Nous proposons dans cette thèse de caractériser quantitativement la variabilité à différentes échelles au cours de l'embryogenèse. Pour ce faire, nous utilisons une combinaison de modèles mathématiques et de résultats expérimentaux. Dans la première partie, nous utilisons une petite cohorte d'oursins digitaux pour construire une représentation prototypique du lignage cellulaire, reliant les caractéristiques des cellules individuelles avec les dynamiques à l'échelle de l'embryon tout entier. Ce modèle probabiliste multi-niveau et empirique repose sur les symétries des embryons et sur les identités cellulaires; cela permet d'identifier un niveau de granularité générique pour observer les distributions de caractéristiques cellulaires individuelles. Le prototype est défini comme le barycentre de la cohorte dans la variété statistique correspondante. Parmi plusieurs résultats, nous montrons que la variabilité intra-individuelle est impliquée dans la reproductibilité du développement embryonnaire. Dans la seconde partie, nous considérons les mécanismes sources de variabilité au cours du développement et leurs relations à l'évolution. En nous appuyant sur des résultats expérimentaux montrant une pénétrance incomplète et une expressivité variable de phénotype dans une lignée mutante du poisson zèbre, nous proposons une clarification des différents niveaux de variabilité biologique reposant sur une analogie formelle avec le cadre mathématique de la mécanique quantique. Nous trouvons notamment une analogie formelle entre l'intrication quantique et le schéma Mendélien de transmission héréditaire. Dans la troisième partie, nous étudions l'organisation biologique et ses relations aux trajectoires développementales. En adaptant les outils de la topologie algébrique, nous caractérisons des invariants du réseaux de contacts cellulaires extrait d'images de microscopie confocale d'épithéliums de différentes espèces et de différents fonds génétiques. En particulier, nous montrons l'influence des histoires individuelles sur la distribution spatiales des cellules dans un tissu épithélial. / We propose in this thesis to characterize variability quantitatively at various scales during embryogenesis. We use a combination of mathematical models and experimental results. In the first part, we use a small cohort of digital sea urchin embryos to construct a prototypical representation of the cell lineage, which relates individual cell features with embryo-level dynamics. This multi-level data-driven probabilistic model relies on symmetries of the embryo and known cell types, which provide a generic coarse-grained level of observation for distributions of individual cell features. The prototype is defined as the centroid of the cohort in the corresponding statistical manifold. Among several results, we show that intra-individual variability is involved in the reproducibility of the developmental process. In the second part, we consider the mechanisms sources of variability during development and their relations to evolution. Building on experimental results showing variable phenotypic expression and incomplete penetrance in a zebrafish mutant line, we propose a clarification of the various levels of biological variability using a formal analogy with quantum mechanics mathematical framework. Surprisingly, we find a formal analogy between quantum entanglement and Mendel’s idealized scheme of inheritance. In the third part, we study biological organization and its relations to developmental paths. By adapting the tools of algebraic topology, we compute invariants of the network of cellular contacts extracted from confocal microscopy images of epithelia from different species and genetic backgrounds. In particular, we show the influence of individual histories on the spatial distribution of cells in epithelial tissues.

Die Körpergröße ist von großer Bedeutung für die Fitness vieler Tiere, weil sie positiv mit Überleben und Reproduktionserfolg korreliert ist. Große Rogner vieler Fischarten sind fruchtbarer und produzieren Nachkommen von höherer Qualität verglichen mit kleineren Weibchen. Auch für Milchner einiger Fischarten wurde ein Einfluss der Körpergröße auf frühe Lebensstadien nachgewiesen. Der größenabhängige paternale Effekt verglichen mit maternalen Effekten ist weniger gut untersucht. Das Verständnis der Variation im Reproduktionserfolg als Funktion der Körpergröße der Laicher ist wichtig, weil die Fischerei die Durchschnittsgröße des Laicherbestands reduziert. In vorliegender Dissertation wurden in Laborversuchen an Zebrafischen (Danio rerio) größenabhängige paternale und maternale Effekte auf den Reproduktionserfolg und die Auswirkungen größenselektiver Entnahme auf Körperlänge, Reifung und Reproduktionserfolg untersucht. Die Köperlänge und Kondition waren wichtige Determinanten der Reifung bei Zebrafischen. Größere Rogner zeigten höheren Reproduktionserfolg als kleinere Fische und ein