No description available.

Lors du développement du système nerveux, de nombreux mécanismes moléculaires sont mis en jeu afin que les axones trouvent leur cible et établissent des synapses. Une fois ces synapses établies, elles restent plastiques et peuvent encore être modifiées d'un point de vue morphologique et fonctionnel en fonction de la taille de la cible ou de l'activité de la synapse. La jonction neuromusculaire (JNM) de la larve de drosophile est un modèle idéal pour étudier cette plasticité synaptique développementale. En effet, la cellule musculaire innervée augmente de taille d'un facteur 50, et la JNM croît en conséquence. Cette croissance met en jeu le cystoquelette microtubulaire, composant central de la terminaison synaptique. Dans cette thèse, nous avons étudié le rôle de la protéine kinase Shaggy dans la croissance de la JNM et avons montré qu'elle joue un rôle inhibiteur dépendant de la protéine associée aux microtubules (MAP) Futsch. Futsch est le représentant d'une des deux familles de MAPs structurales. Ces deux familles comprennent la famille MAP1 (MAP1A, MAP1B et MAP1S) et la famille MAP2/MAP4/Tau. Dans le système nerveux, elles stabilisent les microtubules et favorisent la pousse neuritique. Cependant, lors de synaptogenèse, leur rôle est méconnu. Chez la drosophile, il n'existe qu'un membre de chaque famille : Futsch (MAP1) et Tau (MAP2/MAP4/Tau), ce qui simplifie l'étude d'une famille par rapport à l'autre par l'absence de redondance. Nous avons ensuite étudié le rôle de ces MAPs sur la stabilité des microtubules, ce qu'il en résulte concernant la croissance de la JNM et quels acteurs, notamment ceux de la voie de signalisation Wnt/Wingless, peuvent réguler ces protéines.

No description available.

No description available.

Crumbs is a transmembrane protein and apical determinant in Drosophila epithelial cells. Its cytoplasmic tail contains a PDZ and a FERM domain-binding site through which Crumbs interacts with the FERM proteins Yurt, Moesin and Expanded. Recent evidence suggests that Crumbs can also interact with the uncharacterised FERM proteins CG34347 and Cdep. The main objective of my thesis was to generate mutations in CG34347 and Cdep to facilitate the functional analysis of these genes. I generated a mutation for Cdep that remains to be characterised and two mutant lines for CG34347; one lacking the first exon and one lacking the entire gene, using a FRT-based recombination strategy. Both CG34347 mutants cause severe ovarian defects. The most consistent defect is a multilayering of the interfollicular stalk. These defects are also observed when Notch, Hippo, Wingless and Hedgehog signalling pathways are overactive in ovaries suggesting that CG34347 participates in one of those pathways.

Crumbs is a transmembrane protein and apical determinant in Drosophila epithelial cells. Its cytoplasmic tail contains a PDZ and a FERM domain-binding site through which Crumbs interacts with the FERM proteins Yurt, Moesin and Expanded. Recent evidence suggests that Crumbs can also interact with the uncharacterised FERM proteins CG34347 and Cdep. The main objective of my thesis was to generate mutations in CG34347 and Cdep to facilitate the functional analysis of these genes. I generated a mutation for Cdep that remains to be characterised and two mutant lines for CG34347; one lacking the first exon and one lacking the entire gene, using a FRT-based recombination strategy. Both CG34347 mutants cause severe ovarian defects. The most consistent defect is a multilayering of the interfollicular stalk. These defects are also observed when Notch, Hippo, Wingless and Hedgehog signalling pathways are overactive in ovaries suggesting that CG34347 participates in one of those pathways.

No description available.

No description available.

No description available.

A major goal of evolutionary developmental biology is to explore mechanisms and events underlying evolution of the myriad body plan morphologies expressed both genetically and phenotypically within the animal kingdom. Arthropods exhibit an astounding array of morphological diversity both within and between representative sub-phyla, thus providing an ideal phylum through which to address questions of body plan innovation and diversification. Major arthropod groups are recognised and defined by the distinct form and number of articulated appendages present along the antero-posterior axis of their segmented bodies. A great deal is known about the developmental genetics of limb development in the model insect Drosophila melanogaster, added to which, much comparative gene expression data and a growing body of functional genetic data is emerging for other arthropod species. Arthropod limb primordia are consistently marked by expression of the homeobox gene Distal-less (Dll), and the focus of this thesis is to compare signalling mediated by early Dll regulatory genes activity along antero-posterior and dorso-ventral embryonic axes during limb specification in Drosophila, with the activity of their orthologs in the widely disparate chelicerate, the spider mite Tetranychus urticae - interpreting new data with that available for other arthropods. Having made a detailed study of spider mite embryonic (and post-embryonic) development, to provide a basis for understanding mRNA transcription and protein activity patterns, I confirmed typical expression of Tetranychus Dll in prosomal limb primordia. I obtained limited results for the candidate antero-posterior positioning genes wingless and engrailed, although one of the two engrailed paralogs I identified is reportedly expressed in posterior segmental compartments, consistent with possible conservation of Engrailed-Wingless interactions in metameric patterning and positive regulation of Dll in arthropod limb specification. In Drosophila, wingless-dependent Dll transcription is restricted along the dorso-ventral axis by dorsal Dpp-mediated and ventral EGFR-mediated signalling gradients. Based on data from Tetranychus and other arthropods, neither dorsal nor ventral signalling regimes appear conserved outside the Drosophila system. Dll suppression in fly abdominal segments occurs due to powerful Hox (Ubx/AbdA) repression of the early Dll cis-regulatory element; this is discussed in relation to the independently evolved limbless chelicerate opisthosoma, informed by hypothetical scenarios of cis (regulatory DNA) and trans (coding sequence) evolution. Given practical difficulties and limitations encountered while working with spider mites, I offer a final assessment of the place of Tetranychus urticae as a non-model, and yet still valuable chelicerate species to consider carrying into the exciting future of evolutionary developmental biology.