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Lumen formation in the tracheal branches. (A) The embryonic trachea is formed from 10 placodes of ectodermal cells that invaginate into the interior of the embryo. D: dorsal; V: ventral; A: anterior and P: posterior. (B) Internalized tracheal cells migrate out to form the six primary branches, some of which fuse with branches from adjacent metameres to form an interconnected network (C). (D) Schematic diagram of one tracheal metamere showing the dorsal trunk (anterior and posterior; Dta and Dtp), lateral trunk (anterior and posterior; Lta and Ltp), dorsal branch (DB), visceral branch (VB), spiracular branch (SB) and ganglionic branch (GB). (E) Two DBs, each with a terminal cell (TC, red) and a fusion cell (FC, green). (F) The interconnected tracheal network of a stage 15 embryo has a single central lumen. (G) Terminal cell (TC) forms a lumen de novo as the cell elongates; db: dorsal branch, dt: dorsal trunk. Embryos in A-C were processed for RNA in situ hybridization to trachealess to label tracheal cells. Embryo in E was stained for DSRF (red) to label TC, Dysfusion to label FC (green) and 2A12 (blue) to label the lumen of the DB. Embryo in F was stained for 2A12 (white) to label the lumen and GFP to detect actin-GFP expressed specifically in the trachea with breathless-GAL4. Diagram in D is not drawn to scale. Panel G was kindly provided by J. Casanova with permission from the Nature Publishing Group.

Lumen formation in the tracheal branches. (A) The embryonic trachea is formed from 10 placodes of ectodermal cells that invaginate into the interior of the embryo. D: dorsal; V: ventral; A: anterior and P: posterior. (B) Internalized tracheal cells migrate out to form the six primary branches, some of which fuse with branches from adjacent metameres to form an interconnected network (C). (D) Schematic diagram of one tracheal metamere showing the dorsal trunk (anterior and posterior; Dta and Dtp), lateral trunk (anterior and posterior; Lta and Ltp), dorsal branch (DB), visceral branch (VB), spiracular branch (SB) and ganglionic branch (GB). (E) Two DBs, each with a terminal cell (TC, red) and a fusion cell (FC, green). (F) The interconnected tracheal network of a stage 15 embryo has a single central lumen. (G) Terminal cell (TC) forms a lumen de novo as the cell elongates; db: dorsal branch, dt: dorsal trunk. Embryos in A-C were processed for RNA in situ hybridization to trachealess to label tracheal cells. Embryo in E was stained for DSRF (red) to label TC, Dysfusion to label FC (green) and 2A12 (blue) to label the lumen of the DB. Embryo in F was stained for 2A12 (white) to label the lumen and GFP to detect actin-GFP expressed specifically in the trachea with breathless-GAL4. Diagram in D is not drawn to scale. Panel G was kindly provided by J. Casanova with permission from the Nature Publishing Group.

