O carcinoma espinocelular (CEC) de cabeça e pescoço é uma neoplasia maligna de prognóstico desfavorável e baixa taxa de sobrevida. Entender os processos biológicos envolvidos na carcinogênese poderá ser de extrema importância para o desenvolvimento de novas tecnologias de tratamento e melhora do prognóstico em pacientes acometidos pela doença. A maior causa de insucessos clínicos em termos de terapia e prognóstico em pacientes com câncer é a invasão tecidual e o desenvolvimento de potencial metastático. A migração celular é indispensável para a progressão tumoral e as células apresentam motores moleculares desempenhados especialmente pela família da Miosina II não muscular (MNMII). Codificadas por diferentes genes, existem três isoformas conhecidas em células de mamíferos (MNMIIA, MNMIIB, MNMIIC). As MNMIIs estão envolvidas em funções celulares como migração, adesão e citocinese. Sendo o entendimento da migração, adesão celular e citocinese fatores chave na progressão tumoral, e que o a invasão tecidual e o desenvolvimento de potencial metastático são essenciais na definição do prognóstico dos pacientes, o objetivo deste estudo foi descrever o perfil e exposição à fatores de risco como álcool e fumo dos pacientes diagnosticados com CEC de cabeça e pescoço, graduação histológica, parâmetros clínicos tumorais (TNM), padrão de expressão das isoformas de MNMII (MNMIIA, MNMIIB, MNMIIC) no centro do tumor, zona de invasão e tecido epitelial não neoplásico adjacente ao tumor, relacionando a expressão e localização dessas proteínas com os dados descritos bem como evolução dos pacientes após 5 anos de acompanhamento. De acordo com os resultados sugere-se que a MNMIIB expressa no EA possa indicar o potencial de metástase regional do CEC e a MNMIIC presente na zona de invasão tumoral (ZI) seja um fator predictor de prognóstico ruim da doença. Sendo assim, é possível propor que a avaliação de imunorreatividade da MNMIIB no EA e MNMIIC na ZI seja utilizada na análise das peças operatórias, como complemento à análise morfológica de rotina. / Squamous cell carcinoma (SCC) of the head and neck is a malignant neoplasm of poor prognosis and low survival rate. Understand the biological processes involved in carcinogenesis can be extremely important for the development of new treatment technologies and improved prognosis in patients affected by the disease. The major cause of clinical failure in terms of therapy and prognosis in cancer patients is the development of tissue invasion and metastatic potential. Cell migration is essential for tumor progression and the cells have molecular motors especially formed from non-muscular myosin II family (NMMII). Encoded by different genes, there are three known isoforms in mammalian cells (NMMIIA, NMMIIB, NMMIIC). The NMMIIs are involved in cellular functions such as migration, adhesion, and cytokinesis. As the understanding of migration, cell adhesion and cytokinesis key factors in tumor progression, and that the tissue invasion and metastatic potential for development are essential in defining the prognosis of patients, the objective of this study was to describe the profile and exposure to risk factors such as alcohol and tobacco of patients diagnosed with head and neck SCC, histological grading, tumor clinical parameters (TNM), pattern of expression of isoforms NMMII (NMMIIA, NMMIIB, NMMIIC) in the center of the tumor (CT), tumor invasion zone area and not neoplastic adjacent to the tumor (AE), relating the expression and localization of these proteins with the data described and outcome of patients after 5 years of follow-up. According to the results it is suggested that the NMMIIB expressed in AE may indicate the potential regional metastasis of SCC and NMMIIC present in the tumor invasion zone (IZ) is a predictor factor of poor prognosis of the disease. Therefore, it is possible to propose that immunoreactivity assessment of NMMIIB in EA and NMMIIC in IZ could be used in the analysis of operative parts, as a complement to routine morphological analysis.

