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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.
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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
Gastrula Stages shield germ ring 50% 75% 90% bud 10 hr
Somitogenesis 3-somite 6-somite 18-somite 26-somite 22 hr
Three germ layers Side view Animal pole Skin & nervous system Muscle & cardiovascular Gut and liver Vegetal pole top view
Involution Mesoderm & endoderm inside Ectoderm outside
Dorsal-Ventral ventral dorsal ventral dorsal Side view top view
Convergence-Extension convergence extension
Cell fates dorsal dorsal Cross section Dorsal view
Convergence-extension cell movements Slow dorsal migration Convergence Extension
Convergence-extension cell movements Slow dorsal migration Fast dorsal migration Convergence Extension
Convergence-extension cell movements Packing, inhibition of protrusions Slow dorsal migration Fast dorsal migration Convergence Extension
Convergence-extension cell movements Packing, inhibition of protrusions Intercalation Slow dorsal migration Fast dorsal migration Convergence Extension
Summary Convergence- extension Formation of tissue boundaries Cleavage Formation of germ layers
Early Development movies Histone2B 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”
Early Development Movies 512-cell Movie 10 Divisions symmetric prior to 512-cell Divisions asymmetric after 512-cell Radial waves just after 512-cell
Early Development Movies Animal view Vegetal view dorsal dorsal dorsal dorsal dorsal
Early Development Movies Movie 2
Early Development Movies Non-moving nucleus Fast moving nucleus
Early Development Movies Movie 3
Early Development Movies Animal view Lateral view
Early Development Movies dorsal
How are the germ layers established? What determines polarity? Two major Questions
Nodal mutant sqt;cyc -/- wild-type No endoderm No 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)
The Organizer Shield (Organizer)
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
Mutants in the dorsal-ventral pathway Snailhouse (snh) = bmp7 mutant Chordino (din) = chordin mutant
Bmp regulates cell movement High Bmp Low Bmp