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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. 17 hours in the life of a zebrafish embryo. Blastula Stages. 4-cell. 8-cell. 32-cell. 1- cell. 2-cell. 512-cell. 1000-cell. sphere. 30% epiboly.

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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. 17 hours in the life of a zebrafish embryo

  3. 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

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

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

  6. Zebrafish development

  7. Early development ?

  8. Three germ layers Side view Skin & nervous system Muscle & cardiovascular Gut and liver top view

  9. Gastrulation simplified

  10. Involution Mesoderm & endoderm inside Ectoderm outside

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

  12. Involuting cell movements during gastrulation

  13. Convergence-Extension convergence extension

  14. Convergence-extension

  15. Cell fates dorsal dorsal Cross section Dorsal view

  16. Convergence-extension

  17. Convergence-extension

  18. Convergence-extension

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

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

  21. Signaling from the YSL

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

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

  24. Dorsal-ventral patterning shield

  25. Bozozok

  26. The Organizer

  27. 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

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

  29. Bmp regulates cell movement High Bmp Low Bmp

  30. Summary

  31. Xenopus egg

  32. Xenopus egg

  33. Cleavage of Xenopus embryo Animal pole view Midblastula transition (MBT) occurs at 12th cleavage = start of zygotic transcription

  34. Gastrulation in Xenopus vegetal pole view

  35. Fate map

  36. Cross sectional view

  37. Gastrulation Gastrulation begins dorsally and spreads ventrally

  38. Gastrulation in Xenopus

  39. Gastrulation in Xenopus

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

  41. Nieuwkoop’s experiment 1967

  42. Nieuwkoop’s experiment 1967

  43. Nodals Xnrs induce mesoderm (and endoderm)

  44. Why are the Xnrs expressed vegetally?

  45. VegT VegT is a transcription factor

  46. VegT

  47. VegT VegT activates the transcription of the Xnr genes

  48. VegT

  49. Formation of the dorsal side

  50. Formation of the dorsal side

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