Serotonin synchronises convergent extension of ectoderm with morphogeneticgastrulation movements in Drosophila

During Drosophila gastrulation, convergent extension of the ectoderm is req uired for germband extension. Adhesive heterogeneity within ectodermal cell s has been proposed to trigger the intercalation of cells responsible for t his movement. Segmentation genes would impose this heterogeneity by establi shing a pair-rule pattern of cell adhesion properties. We previously report ed that the serotonin receptor (5-ht(2Dro)) is expressed in the presumptive ectoderm with a pair-rule pattern. Here, we show that the peaks of 5-ht(2D ro), expression and serotonin synthesis coincide precisely with the onset o f convergent extension of the ectoderm. Gastrulae genetically depleted of s erotonin or the 5-ht(2Dro) receptor do not extend their germband properly, and the ectodermal movements becomes asynchronous with the morphogenetic mo vements in the endoderm and mesoderm. Associated with the beginning of this desynchronisation, is an altered subcellular localisation of adherens junc tions within the ectoderm. Combined, these data highlight the role of the e ctoderm in Drosophila gastrulation and support the notion that serotonin si gnalling through the 5-HT2Dro receptor triggers changes in cell adhesivenes s that are necessary for cell intercalation. (C) 1999 EIsevier Science Irel and Ltd. All rights reserved.