O carcinoma espinocelular (CEC) de cabeça e pescoço é uma neoplasia maligna de prognóstico desfavorável e baixa taxa de sobrevida. Entender os processos biológicos envolvidos na carcinogênese poderá ser de extrema importância para o desenvolvimento de novas tecnologias de tratamento e melhora do prognóstico em pacientes acometidos pela doença. A maior causa de insucessos clínicos em termos de terapia e prognóstico em pacientes com câncer é a invasão tecidual e o desenvolvimento de potencial metastático. A migração celular é indispensável para a progressão tumoral e as células apresentam motores moleculares desempenhados especialmente pela família da Miosina II não muscular (MNMII). Codificadas por diferentes genes, existem três isoformas conhecidas em células de mamíferos (MNMIIA, MNMIIB, MNMIIC). As MNMIIs estão envolvidas em funções celulares como migração, adesão e citocinese. Sendo o entendimento da migração, adesão celular e citocinese fatores chave na progressão tumoral, e que o a invasão tecidual e o desenvolvimento de potencial metastático são essenciais na definição do prognóstico dos pacientes, o objetivo deste estudo foi descrever o perfil e exposição à fatores de risco como álcool e fumo dos pacientes diagnosticados com CEC de cabeça e pescoço, graduação histológica, parâmetros clínicos tumorais (TNM), padrão de expressão das isoformas de MNMII (MNMIIA, MNMIIB, MNMIIC) no centro do tumor, zona de invasão e tecido epitelial não neoplásico adjacente ao tumor, relacionando a expressão e localização dessas proteínas com os dados descritos bem como evolução dos pacientes após 5 anos de acompanhamento. De acordo com os resultados sugere-se que a MNMIIB expressa no EA possa indicar o potencial de metástase regional do CEC e a MNMIIC presente na zona de invasão tumoral (ZI) seja um fator predictor de prognóstico ruim da doença. Sendo assim, é possível propor que a avaliação de imunorreatividade da MNMIIB no EA e MNMIIC na ZI seja utilizada na análise das peças operatórias, como complemento à análise morfológica de rotina. / Squamous cell carcinoma (SCC) of the head and neck is a malignant neoplasm of poor prognosis and low survival rate. Understand the biological processes involved in carcinogenesis can be extremely important for the development of new treatment technologies and improved prognosis in patients affected by the disease. The major cause of clinical failure in terms of therapy and prognosis in cancer patients is the development of tissue invasion and metastatic potential. Cell migration is essential for tumor progression and the cells have molecular motors especially formed from non-muscular myosin II family (NMMII). Encoded by different genes, there are three known isoforms in mammalian cells (NMMIIA, NMMIIB, NMMIIC). The NMMIIs are involved in cellular functions such as migration, adhesion, and cytokinesis. As the understanding of migration, cell adhesion and cytokinesis key factors in tumor progression, and that the tissue invasion and metastatic potential for development are essential in defining the prognosis of patients, the objective of this study was to describe the profile and exposure to risk factors such as alcohol and tobacco of patients diagnosed with head and neck SCC, histological grading, tumor clinical parameters (TNM), pattern of expression of isoforms NMMII (NMMIIA, NMMIIB, NMMIIC) in the center of the tumor (CT), tumor invasion zone area and not neoplastic adjacent to the tumor (AE), relating the expression and localization of these proteins with the data described and outcome of patients after 5 years of follow-up. According to the results it is suggested that the NMMIIB expressed in AE may indicate the potential regional metastasis of SCC and NMMIIC present in the tumor invasion zone (IZ) is a predictor factor of poor prognosis of the disease. Therefore, it is possible to propose that immunoreactivity assessment of NMMIIB in EA and NMMIIC in IZ could be used in the analysis of operative parts, as a complement to routine morphological analysis.

