Introduction to  PATTERNING THE EMBRYO Stefan Hoppler [email_address] 550974 DB3801
The concept of phylotypic stage example:  chordates Early embryonic stages are diverse in related animals   (possibly due ...
Organisation of 3rd year DB modules example:  chordates Phylotypic stage DB 3801 Lectures: Patterning the Embryo DB 3802 L...
The phylotypic stage in arthropods (insects): Segmented Germband Embryo <ul><li>Anteroposterior organization </li></ul><ul...
The phylotypic stage in chordates (vertebrates):  Pharyngula <ul><li>Anteroposterior organization </li></ul><ul><li>Dorsov...
Embryonic body axes <ul><li>Invertebrates have at least 2 body axes: </li></ul><ul><li>Anterior-Posterior (A-P) </li></ul>...
Vertebrates have three body axes normal vertebrate animal human anatomy <ul><li>3 body axes: </li></ul><ul><li>Anterior-Po...
Vertebrates and many Invertebrates are built from three germ layers
Vertebrates are built  from three germ layers Outside Inside Ectoderm: Skin and neural tissue Mesoderm: Muscles, Kidney et...
Integrating germ layers and embryonic axes in three dimensions: Morphogenesis, Gastrulation and Neurulation Gastrulation i...
DB 3801 Organisation of Lectures Introduction Early Development in Drosophila (3 lectures)    Transcription Factor Famili...
DB 3801 Practical Classes: chemical genetics on Xenopus embryos (modified after Slack, Fig. 7.15)
DB 3801 Practical Classes: chemical genetics on Xenopus embryos <ul><li>Four groups: </li></ul><ul><li>Lithium at early st...
DB 3801 Practical Classes: chemical genetics on Xenopus embryos <ul><li>Experimental progression: </li></ul><ul><li>Fertil...
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Introduction to PATTERNING THE EMBRYO

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  • Triploblasts: metazoan animals with three germ layers Diploblasts: only Cnidaria (Hydra, Nematostella, other jellyfish and sea anemones), and some people consider Sponges and Placozoa (Tichoplax) also diploblasts.
  • Introduction to PATTERNING THE EMBRYO

    1. 1. Introduction to PATTERNING THE EMBRYO Stefan Hoppler [email_address] 550974 DB3801
    2. 2. The concept of phylotypic stage example: chordates Early embryonic stages are diverse in related animals (possibly due to ecologically different reproductive strategies). Late embryonic stages are diverse in related animals (possibly due to ecologically different adult strategies). Most conserved embryonic stages in related animals (possibly due to developmental genetic constraints and relative lack of selective pressure to specialize).
    3. 3. Organisation of 3rd year DB modules example: chordates Phylotypic stage DB 3801 Lectures: Patterning the Embryo DB 3802 Lectures: Development of Organ Systems
    4. 4. The phylotypic stage in arthropods (insects): Segmented Germband Embryo <ul><li>Anteroposterior organization </li></ul><ul><li>Dorsoventral organization </li></ul><ul><li>All three germ layers (triploblast)(ectoderm, mesoderm, endoderm) </li></ul><ul><li>Segmental organization, with different segmental identity </li></ul><ul><ul><li>(Insects with 3 gnathal, 3 thoracic and several abdominal segments) </li></ul></ul><ul><li>Appendage buds (imaginal disks in insects) are set aside </li></ul><ul><li>Ventral Nerve Cord </li></ul><ul><li>Cell differentiation is just starting (nerves, muscles etc.) </li></ul>
    5. 5. The phylotypic stage in chordates (vertebrates): Pharyngula <ul><li>Anteroposterior organization </li></ul><ul><li>Dorsoventral organization </li></ul><ul><li>All three germ layers (triploblast)(ectoderm, mesdoderm, endoderm) </li></ul><ul><li>Notochord and segmented somites </li></ul><ul><li>Dorsal hollow nerve cord with anterior specialisation (sense organs) </li></ul><ul><ul><li>(CNS and brain in vertebrates) </li></ul></ul><ul><li>Ventral heart </li></ul><ul><li>Post-anal tail bud </li></ul><ul><li>Pharyngeal arches (gill slits in aquatic chordates) </li></ul>
    6. 6. Embryonic body axes <ul><li>Invertebrates have at least 2 body axes: </li></ul><ul><li>Anterior-Posterior (A-P) </li></ul><ul><li>Dorsal-Ventral (D-V) </li></ul>Drosophila <ul><li>Vertebrates have 3 body axes: </li></ul><ul><li>Anterior-Posterior (A-P) </li></ul><ul><li>Dorsal-Ventral (D-V) </li></ul><ul><li>Left-Right (L-R) </li></ul>anterior posterior ventral dorsal right left Adult Xenopus
    7. 7. Vertebrates have three body axes normal vertebrate animal human anatomy <ul><li>3 body axes: </li></ul><ul><li>Anterior-Posterior (A-P) </li></ul><ul><li>Dorsal-Ventral (D-V) </li></ul><ul><li>Left-Right (L-R) </li></ul>
    8. 8. Vertebrates and many Invertebrates are built from three germ layers
    9. 9. Vertebrates are built from three germ layers Outside Inside Ectoderm: Skin and neural tissue Mesoderm: Muscles, Kidney etc. Endoderm: Gut, Lungs etc.
    10. 10. Integrating germ layers and embryonic axes in three dimensions: Morphogenesis, Gastrulation and Neurulation Gastrulation in: Sea urchin Drosophila Xenopus The internal germ layers (endoderm, mesoderm) are placed inside the embryo
    11. 11. DB 3801 Organisation of Lectures Introduction Early Development in Drosophila (3 lectures)  Transcription Factor Families Early Development in C. elegans (2 lectures) Early Development in Xenopus (3 lectures)  Cell-cell signalling mechanisms Early mammalian development (2 lectures) Morphogenesis in early development (2 lectures)
    12. 12. DB 3801 Practical Classes: chemical genetics on Xenopus embryos (modified after Slack, Fig. 7.15)
    13. 13. DB 3801 Practical Classes: chemical genetics on Xenopus embryos <ul><li>Four groups: </li></ul><ul><li>Lithium at early stages (The classic textbook experiment, as in Slack: Fig. 7.15 c) </li></ul><ul><li>Lithium treatment after MBT (as in Hamilton et al., 2001) </li></ul><ul><li>Treatment with novel GSK3 inhibitor (BIO, Meijer et al., 2003) </li></ul><ul><li>Treatment with Retinoic Acid (which somehow inhibits endogenous Wnt signalling, Li et al., 2008) </li></ul>
    14. 14. DB 3801 Practical Classes: chemical genetics on Xenopus embryos <ul><li>Experimental progression: </li></ul><ul><li>Fertilize Xenopus eggs with sperm. </li></ul><ul><li>Remove Jelly coat with Cystein solution. </li></ul><ul><li>Treatment of Embryos (with appropriate chemical/drug, at appropriate concentration; or alternatively with appropriate control; at appropriate embryonic stage and for appropriate duration) </li></ul><ul><li>Nurse developing embryos until Pharyngula stage (approx. stage 32). </li></ul><ul><li>Fix embryos; analyse result (DAI), document result (take pictures), count numbers (create bar chart). </li></ul>

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