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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. Blastula Stages. 4-cell. 8-cell. 32-cell. 1- cell. 2-cell. 512-cell. 1000-cell. sphere. 30% epiboly. dome. 4 2/3 hrs. Transcription begins. - PowerPoint PPT Presentation
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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
Blastula Stages
1-cell 2-cell 4-cell 8-cell 32-cell
512-cell 1000-cell
Transcription begins
sphere dome 30% epiboly
4 2/3 hrs
Gastrula Stages
50% germ ring shield
75% 90% bud
10 hr
Somitogenesis
3-somite 6-somite 18-somite
26-somite
22 hr
Early development
?
Three germ layers
Side view
top view
Skin & nervous system
Muscle & cardiovascular
Gut and liver
Animal pole
Vegetal pole
Gastrulation simplified
Involution
Mesoderm & endoderm insideEctoderm outside
Dorsal-Ventral
Side view
top view
dorsal
dorsal
ventral
ventral
Involuting cell movements during gastrulation
Convergence-Extension
convergence
extension
Convergence-Extension
Cell fates
Dorsal viewCross section
dorsal
dorsal
Convergence-extension
Slow dorsal migration
Convergence Extension
Convergence-extension cell movements
Slow dorsal migration
Fast dorsal migration
Convergence Extension
Convergence-extension cell movements
Slow dorsal migration
Fast dorsal migration
Convergence Extension
Packing, inhibition of protrusions
Convergence-extension cell movements
Slow dorsal migration
Fast dorsal migration
Packing, inhibition of protrusions
Intercalation
Convergence Extension
Convergence-extension cell movements
Summary
Formation ofgerm layers
Convergence-extension
Formation oftissue boundaries
Cleavage
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”
Movie 10512-cell
Divisions symmetric prior to 512-cell
Divisions asymmetric after 512-cell
Radial waves just after 512-cell
Early Development Movies
Early Development Movies
Animal view Vegetal view
dorsal dorsal
dorsaldorsal
dorsal
Early Development Movies
Movie 2
Early Development Movies
Non-moving nucleus
Fast moving nucleus
Movie 3
Early Development Movies
Early Development Movies
Animal view Lateral view
Movie 8 & 9
Early Development Movies
dorsal
Movie 14
Early Development Movies
Movie 16
Two major Questions
• How are the germ layers established?
• What determines polarity?
Signaling from the YSL
Nodal mutant
wild-type sqt;cyc -/-
No endodermNo head & trunk mesoderm
Movie 6
Normally ~1550 cells internalize; in MZoep ~60 internalize
Germ layer patterning
YSL signal Sqt and Cyc Endoderm Head and Trunk Mesoderm
Tail mesoderm
Dorsal-ventral patterning
Shield(Organizer)
Bozozok
The Organizer
Shield(Organizer)
Bmp promotes ventral fates
Organizer signals are BMP binding factors: Noggin, Chordin
Bmp signals promote ventral fates (skin, ventral mesoderm) and oppose dorsal fates (neural, dorsal mesoderm)
Mutants in the dorsal-ventral pathway
Snailhouse (snh)= bmp7 mutant
Chordino (din)= chordin mutant
Bmp regulates cell movement
High Bmp Low Bmp
Summary