signifikanter Einfluss der Milchnerkörperlänge auf die frühen Lebensstadien ihrer Nachkommen wurde dokumentiert. Längere Männchen wurden von Rognern auch bei der Paarung bevorzugt. Die größenabhängigen maternalen und paternalen Effekte waren ausschlaggebend für den erhöhten Reproduktionserfolg von Zebrafischlaichbeständen, die, verglichen mit kleinen Laichern, aus großen oder zufällig zusammengesetzten Individuen zusammengesetzt waren. Die größenselektive Entnahme führte zu phänotypischen und genetischen Veränderungen, die nach Einstellung der experimentellen Befischung persistierten. Das deutet an, dass die durch die Fischerei ausgelöste Evolution schwierig umkehrbar sein könnte. Die Köpergröße ist von überragender Bedeutung in der Reproduktionsbiologie des Zebrafisches und der Schutz großer Laichfische kann wichtig für den Erhalt der Reproduktionskapazität von befischten Beständen sein. / Body size is a fundamentally important trait for fitness in many animal species because it correlates positively with survival and reproductive success. In many fish species, large females exhibit higher fecundity and produce higher quality offspring compared to small females. Similarly, male body size can affect offspring quality and early life-history traits but the importance of these effects to the reproductive biology of fish is poorly studied. The extent to which variation in reproductive success is explained by parental body size is an important research topic because size-selective fishing usually reduces the average size of reproducing adults in a population. In my dissertation, I studied the parental size effects on reproductive success in a model species (zebrafish, Danio rerio). I also studied the effects of size-selective harvesting on body size, maturation and reproductive output. Body size and condition factor were important determinants of the initiation of maturation in zebrafish. Large females were found to have higher reproductive success compared to small females and a significant effect of male body size on early life-history traits was documented. I found that large males were also favored by the females resulting to differential allocation of reproductive resources toward large males. The maternal- and paternal-size effects ultimately led to elevated reproductive success of experimental spawning stocks consisting of large or random-sized individuals compared to spawning stocks consisting of small individuals. Size-selective harvesting induced rapid phenotypic and genetic changes, which persisted after selection was halted. This suggests that fishing-induced changes might be hard to reverse. My results emphasize the importance of body size to the reproductive biology of zebrafish and suggest that protecting large fish might be important to maintain the reproductive potential of exploited fish stocks.

L’uranium (U) est naturellement présent à l’état de trace dans l’eau (µg.L-1), sa concentration pouvant atteindre localement quelques mg.L-1 du fait des activités anthropiques. Plusieurs études écotoxicologiques sur Danio rerio ont mis en évidence la toxicité, e.g. le stress oxydant, la génotoxicité mais aussi la reprotoxicité (i.e. moins de pontes et d’œufs pondus chez les poissons contaminés) de l’U dont les mécanismes ne sont pas connus.L’objectif de cette étude est de contribuer à la compréhension de la reprotoxicité de l’U par l’élucidation de mécanismes moléculaires perturbés après contamination. Pour cela, des investigations ont été menées sur les ovaires de poissons zèbre Danio rerio, reproduits (R) ou non (NR), après exposition par voie directe en condition de laboratoire à des concentrations représentatives d’environnements contaminés.Ce travail de thèse a été divisé en deux volets. Un premier volet analytique avait pour but la poursuite des développements de méthodes pour l’identification des complexes U-protéines en condition non dénaturante, autour du couplage de techniques de séparation (chromatographie d’exclusion stérique SEC, électrophorèse hors gel OGE) et de détection sensible par spectrométrie de masse élémentaire (ICP MS) et moléculaire (ESI MS). Le second volet a été dédié à l’étude de la reprotoxicité de l’U à l’échelle moléculaire, avec i) l’étude des complexes natifs U-protéines (approche métallomique), et ii) l’analyse différentielle de l’expression des protéines (approche protéomique).Les développements analytiques ont permis de garder le tampon physiologique et non dénaturant d’extraction pour l’étape de séparation OGE, améliorant le taux de recouvrement en U. En écotoxicologie, les principaux résultats montrent que l’ovaire est un organe accumulateur de l’U et que le statut de reproduction a une influence sur le niveau d’accumulation (R<NR). En revanche, cet état a peu d’influence sur sa distribution protéique pour laquelle 4 fractions (dont 1 principale) ont été identifiées, toutes contenant aussi du phosphore. L’identification des