1. Drosophila dorsal/ventral axis detemination
How are different tissue types specified at distinct positions on the embryonic dorsal-ventral axis?

2. Cell fate specification at the blastoderm stage
amnio-serosa
dorsal
dorsal ectoderm
neuro-ectoderm
mesoderm
ventral
fate map
mesoderm formation

3. Dorsal-Ventral fate map
Figures\Chapter09\DevBio7e09332.jpg

4. Genes identified in a famous screen for Drosophila mutants with embryo patterning defects
Torpedo
Gurken

5. Localized maternal mRNA sets up anterior and posterior poles
Figures\Chapter09\DevBio7e09112.jpg

6. Gurken protein specifies the Anterior-Posterior axis of the Drosophila embryo during oogenesis
Figures\Chapter09\DevBio7e09111.jpg
(Similar to EGF)

7. Gurken also signals dorsal pole formation during oogenesis
oocyte nucleus D D
10A
1-6 7 8 A + P -
gurken expression in the oocyte
1-6 -
anterior
posterior V
Gurken mRNA also relocalizes to anterior dorsal side. V
follicle cells
Microtubules reorient, nucleus migrates to minus end
microtubules 8
gurken expression in the oocyte
10A - + -

8. Localization of the Gurken mRNA and protein between the oocyte nucleus and the dorsal anterior cell membrane
Figures\Chapter09\DevBio7e09361.jpg

9. Gurken signaling inhibits production of an extracellular signal (Spätzle) by follicle cells
Torpedo = EGF receptor
(in follicle cells)
Gurken = Epidermal Growth Factor (EGF)
Oocyte
pipe
expression X
Ventral follicle cell
Pipe (Golgi?) X
Wind (ER?) X
Nucleus
modified from van Eeden & St.Johnston

10. Maternal effect mutations in dorso-ventral patterning
Somatic (follicle cells)
ndl, pipe, wbl
gd, snk, ea - serine proteases
Spätzle spz - ligand
Germline (nurse cells)
nudel, pipe, wbl
dorsal RNA
Toll protein
Spätzle protein
Dorsal protein
Toll
Tl - membrane receptor
tube - cytoplasmic protein
pelle - ser/thr protein kinase
Dorsal protein
amnio serosa
cactus
cact - cytoplasmic inhibitor of Dorsal nuclear translocation
dorsal ectoderm
neuro-ectoderm
dorsal
dl - transcription factor (morphogen)
mesoderm Dl
nuclear protein

11. dorsal and cactus mutants (maternal germline effect)
dorsal mutant
cactus mutant
Wild type
ventral A8 T1 T2 A7
dorsalized
ventralized T3 A1 A2 A3 A4 A5 A6

12. Translocation of Dorsal protein into ventral nuclei but not lateral or dorsal nuclei
Figures\Chapter09\DevBio7e09340.jpg
Wild type toll mutant cactus mutant

13. Generation of Dorsal-Ventral polarity in Drosophila
Figures\Chapter09\DevBio7e09351.jpg

14. Generation of Dorsal-Ventral Polarity in Drosophila
Figures\Chapter09\DevBio7e09352.jpg

15. Inject wild-type cytoplasm
The Toll pathway in dorso-ventral pattern formation
Inject wild-type cytoplasm
into toll mutant eggs
toll mutant
ventral
dorsalized
local
rescue
dorsal ectoderm
Wild type
dorsal
neuro-ectoderm
(denticle belts)
mesoderm
polarity reversal

16. Conserved pathway for regulating nuclear transport of transcription factors in Drosophila and mammals
Figures\Chapter09\DevBio7e09381.jpg

17. Cells with highest nuclear Dorsal levels become mesoderm
Figures\Chapter09\DevBio7e09382.jpg

18. Zygotically expressed genes
Figures\Chapter09\DevBio7e09390.jpg

19. Action of Dorsal protein in ventral cells
Figures\Chapter09\DevBio7e09400.jpg

20. Action of Dorsal protein in ventral cells
High affinity for promoter,
Not much Dorsal needed to activate
Figures\Chapter09\DevBio7e09400.jpg

21. Action of Dorsal protein in ventral cells
Lower affinity for promoter,
More Dorsal needed to activate
Figures\Chapter09\DevBio7e09400.jpg

22. Zygotically expressed genes
Figures\Chapter09\DevBio7e09390.jpg

23. Action of Dorsal protein in ventral cells
Snail repression of rhomboid creates domains with distinct gene expression patterns
Figures\Chapter09\DevBio7e09400.jpg

24. Dorso-ventral pattern formation: summary
twist
dpp
Dorsal protein
dorsal RNA
Toll protein
Spätzle protein
nudel, pipe, windbeutel
oocyte nucleus dorsal
> repression of ventral fate
in dorsal follicle cells
ventral production of ligand
> activation of Toll receptor
> graded nuclear uptake
of Dorsal morphogen
> regulation of zygotic
target gene expression
> cell fates along DV axis

25. Use of a similar regulatory system to pattern insects and vertebrates

26. Patterns ectoderm in Drosophila
Patterns mesoderm in vertebrates

27. Gastrulation in Drosophila
Figures\Chapter09\DevBio7e09051.jpg

28. Figures\Chapter09\DevBio7e09052.jpg

29. Schematic representation of gastrulation in Drosophila
Figures\Chapter09\DevBio7e09061.jpg

30. Figures\Chapter09\DevBio7e09062.jpg

31. Figures\Chapter09\DevBio7e09053.jpg