To understand the role of nonmuscle myosin II in cardiac and skeletal muscle, we used a number of polyclonal antibodies, three detecting nonmuscle myosin heavy chain II-B (NMHC II-B) and two detecting NMHC II-A, to examine the localization of these two proteins in fresh-frozen, acetone-fixed sections of normal human and mouse hearts and human skeletal muscles. Results were similar in both species and were confirmed by examination of fresh- frozen sections of human hearts subjected to no fixation or to treatment with either 4% p-formaldehyde or 50% glycerol. NMHC II-B was diffusely distributed in the cytoplasm of cardiac myocytes during development, but after birth it was localized to the Z-lines and intercalated discs. Dual labeling showed almost complete colocalization of NMHC II-B with α-actinin. Whereas endothelial cells, smooth muscle cells and fibroblasts showed strong immunoreactivity for NMHC II-A and NMHC II-B, cardiac myocytes only showed reactivity for the latter. The Z-lines of human skeletal muscle cells, in contrast to those of cardiac myocytes, gave positive reactions for both NMHC II-A and NMHC II-B. The presence of a motor protein in the Z-lines and intercalated discs raises the possibility that these structures may play a more dynamic role in the contraction/relaxation mechanism of cardiac and skeletal muscle than has been previously suspected.

Während der Gewebeentwicklung beeinflusst die Anpassung der mechanischen Spannung bei Zell-zu-Zell-Kontakten das Gewebewachstum, die Musterbildung und die Morphogenese. Die Erzeugung und Kontrolle der mechanischen Spannung hängt von Komponenten des Zytoske- letts wie dem Aktomyosin und den Mikrotubuli-Netzwerken ab. Die Bildung von Komparti- mentgrenzen ist ein wichtiger Entwicklungsprozess, der auf der Anpassung mechanischer Spannungen beruht. Kompartimentgrenzen sind Abstammungsbeschränkungen, die Zellen mit unterschiedlichen Funktionen und Identitäten innerhalb von Geweben trennen. Zellverbindun- gen entlang der Kompartimentgrenzen sind häufig durch eine Anreicherung von filamentösen (F-) Aktin sowie nicht-muskulären Myosin II (Myosin II) Motorprotein und erhöhter mechani- scher Spannung gekennzeichnet. Die Mechanismen, durch die F-Aktin und Myosin II an die- sen Verbindungsstellen angereichert werden, sind jedoch kaum verstanden. Hier zeigen wir, dass an der sich bildenden anteroposterioren Kompartimentgrenze der Puppenepidermis von Drosophila melanogaster F-Aktin und Myosin II vorübergehend angereichert werden. Die An- reicherung von F-Aktin scheint nicht von mechanischer Spannung abzuhängen. Die Fluores- zenzerholung nach Photobleichversuchen (Fluorescence recovery after photobleaching, FRAP) weist eher darauf hin, dass Myosin II vorzugsweise an Zellübergängen entlang der Komparti- mentgrenze stabilisiert wird. Darüber hinaus zeigen wir unter Verwendung einer photokonver- tierbaren Form von Myosin II, dass Myosin II vorzugsweise aus einem zytosolischen Pool an Zellverbindungen entlang der Kompartimentgrenze rekrutiert wird. Um die Rolle des Mikro- tubuli-Netzwerks bei der Bildung von Kompartimentgrenzen zu testen, haben wir außerdem dessen Organisation in der Puppenepidermis charakterisiert. Wir zeigen, dass sich Mikrotubuli und das Mikrotubuli-Minus-Ende-bindende Protein Patronin in einem Streifen anteriorer Zellen entlang der Kompartimentgrenze ansammeln. Interessanterweise haben die Zellen in diesem Streifen, im Vergleich zu anderen Zellen in der Epidermis, eine unterschiedliche Form. Zusammengefasst enthüllen unsere Daten Unterschiede in der Organisation der Mikrotubuli, die mit Kompartimentgrenzen verbunden sind, und zeigen, dass die Anreicherung von Myosin II entlang der Kompartimentgrenze der Puppen-Abdominalepidermis sowohl eine bevorzugte Stabilisierung als auch eine Rekrutierung beinhaltet.

No description available.

