Animal Development Lecture 6 - nchu.edu.t · Recipe for Animal Development ... (Wilt and Hake, Ch...
Transcript of Animal Development Lecture 6 - nchu.edu.t · Recipe for Animal Development ... (Wilt and Hake, Ch...
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Lecture 6
Development of theDrosophila
Animal Development
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Recipe for Animal Development
Differentiate: selectively activate gene expression
Make an egg
Cut it up
Move cell groups
Produce a three-layered embryos
3The reproductive system of the female Drosophila.
Accessory organs Wheresperm arestored.
(Wilt and Hake, Ch 3, 2004)
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Oocyte materials:maternal components
The oocyte itself
The nurse cells
mRNA, proteins
mRNA, proteins, ribosomes and organelles
Follicle cells: somatic cells
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Progressivedevelopment ofthe Drosophilaoocyte.
8-day journey (14 stages):Temperature-dependent
(Wilt and Hake, Ch 3, 2004)
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Distribution and amount of yolk in eggs
Amount Distribution Occurs in Cleavage type
Isolecithal(sparse amount)
Mesolecithal(moderate amount)
Telolecithal(large amount)
Centrolecithal(large amount)
Even
Predominateson one side
Very dense,excludesCytoplasm toone side
Yolk in center
Many invertebratesmammals
Amphibia
Birds, reptiles, fish
Insect
Variable butcomplete
Radial
Incomplete,meroblastic
Surfacecleavage
(Wilt and Hake, Ch 2, 2004)
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Egg development in Drosophila.
(Wolpert, Ch5, 2002)
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The formation of nursecells, oocyte and ringcanals in Drosophilaoogenesis.CCytoplasmicytoplasmic bridgebridge
(Wilt and Hake, Ch 3, 2004)
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The formation of nursecells, oocyte and ringcanals in Drosophilaoogenesis.
(Wilt and Hake, Ch 3, 2004)
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The nurse cells
undergo duplications of chromosome
No cytokinesis
* Highly polyploid (256 x diploid)
* Large cells
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The Drosophila egg chamber after yolk depositionhas started, stage 10A.
(Wilt and Hake, Ch 3, 2004)
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Oogenesis in Drosophila
Meiosis
Genetic recombination
A stock piling of materials from theoutside
- nurse cells, fat body and follicle cells
A spatial ordering of these materials inthe oocyte
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A developing Drosophila oocyte (right) isshown attached to its 15 nurse cells (left)and surrounded by a monlayer of 700follicle cells.
The oocyte and follicle layer are cooperating todefine the future dorso-ventral axis of the eggand embryo.
(Wolpert, Ch 5, 2002)
Gurken mRNA
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Specificationof the antero-posterior anddorso-ventralaxes duringDrosophilaoogenesis.
Synthesized in the oocyte
Anterior end of the oocyte
Posterior end of the oocyte
(Wolpert, Ch 5, 2002)
15(Wolpert, Ch 5, 2002)
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Fertilization in Drosophila
Sperm enters an opening in the chorioncalled the micropyle.
The egg is activated.
Meiosis is completed.
Syngamy takes places.
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The first 8cyclestake placeevery 9min.
The nucleibegin tomigrate tothesuperficialcorticalcytoplasmic layer. Syncytial blastoderm
(Wilt and Hake, Ch 3, 2004)
18Cleavage and cellular blastoderm formation.
Pole cells: * the first true cells* form the primordial germ cells
The nuclei beginto migrate to thesuperficialcorticalcytoplasmic layer.
(Wilt and Hake, Ch 3, 2004)
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Cellularization of thesyncytial blastoderm I.
(Wilt and Hake, Ch 3, 2004)
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Cellularization of thesyncytial blastoderm II.
Cellular blastoderm
(Wilt and Hake, Ch 3, 2004)
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Larva hatches and starts feeding
By middle of14
Extensive anteroposterior pattern and dorsoventralpattern are complete before morphogeneisis begins
Late in 14Morphogenesis begins
Early in 14Cell membranes form between cortical nuclei;Zygotic gene expression increases
9Pole cells bud off from the rest of the egg;A low level of zygotic gene expression occurs
7-10Nuclei migrate to the cortex
1-8Nuclear proliferation occurs very rapidly
CyclesActivity
Early development of Drosophilia
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Cellular blastoderm
Syncytial blastodermAll nuclei are developmentally equivalent
Cellular fate has more or less restrictedalong particular pathway
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ChimeraAn organ or tissue composed of cells fromtwo genetically distinct sources
An organism that consists of cells derivedfrom more than one individual (zygotelineages), usually of different genotype
More strict definition
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Primary Chimaerasformed at a very early embryonic stage
Secondary Chimaeras
all tissues in the body are potentially chimeric
formed during later post-implantation or postnatalstages by tissue grafting or transplantation
only one or a few tissues might be chimeric
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Mosaic
An organism that consists of cells of more than
one genotype
The genotypically different cells all derived from a
single zygote
More strict definition
26Transplantation analysis of pole cells and polar plasm.
(Wilt and Hake, Ch 3, 2004)
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Cytoplasmic-nuclear interaction
Orthotopic transplantation
Heterotopic transplantation
28A fate map of Drosophila.
(Wilt and Hake, Ch 3, 2004)
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Organization of the cellular blastoderm.
(Wilt and Hake, Ch 3, 2004)
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Organization of the cellularblastoderm.
(Wilt and Hake, Ch 3, 2004)
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Developmentally equivalent nucleigenerated during cleavage interactwith different cytoplasmic areas of theegg.
