2. Life as a worm-- the nematode C. elegans

3. Life as a worm-- the nematode C. elegans

4. Hermaphrodites do it by themselves

5. An entire C. elegans hermaphrodite worm consists of exactly 959 cells
EVERY SINGLE TIME,
allowing one to follow the cell lineage.

7. Most lineages do not consist of single tissue types
but the germline and the gut
both arise from single founder cells

8. Most lineages do not consist of single tissue types
but the germline and the gut
both arise from single founder cells

9. the secret of embryonic development
Within this lineage is
the secret of embryonic development

10. Even cell death is programmed into the lineage
C. elegans was used to identify
the machinery that regulates
programmed cell death in ALL animals

11. The Nobel Prize in Physiology or Medicine 2002
"for their discoveries concerning ’
genetic regulation of organ development
and programmed cell death'"
Sidney Brenner
H. Robert Horvitz
John Sulston

12. One mechanism is through asymmetric segragation of determinants
How can lineage control cell fate?
One mechanism is through
asymmetric segragation of determinants

13. segregated into one cell at the 16-cell stage. That cell is the
A determinant
within the P granules
is asymmetrically
segregated into one cell
at the 16-cell stage.
That cell is the
progenitor of the
germline!
DNA
P granules
Gilbert 8.33

14. In par mutants P granules are found in ALL daughter cells
wildtype
par-3 mutant

16. Mutations can alter lineages in many ways

17. Changes in the pattern of cell division
Example #1- lin-22
Changes in the pattern of cell division

18. Changes in the pattern of cell division
Example #1- lin-22
Changes in the pattern of cell division
lin-22 is homologous to the Drosophila pair-rule gene hairy

19. Changes in the timing of cell division
Example #2- lin-14
Changes in the timing of cell division L1 L2 L1 L2 L1 L1 L1

20. The vulva provides a great model for how cell interactions shape
cell lineage!
Vulva

22. Cell ablations help define the key players

23. All cells are created equal
(or, the road to fame is paved with dead bodies)

27. The vul mutations helped define the RTK-Ras pathway,
which is mutationally activated
in about half of all human tumors

29. Does this remind you of anything we learned earlier?