Cell cycle genes regulate vestigial and scalloped to ensure normal proliferation in the wing disc of Drosophila melanogaster.

In Drosophila, the Vestigial-Scalloped (VG-SD) dimeric transcription factor is required for wing cell identity and proliferation. Previous results have shown that VG-SD controls expression of the cell cycle positive regulator dE2F1 during wing development. Since wing disc growth is a homeostatic process, we investigated the possibility that genes involved in cell cycle progression regulate vg and sd expression in feedback loops. We focused our experiments on two major regulators of cell cycle progression: dE2F1 and the antagonist dacapo (dap). Our results reinforce the idea that VG/SD stoichiometry is critical for correct development and that an excess in SD over VG disrupts wing growth. We reveal that transcriptional activity of VG-SD and the VG/SD ratio are both modulated upon down-expression of cell cycle genes. We also detected a dap-induced sd upregulation that disrupts wing growth. Moreover, we observed a rescue of a vg hypomorphic mutant phenotype by dE2F1 that is concomitant with vg and sd induction. This regulation of the VG-SD activity by dE2F1 is dependent on the vg genetic background. Our results support the hypothesis that cell cycle genes fine-tune wing growth and cell proliferation, in part, through control of the VG/SD stoichiometry and activity. This points to a homeostatic feedback regulation between proliferation regulators and the VG-SD wing selector

Integration of differentiation signals during indirect flight muscle formation by a novel enhancer of Drosophila vestigial gene

AbstractThe gene vestigial (vg) plays a key role in indirect flight muscle (IFM) development. We show here that vg is controlled by the Notch anti-myogenic signaling pathway in myoblasts and is regulated by a novel 822 bp enhancer during IFM differentiation. Interestingly, this muscle enhancer is activated in developing fibers and in a small number of myoblasts before the fusion of myoblasts with the developing muscle fibers. Moreover, we show that this enhancer is activated by Drosophila Myocyte enhancing factor 2 (MEF2), Scalloped (SD) and VG but repressed by Twist, demonstrating a sensitivity to differentiation in vivo. In vitro experiments reveal that SD can directly bind this enhancer and MEF2 can physically interact with both SD and TWI. Cumulatively, our data reveal the interplay between different myogenic factors responsible for the expression of an enhancer activated during muscle differentiation

in vivo analysis of Drosophila deoxyribonucleoside kinase function in cell cycle, cell survival and anti-cancer drugs resistance.

in vitro studies have shown that Drosophila melanogaster has a highly efficient single deoxyribonucleoside kinase (dNK) multisubstrate enzyme. dNK is related to the mammalian Thymidine Kinase 2 (TK2) group involved in the nucleotide synthesis salvage pathway. To study the dNK function in vivo, we constructed transgenic Drosophila strains and impaired the nucleotide de novo synthesis pathway, using antifolates such as aminopterin. Our results show that dNK overexpression rescues both cell death and cell cycle arrest triggered by this anti-cancer drug, and confers global resistance on the fly. Moreover, we show that fly viability and growth depend on the exquisite ratio between dNK expression and its substrate thymidine (dT) in the medium, and that increased dT concentrations trigger apoptosis and a decrease in body mass when dNK is mis-expressed. Finally, dNK expression, unlike that of TK2, is cell cycle dependent and under the control of CyclinE and the dE2F1 transcription factor involved in the G1/S transition. dNK is therefore functionally more closely related to mammalian TK1 than to TK2. This strongly suggest that dNK plays a role in cell proliferation in physiological conditions

Nouveau rôle de la signalisation insuline dans le développement du système nerveux périphérique chez Drosophila melanogaster

La signalisation insuline est une voie extrêmement bien conservée chez Drosophila, et ses rôles au cours du développement sont nombreux : impliquée dans des processus de prolifération/apoptose, elle est également connue pour agir sur la croissance, le métabolisme et le temps de développement tissulaire. Au cours de la neurogenèse, les mouches déficientes pour le gène InR ont de gros problèmes développementaux des systèmes nerveux central et périphérique, avec perte des cellules neuronales, et ce dès les premiers stades embryonnaires. Si la signalisation insuline semble réguler prolifération et différenciation cellulaires au cours de la neurogenèse chez les mammifères, peu de choses sur un tel lien sont encore connues chez la drosophile.En surexprimant Y InR dans les groupes proneuraux thoraciques, on obtient des individus présentant des soies surnuméraires, proches de celles normalement présentes. Au cours de ma thèse, après avoir vérifié qu'il s'agissait bien d'un rôle physiologique de la signalisation insuline, et non une prolifération des précurseurs suite à la surexpression de l'/nR dans ces groupes, nous avons montré que toute la cascade de signalisation était impliquée, jusqu'au facteur de transcription FOXO (forkhead-related transcription factor). Nous avons ensuite défini que la signalisation insuline intervenait au moment de la sélection des SOPs (sensory organ precursors) au sein des groupes proneuraux, et ce en régulant, très probablement de façon indirecte, les taux de protéines proneurales. Nos travaux indiquent une possible interaction de la signalisation InR avec la voie Ras/MAPK dans ce processus, et tout porte à croire que l' inhibition latérale , médiée par la voie Notch, ne serait pas inhibée. D'autres résultats laissent penser que cette signalisation insuline pourrait également intervenir plus tardivement au cours du développement, au moment des divisions asymétriques. Tous nos résultats nous ont donc permis de conclure sur un nouveau rôle de la signalisation insuline au cours du développement des organes mécano-sensoriels chez Drosophila.PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Analyse fonctionnelle du facteur de transcription Vestigial-Scalloped dans la croissance du disque imaginal alaire chez Drosophila melanogaster

