1. Early Development: Invertebrates  Brief overview of early developmental themes  Early development of Sea Urchin  Early development of Caenorhabditis elegans

2. Invertebrates? So what?  Very easy to study  Genetics and molecular events are highly conserved

3. Cleavage initiation  Maternal Factors  Mitosis Promoting Factor  No Gaps at first  Mid Blastula transition- Gene activation from Zygote nucleus.

4. Cell and nuclear division  Karyokinesis  Cytokinesis  Centrioles and axis determination.

5. Patterns of Cell division

6. Gastrulation

7. Cell specification and Axis formation  Cell-cell signaling or acquisition of cellular factors  Bound to egg cytoplasm  Actively transported  Associate with centrioles

8. Sea Urchin: Initial Cleavage

9. Fate Mapping of Sea Urchin embryo

10. Global regulatory networks  Maternal Factors  Disheveled and  -catenin   -catenin and TCF- Micromere differentiation

11. Double Negative Gate GeneA Gene B Gene D Gene C Gene E Gene F

12. Double Negative Gate: Micromere Pmar1 HesC Thr Alx1 Ets Delta Otx/  -catenin

13. Double Negative Gate: Veg 2 cell Pmar1 HesC Thr Alx1 Ets Delta

14. Specification of Vegetal Cells  Wnt signaling; Early Signal (ES); Delta (Notch)   -catenin  Blimp1  wnt  autocrine; Endoderm differentiation  Pmar1 and HesC regulate ES, which leads to mesoendoderm differentiation.  Delta  Mesoderm differentiation.

15. Axis specification  Animal/Vegetal= Anterior/Posterior axis  Nodal regulates Oral/Aboral axis

16. Gastrulation  Blastula hatches from Fertilization envelope.  Skeletogenic mesenchyme ingression.  Vegetal plate involutes beginning invagination.

17. Gastrulation

20. Caenorhabditis elegans

21. C. elegans and Initial Cleavage

22. Anterior-Posterior Axis  Sperm Pronucleus location  Cyk-4 activates GTPases  relocates PAR proteins to anterior  P-granules: Ribonucleoprotein complex  RNA helicases  Poly A polymerases  Translation initiators

23. Dorsal-Ventral/Left-Right Axis formation

24. Specification: Autonomous  Maternal cytoplasmic factors  SKN-1: EMS fate determination.  PAL-1: Differentiation of P2 somatic descendents  PIE-1: placed into P blastomeres via PAR-1, inhibits SKN-1 and PAL-1 in P cells.

25. Specification: Conditional  Cell-cell signaling (Juxtacrine)  Paracrine signaling

26. Gastrulation