to coordinate medusa swimming. A possibly light-sensitive concentration of neurons at the base of the primary tentacles suggests that staurozoan primary tentacles are homologous to medusozoan rhopalia. The unique neuromusculature of nematocyst clusters suggests a defensive or predatory function for these staurozoan synapomorphies. / Graduate / 0287 / 0317

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Les agents anti-microtubules (MTAs), comme les taxanes et les vinca-alcaloïdes, sont des anticancéreux largement utilisés en pratique clinique. Ils agissent d'une part en perturbant les fonctions du réseau microtubulaire, conduisant à un arrêt du cycle cellulaire. D'autre part, à côté de cet effet anti-prolifératif, les MTAs sont capables d'induire divers signaux responsables de l'exécution du programme apoptotique via la voie mitochondriale intrinsèque. La famille Bcl-2 joue un rôle primordial dans l'induction de l'apoptose par ces agents. Aussi, au cours de ce travail, nous nous sommes d'abord intéressés à l'origine de la diminution de Bcl-2 lors de l'apoptose médiée par la vinorelbine. Nous avons ainsi mis en évidence la régulation transcriptionnelle de bcl-2 grâce à l'identification d'un nouveau site de liaison de p53 sur le promoteur de bcl-2. Dans un second temps, nous avons évalué l'influence de la famille Bcl-2 dans la réponse aux MTAs. En effet, nous nous sommes focalisés sur la sensibilité paradoxale aux MTAs de certaines tumeurs surexprimant Bcl-2, in vitro et in vivo chez la souris nude. Nous avons montré l'implication de Bim dans cette augmentation de sensibilité, qui agit en perturbant le réseau mitochondrial. Enfin, nous avons investigué le mécanisme moléculaire liant la surexpression de Bcl-2 et celle de Bim. Nous avons montré que la surexpression de Bcl-2, en inhibant l'activité transcriptionnelle de p53, permettait une meilleure activité du facteur de transcription FoxO3a, principal acteur de la régulation génique de Bim. / Microtubule targeting agents (MTAs), such as taxanes and vinca-alkaloïds, are anticancer drugs widely used in clinical practice. Firstly, they are known to disturb functions of microtubular network, leading to cell cycle arrest. On the other hand, beside this anti-proliferative effect, MTAs are able to trigger signaling cascades leading to apoptosis execution, through intrinsic mitochondrial pathway. Bcl-2 family proteins play a crucial role in induction of MTAs-induced apoptosis. In this work, we first studied the origin of Bcl-2 downregulation in vinorelbine-mediated apoptosis. We thus highlighted a transcriptional mechanism through the identification of a novel p53 binding site in the bcl-2 promoter. Second, we evaluated the influence of Bcl-2 family in response to MTAs. Indeed, we focused on paradoxical sensitivity to MTAs of some tumors overexpressing Bcl-2, in vitro and in vivo in nude mouse. Bim was involved in this enhanced sensitivity, by disrupting the mitochondrial network. We then investigated the molecular mechanism linking Bcl-2 and Bim overexpressions. We showed that Bcl-2 overexpression, by inhibiting the transcriptional activity of p53, leads to an increase in activity of the transcription factor FoxO3a, the main actor in Bim transcriptional regulation. Our work underlines the importance of Bcl-2 family and especially Bim as potential biomarker in predicting MTA's efficacy.

