Slide 1Slide 2Slide 3Slide 4Slide 5Slide 6Slide 7Slide 8Slide 9Slide 10Slide 11Slide 12Slide 13Slide 14Anterior-Posterior Pattern Formation in FliesSlide 16Slide 17Slide 18Slide 19Slide 20Slide 21Slide 22Slide 23Slide 24Slide 25Slide 26Slide 27Wild type fushi tarazu mutantSlide 2908_18_reporter.gene.jpgSlide 31Regulation of the Second Stripe of Transcription from the even-skipped GeneSlide 33Slide 34Slide 35Slide 36Segments and ParasegmentsSlide 38Slide 39Slide 40Slide 41Slide 42Slide 43Slide 44Slide 45Slide 46Slide 47Slide 48Slide 49Slide 50Slide 51Slide 52Slide 53Homeotic Gene Expression 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 systemsWild type blastoderm fate mapbicoid mutantAnterior: bicoid is required for head and thorax abdomenabdomenhead+ thoraxBicoid protein gradient in syncytial blastoderm embryo- diffuses after translation from localized mRNA- protein unstableTransplantation of egg cytoplasm An organizer of the anterior-posterior pattern is located at the anterior pole wtrescue ofpattern wthead in the center polarity reversal wtthorax at posterior pole polarity reversal abdomen only polarity normalbicoid mRNAbicoid mRNA induces head and thorax bicoid (bcd) gene encodes a homeo-domain transcription factorInjection of bicoid mRNA:anterior (head) structures at site of injectionno head& reorganization of polarityTransplantation of egg cytoplasm Posterior cytoplasm also has polarizing activitywtrescue ofpattern wthead in the center polarity reversal wtthorax at posterior pole polarity reversal wtdouble abdomenpolarity reversal abdomen only polarity normalNanos is the maternal effector of the posterior systemrescue of all posterior-system mutantsby injection of nanos mRNAmutant rescued rescuedEmbryonic polarity genesAnterior-Posterior Pattern Formation in Fliesbcd mRNABcd proteintarget genes Bcd gradient and expression domains of target genesThe Bcd gradient is converted into domains of gene expression Bcd protein binds differentially to enhancers of target genesDifferent thresholds of Bcd concentration are required to turn on different genes target genes are zygotically expressed gap genes low affinityhigh affinityBicoid and Nanos regulate Gap genesHunchbackKrüppelKnirpsExpression patterns of proteins encoded by gap genesBicoid protein: transcriptional and translational regulatorzygotic target genes maternal target mRNAHbmat proteingiantnanos mRNAoskar mRNAStau proteinHbzyg proteinbcd mRNAgene X Bcd proteinknirpsNanos proteinoocytenurse cells follicle cellsMaternal anterior and posterior systems Hunchback (Hb), knirps and giant are zygotic gap genes (soma)head + thorax abdomenGap gene mutants lack different body regionsWild typeKrüppel hunchbackknirpsGap gene mutants lack different body regionsHunchbackKrüppelThe gap genes regulate each other and form domains with unique combinations of gene expressionAnterior-Posterior Pattern Formation in FliesWild typefushi tarazu mutantPair-rule mutantsEven-skipped expression pattern08_18_reporter.gene.jpgModularity of the Drosophila even-skipped promoterparasegmentKrüppelhunchbackgianteve stripe #2 repressorrepressoractivator1 2 3 4 5Regulation of expression stripe no. 2 of Even-skipped (eve) multiple binding sites in enhancer of eve repressorsactivatorsRegulation of the Second Stripe of Transcription from the even-skipped GeneRegulation of the even-skipped geneFushi tarazu expression earlylateEve, Ftz expressionRefinement of expression domains over timeAnterior-Posterior Pattern Formation in FliesSegments and ParasegmentsSegment polarity mutantsSegment polarity mutantsWingless signaling specifies cell fates in the ventral epidermisarm mutantWild typeAnteriorcellsmakeHairPosteriorcellsmakeNakedcuticleExpression of segment polarity gene wingless 024681012LAfghgap135791113Segment polarity genes – 14 stripesThe Even-skipped and Fushi tarazu pair-rule transcription factors activate the segment-polarity gene EngrailedIntercellular feedback maintains pair-rule gene expression statesIntercellular feedback maintains pair-rule gene expression statesWnt signaling pathway-+ -----+++++Anterior-Posterior Pattern Formation in FliesDrosophila homeotic mutationsWild typeAntennapedia mutantUltrabithorax mutantWild typeHomeotic Gene Expression in
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