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Etude du rôle du gène vestigial dans la régulation de la prolifération cellulaire chez Drosophila melanogaster

PARIS7-Bibliothèque centrale (751132105) / SudocSudocFranceF

Implication des gènes twist et vestigial dans les phénomènes d'apoptose, de prolifération et de différenciation cellulaire

PARIS-BIUSJ-Thèses (751052125) / SudocPARIS-BIUSJ-Physique recherche (751052113) / SudocSudocFranceF

The insulin receptor is required for the development of the Drosophila peripheral nervous system.

International audienceThe Insulin Receptor (InR) in Drosophila presents features conserved in its mammalian counterparts. InR is required for growth; it is expressed in the central and embryonic nervous system and modulates the time of differentiation of the eye photoreceptor without altering cell fate. We show that the InR is required for the formation of the peripheral nervous system during larval development and more particularly for the formation of sensory organ precursors (SOPs) on the fly notum and scutellum. SOPs arise in the proneural cluster that expresses high levels of the proneural proteins Achaete (Ac) and Scute (Sc). The other cells will become epidermis due to lateral inhibition induced by the Notch (N) receptor signal that prevents its neighbors from adopting a neural fate. In addition, misexpression of the InR or of other components of the pathway (PTEN, Akt, FOXO) induces the development of an abnormal number of macrochaetes that are Drosophila mechanoreceptors. Our data suggest that InR regulates the neural genes ac, sc and sens. The FOXO transcription factor which is localized in the cytoplasm upon insulin uptake, displays strong genetic interaction with the InR and is involved in Ac regulation. The genetic interactions between the epidermal growth factor receptor (EGFR), Ras and InR/FOXO suggest that these proteins cooperate to induce neural gene expression. Moreover, InR/FOXO is probably involved in the lateral inhibition process, since genetic interactions with N are highly significant. These results show that the InR can alter cell fate, independently of its function in cell growth and proliferation

Mef2 Interacts with the Notch Pathway during Adult Muscle Development in Drosophila melanogaster

International audienc

Alteration of TEAD1 expression levels confers apoptotic resistance through the transcriptional up-regulation of Livin.

BACKGROUND: TEA domain (TEAD) proteins are highly conserved transcription factors involved in embryonic development and differentiation of various tissues. More recently, emerging evidences for a contribution of these proteins towards apoptosis and cell proliferation regulation have also been proposed. These effects appear to be mediated by the interaction between TEAD and its co-activator Yes-Associated Protein (YAP), the downstream effector of the Hippo tumour suppressor pathway. METHODOLOGY/PRINCIPAL FINDINGS: We further investigated the mechanisms underlying TEAD-mediated apoptosis regulation and showed that overexpression or RNAi-mediated silencing of the TEAD1 protein is sufficient to protect mammalian cell lines from induced apoptosis, suggesting a proapoptotic function for TEAD1 and a non physiological cytoprotective effect for overexpressed TEAD1. Moreover we show that the apoptotic resistance conferred by altered TEAD1 expression is mediated by the transcriptional up-regulation of Livin, a member of the Inhibitor of Apoptosis Protein (IAP) family. In addition, we show that overexpression of a repressive form of TEAD1 can induce Livin up-regulation, indicating that the effect of TEAD1 on Livin expression is indirect and favoring a model in which TEAD1 activates a repressor of Livin by interacting with a limiting cofactor that gets titrated upon TEAD1 up-regulation. Interestingly, we show that overexpression of a mutated form of TEAD1 (Y421H) implicated in Sveinsson's chorioretinal atrophy that strongly reduces its interaction with YAP as well as its activation, can induce Livin expression and protect cells from induced apoptosis, suggesting that YAP is not the cofactor involved in this process. CONCLUSIONS/SIGNIFICANCE: Taken together our data reveal a new, Livin-dependent, apoptotic role for TEAD1 in mammals and provide mechanistic insight downstream of TEAD1 deregulation in cancers