title: Local and tissue-scale forces drive oriented junction growth during tissue extension.
abstract: Convergence-extension is a widespread morphogenetic process driven by polarized cell intercalation. In the Drosophila germ band, epithelial intercalation comprises loss of junctions between anterior-posterior neighbours followed by growth of new junctions between dorsal-ventral neighbours. Much is known about how active stresses drive polarized junction shrinkage. However, it is unclear how tissue convergence-extension emerges from local junction remodelling and what the specific role, if any, of junction growth is. Here we report that tissue convergence and extension correlate mostly with new junction growth. Simulations and in vivo mechanical perturbations reveal that junction growth is due to local polarized stresses driven by medial actomyosin contractions. Moreover, we find that tissue-scale pulling forces at the boundary with the invaginating posterior midgut actively participate in tissue extension by orienting junction growth. Thus, tissue extension is akin to a polarized fluid flow that requires parallel and concerted local and tissue-scale forces to drive junction growth and cell-cell displacement.
authors.affiliation: Aix Marseille Université, CNRS, IBDM UMR7288 13009 Marseille, France.
authors.forename: Claudio
authors.initials: C
authors.lastname: Collinet
authors.affiliation: EMBL Heidelberg, Meyerhofstrasse 1 69117 Heidelberg, Germany.
authors.forename: Matteo
authors.initials: M
authors.lastname: Rauzi
authors.affiliation: Aix Marseille Université, CNRS, IBDM UMR7288 13009 Marseille, France.
authors.forename: Pierre-François
authors.initials: PF
authors.lastname: Lenne
authors.affiliation: Aix Marseille Université, CNRS, IBDM UMR7288 13009 Marseille, France.
authors.forename: Thomas
authors.initials: T
authors.lastname: Lecuit
mesh_terms: D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000235:genetics*; D015820:Cadherins / Q000235:genetics / Q000378:metabolism; D002448:Cell Adhesion / Q000235:genetics; D058948:Cell Tracking / Q000379:methods; D029721:Drosophila Proteins / Q000235:genetics* / Q000378:metabolism; D004331:Drosophila melanogaster / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D004625:Embryo, Nonmammalian / Q000196:embryology / Q000378:metabolism*; D036681:Fluorescence Recovery After Photobleaching; D018507:Gene Expression Regulation, Developmental; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D007365:Intercellular Junctions / Q000378:metabolism; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D034622:RNA Interference; D059008:Time-Lapse Imaging; D000097573:Red Fluorescent Protein
chemical_list: D015820:Cadherins; D029721:Drosophila Proteins; D049452:Green Fluorescent Proteins; D008164:Luminescent Proteins; D000097573:Red Fluorescent Protein