cibles potentielles de l’U et des protéines exprimées différentiellement (vtg, GST, GAPDH,…) a montré que les processus biologiques perturbés suite à la contamination sont de deux niveaux : 1/ générique (stress oxydant) et 2/ plus spécifique de la gonade (développement et maturation des ovocytes). En conclusion, ces deux approches complémentaires ont permis de mettre en évidence un effet direct (complexation) et indirect (expression protéique modulée) de l’U, et de proposer l’hypothèse d’un défaut de maturation des ovocytes après contamination. Ce défaut pourrait impacter le développement embryonnaire et in fine expliquer la reprotoxicité observée lors d’études écotoxicologiques précédentes. / Uranium (U) is naturally presents at trace level (µg.L-1) in aquatic environment; its concentration can increase up to a few mg.L-1 due to human activities. Several ecotoxicological studies have shown uranium toxicity in contaminated zebrafishes Danio rerio, e.g. oxidative stress, genotoxicity and reprotoxicity (i.e. lower number of spawn and eggs laid) but mechanisms are not well known.The objective of this study is to contribute to the understanding of uranium reprotoxicity by elucidating the disrupted molecular mechanisms after contamination. Therefore, investigations have been carried out on ovaries from reproduced (R) and non-reproduced (NR) zebrafishes after waterborne exposure in laboratory conditions at environmentally relevant concentrations.This project was divided into two parts. Firstly, analytical investigations were carried out to continue the development of non-denaturing methods for U-protein identification by coupling separative techniques (size exclusion chromatography SEC, off gel electrophoresis OGE) with elemental (ICP MS) and molecular (ESI MS) sensitive mass spectrometry detection. Secondly, studies of U reprotoxicity were investigated by studying i) native U-protein complexes (metallomics approach) and ii) differential analysis of protein expression (proteomics approach)Analytical developments allowed keeping the physiological and non-denaturing extraction buffer for OGE separation step, improving U recovery. In ecotoxicology, the major results showed that ovary is an U accumulating organ and that the reproduction status modifies the accumulation level (R<NR). However, this status is of little influence on its distribution on proteins with 4 fractions (including a major one) determined, all of them coeluting with phosphorus. The identification of U potential targets and of protein expression differences (vtg, GST, GAPDH…) showed that biological processes disrupted after contamination are at two levels: 1/ generic (oxidative stress) and 2/ more specific to gonad (oocyte development and maturation).As a conclusion, these two complementary approaches showed a direct (complexation) and indirect (modification of protein expression) effects of U, and enabled to hypothesize a lack of oocyte maturation after contamination. This defect could impact embryo development and in fine explain the reprotoxicity observed in previous ecotoxicological studies.

Diese Dissertation ist ein Beitrag zum Forschungsfeld der Stressökologie, im Spe-ziellen der Verhaltensökotoxikologie. Das spontane lokomotorische Verhalten der Fischarten Danio rerio und Leucaspius delineatus wurde unter sublethaler Expo-sition mit dem Cyanobakterientoxin Microcystin-LR (MC-LR) und dem Xenobio-tikums 2.4.4`-Trichlorobiphenyl (PCB 28) quantifiziert. Die Schwimmgeschwin-digkeit und Anzahl der Wendungen wurden kontinuierlich mit einem automati-schen Video-Monitoringsystem unter Laborbedingungen aufgezeichnet. In Hin-blick auf zyklische Aspekte wurden die Verhaltensanalysen mit chronobiologi-schen Methoden kombiniert. Hiermit wurde gezeigt, dass MC-LR und PCB 28 zu signifikanten Effekten in Verhalten und Aktivitätsrhythmik beider Fischarten führten. Höhere Konzentrati-onen beider Untersuchungssubstanzen verursachten eine deutliche Aktivitätsredu-zierung bei Danio rerio und Leucaspius delineatus. Einige der festgestellten Do-sis-Wirkungsbeziehungen entsprechen der Hormesistheorie, z. B. war bei geringe-ren MC-LR Konzentrationen ein Aktivitätsanstieg und bei höheren ein Aktivitäts-abfall beider Fischarten zu verzeichnen. Die Exposition mit MC-LR und PCB 28 verringerte bei beiden Testfischarten die Synchronisation der Aktivität mit dem Zeitgeber Licht. Dies führte bei beiden Fischarten zu einer Phasenverschiebung. Bei Leucaspius delineatus war unter dem Einfluss von MC-LR eine Phasenumkehr zu verzeichnen, die Fische wechselten von Tag- zu Nachtaktivität. Die Cosinor Analyse zeigte Dosis abhängige Veränderungen der circadianen Rhythmen der Schwimmaktivität (z.B. MESOR, Akrophase) unter Einfluss von MC-LR und PCB 28 an. Die Power Spektral Analyse indizierte für beide Fischar-ten unter Einwirkung von MC-LR and PCB 28 eine reduzierte Dominanz des cir-cadianen Rhythmuspeaks. Da die registrierten Unterschiede in