1. 17 hours in the life of a zebrafish embryo
Karlstrom and Kane, 1996

2. Blastula Stages 2-cell 4-cell 8-cell 32-cell 512-cell 1000-cell sphere
dome
30% epiboly
4 2/3 hrs
Transcription begins
Kimmel et al., 1995

3. Gastrula Stages shield 50% germ ring 75% 90% bud 10 hr
Kimmel et al., 1995

4. Somitogenesis 3-somite 6-somite 18-somite 26-somite 22 hr
Kimmel et al., 1995

5. Zebrafish development
Karlstrom and Kane, 1996

6. Early development ?

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

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

9. Gastrulation simplified

10. Cell movements during gastrulation
involution
Convergence-
extension
epiboly

11. Mesoderm & endoderm inside
Involution
Mesoderm & endoderm inside
Ectoderm outside

12. Epiboly

13. Convergence-Extension

14. Convergence-extension

15. Convergence-extension

16. Convergence-Extension
Marlow et al., 1998

17. Dorsal-Ventral
Side view
ventral
dorsal
top view

18. Fate maps reflect movement

19. Dorsal-ventral patterning
Shield
(Organizer)

20. The Organizer
Shield
(Organizer)

21. Repeating the Spemann organizer experiment

22. 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

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

24. Summary

25. Questions
How are gradients established and interpreted?
How do cells form distinct compartments?
How do groups of cells arrange into tissues and organs?

26. Neural Tube closure

27. Forming tubes
Navis and Bagnat, 2015

28. References
Feldman B, Gates MA, Egan ES, Dougan ST, Rennebeck G, Sirotkin HI, Schier AF, Talbot WS. (1998). Zebrafish organizer development and germ-layer formation require nodal-related signals. Nature. 395: Karlstrom RO, Kane DA. (1996). A flipbook of zebrafish embryogenesis. Development. 123:461. Keller PJ, Schmidt AD, Wittbrodt J, Stelzer EH. (2008). Reconstruction of zebrafish early embryonic development by scanned light sheet microscopy. Science. 322: Kimmel CB, Ballard WW, Kimmel SR, Ullmann B, Schilling TF. (1995). Stages of embryonic development of the zebrafish. Dev Dyn. 203: Marlow F, Zwartkruis F, Malicki J, Neuhauss SC, Abbas L, Weaver M, Driever W, Solnica-Krezel L. (1998). Functional interactions of genes mediating convergent extension, knypek and trilobite, during the partitioning of the eye primordium in zebrafish. Dev Biol. 203: Navis A, Bagnat M 2015 Developing pressures: fluid forces driving morphogenesis. Current Opinion in Genetics & Development 2015, 32:24–30