Contexts in source publication

Context 1
... Drosophila trachea serves as the respiratory organ of the animal, and like the vertebrate lung, salivary gland and vasculature it is a branched network of tubes. The pattern of the larval trachea is established during embryogenesis when cells from ten tracheal placodes or plates of approximately 90 ectodermal epithelial cells on each side of the embryo, invaginate into the underlying mesoderm to form elongated sacs ( Figure 3A). In response to Fibroblast Growth Factor (FGF) or Branchless (Bnl), which is expressed in surrounding ectodermal and mesodermal cells (Ohshiro et al., 2002;Sutherland et al., 1996;Zhan et al., 2010), the invaginated tracheal cells which express the FGF receptor, Breathless (Btl), migrate towards the Bnl source to form the six primary branches ( Figure 3B and C). ...
Context 2
... pattern of the larval trachea is established during embryogenesis when cells from ten tracheal placodes or plates of approximately 90 ectodermal epithelial cells on each side of the embryo, invaginate into the underlying mesoderm to form elongated sacs ( Figure 3A). In response to Fibroblast Growth Factor (FGF) or Branchless (Bnl), which is expressed in surrounding ectodermal and mesodermal cells (Ohshiro et al., 2002;Sutherland et al., 1996;Zhan et al., 2010), the invaginated tracheal cells which express the FGF receptor, Breathless (Btl), migrate towards the Bnl source to form the six primary branches ( Figure 3B and C). Some of the primary branches, such as the visceral branch (VB) and the anterior and posterior dorsal trunk (DT), grow along the anterior-posterior axis, whereas other branches, such as the dorsal branch (DB), lateral trunk (LT) and ganglionic branch (GB), grow along the dorsal-ventral axis ( Figure 3D). ...
Context 3
... response to Fibroblast Growth Factor (FGF) or Branchless (Bnl), which is expressed in surrounding ectodermal and mesodermal cells (Ohshiro et al., 2002;Sutherland et al., 1996;Zhan et al., 2010), the invaginated tracheal cells which express the FGF receptor, Breathless (Btl), migrate towards the Bnl source to form the six primary branches ( Figure 3B and C). Some of the primary branches, such as the visceral branch (VB) and the anterior and posterior dorsal trunk (DT), grow along the anterior-posterior axis, whereas other branches, such as the dorsal branch (DB), lateral trunk (LT) and ganglionic branch (GB), grow along the dorsal-ventral axis ( Figure 3D). Tracheal cell migration is followed by fusion between the contralateral DBs, DT and LT branches of adjacent segmentally arranged metameres on each side of the embryo to form an interconnected tracheal network with a single central lumen ( Figure 3F). ...
Context 4
... of the primary branches, such as the visceral branch (VB) and the anterior and posterior dorsal trunk (DT), grow along the anterior-posterior axis, whereas other branches, such as the dorsal branch (DB), lateral trunk (LT) and ganglionic branch (GB), grow along the dorsal-ventral axis ( Figure 3D). Tracheal cell migration is followed by fusion between the contralateral DBs, DT and LT branches of adjacent segmentally arranged metameres on each side of the embryo to form an interconnected tracheal network with a single central lumen ( Figure 3F). ...
Context 5
... primary branch outgrowth, the tracheal lumen is initially closed at the branch tips. Later in development, a continuous tubular network is formed during anastomosis, when specialized cells, known as fusion cells, which are found at the tips of migrating branches such as the DT and DB, recognize each other's partner in the adjacent metamere and connect to form a continuous lumen ( Figure 3E) ( Baer et al., 2009). Although these specialized cells are called fusion cells, they, in fact, do not fuse themselves and instead mediate the fusion of two separate tubular structures. ...
Context 6
... cells (TCs) at the tips of some tracheal branches form intracellular lumens de novo ( Figure 3E and G). Although de novo lumen formation in TCs was initially thought to occur by the "cell hollowing" mechanism ( Lubarsky and Krasnow, 2003), recent studies by Gervais and Casanova (2010) show that the intracellular lumen forms by the inward growth of new apical membrane from the surface that is in contact with the adjacent tracheal cell and not through a cell-hollowing mechanism, shedding significant insight into this process. ...
Context 7
... de novo lumen formation in TCs was initially thought to occur by the "cell hollowing" mechanism ( Lubarsky and Krasnow, 2003), recent studies by Gervais and Casanova (2010) show that the intracellular lumen forms by the inward growth of new apical membrane from the surface that is in contact with the adjacent tracheal cell and not through a cell-hollowing mechanism, shedding significant insight into this process. The TC elongates as its lumen is formed intracellularly and both these processes are accompanied by the asymmetric accumulation of the actin and microtubule cytoskeletal systems ( Figure 3G). Genetic perturbation of the microtubule network results in defects in TC lumen elongation suggesting a critical role for microtubules in TC lumen formation. ...

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La régulation transcriptionnelle est le sujet principal de nombreuses recherches et est un mécanisme indispensable pour assurer les fonctions cellulaires de tout organisme. Les avancées technologiques dans le monde de la microscopie ouvrent de nouvelles opportunités pour visualiser différentes étapes de ce mécanisme. Notamment les dynamiques et la localisation d’un FT a l’échelle super-résolutive. Cependant, un unique FT n’est pas suffisant pour réguler finement l’activation ou la répression de la transcription d’un gène. En effet, différents complexes de FT coopèrent pour atteindre une telle précision de régulation. La visualisation de la fixation d’un complexe (binaire) sur sa séquence régulatrice cible serait donc un atout pour mieux déchiffrer la régulation transcription elle.La première partie de mon travail de Thèse a consisté à mettre en place des outils permettant de visualiser en microscopie confocale et super-résolution, la fixation de complexes Hox-cofacteur sur des séquences ADN cibles spécifiques. Ces outils ont été appliques pour quantifier l’enrichissement de différents complexes Hox/Exd au niveau d’un enhancer connu (appelé fkh250) du gène cible forkhead (fkh) dans les glandes salivaires de la larve de drosophile. J’ai combine la méthode de BiFC (confocale) ou BiFC-PALM (super-résolution) et le système ParB/INT pour visualiser simultanément les complexes Hox/Exd et l’enhancer fkh250, respectivement.Mes analyses confirment un enrichissement spécifique des complexes Hox/Exd sur les différents types d’enhancer fkh250. Surtout, des résultats préliminaires indiquent la possibilité de quantifier le nombre exact de complexes Hox/Exd fixes sur l’enhancer fkh250 a l’échelle super-résolutive.La deuxième partie de mon travail de thèse concerne l’analyse d’une nouvelle interaction entre les protéines Hox avec la Lamine C (LamC) pour une répression transcriptionnelle active des gènes lies a l’autophagie (atg) dans le corps gras de la larve de drosophile. Ce travail a permis de révéler un profil de co-expression typique des protéines Hox et de la LamC, au sein du noyau par imagerie confocale ≪ Lightning ≫ et l’importance de contrôler le positionnement des loci génomiques pour une régulation fine de la transcription.