Animal morphogenesis is largely driven by concerted changes in the shape of individual cells. However, how cell shape changes are regulated and coordinated in developing animals is not well understood. Here we show that the two perpendicular signaling gradients of the morphogens Dpp, a TGF-β homologue, and Wingless, a Wnt family member, maintain tissue homoeostasis and control cell shape changes in the developing Drosophila wing. Clones of cells lacking Dpp or Wingless signaling invaginate apically, shorten apico-basally and subsequently extrude basally without disruption of the epithelium. During early larval development, the onset of Dpp and Wingless signaling correlates with the cuboidal-to-columnar cell shape transition of wing disc cells. Gradients in apical-basal length of columnar cells correlate during late larval development with the gradients of Dpp and Wingless signaling activities. Cells receiving high levels of Dpp and Wingless signaling are most elongated and apically constricted. Low levels of Dpp and Wingless signaling correlate with a shorter and apically wider cell morphology. Dpp and Wingless signaling is cell-autonomously required for maintaining the elongated columnar cell shape of late larval wing disc cells. Overactivation of these pathways results in precocious cell elongation during early larval development. These morphogenetic responses to Dpp and Wingless require the transcription factor complexes Mad and Tcf/β-catenin, respectively, indicating that they are mediated by changes in gene expression. The morphogenetic function of Wingless is in part mediated by one of its target genes, the transcription factor Vestigial. Wingless signaling promotes an enrichment of E-cadherin at the adherens junctions, and we show that E-cadherin is required to maintain apical-basal cell length. Dpp signaling controls the subcellular distribution of the activities of the small GTPase Rho1 and the regulatory light chain of non-muscle myosin II (MRLC). Alteration of Rho1 or MRLC activity has a profound effect on apical-basal cell length. Finally, we demonstrate that a decrease in Rho1 or MRLC activity rescues the shortening of cells with compromised Dpp signaling. Our results identify cell-autonomous roles for Dpp and Wingless signaling in promoting and maintaining the elongated columnar shape of wing disc cells. Furthermore, they suggest that Dpp and Wingless signaling control cell shape by regulating the actin-MyosinII/E-cadherin network. / Morphogenese in Tieren wird in hohem Maße von konzertierten Zellformveränderungen einzelner Zellen bewirkt. Es ist jedoch noch nicht hinreichend verstanden, wie Zellformveränderungen in sich entwickelnden Tieren reguliert und koordiniert werden. Hier zeigen wir, dass die zwei zueinander senkrecht stehenden Signalgradienten der Morphogene Dpp, eines TGF-β Homologs, und Wingless, eines Mitglieds der Wnt Familie, im sich entwickelnden Drosophila-Flügel Gewebe-Homöostase aufrechterhalten und Zellformveränderungen kontrollieren. Klone von Zellen, denen Dpp oder Wingless Signalaktivität fehlt, invaginieren von ihrer apikalen Seite her, verkürzen sich in apiko-basaler Richtung und extruieren im Folgenden auf der basalen Seite des Epithels, ohne es zu zerstören. Während der frühen Larvalentwicklung korreliert das Anschalten der Dpp und Wingless Signale mit der Zellformveränderung der Flügelscheibenzellen von kuboidal zu kolumnar. Gradienten in der apiko-basalen Länge von kolumnaren Zellen korrelieren während der späten Larvalentwicklung mit den Gradienten der Dpp und Wingless Signalaktivitäten. Zellen, die hohe Werte an Dpp und Wingless Signalen empfangen, sind am meisten elongiert und apikal konstringiert. Niedrige Werte von Dpp und Wingless Signalen korrelieren mit kürzerer und apikal weiterer Zellmorphologie. Dpp und Wingless Signale werden zellautonom gebraucht für die Aufrechterhaltung der elongierten Zellform von späten larvalen Flügelscheibenzellen. Die Überaktivierung dieser Signalwege führt zu vorzeitiger Zellverlängerung während der frühen Larvalentwicklung. Diese morphogenetischen Antworten