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http://flymove.uni-muenster.de/Processes/Segmentation/SegmentGes.html
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WT wg
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A>P <A loss of P <A A> P P Mirror image duplication
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WT en
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WTen anterior posterior
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http://flymove.uni-muenster.de/Processes/Segmentation/SegmentGes.html
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CHRISTIANE NUSSLEIN-VOLHARD Max Planck Institute Tuebingen, Germany
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Saturation mutagenesis: -identify mutations in all possible genes involved in embryo patterning -saturation reached at ~5 mutations per gene
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Saturation mutagenesis: -saturation reached at ~5 mutations per gene tossing marbles into bins How many bins are there? -identify mutations in all possible genes involved in embryo patterning
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Saturation mutagenesis: -saturation reached at ~5 mutations per gene 15 marbles tossed into bins 5 5 5 Probability of missing fourth bin in 15 trys: -identify mutations in all possible genes involved in embryo patterning
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Saturation mutagenesis: -saturation reached at ~5 mutations per gene 15 marbles tossed into bins 5 5 5 0.75 15 = 0.013 Probability of missing fourth bin in 15 trys: -identify mutations in all possible genes involved in embryo patterning
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Saturation mutagenesis: -saturation reached at ~5 mutations per gene 15 marbles tossed into bins 5 5 5 0.75 15 = 0.013 Probability of missing fourth bin in 15 trys: ~99% probability there are only 3 bins -identify mutations in all possible genes involved in embryo patterning
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Genes that control pattern and polarity in the embryo: Maternal genes: 1. anterior-posterior -bicoid -nanos 2. terminal -torso 3. dorsal ventral anterior posterior dorsal ventral Zygotic genes: 1. Gap genes 2. Pair-rule genes 3. Segment polarity genes 4. Homeotic genes early late
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Triple mutant: -no information nanos, torso double: -only bicoid bicoid, torso double: -only nanos bicoid, nanos double: -only torso
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Maternal genes: Bicoid Hunchback Gap genes: Hunchback Kruppel Knirps Giant Pair-rule genes: Even-skipped Ftz Runt Prd Odd-skipped Segment polarity genes: Engrailed Wingless Decapentaplegic Hedgehog Homeotic genes: Ubx abdA abdB Antp
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WTknirps
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Knirps phenotype expression
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Kruppel Mirror image duplication phenotype expression
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Maternal genes: Bicoid Hunchback Gap genes: Hunchback Kruppel Knirps Giant Pair-rule genes: Even-skipped Ftz Runt Prd Odd-skipped Segment polarity genes: Engrailed Wingless Decapentaplegic Hedgehog Homeotic genes: Ubx abdA abdB Antp
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Pair rule: Even-skipped phenotype expression
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Hairy Runt Eve Ftz
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Segment polarity: patched
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WT wg
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Maternal genes: Bicoid Hunchback Gap genes: Hunchback Kruppel Knirps Giant Pair-rule genes: Even-skipped Ftz Runt Prd Odd-skipped Segment polarity genes: Engrailed Wingless Decapentaplegic Hedgehog Homeotic genes: Ubx abdA abdB Antp
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Lecture 3…
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WT en
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WT wg
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http://www.ucalgary.ca/UofC/eduweb/virtualembryo/D_m_segment_I.html
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knirps kruppel giant Even-skipped Gap genes Pair-rule stripes
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bicoid hunchback knirps
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Knirps phenotype expression
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Ma et al. (1996) Development 122 (4): 1195. BICOID bindings sites in the Hunchback and Knirps enhancers The EMBO Journal (1998) 17, 5998–6009 Hunchback Knirps
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The EMBO Journal (1998) 17, 5998–6009
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Cell. 2007 Jul 13;130(1):141-52. Cell. 2007 Jul 13;130(1):153-64.
