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Reaggregation of amphibian cells
- When cells taken from portion of the main gastrula:
- exposed to alkaline pH to separate them
- REAggregation: cells spontaneously move back to the location they were in before (ie: inside cell or outside cell)
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Cadherin-mediated cell adhesion
- Transmembrane protein with a Ca binding site on Extracellular portion, along with adhesive recognition site
- Catenins and Phosphorylation sites on the inner membrane portion, Catenins bind to the ACTIN in the cell
- Cadherin interacts with other cadherins
- Cadherin important for maintaining COHESION b/w DEVELOPING cells
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Cell migration with actin stages
- 1. Polarization: cell defines its front and back, directed by diffusing signals or signals from ECM
- 2. Protrusion of LEADING edge: Poly of actin acts as MECHANICAL force, forms filipodia
- 3. Adhesion: cell sticks to ExtraCellular substrates, ie INTEGRINS
- 4. Release of Adhesion in REAR cells: allows cells to migrate in FORWARD direction
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Cell signaling INDUCTION
- Close RANGE of cell-cell interaction causes them to change:
- 1. shape
- 2. mitotic rate
- 3. cell fate
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Paracrine factors and four types
- inducers that produce signals (could be a secreted factor) that interact from one cell to the other
- 1. Fibroblast growth factor (FGF) family
- 2. Hedgehog
- 3. Wnt
- 4. TGF-Beta
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REsponder
Tissue being induced, must have RECEPTORprotein for inducing factor
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Competence
Ability for cell to RESPOND to a signal
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Signal transduction example
- Ligand binding domain binds to a ligand in ECM
- This causes active tyrosine kinase to undergo phosphorylation and other mechanisms in the cytoplasm to cause the signaling cascade leading to expression or repression of TRANSCRIPTION of genes
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