der Reaktion beider Fischarten auf MC-LR und PCB 28 eher gering waren, sind Ergebnisse der Art Danio rerio, die häufig in Toxizitätstests verwendet wird, mit denen der einheimischen Art Leucaspius deli-neatus vergleichbar. Die Ergebnisse belegen, dass Verhaltensuntersuchungen in Kombination mit chronobiologischen Auswertemethoden eine sensitive und zuverlässige Abschät-zung des Gefährdungspotentials von Substanzen sowohl auf dem Gebiet der Öko-toxikologie als auch für Biomonitoring ermöglichen. / This thesis contributes to the field of stress ecology specifically behavioural ecotoxicology. The spontaneous locomotor behavior of two fish species Danio re-rio and Leucaspius delineatus was recorded and quantified continuously under sublethal exposure to the cyanotoxin microcystin-LR (MC-LR) and the xenobioti-cum 2.4.4`-trichlorobiphenyl (PCB 28). By using an automated video-monitoring system, the swimming velocity and the number of turns were assessed under labo-ratory conditions. For analysing cyclic aspects basic behavioural analyses were combined with chronobiological procedures as cosinor analysis and power spec-tral analysis. Both MC-LR and PCB 28 acted as stressors and caused significant changes in the behaviour and circadian activity rhythms of Danio rerio as well as Leucaspius de-lineatus. So for both species elevated concentrations of the stressors led to a re-duction of their activity. Some dose-responses correspond to the hormesis theory, e.g., there was an increase of daytime activity at lower MC-LR concentrations and a decrease at elevated concentrations of MC-LR for both species. A degree of desynchronisation of activity to the zeitgeber light, which led to a phase shift was caused by the chemicals in both fish species. In Leucaspius de-lineatus this shift was so drastic that this species reversed their significant diurnal activity and became nocturnal under the influence of MC-LR. The Cosinor analysis revealed MC-LR- and PCB 28-induced, dose-dependent al-terations of the circadian rhythms of activity (e.g., MESOR, acrophase). The power spectral analysis showed that the dominance of the circadian rhythmic peak (of 24 h) was reduced under MC-LR and PCB 28 for both species. Since the observed differences in the reactions of both species to MC-LR and PCB 28 were rather small, the results of the species Danio rerio which is widely used for environmental risk assessment tests, are comparable to those of the native European species Leucaspius delineatus. The findings of this study proved that the basic behavioural analyses combined with chronobiological procedures could be valuable tools for the study of stressful or even harmful environmental factors in the field of ecotoxicology as well as for biomonitoring.

The term &amp;quot;pattern formation&amp;quot; refers to the process by which order unfolds in development. The present thesis deals with a particular aspect of molecular pattern formation during vertebrate embryogenesis. The model system in the focus of this study is the zebrafish, Danio rerio. In the early developmental phases of the zebrafish, Fibroblast growth factors (Fgfs) are involved in the molecular patterning of various tissues, including two regions of the brain, the forebrain and the midbrain-hindbrain region, affecting cellular processes as diverse as cell proliferation, differentiation, and axonal targeting. The goal of this study was to better understand the mechanisms by which Fgf signaling regulates pattern formation and embryogenesis. I addressed this question on several levels, investigating the extent of intracellular signaling (MAPK activation) relative to sources of Fgf expression, and the transcriptional responses of cells to Fgf signaling during embryogenesis. By a macroarray analysis, I identified putative transcriptional targets of Fgf signaling in late gastrulation, providing a set of molecules that are likely to act as functional players in relaying the patterning information encoded by Fgf signals. Among those are the secreted signaling molecules Chordin and Wnt8, as well as Isthmin, a novel secreted molecule that I found capable to interfere with anterior embryonic patterning. In addition, I identified two ETS domain transcription factors, Erm and Pea3, which constitute bona fide integrators of FgfR signaling. By gain- and loss-of-function studies, I demonstrate that transcript levels of erm and pea3 are tightly regulated by Fgf signaling. Detailed analysis of the expression patterns of erm and pea3 along with other Fgf target genes also provides evidence for a differential read-out of Fgf concentration in the embryo, consistent with a role of Fgf as a vertebrate morphogen. The discovery of novel molecular components downstream of Fgf receptor activity paves a way to characterize previously unknown or underestimated developmental roles of Fgfs in the molecular patterning of the forebrain, the eye and parts of the neural crest.