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Is cooperativity sufficient? Spatial Bistability Generates hunchback Expression Sharpness in the Drosophila Embryo Francisco J. P. Lopes1,2,3*, Fernando M. C. Vieira3,4, David M. Holloway5,6,7, Paulo M. Bisch3, Alexander V. Spirov1,2 PLOS Computational Biology (2008) 4:e1000184
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BCD Hb n=~5 Positive feedback loop + Cooperative binding
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Bi-stable dynamics
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BCD Hb n=~5 Positive feedback loop + Cooperative binding
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BCD Hb n=~5 Cooperative binding No feedback
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No feedback – no bi-stability
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lowering Hill co-efficient shifts curve, but still bi-stable
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http://www.ucalgary.ca/UofC/eduweb/virtualembryo/D_m_segment_I.html
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Giant Kruppel Giant
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Wild Type bicoid Giant expression
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Kruppel Mirror image duplication phenotype expression
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Knirps phenotype expression
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Pair rule: Even-skipped phenotype expression
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knirps kruppel giant Even-skipped Concentration dependent effects of Hunchback Bicoid Fishhook
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WT eve expression Stripe 2- enhancer lacZ Stripe 3+7 enhancer lacZ
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WT kni hb kni tor kni hb tor Gap gene regulation of stripe 3
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Stage 14 Later cellularized Knirps defines boundaries of stripe 3 and 7
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Bicoid binding site deleted Expression partially restored by compensating removal of Giant repressor site
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Deletion of GIANT binding sites expands band Even-skipped expression
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Lecture 2 -segment polarity -wing polarity -evolution of development
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WT wg
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WTen anterior posterior
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Segment Parasegment A P A P A P
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EvenOddEven Parasegments Segments denticals wg en runt prd eve ftz prd runt ftz prd runt
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Hairy Runt Eve Ftz
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EvenOddEven Parasegments runt eve hairy hunchback giant kruppel bicoid
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EvenOddEven Parasegments Segments denticals wg en runt prd eve ftz prd runt ftz prd runt
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Hedge hog
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Segment polarity: patched
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En mRNA Hh protein Hh is a short range signal
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wg en pppp ptc Cells on the en side secrete hh peptide, but lack the hh receptor encoded by ptc In the absence of the hh peptide wg is repressed by the ptc signalling pathway hh wg hh wg en ci
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Armadillo (beta-catenin) frizzled wg TCF dsh
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gene phenotypevertebrate ortholog Wingless (Wnt1) segment polarity, many others Wnt1 DWnt2Pigment cells gonads; Kozopas 1998Wnt7 adult muscle Kozopas 2002 Trachea (with wg) Llimargas 2001 DWnt3/5 Axon Guidance (through Derailed)Wnt5 Yoshikawa 2003 DWnt4Cell Movement in ovary Cohen 2002Wnt9 Dorsoventral specificity of retinal projections (Sato 2006) DWnt6 Wnt6 DWnt8Antagonist Dorsal, no ortholog immunity phenotype (Gordon et al, 2005; Ganguly et al, 2005) DWnt10 Wnt10
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Gene Phenotype of Knockouts or other functions 19 mammalian Wnts Wnt1midbrain, cerebellu; neural crest derivatives; hymocyte number Wnt2placental defects Monkley, 1996 Wnt2b/13retinal cell differentiation Kubo, 2003, Kubo, 2005 Wnt3early gastrulation defect; Axis formation; Hair growth; medial-lateral retinotectal topography; hippocampal neurogenesis Wnt3a vestigial tail; neural crest; hippocampus;Segmentation oscillation clock; left right asymmetry Wnt4kidney defects; sex determination; side-branching in mammary gland; number of thymocytes migration of steroidogenic adrenal precursors into the gonad Jeays-Ward 2003 Anterior-posterior guidance of commissural axons. Wnt5a truncated limbs, truncated AP axis, reduced number proliferating cells Yamaguchi 1999 Distal lung morphogenesi; chondrocyte differentiation, longitudinal skeletal outgrowth; Inhibits B cell proliferation and functions as a tumor suppressor Defects in posterior growth of the female reproductuve tract Wnt5b Wnt6 Wnt7alimb polarity; uterine patterning during the development of the mouse female reproductive tract Delayed maturation synapses in Cerebellum Wnt7bPlacental developmen; lung hypoplasia; macrophage-induced programmed cell death Wnt8a Wnt8b Wnt9aJoint integrity Wnt9bmesenchymal to epithelial transitions Wnt10a Wnt10b decreased trabecular bone; myogenic and Adipogenic program; overexpression inhibits adipogenesis Wnt11Ureteric branching defects; cardiogenesis Wnt16
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WTen anterior posterior
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ptc en
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dpp en ptc Cells on the en side secrete hh peptide, but lack the hh receptor encoded by ptc In the absence of the hh peptide dpp is repressed by the ptc signalling pathway hh dpp hh dpp en
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ptc en
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MAD signaling factor is activated by the dpp receptor: phosphorylation state of MAD forms a signaling gradient
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Conservation of Hedgehog
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haltere
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ANTp loss of function transforms leg to antenna-like appendage
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Antennapedia Wild type Antp c.a. 1949
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Ubx mutant ? ?
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fly Dragon fly crustacean Ubx abd A Evolution of development
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~550 MYA
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Segment polarity: patched
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wg en runt prd eve ftz ptc
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En en- En en- En en- het DNA replication Mitotic Cross-over Mutant daughter cell
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Creating genetic mosaic flies by mitotic recombination
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WTen anterior posterior
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Hunchback is sensitive to ~10% changes in BICOID protein concentration
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1. The gradient is approximately (but not necessarily exactly) an exponential decay in intranuclear (and cytoplasmic) concentration that is established rapidly (less than 90 min). 2. Bcd diffuses relatively slowly (D = 0.3 mm2/s) in the cortical cytoplasm containing the nuclei. 3. The Bcd gradient is stable over nuclear cycles 10– 14, when the number of nuclei is growing by a factor of two with each division and Bcd is concentrated and released from nuclei in a dynamic process. In particular, the initial postinterphase concentration in nuclei in successive cycles is constant to at least 10%. 4. Bcd is not simply trapped in nuclei; rather, it is in dynamic equilibrium between influx and efflux with the cytoplasm and, possibly, intranuclear degradation. 5. The spatial shape of the Bcd gradient (the length constant for an exponential decay) scales with embryo length over a factor of five range in lengths in different dipteran species (Gregor et al., 2005).
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