title: Oriented cell divisions in the extending germband of Drosophila.
abstract: Tissue elongation is a general feature of morphogenesis. One example is the extension of the germband, which occurs during early embryogenesis in Drosophila. In the anterior part of the embryo, elongation follows from a process of cell intercalation. In this study, we follow cell behaviour at the posterior of the extending germband. We find that, in this region, cell divisions are mostly oriented longitudinally during the fast phase of elongation. Inhibiting cell divisions prevents longitudinal deformation of the posterior region and leads to an overall reduction in the rate and extent of elongation. Thus, as in zebrafish embryos, cell intercalation and oriented cell division together contribute to tissue elongation. We also show that the proportion of longitudinal divisions is reduced when segmental patterning is compromised, as, for example, in even skipped (eve) mutants. Because polarised cell intercalation at the anterior germband also requires segmental patterning, a common polarising cue might be used for both processes. Even though, in fish embryos, both mechanisms require the classical planar cell polarity (PCP) pathway, germband extension and oriented cell divisions proceed normally in embryos lacking dishevelled (dsh), a key component of the PCP pathway. An alternative means of planar polarisation must therefore be at work in the embryonic epidermis.
authors.affiliation: Medical Research Council, National Institute for Medical Research, The Ridgeway, Mill Hill, London NW71AA, UK. ssilva@nimr.mrc.ac.uk
authors.forename: Sara Morais
authors.initials: SM
authors.lastname: da Silva
authors.forename: Jean-Paul
authors.initials: JP
authors.lastname: Vincent
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000502:physiology; D000818:Animals; D030801:Animals, Genetically Modified; D019521:Body Patterning / Q000502:physiology*; D018797:Cell Cycle Proteins; D002455:Cell Division / Q000502:physiology*; D016764:Cell Polarity / Q000502:physiology*; D000072261:Dishevelled Proteins; D004330:Drosophila / Q000166:cytology / Q000196:embryology*; D029721:Drosophila Proteins / Q000235:genetics; D004625:Embryo, Nonmammalian; D004817:Epidermis / Q000196:embryology; D018398:Homeodomain Proteins / Q000235:genetics; D008954:Models, Biological; D009024:Morphogenesis / Q000235:genetics; D010750:Phosphoproteins / Q000502:physiology; D017027:Protein Tyrosine Phosphatases / Q000235:genetics; D014157:Transcription Factors / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D018797:Cell Cycle Proteins; D000072261:Dishevelled Proteins; D029721:Drosophila Proteins; D018398:Homeodomain Proteins; D010750:Phosphoproteins; D014157:Transcription Factors; C000606588:dsh protein, Drosophila; C052837:eve protein, Drosophila; D017027:Protein Tyrosine Phosphatases; C059217:stg protein, Drosophila