Chapter 10 pt 1 Review PDF
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This document reviews the development of Drosophila wings and legs, focusing on the roles of signaling pathways, genes, and structures during organogenesis of these appendages. It details the processes of invagination, folding, and morphogenesis. Various molecular players are discussed, such as Hox genes, signalling molecules (e.g., Dpp, Wingless), and gene expression patterns.
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Chapter 10 pt 1 Organogenesis imaginaldiscs invaginatedfromtheembryotic ectoderm remains untilmetamorphosi develope insegments hox genes if somecellsinthediscareremoved ordestroyed it will regrowcorrectly parallelevolution independent evolutionof similartraits Adult Wing emergeat...
Chapter 10 pt 1 Organogenesis imaginaldiscs invaginatedfromtheembryotic ectoderm remains untilmetamorphosi develope insegments hox genes if somecellsinthediscareremoved ordestroyed it will regrowcorrectly parallelevolution independent evolutionof similartraits Adult Wing emergeat metamorphosisafter folding evaginationof ID turnsinsideouttextendsoutward dorsal ventral surfaces dividedintoA Pcompartments thewingID hascellsthat specify notumthingebu not thewingitself vestigial TFcoactivatorthat is expressedonly inthe wing is sufficient forwingdevelopment expressionpromotedbyNotch Wingless signalling Dpp Patterns theDrosophilia wing disc expressedinresponse tothesignallingcenter at the AIP compartmentboundary engrailed Hedgehogare inthe posterior of ID expressionstarts w pairrule stayson gender selector hedgehog can act as a morphogen proteingradientstarts inposterior butcandiffu transcriptionaleffector Ci turned on byHh onlyexpressed in theanteriorcells highlevelsof Ci ontheboarder of A P needstobeincontact w hedgehog post increasedpp partofthe BMDfamily signalling molecule expressed at theboarde in anarrowstrip organizing center specialsignalling patterningthewing Dppgradientrepresses theTF bigger butactivates theTFs spatite's MEorblind omb 0pm need moreDpptoturn on spalt brinker represses spalt optomotor blind Signalling Centor patterns drosophiliawingalong A P axis Dpp morphogen Dpp only omb patternofveins ultimate outcome of A P patterning notdirectlyaffectedbyhedgehog dpp stepsdowntheway it engrailed D Vcompartmentpatters in Drosophilia Wings apterous selectorgene onceonalways on that induces the expression of Serrate notchligand expression ofDelta notchligand in adjacent ventralcells expressedin dorsal compartment Pressio Delta Servate wingless stripe inthe middle combination causes vestigialexpression regulates wing development wingless vestigial stripedown center Vestigial integratesdifferent enhancers vestigialtranscriptional co activator that is necessary sufficient for wing development early in development vestigial isturned onby notch wingless D boundary usingboundary enhancer pmiddle later turned on bywingless dpp vestigial throughthe wholedisc AIP Drosophilia legdiscextends like a collapsed cone imaginaldisccellsinvaginate s legshoots out made of epidermal cells jointed differentringsin imaginaldisc mostdist LegDisc Patterned similarly to wing in thecen Appnowexpressed in dorsal wingless expressed in ventral 1 wing leg Hh engrailed inposterior app same bit wingsdisc M dfng turnedon inpostcells leg dpp expressed only ventrally winglessexpressedclosest to Hh turnson Wingless dpponly overlap in the center distal distal less mutation no distal represseshomothora then inducesdachshund required for theformation of particular leg regions wing wingless expressed in ventral region hox mutations wing leg both start w the same signal to set up axes hoxgene expressed in wrongplace imaginal disc will grow cells knowing wherethey are whattheydo hox genestell cells to interpret whatthey have Limb Buds smallprotrusionsthat arisefromthebody walloftheembryo limbshave 3 developmental axes D V A P PID early limbbudhas2 major components 1 Coreof loose mesenchymalcells comesfrommesoderm givesrise to skeletal elements connectivetissue 2 outerlayerofepithelialcells apical ectodermal ridge thickening oftheectodermat the tip ofthelimb bud runs alongDIV ectodermboundary is a zone of proliferatingcellsasthe leave directly underneath moredifferentiated limbsdifferentiate proximal to distal Genes in LateralPlate Mesoderm specify position limb type combinatorial Hoxcode in thelateralplate mesoderm determines wherethe limbdevelops byactivatingTbx5 Tbx4 Tbx5 forelimb wing turnedon by nox Pitxl turns on Pbx4 leghindlimb leadtotheactivation of FGF signallingmolecule induces FGF10 FGF8thatwillform the AER positivefeedbackloop putFOFbeads in interlimbregion formation of limbbu if FGFis present it willturn on the limb bud FGFS involvedinthepolarizing region posteriorsideoflimb b t important for A P patterning pinky vsthumb once a budhasformed has a polarizing region AER it can develop autonomously AER is required for proximo distal development AERis closely packedcells connected by gap junctions ions smallmoleco can moveb t cells essential forgrowth if removed limbtrunkation proves development is proximal di polarizingregionhas FGF replace AER W FGF nearly normal FGFis responsiblefor outgrowth
