title: EGF signaling and the origin of axial polarity among the insects.
abstract: The eggs of insects are unusual in that they often have bilateral symmetry when they are laid, indicating that both anterior-posterior (AP) and dorsal-ventral (DV) symmetries are broken during oogenesis. The molecular basis of this process is well understood in Drosophila melanogaster, in which symmetry breaking events for both axes depend on the asymmetric position of the oocyte nucleus and on germline-soma signaling mediated by the Tgf alpha-like epidermal growth factor (EGF) ligand Gurken. Germline-soma signaling interactions centered around the oocyte nucleus have been proposed in other insect species, but the molecular nature of these interactions has not been elucidated. We have examined the behavior of the oocyte nucleus and the function of EGF signaling components in the ovaries of the wasp Nasonia vitripennis, the beetle Tribolium castaneum, and the cricket Gryllus bimaculatus. We have found that EGF signaling has broadly conserved roles in mediating the encapsulation of oocytes by the somatic follicle cell layer, in establishing polarity of the egg chambers, and in setting up the DV axis of the embryo. These results provide insights into the evolutionary origins of the unique strategy employed by insects to establish embryonic axial polarity during oogenesis.
authors.affiliation: Institute of Developmental Biology, University of Cologne, Zülpicher Strasse 47b, 50674 Cologne, Germany. jlynch@uni-koeln.de
authors.forename: Jeremy A
authors.initials: JA
authors.lastname: Lynch
authors.forename: Andrew D
authors.initials: AD
authors.lastname: Peel
authors.forename: Axel
authors.initials: A
authors.lastname: Drechsler
authors.forename: Michalis
authors.initials: M
authors.lastname: Averof
authors.forename: Siegfried
authors.initials: S
authors.lastname: Roth
mesh_terms: D000818:Animals; D005075:Biological Evolution; D019521:Body Patterning; D002467:Cell Nucleus / Q000378:metabolism; D004815:Epidermal Growth Factor / Q000378:metabolism*; D019476:Insect Proteins / Q000235:genetics / Q000378:metabolism; D007313:Insecta / Q000033:anatomy & histology / Q000502:physiology; D009865:Oocytes / Q000166:cytology* / Q000378:metabolism; D034622:RNA Interference; D015398:Signal Transduction / Q000502:physiology*
chemical_list: D019476:Insect Proteins; D004815:Epidermal Growth Factor
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