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La ligne latérale postérieure embryonnaire du poisson-zèbre est composée d'un ensemble d'organes sensoriels, appelés neuromastes, qui permet au poisson de détecter les mouvements de l'eau. Le primordium qui génère la ligne latérale postérieure embryonnaire migre de la tête vers l'extrémité de la queue le long d'une piste de cellules sécrétrices de SDF-1, et dépose des groupes de cellules précurseurs des neuromastes. Cette migration dépend de la présence de CXCR4, le récepteur de SDF-1, dans la région en tête du primordium et de la présence du second récepteur de SDF-1, CXCR7, dans la région en queue du primordium. L'objectif de ma thèse est d'identifier des régulateurs de l'expression de cxcr4b au sein du primordium. Nous avons montré que l'inactivation du récepteur des strogènes ESR1 induit l'expression ectopique de cxcr4b dans les cellules de queue du primordium alors que sa surexpression induit une réduction du domaine d'expression de cxcr4b, suggérant que ESR1 agit comme un répresseur de cxcr4b. Cette découverte expliquerait pourquoi les strogènes diminuent la capacité métastatique des cellules du cancer du sein strogéno-dépendants. L'inactivation de ESR1 conduit aussi à l'extinction de l'expression de cxcr7b dans les cellules de queue du primordium, cet effet étant toutefois indirect et induit par la signalisation ectopique SDF-1/CXCR4 dans ces cellules. L'inactivation et la surexpression de ESR1 provoquent toutes deux une migration défectueuse du primordium, confirmant l'importance de ce récepteur dans le contrôle de la migration dépendante de SDF-1. Nous avons aussi montré qu'un effecteur majeur de la signalisation Wnt canonique, LEF-1, contribue au contrôle de l'expression de cxcr4b et de cxcr7b dans les cellules en tête du primordium. Nous montrons que la prolifération cellulaire, qui assure une taille constante du primordium en dépit des dépositions successives de cellules, est réduite en absence de LEF-1, et que cela conduit à une ligne latérale postérieure incomplète. / The zebrafish embryonic posterior lateral line is componed by a set sense organs, called neuromasts, allowing the fish to detect the water movements. The primordium that generates the embryonic posterior lateral line of zebrafish migrates from the head to the tip of the tail along a trail of SDF-1-producing cells, and deposits cell groups that will become the neuromasts. This migration critically depends on the presence of the SDF-1 receptor CXCR4 in the leading region of the primordium and on the presence of a second SDF1 receptor, CXCR7, in the trailing region of the primordium. The aim of my thesis is to identify regulators of the cxcr4b expression within the primordium. Here we show that inactivation of the estrogen receptor ESR1 results in ectopic expression of cxcr4b throughout the primordium, whereas ESR1 overexpression results in a reciprocal reduction in the domain of cxcr4b expression, suggesting that ESR1 acts as a repressor of cxcr4b. This finding could explain why estrogens significantly decrease the metastatic ability of ESR-positive breast cancer cells. ESR1 inactivation alsoleads to extinction of cxcr7b expression in the trailing cells of the migrating primordium; this effect is indirect, however, and due to the down-regulation of cxcr7b by ectopic SDF-1/CXCR4 signaling in the trailing region. Both ESR1 inactivation and overexpression result in aborted migration, confirming the importance of this receptor in the control of SDF-1-dependent migration. We also showed that a major effector of the canonical Wnt signaling, LEF-1, contributes to the control of both cxcr4b and cxcr7b expression in the leading cells of the primordium. We show that cell proliferation, which ensures constant primordium size in spite of sucessive rounds of cell deposition, is reduced upon lef1 inactivation, leading in a truncated posterior lateral line.

(v anglickém jazyce) Development of tooth primordia in mice is an important model for study of odontogenesis. Several dental rudiments develop during the mouse embryogenesis. These structures develop in functional teeth in their phylogenetically older relatives. Similarly, we can initiate growth of teeth from these germs in some mutant mice. In my diploma thesis we have focused on the importance of rudimentary structures with odontogenic potential in postnatal individuals. As a model of development, we have chosen a cell population originating from rudimentary primordia MS (mesial segment) that develops in diastema of the lower jaw during the embryonic day 12.5. Using the inducible Cre-lox technology we have marked the cells which are part of the signal domain of primordia at this time. As a marker of these cells we have used gene Shh. We have found out that these cells persist prenataly and also postnatally. Further we have isolated this cell area and we have tested it using a variety of methods. We have shown that in the cells of postnatal individual are expressed markers of stem cells (Sox2, Bmi1, Gli1) and also genes for major enamel matrix structural proteins: ameloblastin and amelogenin. The same stem cell markers are also expressed in vitro culture of the isolated cells. This cell population...

The Drosophila dorsal Air Sac Primordium (ASP) is a tracheal tube that invasively grows toward and into the wing imaginal disc. The unfolding of Drosophila wing is a process following eclosion with a cuticular bilayer replacing epithelial cells originally packing the wing. We reasoned that protease functions might be needed for the invasion of ASP into the wing imaginal disc as well as the rearrangement of epithelia cells during wing unfolding. Our study is particularly focused on understanding the role of a Cathepsin L like cysteine protease (CP1) in the development of dorsal ASP and wing development of Drosophila melanogaster. To analyze the function of CP1, we overexpressed and knocked down CP1, respectively, using UAS-GAL4 system in combination with RNA interference technology. We found that both the knockdown and overexpression of CP1 in ASP resulted in perturbed growth, migration and weakened invasion of ASPs. We further explored the mechanism by which CP1 regulates ASP development and found that CP1 is capable of degrading collagen IV, a component of extracellular matrix. For wing development, we observed that both the knockdown and overexpression of CP1 in wing imaginal discs interrupted with normal wing development. In summary, our study demonstrated that CP1 facilitates the normal development of ASPs by degrading extracellular matrix and regulates wing development via a complex network of signaling pathways and protein interactions. Knowledge gained from this study has the potential to help us better understand the invasion of tumor cells through the extracellular matrix in humans.