Les hydrocarbures aromatiques polycycliques (HAP) sont des polluants organiques persistants qui sont présents en mélange complexe dans l’environnement et notamment dans les milieux aquatiques. Ils s’adsorbent sur les particules en suspension, s’accumulent dans les sédiments et dans les premiers maillons de la chaîne trophique. L’objectif de cette étude était de mesurer les effets à long terme d’une contamination par des HAP chez un modèle de vertébrés : le poisson zèbre. Dans un premier temps, des embryons ont été exposés pendant les 4 premiers jours de leur développement sur du sédiment naturel enrobé de 3 HAP individuel (phénanthrène, pyrène et benzo[a]pyrène) puis transférés et élevés en eau propre. Dans un deuxième temps, des poissons ont été exposés par voie alimentaire tout au long du cycle de vie et dès le premier repas à 3 fractions de HAP à doses environnementales enrobées sur les aliments : une fraction pyrolytique (PY) extraite d’un sédiment échantillonné dans la Seine et deux fractions pétrogéniques (un fuel lourd (HO) provenant de l’Erika et un pétrole brut type Arabian light (LO)). Les effets à long terme sur la croissance, la survie, la reproduction et le comportement ont été évalués à différents âges. Ces effets ont pu être observés à plusieurs échelles, i.e. de la molécule, aux tissus et organes puis à l’échelle de l’individu. Globalement, chez les poissons contaminés, la croissance est ralentie, la survie larvaire diminuée chez les HO, la fonction reproduction est altérée fortement à la fois au niveau hormonal, tissulaire et phénotypique ainsi que les réponses comportementales léthargiques ou hyper-réactives selon les cas. L’exposition par voie sédimentaire a révélé des effets visibles lorsque les individus atteignaient 6 mois soulignant l’existence d’effets tardifs, notamment sur les réponses comportementales, d’une exposition très précoce y compris chez la descendance. Quant à l’exposition par voie alimentaire, elle a montré une gradation des effets. Toutes fonctions confondues, les résultats obtenus permettent d'établir une hiérarchie dans la toxicité des fractions étudiées : PY < LO ≈ HO. L'approche multi-échelle utilisée dans ce travail a permis, en partant d'informations acquises au niveau moléculaire, tissulaire et individuel, d'aboutir à une compréhension intégrée des conséquences qu'une exposition à des HAP peut avoir sur l'aptitude à la survie des poissons dans leur milieu naturel ainsi qu'à leur capacité à participer au renouvellement des générations futures. / Polycyclic aromatic hydrocarbons (PAHs) are persistent organic pollutants (POPs) which are found in complex mixtures in the environment including aquatic ecosystems. They adsorb on particles, accumulate in sediment and in the first link of the food web. The aim of this study was to measure long term effects of PAHs contamination on a vertebrate model : the zebrafish. In a first study, embryos were exposed on natural sediment spiked with 3 individual PAH (phenanthrene, pyrene and benzo[a]pyrene) during the first four days of their development. In a second study, to evaluate the consequences of long-term chronic exposure to PAHs, zebrafish were exposed, from their first meal (5 days post fertilisation) until they became reproducing adults, to diets spiked with three PAHs fractions at environmentally relevant concentrations (0.3X, 1X and 3X; with the 1X concentration being in the range of 4.6-6.7 μg.g-1 for total quantified PAHs). The fractions used were representative of PAHs of pyrolytic (PY) origin or of two different oils of differing compositions (a heavy fuel (HO) and a light crude oil (LO)). Long term effects on growth, survival, reproduction and behavior were evaluated at different ages. Effects were observed at molecule, tissue, organ and individual scales. In general, for contaminated fish, growth was reduced, larval survival decreased in HO, and reproduction was strongly impaired at hormonal, tissue and phenotypic levels, and behavioral responses were lethargic or hyperactive depending on fractions and stages. Sediment exposure still revealed visible effects when fish were 6 month old. These results hereby showed significant late effects, especially in behavioral responses after an early exposure, including in larvae issued from contaminated fish. In spiked diets contaminated fish, we observed a gradation of effects. Combining all functions, we established of hierarchy in toxicity in the studied fractions: PY < LO ≈ HO. Finally, our results gathered at a multiscale from molecule, to tissue and individuals, indicate that PAH mixtures of different compositions, representative of situations encountered in the wild, can promote lethal and sublethal effects which are likely to be detrimental for fish survival and recruitment into future generations.

