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Note to Instructors

Note to Instructors. The material is kindly contributed by Tim Walston at the University of Wisconsin in Madison

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Note to Instructors

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  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/nancegast.mov (2.3 MB, for slide 21 & slide 24 left), http://www.wormclassroom.org/movies/edu/goldgast2.mov (3MB, for slide 24 right), http://www.wormclassroom.org/movies/edu/goldgast3.mov (4MB, for slide 27)

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

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

  4. Blastomere Identity in C. elegans makes mesoderm (muscle, pharynx) progeny make pharynx and epidermis due to induction from MS 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 AB removed P1 killed P2 removed Pharynx Priess & Thomson (1986) Cell 48:241

  7. SKN-1 (skin excess) is responsible for mesoderm fate Mutation of skn-1 results in EMS producing muscle and hypodermis skn-1 mutant Wild-type Pharynx Gut 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 Wildtype mex-1 2-cell 4-cell Gilbert 5e, Fig. 13.19

  10. SKN-1 activates transcription of med-1 & med-2 Nuclei MED-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 MED-1::GFP Maduro et al. Molec. Cell (2001) 7:475 Modified from Riddle et al. Figure 14.5

  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. EMS requires P2 to make gut No gut; EMS produces 2 MS-like cells 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

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

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

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

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

  19. MOM-2/Wnt fromP2 signals EMS to induce E MOM-2 = Wnt MOM-5 = Frizzled adapted from Gilbert 6e, Fig. 8.46

  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 b-catenin levels and activating transcription

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

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

  25. Ea Ep P4 Apical constriction draws Ea & Ep into the bloastocoel 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 Insert movie “goldgast3.mov” Lee & Goldstein Development (2003) 130:307

  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

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