1. Note to Instructors The material is kindly contributed by Tim Walston at the University of Wisconsin in Madison About the material: the lecture is about early embryonic development in C. elegans. In it, the author looked at fate specification of the 4 cell embryo by PIE-1, SKN-1 and Wnt signaling. He also presented a detailed description of C. elegans gastrulation. There are total 4 movies accompanying this Power Point Presentation (earlyemb.mov, nancegast.mov, goldgast2.mov and goldgast3.mov). The movies can be found in the links: http://www.wormclassroom.org/movies/edu/earlyemb.mov (7 MB, for slide 2), http://www.wormclassroom.org/movies/edu/earlyemb.mov http://www.wormclassroom.org/movies/edu/nancegast.movhttp://www.wormclassroom.org/movies/edu/nancegast.mov (2.3 MB, for slide 21 & slide 24 left), http://www.wormclassroom.org/movies/edu/goldgast2.movhttp://www.wormclassroom.org/movies/edu/goldgast2.mov (3MB, for slide 24 right), http://www.wormclassroom.org/movies/edu/goldgast3.movhttp://www.wormclassroom.org/movies/edu/goldgast3.mov (4MB, for slide 27)

2. C. elegans Blastomere Specification and Gastrulation By Tim Walston at University of Wisconsin in Madison Insert movie “earlyemb.mov”

3. EMS daughters form two major germ layers mesoderm muscle and pharynx endoderm gut

4. Blastomere Identity in C. elegans progeny make pharynx and epidermis due to induction from MS makes mesoderm (muscle, pharynx) makes gut

5. EMS displays both autonomous and conditional specification Cytoplasmic determinants specify MS fate. Cell-cell inductions specify E fate.

6. Mesoderm is autonomously specified Priess & Thomson (1986) Cell 48:241 AB removedP1 killed Pharynx P2 removed

7. SKN-1 (skin excess) is responsible for mesoderm fate Mutation of skn-1 results in EMS producing muscle and hypodermis Wild-type Pharynx Gut skn-1 mutant Gilbert 7th ed. Fig. 8.45

8. SKN-1 is present in EMS and P2 Modified from Riddle et al. Figure 14.5

9. MEX-1 restricts SKN-1 to MS & P2 Gilbert 5e, Fig. 13.19 Wildtype mex-1 2-cell 4-cell

10. SKN-1 activates transcription of med-1 & med-2 NucleiMED-1::GFP Maduro et al. Molec. Cell (2001) 7:475

11. SKN-1 is present in EMS and P2 Modified from Riddle et al. Figure 14.5

12. PIE-1 (pharyngeal & intestinal excess) represses SKN-1 in P2 Modified from Riddle et al. Figure 14.5 MED-1::GFP Maduro et al. Molec. Cell (2001) 7:475

13. EMS displays both autonomous and conditional specification Cytoplasmic determinants specify MS fate. –SKN-1 activates transcription of med-1 & med-2 Cell-cell inductions specify E fate.

14. No gut; EMS produces 2 MS-like cells Gut and pharynx; EMS makes 1 E cell and 1 MS cell Gilbert 7th ed. Fig. 8.46 EMS requires P2 to make gut No gut; EMS produces 2 MS-like cells

15. Blastomere identity in C. elegans: P2 induces E gut granules normalremove P2move P2 adapted from work by Bob Goldstein ABp ABa EMS P2 EMS ABp ABa ABp ABa EMS P2

16. Wnt signaling activates transcription of certain genes Wnt  -catenin degraded No transcription Wnt  -catenin levels accumulate Transcription Gilbert 7th ed. Fig. 6.24

17. mom-2/Wnt and mom-5/Fz are required for E specification mom = more mesoderm mom-2 mutant Thorpe et al. Cell (1997) 90:695

18. P2 specifies gut through MOM-2 Thorpe et al. Cell (1997) 90:695 Gut

19. adapted from Gilbert 6e, Fig. 8.46 MOM-2/Wnt from P2 signals EMS to induce E MOM-2 = Wnt MOM-5 = Frizzled

20. EMS displays both autonomous and conditional specification Cytoplasmic determinants specify MS fate. –SKN-1 activates transcription of med-1 & med-2 Cell-cell inductions specify E fate. –Wnt signaling from P2 induces EMS by regulating  - catenin levels and activating transcription

21. C. elegans gastrulation Nance et al.Development (2003) 130:5339 Insert movie “nancegast.mov”

22. Gastrulation creates multiple body layers Gilbert 7th ed. Fig. 8.48

23. C. elegans has a small blastocoel Nance & Priess Development (2002) 129:387

24. Ea & Ep begin ingression Lee & Goldstein Development (2003) 130:307 Nance et al.Development (2003) 130:5339 Insert movie “nancegast.mov” Insert movie “goldgast2.mov”

25. Apical constriction draws Ea & Ep into the bloastocoel EaEp P4 Lee & Goldstein Development (2003) 130:307

26. P4 and MS cells actively extend over ingressing cells Nance & Priess Development (2002) 129:387

27. C. elegans gastrulation: Apical constriction and directed migrations Lee & Goldstein Development (2003) 130:307 Insert movie “goldgast3.mov”

28. Ingression of other cell types follow Ea & Ep Nance & Priess Development (2002) 129:387

29. Gastrulation creates multiple body layers Gilbert 7th ed. Fig. 8.48