Nous proposons dans cette thèse de caractériser quantitativement la variabilité à différentes échelles au cours de l'embryogenèse. Pour ce faire, nous utilisons une combinaison de modèles mathématiques et de résultats expérimentaux. Dans la première partie, nous utilisons une petite cohorte d'oursins digitaux pour construire une représentation prototypique du lignage cellulaire, reliant les caractéristiques des cellules individuelles avec les dynamiques à l'échelle de l'embryon tout entier. Ce modèle probabiliste multi-niveau et empirique repose sur les symétries des embryons et sur les identités cellulaires; cela permet d'identifier un niveau de granularité générique pour observer les distributions de caractéristiques cellulaires individuelles. Le prototype est défini comme le barycentre de la cohorte dans la variété statistique correspondante. Parmi plusieurs résultats, nous montrons que la variabilité intra-individuelle est impliquée dans la reproductibilité du développement embryonnaire. Dans la seconde partie, nous considérons les mécanismes sources de variabilité au cours du développement et leurs relations à l'évolution. En nous appuyant sur des résultats expérimentaux montrant une pénétrance incomplète et une expressivité variable de phénotype dans une lignée mutante du poisson zèbre, nous proposons une clarification des différents niveaux de variabilité biologique reposant sur une analogie formelle avec le cadre mathématique de la mécanique quantique. Nous trouvons notamment une analogie formelle entre l'intrication quantique et le schéma Mendélien de transmission héréditaire. Dans la troisième partie, nous étudions l'organisation biologique et ses relations aux trajectoires développementales. En adaptant les outils de la topologie algébrique, nous caractérisons des invariants du réseaux de contacts cellulaires extrait d'images de microscopie confocale d'épithéliums de différentes espèces et de différents fonds génétiques. En particulier, nous montrons l'influence des histoires individuelles sur la distribution spatiales des cellules dans un tissu épithélial. / We propose in this thesis to characterize variability quantitatively at various scales during embryogenesis. We use a combination of mathematical models and experimental results. In the first part, we use a small cohort of digital sea urchin embryos to construct a prototypical representation of the cell lineage, which relates individual cell features with embryo-level dynamics. This multi-level data-driven probabilistic model relies on symmetries of the embryo and known cell types, which provide a generic coarse-grained level of observation for distributions of individual cell features. The prototype is defined as the centroid of the cohort in the corresponding statistical manifold. Among several results, we show that intra-individual variability is involved in the reproducibility of the developmental process. In the second part, we consider the mechanisms sources of variability during development and their relations to evolution. Building on experimental results showing variable phenotypic expression and incomplete penetrance in a zebrafish mutant line, we propose a clarification of the various levels of biological variability using a formal analogy with quantum mechanics mathematical framework. Surprisingly, we find a formal analogy between quantum entanglement and Mendel’s idealized scheme of inheritance. In the third part, we study biological organization and its relations to developmental paths. By adapting the tools of algebraic topology, we compute invariants of the network of cellular contacts extracted from confocal microscopy images of epithelia from different species and genetic backgrounds. In particular, we show the influence of individual histories on the spatial distribution of cells in epithelial tissues.

The term &amp;quot;pattern formation&amp;quot; refers to the process by which order unfolds in development. The present thesis deals with a particular aspect of molecular pattern formation during vertebrate embryogenesis. The model system in the focus of this study is the zebrafish, Danio rerio. In the early developmental phases of the zebrafish, Fibroblast growth factors (Fgfs) are involved in the molecular patterning of various tissues, including two regions of the brain, the forebrain and the midbrain-hindbrain region, affecting cellular processes as diverse as cell proliferation, differentiation, and axonal targeting. The goal of this study was to better understand the mechanisms by which Fgf signaling regulates pattern formation and embryogenesis. I addressed this question on several levels, investigating the extent of intracellular signaling (MAPK activation) relative to sources of Fgf expression, and the transcriptional responses of cells to Fgf signaling during embryogenesis. By a macroarray analysis, I identified putative transcriptional targets of Fgf signaling in late gastrulation, providing a set of molecules that are likely to act as functional players in relaying the patterning information encoded by Fgf signals. Among those are the secreted signaling molecules Chordin and Wnt8, as well as Isthmin, a novel secreted molecule that I found capable to interfere with anterior embryonic patterning. In addition, I identified two ETS domain transcription factors, Erm and Pea3, which constitute bona fide integrators of FgfR signaling. By gain- and loss-of-function studies, I demonstrate that transcript levels of erm and pea3 are tightly regulated by Fgf signaling. Detailed analysis of the expression patterns of erm and pea3 along with other Fgf target genes also provides evidence for a differential read-out of Fgf concentration in the embryo, consistent with a role of Fgf as a vertebrate morphogen. The discovery of novel molecular components downstream of Fgf receptor activity paves a way to characterize previously unknown or underestimated developmental roles of Fgfs in the molecular patterning of the forebrain, the eye and parts of the neural crest.

