Transcript Cell-Cell Communication

Cell-Cell Communication
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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.
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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?
Tissue Formation: Cell Adhesion
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Cell surface: same or different amongst cells?
In vitro Tissue culture of cells from the 3 germ layersSelective affinity
Cell Adhesion: differential adhesion.
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There is a hierarchy in cell
interactions
Strength of interaction will
determine fate of cells.
Foty et al. 1996
Cadherins: Brings cells together!
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Calcium-dependent
adherin molecule.
Cadherin-catenin: Classical
Adherens junctions.
Forms a link with
cytoskeleton.
Different forms found in
different tissues
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E, P, N, or R-cadherins
Migrating cells use
protocadherins.
Timing and strength of Cadherin Interaction
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Amount of cadherin on a
cell.
Cadherin type.
Mesenchymal cells of
Chick leg: N-cadherin
upregulated before
condensation.
Attachment of Embryo to
uterine wall: P-cadherin
located in trophoblast
cells, not inner mass.
Getting away: Cell Motility
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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.
Beginning construction of tissues
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Induction (first identified by
Christian Pander).
Inducer vs. responder.
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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!
Beginning construction of tissues
Talking to your neighbors: Paracrine
Signaling
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Fibroblast Growth factor
(FGF)
Hedgehog
Wnt Family
TGF-b
FGF
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Important for limb and
lens development.
Fgf-8 and lens
development
Fgf-4 Dachshund and Limb
development; More equals
less!
FGF and Signal Transduction Pathways
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RTK signal pathway
important for:
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Drosophila eye develop.
Nematode vulvae
Human cancers
Jak-Stat Pathway
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Ex. Chondrocyte
differentiation.
Hedgehog: Got Cholesterol?
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2/3 of protein secreted, cholesterol needed.
Limb devel., neural differentiation, and facial
morphogenesis.
Yes, there is a gene called Sonic Hedgehog.
Wnt family: From fly to mammals!
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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.
TGF-b
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Largest family
Important classes: TGF-b, activin family, bone morphogenic
proteins (BMPs),Vg1 family of proteins (glial derived
neurotrophic factor and Mullerian Inhibitory factor).
Talking to Neighbors: Juxtacrine Signaling
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Eph and ephrin- Signal for
attraction or repulsion of
cells
Notch Proteins- Kidney,
pancreas, and heart
development.
Important receptors for
nervous system.
Staying the way you are!
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Positive Feedback in
transcription
Maintaining Chromatin
density
Autocrine.
Extracellular Matrix and Develop. Biol.
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Cell adhesion
Cell Migration
Formation of epithelial
sheets/tubes.
Fibronectin and Laminin
Integrins and the
interaction with ECM.
Epithelial-Mesenchymal Transition
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Paracrine signal initiates
transition
Benefits for development?
Benefits for Adulthood?