Pericentrin is a molecular scaffold protein. It anchors protein kinases, (PKB, (Purohit, personal communication), PKC, (Chen et al., 2004), PKA Diviani et al., 2000), the γ tubulin ring complex, (γ TuRC) (Zimmerman et al., 2004), and possibly dynein (Purohit et al., 1999) to the spindle pole. The γ TuRC is a ~ 2 MDa complex which binds the minus ends of microtubules and nucleates microtubules in vitro, (Zheng et al., 1995). Prior to this work, nothing was known about the association of the γTuRC with pericentrin. Herein I report the biochemical identification of a large protein complex in Xenopus extracts containing pericentrin, the γ TuRC, and other as yet unidentified proteins. Immunodepletion of γ tubulin results in co-depletion of pericentrin, indicating that virtually all the pericentrin in a Xenopus extract is associated with γ tubulin. However, pericentrin is not a member of the, γ TuRC, since isolated γ TuRCs do not contain pericentrin. The association of pericentrin with the γ TuRC is readily disrupted, resulting in two separable complexes, a small pericentrin containing complex of approximately 740 KDa and the the γ TuRC, 1.9 MDa in Xenopus. Co overexpression/ coimmunoprecipitation and yeast two hybrid studies demonstrate that pericentrin binds the γTuRC through interactions with both GCP2 and GCP3. When added to Xenopus mitotic extracts, the GCP2/3 binding domain uncoupled γ TuRCs from centrosomes, inhibited microtubule aster assembly and induced rapid disassembly of pre-assembled asters. All phenotypes were significantly reduced in a pericentrin mutant with diminished GCP2/3 binding, and were specific for mitotic centro somal asters as I observed little effect on interphase asters or on asters assembled by the Ran-mediated centrosome-independent pathway. Overexpression of the GCP2/3 binding domain of pericentrin in somatic cells perturbed mitotic astral microtubules and spindle bipolarity. Likewise pericentrin silencing by small interfering RNAs in somatic cells disrupted γ tubulin localization and spindle organization in mitosis but had no effect on γ tubulin localization or microtubule organization in interphase cells. Pericentrin silencing or overexpression induced G2/antephase arrest followed by apoptosis in many but not all cell types. I conclude that pericentrin anchoring of γ tubulin complexes at centrosomes in mitotic cells is required for proper spindle organization and that loss of this anchoring mechanism elicits a checkpoint response that prevents mitotic entry and triggers apoptotic cell death. Additionally, I provide functional and in vitro evidence to suggest that the larger pericentrin isoform (pericentrin B/ Kendrin) is not functionally homologous to pericentrin/pericentrin A in regard to it's interaction with the γ TuRC.

As concepções de moduladores da dinâmica dos microtúbulos, que levam ao bloqueio do ciclo celular, e de bloqueadores de canais de cálcio tipo L (Cav), tais como o 1,4-di-hidropiridinas e análogos, que diminuem a resistência do organismo humano aos tratamentos quimioterápicos através da inibição da proteína de transmembrana P-gp, são estratégias importantes tanto para terapias antitumorais quanto para leishmanicida. Esta abordagem tem mostrado resultados interessantes na diminuição da resistência à quimioterapia em câncer chamada de MDR (do inglês Multi Drug Resistence), além de também serem uma estratégia importante para controlar a fase inicial da leishmaniose. Diante desse contexto, e baseado no estudo de Ueki 2013 e colaboradores que, a partir de estudos anteriores, os quais relatam a superexpressão das enzimas estona deacetilase (HDAC) e catepsina L (CTSL) em células tumorais, propuseram um pró-fármaco seletivo, planejado a partir de um espaçador de lisina acetilada, que garante a liberação do fármaco seletivamente nas células tumorais, trabalhamos no desenvolvimento de uma nova proposta de pró-fármaco trifuncional. Nossa proposta foi desenvolvida a partir de estudos de triagem virtual, baseados em ligantes e em estrutura, predição das propriedades farmacocinéticas e toxicológicas (ADME/Tox) e também técnicas de bioinformática para a construção de um modelo de canal de cálcio, devido à inexistência de estruturas, do mesmo, que estivessem depositadas no banco de dados de proteínas PDB (Protein Data Bank). Paralelamente, nosso grupo de síntese colaborador sintetizou, através de técnicas de \"Click Chemistry\" e reações de Mitsunobu multicomponentes, uma biblioteca de novos híbridos trifuncionais, os quais, após estudos de atividade biológica, foram avaliados (in silico) frente à estrutura da tubulina, e os compostos mais promissores desta biblioteca serviram de base para novos estudos de triagem virtual. Para a obtenção dos nossos hits, executamos 4 estratégias de