Gastrulation

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Gastrulation
It is not birth, marriage or death, but
gastrulation, which is truly the most important
event in your life Lewis Wolpert
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17 hours in the life of a zebrafish embryo
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Blastula Stages
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Gastrula Stages
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Somitogenesis
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Zebrafish development
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Early development
?
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Three germ layers
Side view
Animal pole
Skin nervous system
Muscle cardiovascular
Gut and liver
Vegetal pole
top view
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Gastrulation simplified
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Involution
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Dorsal-Ventral
Side view
top view
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Involuting cell movements during gastrulation
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Convergence-Extension
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Convergence-Extension
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Convergence-extension
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Cell fates
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Convergence-extension
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Convergence-extension
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Convergence-extension cell movements
Slow dorsal migration
Convergence
Extension
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Convergence-extension cell movements
Slow dorsal migration
Fast dorsal migration
Convergence
Extension
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Convergence-extension cell movements
Slow dorsal migration
Fast dorsal migration
Packing, inhibition of protrusions
Convergence
Extension
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Convergence-extension cell movements
Slow dorsal migration
Fast dorsal migration
Packing, inhibition of protrusions
Intercalation
Convergence
Extension
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Convergence-extension cell movements
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Summary
Convergence- extension Formation of tissue
boundaries
Cleavage
Formation of germ layers
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Early Development movies
Histone 2B
GFP
Made RNA Injected embryos at the 1-cell
stage Imaged with Digital Scanned Laser Light
Sheet Fluorescence Microscopy (capture whole
embryo image every 60-90s) Produced a digital
embryo
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Early Development Movies
Divisions symmetric prior to 512-cell Divisions
asymmetric after 512-cell Radial waves just
after 512-cell
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Early Development Movies
dorsal
dorsal
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Early Development Movies
Slow-moving nucleus
Fast moving nucleus
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Early Development Movies
dorsal
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Early Development Movies
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Two major Questions

• How are the germ layers established?
• What determines polarity?

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Signaling from the YSL
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Nodal mutant
sqtcyc -/-
wild-type
No endoderm No head trunk mesoderm
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Normally 1550 cells internalize in MZoep 60
internalize
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Germ layer patterning
YSL signal Sqt and Cyc
Endoderm Head and Trunk Mesoderm
Tail mesoderm
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Dorsal-ventral patterning
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Bozozok
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The Organizer
Shield (Organizer)
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Bmp promotes ventral fates
Bmp signals promote ventral fates (skin, ventral
mesoderm) and oppose dorsal fates (neural, dorsal
mesoderm)
Organizer signals are BMP binding factors
Noggin, Chordin
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Mutants in the dorsal-ventral pathway
Snailhouse (snh) bmp7 mutant
Chordino (din) chordin mutant
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Bmp regulates cell movement
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Summary