1. Biology 624 - Developmental Genetics Lecture #4 – Gastrulation Movements

2. GASTRULATION is a complex series of cell movements that: --rearranges cells, giving them new neighbors --results in the formation of 3 GERM LAYERS that will form the subsequent embryo: ectoderm, endoderm and mesoderm --forms the main body axes of the embryo (they were specified earlier but not formed)

3. 16h 0h6h 1.5h cleavage GASTRULATION organogenesis * 4.5d 24h first cleavage GASTRULATION segmentation * organogenesis 6.5d 20d14d implantation 4d 24h cleavage GASTRULATION segmentation * organogenesis 7d 21d 0h10h 2.5h24h cleavageGASTRULATION organogenesis * dorsal closure 5h 2.8h cleavage GASTRULATION segmentation * organogenesis 24h 48-72h 10h 18h 3.5h cleavageGASTRULATIONneurulation * organogenesis 36h

4. Invagination- the infolding of a region of cells

5. Involution- the inturning of an expanding outer layer of cells

6. Ingression- the migration of individual cells from surface to interior

7. Delamination- the splitting of one sheet of cells into two parallel sheets of cells

8. Epiboly- the movement of epithelial sheets that spread as a unit to cover the embryo

9. Convergent extension- the lengthening of a group of cells in the long axis while shortening in the perpendicular axis Convergent Extension

10. Cell Movements during Convergent Extension in Zebrafish

11. Fate map of the fly embryo at cellular blastoderm stage

12. Early Gastrulation in Drosophila

13. Figure 9.40 Gastrulation in Drosophila

14. Schematic Representation of Mid-Gastrulation in Drosophila

15. Germ Band Extension in Drosophila

16. GERM BAND EXTENDED PROCESSES: --organogenesis – e.g. nervous system forms by neuroblast ingression from ectoderm --segmentation – A-P segment unique identity set up --imaginal disc specification – cells set aside that will survive pupation

17. Germ Band Retraction in Drosophila

18. Gastrulation in Drosophila - lateral view

19. Gastrulation in Drosophila – Vade Mecum Movie

20. (Gryzik and Muller, 2004) WildType Stage 7Stage 9Stage 8 early gastrulation extended germ band mid- gastrulation Neurotactin, membrane marker Twist, mesoderm marker Mutant FGF Signaling is Critical to Gastrulation in Drosophila

21. (Leptin and Affolter, 2004) Model for FGF signaling in Drosophila gastrulation

22. Fate Map of the Blastula of the Frog Xenopus laevis

23. Cell Movements During Frog Gastrulation - Early

24. Cell Movements During Frog Gastrulation - Mid

25. Cell Movements During Frog Gastrulation - Late

26. Epiboly of the Ectoderm Is Accomplished by Cell Division and Intercalation

27. Convergent extension- the lengthening of a group of cells in the long axis while shortening in the perpendicular axis Convergent Extension

28. Movie of Xenopus Gastrulation

29. Xenopus Gastrulation – Vade Mecum

30. Fibronectin and Amphibian Gastrulation Normal FN block peptides

31. Blastocoel Roof Explants deposit matrix that directs the migration of mesoderm from Nagel et al, 2004

32. FGF Expression during avian gastrulation and the putative role of Sprouty/spred from Keller, 2005

33. Wnt Signaling Mediates Two Distinct Aspects of Gastrulation (Huelsken and Birchmeier, 2001) Convergent Extension Tissue Separation

34. (Habas et al, 2003) Amphibian Convergence Extension Requires Non- canonical Wnt Signaling

35. CE in Zebrafish Requires Oriented Cell Division (Gong et al, 2004) This is the dorsal ectoderm of embryos in gastrulation, Xdd is a Disheveled mt, animal pole is up

36. WTspt- papc Expression is Defective in spt Mutant Embryos

37. At the end of gastrulation-- --the basic body plan is set up --the three germ layers have formed and will produce all embryonic structures except the germline

38. ECTODERM-- --skin, nervous system, neural crest MESODERM-- --muscle, bones, blood and vessels, kidney, gonads, connective tissue ENDODERM-- --gut, liver, lungs, pancreas

40. C. elegans embryogenesis 16h0h6h1.5h cleavageGASTRULATIONorganogenesis *

41. Drosophila embryogenesis 0h10h2.5h24h cleavageGASTRULATION organogenesis * dorsal closure

42. Frog embryogenesis 36h 18h3.5h cleavageGASTRULATIONneurulation * organogenesis

43. Zebrafish embryogenesis 5h2.8h cleavage GASTRULATION segmentation * organogenesis 24h 48-72h 10h

44. Chick embryogenesis 4d24h cleavage GASTRULATION segmentation * organogenesis 7d 21d Egg laid

45. Mouse embryogenesis 4.5d24h first cleavage GASTRULATION segmentation * organogenesis 6.5d 20d14d implantation