triagem virtual, separadas em 2 tarefas. Ao final, selecionarmos um total 59 hits, dos quais, 9 hits apresentam promissoras atividades bloqueadoras do canal de cálcio e 65 hits apresentam promissoras atividades moduladoras da tubulina. Estes hits seguem em estágio de compra e ensaios in vitro e após comprovada a eficácia dos mesmos, estes futuramente farão parte de uma nova proposta de pró-farmaco trifuncional. / The concepts of modulating microtubule dynamics, and calcium channel L-types (CAV) blockers are important strategies for anticancer and antileishmanial therapies. Microtubule modulators that blocks the cell cycle and the calcium channel blockers, such as, 1,4-dihydropyridines and analogues, reduce the resistance of the human body to chemotherapeutic treatments by inhibiting transmembrane P-gp protein. This approach has shown interesting results in reduced resistance to chemotherapy in cancer called MDR (Multi Drug Resistance), and an important strategy for controlling the early stage of leishmaniasis. In this context, we work to develop a new proposal for trifunctional prodrug. We have based on the study of Ueki 2013 and collaborators, which, from earlier studies with reported overexpression of both deacetylase estona enzymes (HDACs) and cathepsin L (CTSL) in tumor cells, proposed a selective prodrug. We considering an acetylated lysine link/spacer, which ensures the release of the drug selectively in tumor cells, have now designed this selective prodrug. Our proposal was developed from virtual screening studies, based on ligands and structure, prediction of pharmacokinetic and toxicological properties (ADME / Tox) and also bioinformatics techniques for the construction of a calcium channel model, due to the inexistence of Structures of the same that were deposited in the database of proteins PDB (Protein Data Bank). At the same time, our collaborating synthesis group synthesized, through Click Chemistry techniques and Mitsunobu multicomponent reactions, a library of new trifunctional hybrids, which, after studies of biological activity, were evaluated (in silico) against the structure of tubulin , And the most promising compounds from this library served as the basis for further virtual screening studies. To obtain our hits, we performed 4 virtual screening strategies, separated into 2 tasks. In the end, we selected 59 hits, of which 9 hits show promising calcium channel blocking activities and 65 hits show promising tubulin modulating activities. These hits follow in vitro purchase and testing, and after proven effectiveness, they will be part of a new tri prodrug proposal.

O planejamento de moduladores da dinâmica dos microtúbulos, a partir da ligação à αβ-tubulina, constitui importante estratégia para a terapia do câncer. Os efeitos de inibição da polimerização da tubulina ou de estabilização dos microtúbulos são promovidos pela interação de compostos em cavidades específicas da proteína alvo. A interferência com a dinâmica dos microtúbulos nas células em rápida multiplicação provoca o bloqueio do ciclo celular, disparando sinais bioquímicos que culminam em apoptose. Os taxanos são os agentes antimitóticos mais importantes dentre os estabilizadores de microtúbulos, ao passo que os alcalóides da vinca e a colchicina são membros representativos dos inibidores da polimerização. Entretanto, o aparecimento de resistência, baixa biodisponibilidade e reações adversas graves são fatores que têm impulsionado a pesquisa por novos agentes anticâncer. Dentre os ligantes identificados recentemente para o sítio do taxol, o discodermolídeo e a dictiostatina, produtos naturais de origem marinha, são potentes estabilizadores de microtúbulos que apresentam maior solubilidade que o taxol e atividade contra células de câncer resistentes aos taxanos. Por essa razão, o modo de ligação desses compostos à cavidade de interação da β-tubulina tem sido objeto de investigação. Modelos preditivos de HQSAR foram desenvolvidos para derivados sintéticos do discodermolídeo e utilizados em conjunto com estudos baseados na estrutura do receptor, em concordância com evidências experimentais, para a proposição de modelos de interação para os análogos na cavidade do taxol. Os modelos de conformação bioativa foram utilizados no alinhamento estrutural do conjunto de dados para estudos de QSAR 3D CoMFA e comparação com o alinhamento baseado nas estruturas minimizadas dos ligantes. A caracterização de padrões de reconhecimento molecular foi útil para a proposição de um modelo farmacofórico baseado nas estruturas dos produtos naturais estabilizadores de microtúbulos. Um modelo farmacofórico simplificado foi integrado ao processo de triagem virtual consistindo na aplicação de filtros hierárquicos sucessivos para a identificação de novos estabilizadores