auf Dpp und Wingless benötigen die Transkriptionsfaktor-Komplexe Mad beziehungsweise Tcf/β-catenin, was darauf hindeutet, dass sie durch Änderungen in der Genexpression vermittelt werden. Die morphogenetische Funktion von Wingless wird teilweise durch eines seiner Zielgene, Vestigial, vermittelt. Wingless Signale fördern die Anreicherung von E-cadherin an den Adherensverbindungen. Wir zeigen hier, dass E-cadherin gebraucht wird, um apiko-basale Zelllänge aufrechtzuerhalten. Dpp Signale kontrollieren die subzelluläre Verteilung der Aktivitäten der kleinen GTPase Rho1 und der regulatorischen leichten Kette von nicht-muskulärem Myosin II (MRLC). Eine Änderung in der Rho1 oder MRLC Aktivität hat weitreichende Auswirkungen auf die apiko-basale Zelllänge. Schließlich zeigen wir noch, dass eine Verringerung der Rho1 oder MRLC Aktivitäten die Zellverkürzung von Dpp-Signal kompromittierten Zellen rettet. Unsere Resultate identifizieren zellautonome Rollen für Dpp und Wingless Signale in der Förderung und Aufrechterhaltung der elongierten kolumnaren Zellform von Flügelimaginalscheibenzellen. Darüber hinaus suggerieren sie, dass Dpp und Wingless Signale die Zellform durch die Regulierung des Aktin-MyosinII/E-cadherin-Netzwerks kontrollieren.

Animal morphogenesis is largely driven by concerted changes in the shape of individual cells. However, how cell shape changes are regulated and coordinated in developing animals is not well understood. Here we show that the two perpendicular signaling gradients of the morphogens Dpp, a TGF-β homologue, and Wingless, a Wnt family member, maintain tissue homoeostasis and control cell shape changes in the developing Drosophila wing. Clones of cells lacking Dpp or Wingless signaling invaginate apically, shorten apico-basally and subsequently extrude basally without disruption of the epithelium. During early larval development, the onset of Dpp and Wingless signaling correlates with the cuboidal-to-columnar cell shape transition of wing disc cells. Gradients in apical-basal length of columnar cells correlate during late larval development with the gradients of Dpp and Wingless signaling activities. Cells receiving high levels of Dpp and Wingless signaling are most elongated and apically constricted. Low levels of Dpp and Wingless signaling correlate with a shorter and apically wider cell morphology. Dpp and Wingless signaling is cell-autonomously required for maintaining the elongated columnar cell shape of late larval wing disc cells. Overactivation of these pathways results in precocious cell elongation during early larval development. These morphogenetic responses to Dpp and Wingless require the transcription factor complexes Mad and Tcf/β-catenin, respectively, indicating that they are mediated by changes in gene expression. The morphogenetic function of Wingless is in part mediated by one of its target genes, the transcription factor Vestigial. Wingless signaling promotes an enrichment of E-cadherin at the adherens junctions, and we show that E-cadherin is required to maintain apical-basal cell length. Dpp signaling controls the subcellular distribution of the activities of the small GTPase Rho1 and the regulatory light chain of non-muscle myosin II (MRLC). Alteration of Rho1 or MRLC activity has a profound effect on apical-basal cell length. Finally, we demonstrate that a decrease in Rho1 or MRLC activity rescues the shortening of cells with compromised Dpp signaling. Our results identify cell-autonomous roles for Dpp and Wingless signaling in promoting and maintaining the elongated columnar shape of wing disc cells. Furthermore, they suggest that Dpp and Wingless signaling control cell shape by regulating the actin-MyosinII/E-cadherin network. / Morphogenese in Tieren wird in hohem Maße von konzertierten Zellformveränderungen einzelner Zellen bewirkt. Es ist jedoch noch nicht hinreichend verstanden, wie Zellformveränderungen in sich entwickelnden Tieren reguliert und koordiniert werden. Hier zeigen wir, dass die zwei zueinander senkrecht stehenden Signalgradienten der Morphogene Dpp, eines TGF-β Homologs, und