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Cell-Cell Communication

Cell-Cell Communication. Modes of Cellular Adhesion Movement of Cells/Tissues We’re here, now what? Cell Signaling and differentiation Contacting outside help: Role of Extracellular matrix Epithelial- Mesenchymal Transitions. Cell-Cell Communication and Dev. Bio. What makes up a tissue?

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Cell-Cell Communication

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  1. Cell-Cell Communication • Modes of Cellular Adhesion • Movement of Cells/Tissues • We’re here, now what? Cell Signaling and differentiation • Contacting outside help: Role of Extracellular matrix • Epithelial-Mesenchymal Transitions

  2. Cell-Cell Communication and Dev. Bio. • What makes up a tissue? • Location, location, location! • What starts organogenesis? More importantly, what determines that it is time to start organogenesis? • What determines if a cell continues to grow once an organ begins to form? • Which way is what? How do we obtain polarity in the embryo?

  3. Tissue Formation: Cell Adhesion • Cell surface: same or different amongst cells? • In vitro Tissue culture of cells from the 3 germ layers- Selective affinity

  4. Cell Adhesion: differential adhesion. • There is a hierarchy in cell interactions • Strength of interaction will determine fate of cells. Foty et al. 1996

  5. Cadherins: Brings cells together! • Calcium-dependent adherin molecule. • Cadherin-catenin: Classical Adherens junctions. • Forms a link with cytoskeleton. • Different forms found in different tissues • E, P, N, or R-cadherins • Migrating cells use protocadherins.

  6. Timing and strength of Cadherin Interaction • Amount of cadherin on a cell. • Cadherin type. • Mesenchymal cells of Chick leg: N-cadherinupregulated before condensation. • Attachment of Embryo to uterine wall: P-cadherin located in trophoblast cells, not inner mass.

  7. Getting away: Cell Motility • Polarization occurs, cytoskeleton reorganization. • Protrusion of leading edge: Filopodia and Lamellipodia. • Adhesion to Extracellular matrix (ECM). Formation of focal adhesions. • Release of focal adhesions in trailing edge of cell.

  8. Beginning construction of tissues • Induction (first identified by Christian Pander). • Inducer vs. responder. • Inducer: Usually Paracrine factor • Responder: cell that changes behavior in response to inducer • Initial induction may make cell competent for a second inducer: lens formation. • Reciprocal Induction: Returning the favor!

  9. Beginning construction of tissues

  10. Talking to your neighbors: Paracrine Signaling • Fibroblast Growth factor (FGF) • Hedgehog • Wnt Family • TGF-b

  11. FGF • Important for limb and lens development. • Fgf-8 and lens development • Fgf-4 Dachshund and Limb development; More equals less!

  12. FGF and Signal Transduction Pathways • RTK signal pathway important for: • Drosophila eye develop. • Nematode vulvae • Human cancers • Jak-Stat Pathway • Ex. Chondrocyte differentiation.

  13. Hedgehog: Got Cholesterol? • 2/3 of protein secreted, cholesterol needed. • Limb devel., neural differentiation, and facial morphogenesis. • Yes, there is a gene called Sonic Hedgehog.

  14. Wnt family: From fly to mammals! • Induces dorsal cell of somites to become muscle and specification of the midbrain cells. • Similar to Hedgehog..activation of system often accomplished by inhibiting an inhibitor.

  15. TGF-b • Largest family • Important classes: TGF-b, activin family, bone morphogenic proteins (BMPs), Vg1 family of proteins (glial derived neurotrophic factor and Mullerian Inhibitory factor).

  16. Talking to Neighbors: Juxtacrine Signaling • Eph and ephrin- Signal for attraction or repulsion of cells • Notch Proteins- Kidney, pancreas, and heart development. • Important receptors for nervous system.

  17. Staying the way you are! • Positive Feedback in transcription • Maintaining Chromatin density • Autocrine.

  18. Extracellular Matrix and Develop. Biol. • Cell adhesion • Cell Migration • Formation of epithelial sheets/tubes. • Fibronectin and Laminin • Integrins and the interaction with ECM.

  19. Epithelial-Mesenchymal Transition • Paracrine signal initiates transition • Benefits for development? • Benefits for Adulthood?

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