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Gastrulation

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

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  1. Gastrulation It is not birth, marriage or death, but gastrulation, which is truly the most important event in your life Lewis Wolpert

  2. 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

  3. Gastrula Stages shield germ ring 50% 75% 90% bud 10 hr

  4. Somitogenesis 3-somite 6-somite 18-somite 26-somite 22 hr

  5. Early development ?

  6. Three germ layers Side view Animal pole Skin & nervous system Muscle & cardiovascular Gut and liver Vegetal pole top view

  7. Gastrulation simplified

  8. Involution Mesoderm & endoderm inside Ectoderm outside

  9. Dorsal-Ventral ventral dorsal ventral dorsal Side view top view

  10. Involuting cell movements during gastrulation

  11. Convergence-Extension convergence extension

  12. Convergence-Extension

  13. Cell fates dorsal dorsal Cross section Dorsal view

  14. Convergence-extension

  15. Convergence-extension cell movements Slow dorsal migration Convergence Extension

  16. Convergence-extension cell movements Slow dorsal migration Fast dorsal migration Convergence Extension

  17. Convergence-extension cell movements Packing, inhibition of protrusions Slow dorsal migration Fast dorsal migration Convergence Extension

  18. Convergence-extension cell movements Packing, inhibition of protrusions Intercalation Slow dorsal migration Fast dorsal migration Convergence Extension

  19. Summary Convergence- extension Formation of tissue boundaries Cleavage Formation of germ layers

  20. 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”

  21. Early Development Movies 512-cell Movie 10 Divisions symmetric prior to 512-cell Divisions asymmetric after 512-cell Radial waves just after 512-cell

  22. Early Development Movies Animal view Vegetal view dorsal dorsal dorsal dorsal dorsal

  23. Early Development Movies Movie 2

  24. Early Development Movies Non-moving nucleus Fast moving nucleus

  25. Early Development Movies Movie 3

  26. Early Development Movies Animal view Lateral view

  27. Movie 8 & 9

  28. Early Development Movies dorsal

  29. Movie 14

  30. Early Development Movies

  31. Movie 16

  32. How are the germ layers established? What determines polarity? Two major Questions

  33. Signaling from the YSL

  34. Nodal mutant sqt;cyc -/- wild-type No endoderm No head & trunk mesoderm

  35. Movie 6 Normally ~1550 cells internalize; in MZoep ~60 internalize

  36. Germ layer patterning YSL signal Sqt and Cyc Endoderm Head and Trunk Mesoderm Tail mesoderm

  37. Dorsal-ventral patterning Shield (Organizer)

  38. Bozozok

  39. The Organizer Shield (Organizer)

  40. 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

  41. Mutants in the dorsal-ventral pathway Snailhouse (snh) = bmp7 mutant Chordino (din) = chordin mutant

  42. Bmp regulates cell movement High Bmp Low Bmp

  43. Summary

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