BIO 313 Embryology Lecture #35 Drosophila Body Plan

1. BIO 313 EmbryologyLecture #35Drosophila Body Plan Embryonic Neuronal (red) and Glial Cells (green) Dr. Karen SchmeichelApril 21, 2008

2. Exam &Practical Return • Final Exam 1 week from today • Thank you notes!! • Finish with Germ Cell Determination • & Medical Implications • Presentation Rubric and • Review Sheet coming Business:

3. Follow early cleavages of the fly syncytial • blastoderm • Understand gastrulation and observe • the “all important” germ band • extension • Look at segmentation in fly embryos, • a regulated hierarchy of transcriptional • & translational activation and repression Objectives:

4. Fig. 8.3 In flies,cleavage occurs“superficially”

5. Fig. 9.1 Cleavage occurs via a series of synchronized cell divisions with no cytokinesis

6. Fig.9.3 Cellularization ofNucleiin SyncytialBlastoderm

7. Fig. 9.3 Structure of the Cleavage Furrows

8. Movie“Time-Lapse Imaging of Drosophila Embryogenesis” whfreeman.com/lodish6eCh 22

9. Fig. 9.5 Gastrulation: Forming the ventral furrow

10. Fig. 9.5 Gastrulation: Forming the Cephalic Furrow

11. Fig. 9.5 Gastrulation: germ band extension – “Packing the trunk”

12. Vade Mecum VideoFruit Fly>>Embryo>>Gastrulation

13. Fig. 9.6 Schematic representation of gastrulation in Drosophila:NOTE THEGERMLAYERS!

14. Fig.9.7 Comparison of larval and adult segmentation in Drosophila

15. Fig. 9.17 Generalized model of Drosophilaanterior-posterior pattern formation http://bcs.whfreeman.com/lodish6e/ Ch 22 Animation “Gene Control in Embryonic Development

16. Fig. 9.17/26 Krüppel encodes a “Gap” gene Krüppel

17. Fig. 9.17/26/31 Fushi tarazu is a Pair-rule gene

18. Fig. 9.30 Regulation of the pair-rule gene even-skipped depends on how the enhancers are “loaded”

19. Fig. 9.27 Parasegments are shifted one compartment forward in relation to the segments

20. Fig. 9.17/26/32 Engrailed is a segment polarity gene

21. Fig. 9.17 Generalized model of DrosophilaA/Ppattern formation

22. Once fertilized, embryos undergo 10 cell divisions to give rise to a blastoderm formed by superficial cleavages. • Mid-blastula transition occurs shortly after cellularization • Ventral invaginations of ectoderm and mesoderm lead to ventral nerve cord • Invaginations separate cephalic from body structures • Trunk regions are encapsulated within a germ band which wraps around the embryo by virtue of convergent extension of the mesoderm and ectoderm • While at full extension, cells contained within the germ band • undergo important developmental processes, • including imaginal disc formation and segmentation • Once patterned, larval structures are appropriately positioned • to give rise to adult structures in parallel positions. • Segmentation occurs via a precise hierarchy of transcriptional and translational activation and repression via gap, pair-rule and segmentation polarity genes Summary

23. For 4/23 Ch. 9: 253-288 Drosophila Body Plan & Ch.19:593-611 Saga of the Germ Line