de microtúbulos. Caseobliquinas foram ensaiadas como estabilizadoras de microtúbulos, enquanto que intermediários sintéticos da dictiostatina foram avaliados quanto aos seus efeitos na polimerização da tubulina. Nos últimos anos, tem sido intensificada a busca por novos ligantes do sítio da colchicina, dentre os quais os indóis estão entre os mais relevantes. Para quatro conjuntos de dados totalizando 170 derivados de indóis, modelos de HQSAR foram desenvolvidos para a avaliação virtual de uma base de dados. Estudos de QSAR 3D CoMFA e CoMSIA baseados nos farmacóforos foram comparados para 3 conjuntos de dados. Os resultados sugerem que o núcleo indólico pode interagir de maneiras diferentes na cavidade de interação da proteína. Chalconas do tipo 1, inspiradas em ligantes clássicos do sítio da colchicina, foram avaliadas em ensaios celulares e de polimerização da tubulina, levando a síntese e avaliação de uma nova série de chalconas com propriedade antiproliferativa significativa. Por outro lado, derivados de N-acil-hidrazonas apresentaram atividade antimitótica semelhante à colchicina, enquanto as tiosemicarbazonas citotóxicas não interagiram diretamente com a tubulina. / Inhibition of microtubule function is one of the most important approaches to anticancer therapy. Two main effects can be elicited by tubulin/microtubule-interactive agents: inhibition of tubulin assembly or microtubule stabilization. Interference with either the assembly or disassembly of microtubules within the mitotic spindle in rapidly dividing cells disrupts the normal process of cell division and provokes chemical signals that induce apoptosis. On one hand, taxanes are the most prominent among the microtubule-stabilizing antimitotic agents, while on the other hand, colchicine and the vinca alkaloids are representative members of the tubulin polymerization inhibitors. However, due to poor pharmacokinetic properties, high toxicity and resistance, their clinical utility has been limited, generating new opportunities for the development of novel anticancer agents. In recent years, structurally diverse taxoid-site ligands have been identified, including the potent microtubule-stabilizers discodermolide and dictyostatin. These marine sponge-derived natural products have higher water solubility than taxol and exhibit activity against taxane-resistant cell lines. Therefore, the elucidation of their binding modes is important in drug design. Predictive conformation-independent hologram QSAR models were developed for a series of synthetic discodermolide analogs as antiproliferative agents. Receptor-based studies were integrated with molecular recognition patterns, in agreement with experimental evidences, leading to ligand-binding conformations for discodermolide analogs in the taxol-site. The bioactive conformation models were used to the structural alignment of the data set for the development of 3D QSAR CoMFA models, and for comparison with the models constructed with the rigid-body alignment based on minimized structures of the ligands. A set of structural features related to the interaction with the taxol cavity was identified and the molecular recognition patterns were employed to the construction of pharmacophore models based on the microtubule-stabilizing natural products. A final simplified pharmacophore model was integrated in a virtual screening procedure consisting of consecutive hierarchical filters targeting the identification of novel microtubule-stabilizers. Caseobliquins were screened as microtubule-stabilizers, while intermediates for the synthesis of dictyostatin were evaluated by their effects on tubulin assembly. Recently, the search for more simple anti-tubulin agents has renewed the interest in the development of colchicine analogs, often discarded for their high toxicity. Considering the structurally diverse ligands of the colchicine site, the indole derivatives are among the most important ones. Hologram QSAR models were developed for four data sets consisting of 170 indole derivatives, and used to evaluate a data set of commercially available compounds. Pharmacophore-based 3D QSAR CoMFA and CoMSIA models were constructed and compared to three of the individual data sets. The results indicated that the indole nucleus bind to the protein cavity in different ways. Type 1 chalcones, designed based on classical colchicine site ligands, have been screened for their anti-proliferative activity and tubulin assembly inhibition, leading to the synthesis and assessment of a novel series of chalcone analogs with substantial antiproliferative properties. Some N-acylhydrazone derivatives behaved as mitotic arresters in a way similar to that of colchicine, while cytotoxic thiosemicarbazones did not exhibit tubulin-interacting properties.

