2. Drosophila axis detemination; dorsal/ventral polarity How are the embryonic axes set up? How does the embryonic dorsal-ventral axis get translated into differentiation of different tissue types?

3. Wieschaus and Nüsslein-Volhard looked for mutants that affect the fly body plan wildtype

4. Screen for developmental mutants (Drosophila) Lethal hits = 100% (essential genes - ca. 5.000) (efficiency of mutagenesis = number of hits per gene) embryonal-lethal mutants zygotic mutants 25 % with morphological defects3 % - segmentation defects (AP) 0.5 % - tissue types defective (DV) 0.5 % female-sterile mutants8 % 100 % with effects on embryogenesis2 % (= maternal-effect mutants) - antero-posterior pattern0.4 % - dorso-ventral pattern0.3 % ca. 2% of all genes involved in embryo pattern formation (male-sterile mutants) (ca. 100 of >15.000 protein-encoding genes, only 5.000 essential genes)

5. Maternal-effect mutations Genes expressed during oogenesis (= before fertilization) All progeny of heterozygous mother normal All progeny affected only if mother homozygous mutant Zygotic mutations Genes expressed during embryogenesis (= after fertilization) Only genetically mutant embryos affected (25% of progeny of heterozygous mother)

6. Genes identified in a famous screen for Drosophila mutants with embryo patterning defects

7. Gurken protein specifies the Anterior-Posterior axis of the Drosophila embryo during oogenesis (Similar to EGF)

8. Localized maternal mRNA sets up anterior and posterior poles

9. Gurken also signals dorsal pole formation during oogenesis follicle cells anteriorposterior AP V D D V - + - microtubules 71-68 10A gurken expression in the oocyte 10A gurken expression in the oocyte 1-6 migration of nucleus + - - 8 oocyte nucleus

10. Expression of the Gurken Message and Protein Between the Oocyte Nucleus and the Dorsal Anterior Cell Membrane

11. D ORSO-VENTRAL P ATTERN F ORMATION follicle cells Oocyte pipe expression Ventral follicle cell Pipe (Golgi?) X X Nucleus Wind (ER?) X X X X mod. from van Eeden & St.Johnston Gurken = Epidermal Growth Factor (EGF) Torpedo = EGF receptor (in follicle cells)

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

13. Dorsal-Ventral fate map

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

15. Toll Tl - membrane receptor cactus cact - cytoplasmic inhibitor of Dorsal nuclear translocation dorsal dl - transcription factor (morphogen) Zygotic mutations tube - cytoplasmic protein pelle - ser/thr protein kinase Maternal effect mutations ndl, pipe, wbl gd, snk, ea - serine proteases spz - ligand Dorsal protein dorsal RNA Toll protein Spätzle protein Dorsal protein nudel, pipe, wbl amnio serosa dorsal ectoderm neuro- ectoderm mesoderm Dl nuclear protein Dorso-ventral pattern formation

16. Wild type ventralized dorsal mutant cactus mutant dorsalized T1 T2 T3 A1A2 A3A4A5 A6 A7 A8 Dorso-ventral pattern formation dorsal ventral

17. Wild type toll mutant cactus mutant Translocation of Dorsal protein into ventral nuclei but not lateral or dorsal nuclei

18. Generation of Dorsal-Ventral Polarity in Drosophila

20. Wild type toll mutant Inject wild-type cytoplasm mesoderm neuro-ectoderm (denticle belts) dorsal ectoderm Dorso-ventral pattern formation pivotal role of Toll pathway into toll mutant eggs dorsalized local rescue ventral dorsal polarity reversal

21. Conserved pathway for regulating nuclear transport of transcription factors in Drosophila and mammals

24. Action of Dorsal protein in ventral cells

25. High affinity for promoter, Not much Dorsal needed to activate

26. Action of Dorsal protein in ventral cells Lower affinity for promoter, More Dorsal needed to activate

27. twist dpp Dorsal protein dorsal RNA Toll protein Spätzle protein Dorsal protein nudel, pipe, windbeutel Dorso-ventral pattern formation: summary 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

28. Gastrulation in Drosophila

30. Schematic representation of gastrulation in Drosophila

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

34. Patterns mesoderm in vertebrates Patterns ectoderm in Drosophila

35. Anterior-posterior patterning in Drosophila

36. Maternal effect mutations

37. Zygotic effect mutations

38. (receptor) (required to produce ligand from Trunk)