Wingless, eines Mitglieds der Wnt Familie, im sich entwickelnden Drosophila-Flügel Gewebe-Homöostase aufrechterhalten und Zellformveränderungen kontrollieren. Klone von Zellen, denen Dpp oder Wingless Signalaktivität fehlt, invaginieren von ihrer apikalen Seite her, verkürzen sich in apiko-basaler Richtung und extruieren im Folgenden auf der basalen Seite des Epithels, ohne es zu zerstören. Während der frühen Larvalentwicklung korreliert das Anschalten der Dpp und Wingless Signale mit der Zellformveränderung der Flügelscheibenzellen von kuboidal zu kolumnar. Gradienten in der apiko-basalen Länge von kolumnaren Zellen korrelieren während der späten Larvalentwicklung mit den Gradienten der Dpp und Wingless Signalaktivitäten. Zellen, die hohe Werte an Dpp und Wingless Signalen empfangen, sind am meisten elongiert und apikal konstringiert. Niedrige Werte von Dpp und Wingless Signalen korrelieren mit kürzerer und apikal weiterer Zellmorphologie. Dpp und Wingless Signale werden zellautonom gebraucht für die Aufrechterhaltung der elongierten Zellform von späten larvalen Flügelscheibenzellen. Die Überaktivierung dieser Signalwege führt zu vorzeitiger Zellverlängerung während der frühen Larvalentwicklung. Diese morphogenetischen Antworten auf Dpp und Wingless benötigen die Transkriptionsfaktor-Komplexe Mad beziehungsweise Tcf/β-catenin, was darauf hindeutet, dass sie durch Änderungen in der Genexpression vermittelt werden. Die morphogenetische Funktion von Wingless wird teilweise durch eines seiner Zielgene, Vestigial, vermittelt. Wingless Signale fördern die Anreicherung von E-cadherin an den Adherensverbindungen. Wir zeigen hier, dass E-cadherin gebraucht wird, um apiko-basale Zelllänge aufrechtzuerhalten. Dpp Signale kontrollieren die subzelluläre Verteilung der Aktivitäten der kleinen GTPase Rho1 und der regulatorischen leichten Kette von nicht-muskulärem Myosin II (MRLC). Eine Änderung in der Rho1 oder MRLC Aktivität hat weitreichende Auswirkungen auf die apiko-basale Zelllänge. Schließlich zeigen wir noch, dass eine Verringerung der Rho1 oder MRLC Aktivitäten die Zellverkürzung von Dpp-Signal kompromittierten Zellen rettet. Unsere Resultate identifizieren zellautonome Rollen für Dpp und Wingless Signale in der Förderung und Aufrechterhaltung der elongierten kolumnaren Zellform von Flügelimaginalscheibenzellen. Darüber hinaus suggerieren sie, dass Dpp und Wingless Signale die Zellform durch die Regulierung des Aktin-MyosinII/E-cadherin-Netzwerks kontrollieren.

Cardiac myosin binding protein-C (cMyBP-C) is a structural and regulatory component of cardiac thick filaments. It is observed in electron micrographs as seven to nine transverse stripes in the central portion of each half of the A band. Its C-terminus binds tightly to the myosin rod and contributes to thick filament structure, while the N-terminus can bind both myosin S2 and actin, influencing their structure and function. Mutations in the MYBPC3 gene (encoding cMyBP-C) are commonly associated with hypertrophic cardiomyopathy (HCM). In cardiac cells there exists a population of myosin heads in the super-relaxed (SRX) state, which are bound to the thick filament core with a highly inhibited ATPase activity. This report examines the role cMyBP-C plays in regulating the population of the SRX state of cardiac myosin by using an assay that measures single ATP turnover of myosin. We report a significant decrease in the proportion of myosin heads in the SRX state in homozygous cMyBP-C knockout mice, however heterozygous cMyBP-C knockout mice do not significantly differ from the wild type. A smaller, non-significant decrease is observed when thoracic aortic constriction is used to induce cardiac hypertrophy in mutation negative mice. These results support the proposal that cMyBP-C stabilises the thick filament and that the loss of cMyBP-C results in an untethering of myosin heads. This results in an increased myosin ATP turnover, further consolidating the relationship between thick filament structure and the myosin ATPase. Crown Copyright (C) 2016 Published by Elsevier Ltd. All rights reserved.