Câncer é a denominação de um conjunto de mais de cem doenças causadas pelo crescimento e multiplicação desordenados de células anormais capazes de invadir e se disseminar por diversos tecidos e órgãos. É considerado um problema de saúde mundial, sendo uma das maiores causas de morte. Dados da Organização Mundial da Saúde (OMS) indicam que 15% das mortes no mundo serão causadas por câncer em 2015. No Brasil, o Instituto Nacional do Câncer (INCA) estima 580 mil novos casos da doença para 2014. Apesar da vasta quimioterapia disponível, os tratamentos possuem alta toxicidade e estão sujeitos à resistência. Nesse contexto, a presente dissertação de mestrado tem como foco principal a identificação e caracterização de novos compostos com propriedades anticâncer. Os estudos foram realizados com base em dois alvos principais. O primeiro foi a proteína tubulina, um alvo anticâncer validado que é modulado por moléculas importantes como o taxol, a vimblastina e a colchicina. O segundo alvo foi a migração celular, característica relacionada ao processo de metástase, que é responsável por 90% das mortes por câncer. Uma série de acridinonas sintéticas foi avaliada in silico frente à proteína tubulina empregando métodos de modelagem molecular. Para tanto, fez-se uso de estruturas cristalográficas da proteína disponíveis no PDB (Protein Data Bank). Os resultados das análises de docagem molecular indicaram que as moléculas poderiam interagir com o sítio da colchicina e, dessa forma, atuariam como inibidoras da polimerização dos microtúbulos. Ensaios wound healing e em câmara de Boyden permitiram a identificação de quatro compostos com potente efeito de inibição da migração celular (valores de IC50 variando entre 0,294 e 1,7 μM) em uma linhagem metastática (MDA-MB-231). Estes compostos foram submetidos a ensaios de citotoxicidade frente à mesma linhagem tumoral e também apresentaram boa potência, com valores de IC50 variando entre 0,110 e 3 μM. Além disso, ensaios de citotoxicidade em células saudáveis mostraram que estes compostos inviabilizaram seletivamente células tumorais. Para a validação dos estudos in silico, ensaios de polimerização da tubulina foram conduzidos. Os resultados mostraram que as quatro moléculas ativas nos ensaios celulares atuam como inibidores de polimerização dos microtúbulos, com valores de IC50 variando entre 0,9 e 13 μM. Estudos das relações entre a estrutura e atividade (SAR) revelaram alguns aspectos interessantes nesta série de acridinonas, como, por exemplo, a perda de atividade, que se deu tanto nos ensaios celulares quanto nos ensaios bioquímicos, causada pela substituição de um grupo nitro da posição meta- por para- em duas moléculas da série. A progressão do ciclo celular foi analisada por citometria de fluxo e os resultados mostraram que os compostos estudados são capazes de interromper o ciclo celular entre as fases G2 e M. A citometria fluxo também permitiu verificar a indução da apoptose celular devida à ação das moléculas. Em resumo, este trabalho possibilitou a identificação e caracterização de quatro compostos com propriedades antitumorais promissoras que serão utilizados como compostos líderes para posterior desenvolvimento como agentes anticâncer. / Cancer is a set of diseases with high diversity and aggressiveness. It is one of the major causes of death according to the World Health Organization (WHO), being responsible for 15% of worldwide deaths in 2015. In Brazil, the National Institute of Cancer (INCA) estimates 580,000 new cases of cancer for the year of 2014. Despite the vast availability of cancer chemotherapy, the treatments cause high toxic effects and are liable to resistance. In this context, the main goal of the present master\'s dissertation is the identification and the characterization of new compounds having anticancer properties. These studies were conducted based on two main targets. The first one was the protein tubulin, a validated anticancer target that is modulated by important molecules such as taxol, vinblastine and colchicine. The second target was the cellular migration, a feature related to the metastasis process, which causes 90% of the cancer deaths. A series of synthetic acridinones was studied in silico employing molecular modeling methods. For this, crystallographic structures of tubulin were collected from PDB (Protein Data