Drosophila dorsal/ventral axis deteminationSlide 2Slide 3Slide 4Slide 5Gurken protein specifies the Anterior-Posterior axis of the Drosophila embryo during oogenesisGurken also signals dorsal pole formation during oogenesisExpression of the Gurken Message and Protein Between the Oocyte Nucleus and the Dorsal Anterior Cell MembraneGurken signaling inhibits production of an extracellular signal (Spätzle) by follicle cellsSlide 10Slide 11Translocation of Dorsal protein into ventral nuclei but not lateral or dorsal nucleiGeneration of Dorsal-Ventral Polarity in DrosophilaSlide 14Slide 15Conserved pathway for regulating nuclear transport of transcription factors in Drosophila and mammalsSlide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Gastrulation in DrosophilaSlide 28Schematic representation of gastrulation in DrosophilaSlide 30Slide 31Slide 32Slide 33Slide 34Slide 35Slide 36Slide 37Slide 38Slide 39Nuclei divide without cell division in Drosophila to produce a syncytial blastoderm embryoSlide 41Drosophila dorsal/ventral axis deteminationHow are different tissue types specified at distinct positions on the embryonic dorsal-ventral axis?amnio-serosa dorsal ectodermneuro-ectodermmesodermCell fate specification at the blastoderm stagemesoderm formationfate mapdorsalventralDorsal-Ventral fate mapGenes identified in a famous screen for Drosophila mutants with embryo patterning defects TorpedoGurkenLocalized maternal mRNA sets up anterior and posterior polesGurken protein specifies the Anterior-Posterior axis of the Drosophila embryo during oogenesis(Similar to EGF)Gurken also signals dorsal pole formation during oogenesisfollicle cellsanterior posteriorA PVDDV-+-microtubules71-6 810Agurken expression in the oocyte10Agurken expression in the oocyte1-6migration of nucleus+--8oocyte nucleusExpression of the Gurken Message and Protein Between the Oocyte Nucleus and the Dorsal Anterior Cell MembraneGurken signaling inhibits production of an extracellular signal (Spätzle) by follicle cellsfollicle cellsOocytepipe expressionVentral follicle cellPipe (Golgi?)XXNucleusWind (ER?)XXXXmodified from van Eeden & St.JohnstonGurken = Epidermal Growth Factor (EGF)Torpedo = EGF receptor(in follicle cells)Toll Tl - membrane receptor cactus cact - cytoplasmic inhibitor of Dorsal nuclear translocationdorsal dl - transcription factor (morphogen)tube - cytoplasmic proteinpelle - ser/thr protein kinaseSomatic (follicle cells) ndl, pipe, wbl gd, snk, ea - serine proteasesSpätzle spz - ligandGermline (nurse cells)Dorsal proteindorsal RNAToll proteinSpätzle proteinDorsal proteinnudel, pipe, wbl amnio serosadorsal ectodermneuro-ectodermmesodermDl nuclear proteinMaternal effect mutations in dorso-ventral patterningWild type ventralizeddorsal mutantcactus mutantdorsalized T1T2T3A1A2A3A4A5A6A7A8dorsal and cactus mutants (maternal germline effect) dorsal ventralWild type tol l mutant cactus mutantTranslocation of Dorsal protein into ventral nuclei but not lateral or dorsal nucleiGeneration of Dorsal-Ventral Polarity in DrosophilaGeneration of Dorsal-Ventral Polarity in DrosophilaWild typetoll mutantInject wild-type cytoplasmmesodermneuro-ectoderm(denticle belts)dorsal ectodermThe Toll pathway in dorso-ventral pattern formation into toll mutant eggs dorsalizedlocal rescue ventral dorsal polarity reversalConserved pathway for regulating nuclear transport of transcription factors in Drosophila and mammalsCells with highest nuclear Dorsal levels become mesodermZygotically expressed genesAction of Dorsal protein in ventral cellsAction of Dorsal protein in ventral cellsHigh affinity for promoter,Not much Dorsal needed to activateAction of Dorsal protein in ventral cellsLower affinity for promoter,More Dorsal needed to activateZygotically expressed genesAction of Dorsal protein in ventral cellsSnail repression of rhomboid creates domains with distinct gene expression patternstwistdppDorsal proteindorsal RNAToll proteinSpätzle proteinDorsal proteinnudel, pipe, windbeutelDorso-ventral pattern formation: summaryoocyte nucleus dorsal> repression of ventral fatein dorsal follicle cellsventral production of ligand> activation of Toll receptor> graded nuclear uptakeof Dorsal morphogen> regulation of zygotictarget gene expression> cell fates along DV axisUse of a similar regulatory system to pattern insects and vertebratesPatterns mesoderm in vertebratesPatterns ectoderm in DrosophilaGastrulation in DrosophilaSchematic representation of gastrulation in DrosophilaAnterior-posterior patterning in DrosophilaThe fly body plan: each segment has a unique identity and produces distinctive structures3 head3 thorax8 abdomenfate map larva wild-typeanterior bicoidposterior oskarterminal torsoMutations affecting the antero-posterior axis 3 independent maternal systems: anterior, posterior, terminal single mutantsdouble mutants triple mutants additive phenotypes active systemsA P T - P T A - T A P - - - - - P - - - T A - - active systemsMaternal effect mutationsZygotic effect mutationsEmbryo from wild-type motherEmbryo from bicoid motherbicoid mutant phenotypeWild type blastoderm fate mapbicoid mutantAnterior: bicoid is required for head and thorax abdomenabdomenhead+ thoraxBicoid mRNA localization in embryo(tethered to microtubules)Nuclei divide without cell division in Drosophila to produce a syncytial blastoderm embryoFig. 9.1Bicoid protein gradient in syncytial blastoderm embryo- diffuses after translation from localized mRNA- protein
View Full Document
Unlocking...