Chapter 8 - Early Development in invertebrates

1. Chapter 8 - Early Development in invertebrates • The next chapters examine early development in several models, including invertebrates (Ch. 8-9) amphibians (ch 10) and then vertebrates (ch. 11) 1 frog egg becomes ______ cells in __ hours! Fig. 8.1

2. General Animal Development 2. ___________- Extensive cell rearrangement to form endo-, ecto- and meso-derm • _____- One cell is subdivided into many cells to form a blastula 4. ________________- produce germ cells (sperm/egg) Note: Somatic cells denote all non-germ cells 3. ___________- Cells rearranged to produce organs and tissue a. Cleavage Recall from lecture 1

3. a. Cleavage How does egg undergo cleavage without increasing it’s ____? • Answer- it abolishes ___ and ___ phases of ________. • Do you need a cell cycle primer?? • Four cell cycle phases • M- _________ • G1- ________ • __- DNA Synthesis • ___- Gap 2

4. a. Cleavage Reminder- mitosis occurs in __ phase, DNA replication in ____________ From Mol. Biol of the Cell by Alberts et al, p864

5. a. Cleavage • _________________ (cdk, cdc) drive the cell cycle • But ________ (e.g cyclin A, B…) regulate cdk (cdc) activity MPF Example- ___________ __________ _________ (MPF= cyclin B+cdc2)

6. a. Cleavage Again, how does egg undergo cleavage without increasing it’s size? • Answer- it abolishes __ and___ phases of cell cycle M phase Cyclins are _________ in eggs Cyclins are _________ S phase

7. a. Cleavage What actually drives the _______process? • Answer- Two processes- • 1. _________________ (mitotic division of the nucleus) • The mitotic spindle (microtubules composed of tubulin) does this • 2. __________ (mitotic division of the cell) • ___________ “pinch off” (microfilaments composed of actin) Fig. 8.3 _____________ prevents cytokineses

8. General Animal Development 2. __________- Extensive cell rearrangement to form endo-, ecto- and meso-derm • Cleavage- One cell is subdivided into many cells to form a blastula 4. Gameteogenesis- produce germ cells (sperm/egg) Note: Somatic cells denote all non-germ cells 3. Organogenesis- Cells rearranged to produce organs and tissue b. Gastrulation Recall from lecture 1

9. b. Gastrulation 1 2 3 Gastrulation- cells of blastula are dramatically _______________ • Three germ layers are produced Five types of _____________

10. b. Gastrulation 4 5 Gastrulation Five types of movements

11. b. Gastrulation Axis formation • Three axes must be determined- • ___________________ (head-tail) • ________________ (back-belly) • ______________ (right side-left side) Fig. 8.7

12. Now let’s take a look at one beast- the ____________ 1. Cleavage • Cleavages 1 and 2 are through ______________ poles 1 2 • Cleavage 8_______ (animal pole) plus 4_________ and 4____________ (vegetal pole) 4 3 • Cleavage 3 results in four ________ and four ______cells Fig. 8.8

13. Fig. 8.9 • Post cleavage 5 Cell fate map

14. _______________ signal other cells via _________________ to influence fate • Micromere cell fate is _____________- these become ____________ tissue if placed in a dish • All other cells have ____________specification Example- Transplant micromeres to animal pole at ___________ stage • Micromeres cause a second __________ • Animal pole cells become _______cells Fig. 8.13

15. Sea urchin (continued) 2. Gastrulation ________ Late _______ Egg Later stages Note-micromeres produce ______ _________ which will become larval _______ Fig. 8.16 Sea urchin development

16. How do __________ cells know to migrate inside ________? Answer- changing cell ________________ ___________ Fig. 8.19 Extracellular matrix Basal _____ ___________ 98% decrease in ________ affinity 100-fold increase in _____________ affinity Primary __________ cell

17. How does __________ occur? • Terms- • Invagination region is called _________ • Opening created is called the ___________ Answer- swelling of inner _______ layer _______ cells secrete chondroitin sulfate proteoglycan, causing inner layer to swell and cause _________ ________ Inner layer Outer layer

18. Now let’s take a look at another creature- the nematode C. elegans • ___cells at maturity • ____ long • Produces eggs and sperm (___________) • Transparent • __ hours from egg to hatch • Entire genome sequences- ___________ genes What a great model! 1mm

19. C. elegans 1. Cleavage Oviduct Germ cells undergo ______, then begin meiosis as travel down _________ Cleavage Mature eggs passes through the ________ on the way to the _______

20. C. elegans 1. Cleavage • Cleavages 1 produces _______ cell (AB) and ______ cell (P1) 3 1 2 Fig. 8.42 • Remaining cleavages result in a __________ cell and more founder cells • Cleavage 2 results in three _______ cells and one ______ cell (P2)

21. C. elegans How is the ____________ _______ axis determined? • Answer- ___________- ribonucleoprotein complexes • ________ always stay associated with the “P” cell 1 3 What directs the __________? • ____proteins- these specify ______, cell ________ and cytoplasmic __________. 5 Fig. 8.43

22. C. elegans 1. Cleavage • P1 develops ________________ • AB does not (thus is ____________) • What drives P1 lineage? • P granules? No, these do not enter________! • Other possibilities • _____- a bZIP family transcription factor that control EMS cell fate • ______ - a transcription factor required for P2 lineage • ______- inhibits SKN-1 and PAL-1 in P2

23. Does P2 dictate fate of _________ cells? Yes- P2 produces a signal that tells ABp to only _______ and ________ cells, not pharynx like ABa • _____ is the receptor on ABp, and _____ is the ligand on P2 GLP-1 is a ____family protein APX-1 is a _____family protein An example of _________ signaling