Losing totipotencyDetermination: process
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Gastrulation inDrosophila I.
Ectoderm: blueMesoderm: redEndoderm: yellow
(Wilt and Hake, Ch 3, 2004)
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Gastrulation inDrosophila I.
(Wilt and Hake, Ch 3, 2004)
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The formation of neuroblasts.
Cell from the ventral surface move into the interior.The progenitor cell divides, giving rise to bothneuroblasts and glial cells (supporting cells of thenervous system).
(Wilt and Hake, Ch 3, 2004)
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Invagination of epitelial cells
Germ band extension
Ingression of individual cells
Gastrulation in Drosophila
The entire suite of movements thatbegins when cells move interiorly andproduce the distinctive endoderm,mesoderm and ectoderm germ layers.
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The registration ofembryonicparasegments withadult body segments.
(Wilt and Hake, Ch 3, 2004)
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Imaginal discs in theDrosophila larva (a firstinstar larva).
(Wilt and Hake, Ch 3, 2004)
38A summary of the maternal effect genes determining pattern.(Wilt and Hake, Ch 3, 2004)
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The suppression by nanos of posteriorhunchback.
The concentration of bicoid, hunchback and nanos mRNAat the time of fertilization.
(Wilt and Hake, Ch 3, 2004)
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The suppression by nanos of posterior hunchback.After translation, high anteriorly for bicoid, high posteriorlyfor nanos.
(Wilt and Hake, Ch 3, 2004)
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The suppression by nanos of posterior hunchback.At a later time in development, hunchback is very highanteriorly due to stimulation of the hunchback gene bybicoid, but Nanos continues to suppress hunchbacvkmRNA translation posteriorly.
(Wilt and Hake, Ch 3, 2004)
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The pathway ofdorsoventralpattern.
(Wilt and Hake, Ch 3, 2004)
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Interactions between the early oocytes andfollicle cells.
(Wilt and Hake, Ch 3, 2004)
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Interactions betweenthe early oocytes andfollicle cells.
(Wilt and Hake, Ch 3, 2004)
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Interactions between theearly oocytes and folliclecells.
(Wilt and Hake, Ch 3, 2004)
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Epigenesis
The sequences of interactions betweentranscription factors and intercellularsignaling
NETWORKNot linear
47(Wolpert, Ch 5, 2002)
The relationshipbetweenparasegments andsegments in theearly embryo, lateembryo and adultfly.
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Gap genes
Pair-rule genes (two-step process)
Segment polarity genes
Homeotic selector genes
Unstable TFs
unstable TFs
TFs and ligands/receptors
Specific identities
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Gap genes
* Establishment of seven broad
* Set up conditions for regulating thepair-rule genes
By interacting with each other andproducts of the terminal axial system
Active in patterning the sevenrepeating stripes
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Pair-rule genes* Lay down seven broad cellular stripes
around the circumference of theembryo
Segment polarity genes* Divide each of the broad stripes in
two, producing 14 narrower stripes,each with an identifiableanteroposterior polarity
51(Wilt and Hake, Ch 15, 2004)
The regulatorycascade forsegmentformation inDrosophila.
Gap genes1. interact with each
other and withproducts of theterminal (posteriorand anterior) axialsystems;
2. Set up conditionsfor regulating thepair-rule genes.
52(Wilt and Hake, Ch 15, 2004)
The expressiondomains of gapgenes.
Hb
Torso &torsolike
Tll
kr, kni, gt (posterior)
hkb, tll
gt (antierior)
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Protein Genes whose expression is
Name Levels activated repressed
Bicoid High hb, gt
Hunchback high kr, gt, kni
intermediate kr
Low kr
Dorsal high in nucleus twist, snail dpp, zen
54(Wilt and Hake, Ch 15, 2004)
Regulation ofhunchbackby bicoid.
Bicoid
hunchback
55(Wilt and Hake, Ch 15, 2004)
The expression of pair-rule genes.
56(Wolpert, Ch 5, 2002)
The striped patterns of activity of pair-rule genes inthe Drosophila embryo just before cellularization.
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15_14
(Wilt and Hake, Ch 15, 2004)
Early and late promoters of some eve stripes.
activate
repress
Later enhancer;Autoregulatory region
58(Wilt and Hake, Ch 15, 2004)
The structure of the regulatory module of evestripe 2.
Expression-inhibiting sites
Expression-activating sites
59(Wolpert, L. Ch 5, 2002)
The specification of the second even-skipped (eve)stripe by gap gene proteins.
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15_17
(Wilt and Hake, Ch 15, 2004)
The expression domains of some segment polarity genes.
61(Wilt and Hake, Ch 15, 2004)
Interaction between wingless and engrailed.
62(Wilt and Hake, Ch 15, 2004)
An overview of the BX-C and ANT-C complexes.
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•Positional identity of somites along the antero-posterior axis is specified by Hox gene expression
1. All homeobox genes encode TFs which contain a similar DNA-binding region
≒ 60 amino acids homeodomain helix-turn-helixDNA-binding motif 180 bp homeobox
2. Homeobox genes specifying positional identity alongthe antero-posterior axis originally identified in the fruit fly Drosophila
3. Homeotic transformation one structure replace another
4. Vertebrates - 4 separate clusters of Hox genes(Zebrafish has 6 clusters)
arisen by duplications of the genes within a cluster
64(Wilt and Hake, Ch 15, 2004)
The organization of the BX-C complex.
65(Wilt and Hake, Ch 15, 2004)
The organization of the ANT-C complex.
66(Wilt and Hake, Ch 15, 2004)
Posterior dominance of homeotic selector genes.