Bank). The docking results indicated that the molecules could interact with the colchicine site and, thereby, could act as tubulin polymerization inhibitors. The series was assessed by the wound healing and Boyden chamber\'s assays using the metastatic cell line MDA-MB-231. In these assays, four compounds were identified as good inhibitors of cellular migration (IC50 values varying between 0.294 and 1.7 μM). These compounds were evaluated in cytotoxicity assays using the same cell line and presented good potency, with IC50 values varying between 0.110 and 3 μM. Furthermore, cytotoxicity assays using a healthy cell line showed that these compounds act selectively in tumor cells. For the validation of the in silico studies, tubulin polymerization assays were conducted. The results showed that the four active molecules in the cellular assays act as tubulin polymerization inhibitors, with IC50 values varying between 0.9 and 13 μM. Structure-activity relationship (SAR) studies revealed interesting structural aspects in this series of acridinones, for instance, the exchange of the nitro group substituent from the meta- to the para- position in two molecules of the series led to a lack of activity in both cellular and biochemical assays. The cell cycle progression was evaluated by flow cytometry, and the results showed that the four compounds are capable of arrest cells in the G2/M phase. Moreover, the apoptosis induction was verified using flow cytometry. In summary, this work provided the identification and characterization of four new compounds with promising antitumor properties. These molecules will be used as lead compounds for further development as anticancer agents.

<p>Coprophilous ascomycetes are a diverse group of saprobes, of which many belong to three families, Delitschiaceae, Phaeotrichaceae and Sporormiaceae, within the large order Pleosporales. The natural relationships and circumscription of these families are unclear, especially within the family Sporormiaceae, where the generic delimitation have been questioned. There is also a need to understand how different ecological processes affect species richness and occurrence of coprophilous ascomycetes in general. The aim of this thesis was therefore to test earlier classifications of coprophilous taxa within Pleosporales, using phylogenetic analyses of DNA sequences; and to study how the habitat, dung type and herbivores´ food choice may affect the species richness and species composition of coprophilous ascomycetes.</p><p>A phylogenetic study shows that coprophilous taxa have arisen several times within Pleosporales. Sporormiaceae and Delitschiaceae are separate monophyletic groups and should continue to be recognized as two distinct families within Pleosporales. Phaeotrichaceae forms a monophyletic group, and is, unexpectedly, a strongly supported sister-group to Venturiaceae, but if they belong to Pleosporales or not, remains unresolved. Testudinaceae and Zopfiaceae, which previously had an unclear position in Ascomycota, are shown to be members of Pleosporales and should be treated as two separate families. The genus <i>Eremodothis</i> is, however, not related to Testudinaceae, but is nested within Sporormiaceae and should be transferred to <i>Westerdykella</i>.</p><p>The natural relationships within Sporormiaceae are still not fully resolved and consequently, I suggest a rather conservative generic classification, accepting <i>Preussia, Sporormia, Westerdykella</i>, as well as <i>Sporormiella</i>, despite that the latter is not conclusively well supported as monophyletic. Characters previously used in the taxonomy and classification of Sporormiaceae, as choice of substrate, presence or absence of an ostiole, presence or absence of germ slits, and spore ornamentation, were all homoplastic and not very useful for circumscribing monophyletic groups.