Les épithéliums jouent le rôle fondamental de barrière physique et chimique chez les Métazoaires. Les jonctions adhérentes, par le biais de la protéine transmembranaire E-cadhérine (E-cad), assurent une grande partie de l’adhésion intercellulaire. Malgré cette robustesse, les épithéliums peuvent subir des remodelages considérables pendant l’embryogenèse ou la cicatrisation. Lors de la gastrulation de l’embryon de Drosophile, l’épithélium ventro-latéral (la bandelette germinale) subit une élongation le long de l’axe antéropostérieur induite par l’intercalation cellulaire. Le remodelage polarisé des jonctions cellulaires est à la base de ce phénomène: les jonctions parallèles à l’axe dorsoventral (DV) rétrécissent et forment de manière irréversible de nouvelles jonctions parallèles à l’axe antéropostérieur (AP). Ce remodelage dépend de l’enrichissement du moteur moléculaire Myosine II (MyoII) dans les jonctions DV, qui induit une anisotropie de tension. Les protéines des jonctions adhérentes (E-cad, β-catenin) sont, elles aussi, polarisées : elles sont enrichies dans les jonctions AP. Néanmoins, nous ne savions pas si cette polarité de l’adhésion avait un rôle dans le remodelage des jonctions, et nous ne connaissions pas les mécanismes contrôlant cette localisation asymétrique. L’un des mécanismes les mieux connus de la modulation de l’adhésion cellulaire est l’endocytose des protéines d’adhésion. A ce titre, je me suis intéressé au rôle de l’endocytose Clathrine dépendante (ECD) pendant l’intercalation cellulaire. J’ai ainsi pu montrer que l’ECD de E-cad est régulée à la hausse dans la bandelette germinale au niveau jonctionnelle, plus particulièrement au niveau des jonctions DV (qui rétrécissent). L’ECD d’E-cad est nécessaire à l’intercalation et à la distribution polarisée d’E-cad. Elle est régulée par l’organisation de l’actine: la formine Diaphanous ainsi que le moteur moléculaire Myosine II accélèrent le recrutement de la machinerie d’endocytose (AP2 et Clathrine) et régulent la polarité de l’ECD dans l’embryon. Elles sont contrôlées par RhoGEF2, qui est enrichie dans les jonctions DV, et induisent l’endocytose par un mécanisme de clustering latéral d’E-cad. Dans la seconde partie de ma thèse, je me suis intéressé au couplage entre E-cad et la dynamique de MyoII. En effet, l’intercalation dépend aussi de flux contractiles de MyoII qui ont lieu préférentiellement en direction des jonctions DV. J’ai ainsi pu montrer que la direction des flux est induite par les anisotropies de forces d’ancrage de MyoII. Les faibles niveaux d’E-cad et le fort taux d’endocytose dans les jonctions DV augmentent la probabilité de générer une anisotropie d’ancrage et induisent davantage de flux de MyoII vers les jonctions DV. Ce projet met en lumière le rôle fondamental du couplage entre E-cad et MyoII dans la régulation de la morphogenèse. / Epithelia build up strong mechanical and chemichal barriers in Metazoans. Adherens junctions, through the adhesion provided by the transmembrane protein E-cadherin (E-cad), are essential for the mechanical integrity of the tissue. Yet, epithelia can be dramatically remodeled during embryogenesis or wound healing. During gastrulation of Drosophila embryo, the ventrolateral epithelium (the germ band) undergoes a massive elongation along the anteroposterior (AP) axis, driven by cell-cell intercalation. This is based on the polarized remodeling of intercellular junctions whereby junctions parallel to the dorsoventral axis (DV) shrink and form new junctions along AP axis. This remodeling is mediated by the planar polarized enrichment of Myosin II (MyoII) in DV junctions, which generates high tension. Adhesion proteins are also planar polarized, E-cad is enriched in AP junctions, but we did not know if this polarity contributed to cell-cell intercalation and the mechanism driving this polarity. As such, I have studied the role of Clathrin mediated endocytosis (CME) during germ band extension. I have shown that E-cad CME is specifically upregulated at the junction plane in the germ band, and planar polarized (enriched in DV shrinking junctions). It is required for cell-cell intercalation and the planar polarized distribution of E-cad. E-cad CME is regulated by the concerted action of the Formin Diaphanous and Myosin-II, which accelerates CME through the lateral clustering of E-cad. They are controlled by RhoGEF2, which is also enriched in DV junctions. In the second part of my PhD, I have studied the coupling between E-cad and MyoII dynamics. Indeed, planar polarized contractile flows of MyoII are required for DV junction shrinkage, but we did not know the mechanism driving the polarity of these flows. I have shown that the transient anisotropy of anchoring forces between two facing junctions triggers flow. As such, the low steady state amount of E-cad and the high rate of CME in DV junctions trigger more anisotropy and polarize the flow. These results outline the strong crossregulation between E-cad and MyoII and their concerted action in morphogenesis.

