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Gastrulation - Drosophila

Figure 23.14 Homologous Pathways Specifying Neural Ectoderm in Protostomes ( Drosophila ) and Deuterostomes ( Xenopus ) D/V. Gastrulation - Drosophila. http://www.flybase.org/data/images/Animation/ AND Course Site (Movies). 4 STAGES OF ESTABLISHING DORSAL/VENTRAL – 4 SEQUENTIAL PATHWAYS +.

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Gastrulation - Drosophila

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  1. Figure 23.14 Homologous Pathways Specifying Neural Ectoderm in Protostomes (Drosophila) and Deuterostomes (Xenopus) D/V

  2. Gastrulation - Drosophila http://www.flybase.org/data/images/Animation/ AND Course Site (Movies)

  3. 4 STAGES OF ESTABLISHING DORSAL/VENTRAL – 4 SEQUENTIAL PATHWAYS + STAGE PATHWAY PATHWAY OUTCOME • RTK pathway Sets follicle cell D/V state • Proteolytic cascade Sets embryos’ cell D/V state • Toll/Cactus/Doral Sets nuclear D/V state • Dorsal TF thresholds Diff. pathway per D/V address

  4. 4 STAGES OF ESTABLISHING DORSAL/VENTRAL – 4 SEQUENTIAL PATHWAYS + STAGE PATHWAY PATHWAY OUTCOME • RTK pathway Sets follicle cell D/V state • Proteolytic cascade Sets embryos’ cell D/V state • Toll/Cactus/Doral Sets nuclear D/V state • Dorsal TF thresholds Diff. pathway per D/V address

  5. Dorsal fate determined in oocyte, through signaling between oocyte and somatic follicle cells

  6. Gurken protein on future dorsal side of oocyte, facing cells which become dorsal

  7. Human blood clotting cascade – Also a series of (extracellular) proteolytic cleavages

  8. Ventral fates dictated by NUCLEAR presence of the protein Dorsal Dorsalized Ventralized

  9. Gradient of Nuclear Dorsal protein imparts D-V IDs to cells

  10. Twist Protein specifies mesoderm

  11. Lateral inhibition in neurectoderm to specify neruogenesis: Notch mediated All Rhomboid expressing cells express Notch, then undergo a stochastic process for ¼ cells to become neuronal

  12. Lateral inhibition in neurectoderm to specify neruogenesis: Notch mediated

  13. TGF-Beta family Key factor for D-V identities in Vertebrates Key factor for Dorsal identities in Drosophila

  14. Figure 23.14 Homologous Pathways Specifying Neural Ectoderm in Protostomes (Drosophila) and Deuterostomes (Xenopus) D/V

  15. Both axes definedin Drosophila Now to Anterior-Posterior Axis (A-P)

  16. Bicoid mRNA 1. Bicoid RNA ‘caught’ at the ‘entrance’ 2. Unanchored Bicoid RNA returned to the anterior side by dynein on MTs

  17. Show: Bcd-gastrulation Gastrulation-dorsal

  18. In syncitium For control of Hunchback protein – Bicoid is a transcription factor, but Nanos . . .

  19. Nanos is an RNA binding protein that PREVENTS Hunchback Translation

  20. Gap genes are turned on in broad stripes by maternal genes, each other. ALL TFs. Hunchback Gt Kr kn hb (later)

  21. Gt Kr kn hb (later)

  22. Gap genes are turned on in broad stripes by maternal genes, each other Pair rule genes are turned on in 7 stripes each, harder to conceptualize

  23. Each stripe of the P-R gene has its Own enhancer. Even-skipped gene – 7 stripes.

  24. Each stripe has its own enhancer, responding to a different combinatorial of Gap and Maternal proteins

  25. Gap genes are turned on in broad stripes by maternal genes, each other Pair rule genes are all Trascription Factors too – turn on Segment Polarity gene expression

  26. hh hh hh hh Two morphogens/ligands/organizers in adjacent cells

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