</p><p>Field-studies of moose (<i>Alces alces</i>), mountain hare (<i>Lepus timidus</i>) and roe deer (<i>Capreolus capreolus</i>) dung resulted in several new species records, which suggests that coprophilous ascomycetes in boreal Sweden are poorly known. Fungal species richness and occurrence on moose dung varied significantly between habitats. Species diversity was negatively associated with amount of insect attack, and insects feeding either on the dung and/or the fungi may be an important factor explaining the observed pattern. Species richness of coprophilous fungi varied also significantly between different dung types. A study of moose, mountain hare, and roe deer dung did not show any consistent patterns in respect to the animals´ digestive system. There was, however, a general strong positive relationship between the total number of ascomycete species and the number of plant species foraged by the three herbivores. Fungal species with large spores (≥ 50 µm) were over-represented on roe deer dung, and under-represented on moose dung, while the reverse was found for species with small spores (<10µm). This suggests that the foraging level of the herbivore, which in turn mirrors species-specific differences in spore dispersal of the fungi, may be an important factor in explaining species richness and diversity of the coprophilous community.</p>

Coprophilous ascomycetes are a diverse group of saprobes, of which many belong to three families, Delitschiaceae, Phaeotrichaceae and Sporormiaceae, within the large order Pleosporales. The natural relationships and circumscription of these families are unclear, especially within the family Sporormiaceae, where the generic delimitation have been questioned. There is also a need to understand how different ecological processes affect species richness and occurrence of coprophilous ascomycetes in general. The aim of this thesis was therefore to test earlier classifications of coprophilous taxa within Pleosporales, using phylogenetic analyses of DNA sequences; and to study how the habitat, dung type and herbivores´ food choice may affect the species richness and species composition of coprophilous ascomycetes. A phylogenetic study shows that coprophilous taxa have arisen several times within Pleosporales. Sporormiaceae and Delitschiaceae are separate monophyletic groups and should continue to be recognized as two distinct families within Pleosporales. Phaeotrichaceae forms a monophyletic group, and is, unexpectedly, a strongly supported sister-group to Venturiaceae, but if they belong to Pleosporales or not, remains unresolved. Testudinaceae and Zopfiaceae, which previously had an unclear position in Ascomycota, are shown to be members of Pleosporales and should be treated as two separate families. The genus Eremodothis is, however, not related to Testudinaceae, but is nested within Sporormiaceae and should be transferred to Westerdykella. The natural relationships within Sporormiaceae are still not fully resolved and consequently, I suggest a rather conservative generic classification, accepting Preussia, Sporormia, Westerdykella, as well as Sporormiella, despite that the latter is not conclusively well supported as monophyletic. Characters previously used in the taxonomy and classification of Sporormiaceae, as choice of substrate, presence or absence of an ostiole, presence or absence of germ slits, and spore ornamentation, were all homoplastic and not very useful for circumscribing monophyletic groups. Field-studies of moose (Alces alces), mountain hare (Lepus timidus) and roe deer (Capreolus capreolus) dung resulted in several new species records, which suggests that coprophilous ascomycetes in boreal Sweden are poorly known. Fungal species richness and occurrence on moose dung varied significantly between habitats. Species diversity was negatively associated with amount of insect attack, and insects feeding either on the dung and/or the fungi may be an important factor explaining the observed pattern. Species richness of coprophilous fungi varied also significantly between different dung types. A study of moose, mountain hare, and roe deer dung did not show any consistent patterns in respect to the animals´ digestive system. There was, however, a general strong positive relationship between the total number of ascomycete species and the number of plant species foraged by the three herbivores. Fungal species with large spores (≥ 50 µm) were over-represented on roe deer dung, and under-represented on moose dung, while the reverse was found for species with small spores (&lt;10µm). This suggests that the foraging level of the herbivore, which in turn mirrors species-specific differences in spore dispersal of the fungi, may be an important factor in explaining species richness and diversity of the coprophilous community.