Un tissu épithélial est composé de cellules polarisées, étroitement liées les unes aux autres par des jonctions adhérentes. La perte de ces jonctions adhérentes est la première étape dans le développement des cancers au niveau des tissus épithéliaux. Il est donc important de comprendre les mécanismes d’attachement inter-cellulaire. Pour étudier ces interactions, nous utilisons comme modèle l’embryon de drosophile, où une fine régulation des jonctions adhérentes est requise pour l’une des étapes précoces de développement. Durant cette étape du développement, les cellules épithéliales changent de voisines le long de l’axe antéro-postérieur sans perdre leur adhérence cellulaire. Ce processus d’intercalation cellulaire est dû au recrutement polarisé du moteur moléculaire Myosine II au niveau des jonctions qui se désassemblent. Il a été mis en évidence qu’au cours de ce processus la perte de fonction de la voie JAK/STAT perturbe la localisation de la Myosine II. Au cours de ma thèse, j’ai réalisé un crible génétique dans un contexte mutant pour le ligand de la voie JAK/STAT pour me permettre d’identifier des interacteurs potentiellement impliqués dans le contrôle spatial de Myosine II. J’ai pu mettre en évidence plusieurs gènes pouvant être impliqués dans cette intercalation. Parmi ces candidats, je me suis focalisée sur celui montrant le plus fort phénotype : le gène CG13992. La caractérisation de ce gène a fut la seconde étape de mon travail de thèse (car seules les séquences nucléotidiques et protéiques étaient connues). Les résultats obtenus ont permis de mettre en évidence l’implication de ce gène dans la localisation de la Myosine II mais ils restent à confirmer. / Epithelial tissue is composed of polarized cells, which are closely attached to each other by adherens junctions. The loss of adherens junctions is often a key step in the development of cancer in epithelial tissues. It is therefore important to understand the mechanisms of attachment between the cells. To study such epithelial plasticity, we use the Drosophila embryo as a model system, where a fine regulation of adherens junctions is required for one of the early processes of development: germ band elongation. During this process, epithelial cells change their neighbors along the anterior-posterior axis (cell cell intercalation) without loss of cell adhesion. Polarized recruitment of the molecular motor Myosin II at the junctions, that disassemble and reassemble, underlies the intercalation process. In part, intercalation relies on the normal activity of the the JAK / STAT pathway that is crucial for the spatial control of Myosin II. During my PhD, I conducted a genetic screen, in a mutant for the ligand of the JAK / STAT pathway, designed to identify second site interactors for Myosin II control. I identified several genes that appear to be involved in the intercalation process. Among these candidates, I focused on one with the strongest phenotype: the gene CG13992. The functional characterization of this gene was the second stage of my thesis (because only the nucleotide and the protein sequences were known). Preliminary results highlight the involvement of this gene in the localization of Myosin II that remain to be confirmed.