Die salzhaltigen Abwässer des Kalibergbaues führen in natürlichen Süßwassersystemen zu Ionenimbalanzen und einer sekundären Versalzung der Werra in Deutschland. Die Auswirkungen dieser Ionenungleichgewichte auf die Reproduktion von Süßwasserfischen wurden unter Verwendung der Modellfischart Danio rerio untersucht. Angepasst an die aktuellen Grenzwerte für die Einleitung der Abwässer aus dem Kalibergbau wurden fünf verschiedene Kombinationen erhöhter Ionenkonzentrationen getestet. Während eines partiellen Lebenszyklustests wurden adulte Fische 35 Tage lang in den Salzkombinationen exponiert. Anschließend wurden die Nachkommen dieser Fische bis zum 8. Tag nach der Befruchtung den gleichen Salzkonzentrationen ausgesetzt. Zusätzlich wurden Early-Life-Stage-Tests (ELST) mit den Nachkommen von nicht exponierten Eltern durchgeführt. Im Vergleich zu natürlich vorkommenden Ionenkonzentrationen und -verhältnissen in Süßwassersystemen war die Befruchtungsrate der Eier für alle Ionenkombinationen signifikant niedriger, die Koagulations- und Deformationsrate jedoch signifikant höher. Die ELST ergaben bei den Embryonen und Larven u.a. vorzeitige und verlängerte Schlupfzeiten, verringerte Überlebensraten, erhöhte Deformationsraten und Herzschlagfrequenzen sowie Unregelmäßigkeiten des Ganzkörpergehalts von K, Mg, Na und Ca und des Ganzkörper-Ionenverhältnisses von Ca:Mg bei erhöhten Ionenkonzentrationen und Ionenimbalanzen. Im Vergleich zu den Effekten auf die Fortpflanzung und Entwicklung der Nachkommen waren die Effekte auf die adulten Tiere moderat. Die Ergebnisse dieser Dissertation zeigen, dass Teillebenszyklus-Tests besser als Fischeitests oder ELST geeignet sind, die Effekte von durch Abwasser verursachten Ionenimbalanzen, auf die Fortpflanzung und frühe Entwicklung von Süßwasserfischen, zu untersuchen. Weder die momentan gültigen noch die zukünftig herabgesetzten Grenzwerte bis 2027 sind danach als unschädlich, für die Reproduktion von Süßwasserfischen, zu betrachten. / The potash mining industry discharges saline effluents which generate ion imbalances in natural freshwater systems and cause severe secondary salinization in the river Werra in Germany. The effects of these ion imbalances on reproduction of freshwater fish were investigated using the fish model species Danio rerio. Five different combinations of elevated ion concentrations adjusted to the current threshold values for the discharge of potash mining effluents in Germany were tested. During a partial life cycle test, adult fish were exposed to the salt combinations for 35 days. Subsequently, the offspring were exposed to the same concentrations until hatch, and the larvae were further reared at the exposure concentrations from hatch until the 8th day post fertilization. Additionally, a standard early life stage test with offspring from unexposed parents was performed. Compared to naturally occurring ion concentrations and ratios in freshwater systems, the fertilization rate of the eggs was significantly lower for all ion combinations, while coagulation and deformation rates were significantly higher. Early life stage tests on embryos and larvae revealed premature and prolonged hatching times, reduced survival rates, increased deformation and heart rates and irregularities in whole body content of K, Mg, Na and Ca and whole body Ca:Mg ratios at elevated ion concentrations and imbalances of ion ratios. Compared to effects on reproduction and development of the offspring, effects on the parental generation were moderate. The results of this dissertation indicate that partial life cycle tests instead of fish egg tests or ELST are needed to examine most sensitively the effects of ion imbalances caused by potash mining effluents on reproduction and early development of freshwater fish. Neither the recent German threshold values nor the future reduced values until 2027 are safe for the reproduction of freshwater fish.

