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LECTURE 9: Appendage development

LECTURE 9: Appendage development. Head. Tail. T1. A8. A7. T2. A6. T3. A5. A1. A2. A4. A3. Metamorphosis. Quiltwork Assembly of a Fly. L. 1. M. L. 2. L. 3. 3rd Larval Instar. L. 4. L. 5. Early Pupa. M. s. C. o. L. 1. L. 2. Mid-Pupa->Adult. L. 3. L. 6. L.

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LECTURE 9: Appendage development

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  1. LECTURE 9: Appendage development

  2. Head Tail T1 A8 A7 T2 A6 T3 A5 A1 A2 A4 A3 Metamorphosis Quiltwork Assembly of a Fly

  3. L 1 M L 2 L 3 3rd Larval Instar L 4 L 5 Early Pupa M s C o L 1 L 2 Mid-Pupa->Adult L 3 L 6 L 4 L 5 Outline of Vein Development

  4. Fly Wing M L1 L2 L3 L4 L5

  5. The Players: A/P Axis Engrailed (En) = Transcription factor expressed in posterior cells. Hedgehog (Hh) = Signal whose expression is activated by En. Dpp = Signal whose expression is activated by Hh signaling. Sal = Transcription factor activated by Dpp signaling.

  6. En -> Hh -> Diffuses -> Dpp -> Diffuses -> dpp in A/P Organizer sal -> L2 vein L2 A/P sal Organizer A L3 L3 dpp P Dpp A L4 L4 P dpp sal hh L5 L2 L2 L3 L3 dpp sal L4 L4 L5 L5 Determining the Positions of Veins En

  7. En -> Hh -> Diffuses -> Mutant with reduced hh function dpp in A/P Organizer A A dpp L3 dpp P P L3 L4 L4 dpp dpp hh hh En En WT hh- mutant L2 L2 L3 L3 L4 L4 L5 L5 Hh Determines Positions of L3 and L4 Veins

  8. Dpp -> Diffuses -> Mutant with reduced dpp function sal -> L2 vein L2 sal L2 sal L3 L3 Dpp A A Dpp L4 L4 sal P P sal L5 L5 WT dpp- mutant L2 L2 L3 L3 L4 L4 L5 L5 Dpp Determines Positions of L2 and L5 veins

  9. Dpp -> Diffuses -> En -> Hh -> Diffuses -> sal -> L2 vein dpp in A/P Organizer A/P L 4 L 3 Organizer L5 L 2 E n d p p + s a l D p p s a l h h + d p p A P A P Veins Form At Boundaries Along the A/P Axis

  10. Maternal B i c oi d gradient Hb defines anterior Eve-3 defines anterior defines posterior limit of hb border of eve -3 stripe border of en -5 stripe W i n g Lowest level of Bcd needed to activate hb D i s c H b K n i Ant. Post. e v e - 3 e n - 5 En-5 defines position of Dpp defines anterior Sal defines position dpp stripe in wing disc border of sal domain of L2 vein stripe S a l E n + d p p + X s a l D p p s a l D p p s a l h h + + d p p L 2 A P A P A P L 2 The Developmental Path From Bcd to the L2 Vein

  11. The Players: D/V and P/D Axes Apterous (Ap) = Transcription factor expressed in dorsal cells. Notch (N) = Signaling system that induces margin at D/V border. Distalless = Transcription factor activated at A/P & D/V intersection.

  12. D/V Signaling Is Required for Wing Margin Formation and Wing Outgrowth Ap -> Notch -> Wing Margin D/V Organizer -> Margin Formation Loss of ap in Dorsal Cells = D/V Organizer and Wing Growth -> Margin Formation ap - cells Activation of Notch Along ap Expressing Cells Future Margin D ->V Signal D V V -> D Signal ap Non-expressing Cells Adult wing with ap - patch Wing imaginal disc in larva Adult wing (viewed end on) Intersection of the D/V and A/P Organizers Induces Leg Outgrowth P A Normal Leg distalless Mutant Leg D/V Organizer Distalless Expression D Proximal Distalless V Distal A/P Organizer Fig. 4.4

  13. Initiation of Wing Development in Chickens

  14. ZPA Graft Hh Expression Hh Soaked Beads Normal Wing 0 mg/ml 4 mg/ml ZPA Transplant ZPA 8 mg/ml 16 mg/ml Hh is the ZPA Factor

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