Submitted by Hellen Luz (hellencrisluz@gmail.com) on 2017-09-18T19:58:53Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_ParametrosEscototaxiaModelo.pdf: 1500226 bytes, checksum: 275abf0aa72799c079b3c856bd268f80 (MD5) / Rejected by Irvana Coutinho (irvana@ufpa.br), reason: Aguardar as orientações on 2017-10-10T16:49:03Z (GMT) / Submitted by Hellen Luz (hellencrisluz@gmail.com) on 2017-10-17T17:42:47Z No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_ParametrosEscototaxiaModelo.pdf: 1500226 bytes, checksum: 275abf0aa72799c079b3c856bd268f80 (MD5) / Approved for entry into archive by Edisangela Bastos (edisangela@ufpa.br) on 2017-11-22T18:35:53Z (GMT) No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_ParametrosEscototaxiaModelo.pdf: 1500226 bytes, checksum: 275abf0aa72799c079b3c856bd268f80 (MD5) / Made available in DSpace on 2017-11-22T18:35:53Z (GMT). No. of bitstreams: 2 license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Dissertacao_ParametrosEscototaxiaModelo.pdf: 1500226 bytes, checksum: 275abf0aa72799c079b3c856bd268f80 (MD5) Previous issue date: 2011-02-24 / CAPES - Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / Determinados peixes teleósteos apresentam um caractere comportamental de escototaxia, a preferência por ambientes escuros a ambientes claros. O presente trabalho buscou avaliar alguns parâmetros do comportamento exploratório do paulistinha (Danio rerio Hamilton 1822) na caixa claro-escuro. A evitação do compartimento branco apresenta um padrão bifásico, com um aumento na evitação precedendo uma diminuição (Experimento 1). Essa mesma evi- tação não habitua frente à exposição repetida, independentemente do intervalo inter-sessões, ao contrário da locomoção total (Experimentos 2 e 3); a exposição forçada ao compartimento branco não altera a exploração subseqüente nem a locomoção total (Experimento 4). Esses resultados sugerem que a novidade do aparato não é a dimensão controladora da escototaxia; além disso, esses resultados também sugerem que a preferência pelo compartimento preto não é causada simplesmente pela esquiva ao compartimento branco, ainda que essa certamente tenha um papel importante. O papel da aversividade do compartimento branco foi investigado na segunda série de experimentos. A iluminação sobre o compartimento branco é um fator ansiogênico, já que aumentá-la diminui o tempo que os animais passam sobre este sem afetar a locomoção total (Experimento 5). Esse fenômeno parece se dever a uma diminuição na ca- pacidade de camuflagem com o substrato (cripse), já que alterar a cor do compartimento bran- co para cinza aumenta o tempo passado neste, enquanto alterar a cor do compartimento preto para cinza aumenta o tempo passado no compartimento branco, ambas as alterações não afe- tando a locomoção total (Experimento 6). Além disso, o aumento da proporção ocupada pelo compartimento branco no aparato (de 50% para 75%) diminui o tempo passado neste sem afetar a locomoção total (Experimento 7). Esses resultados sugerem que o compartimento branco é aversivo, e portanto a preferência pelo compartimento preto não é causada simples- mente por propriedades reforçadoras positivas desse ambiente. Tomados em conjunto, os re- sultados das duas séries de experimentos sugerem que a escototaxia resulta do conflito apro- ximação-evitação. O Experimento 8 representa uma manipulação ambiental comum que altera a ansiedade em roedores, o enriquecimento; aqui, animais criados em ambiente enriquecido por duas semanas apresentam menor evitação do compartimento branco. Conclui-se que a escototaxia apresenta bom valor preditivo. / Certain teleost fishes present a behavioral trait of scototaxis, the preference for dark environ- ments and not bright ones. The present work tried to evaluate some parameters of the explora- tory behavior of the zebrafish (Danio rerio Hamilton 1822) in the black/white tank, aiming to establish the reliability of measures in different contexts. White compartment avoidance presents a biphasic pattern, with an increase in avoidance preceding a decrease (Experiment 1). This same avoidance does not habituate to repeated exposure, independently of the inter- session interval, on the contrary of total locomotion (Experiments 2 and 3); forced exposure to the white compartment does not alter the subsequent exploratory behavior (Experiment 4). These results suggest that novelty is not the controlling dimension of scototaxis; besides, these results also suggest that the preference for the Black compartment is not caused simply by avoidance of the white compartment, although this certainly has an important role. The role of the aversiveness of the white compartment was assessed in a second series of experi- ments. The illumination above the white compartment is an anxiogenic factor, since increas- ing it decreases the time spent in the white compartment without affecting total locomotion (Experiment 5). This phenomenon seems to be due to a decrease in the capacity to camouf- lage with the substrate (crypsis), since altering the color of the white compartment to grey increases its exploration, while altering the color of the black compartment to grey increases the time spent in the white compartment (Experiment 6). Besides, the increase in the propor- tion of the apparatus occupied by the white compartment (from 50% to 75%) decreases the time spent in it (Experiment 7). These results suggest that the white compartment is aversive, and therefore the preference for darkness is not caused simply by positive reinforcing proper- ties of the black compartment. Taken together, the results of both series of experiments sug- gest that scototaxis results from an approach-avoidance conflict. Experiment 8 represents a common environmental manipulation which alters anxiety in rodents, environmental enrich- ment; here, animals raised in an enriched aquarium for two weeks present less white avoid- ance. It is concluded that scototaxis has good construct validity.