Cell-Cell Communication Modes of Cellular Adhesion Movement of Cells/Tissues We’re here, now what? Cell Signaling and differentiation Contacting.
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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? 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 Cell surface: same or different amongst cells? In vitro Tissue culture of cells from the 3 germ
layers- Selective affinity
Cell Adhesion: differential adhesion. There is a hierarchy
in cell interactions Strength of
interaction will determine fate of cells.
Foty et al. 1996
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.
Timing and strength of Cadherin Interaction 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 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 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!
Beginning construction of tissues
Talking to your neighbors: Paracrine Signaling Fibroblast Growth
factor (FGF) Hedgehog Wnt Family TGF-b
FGF 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 RTK signal pathway
important for: Drosophila eye
develop. Nematode vulvae Human cancers
Jak-Stat Pathway Ex. Chondrocyte
differentiation.
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.
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.
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).
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.
Staying the way you are! Positive Feedback in
transcription Maintaining
Chromatin density Autocrine.
Extracellular Matrix and Develop. Biol. Cell adhesion Cell Migration Formation of
epithelial sheets/tubes.
Fibronectin and Laminin
Integrins and the interaction with ECM.
Epithelial-Mesenchymal Transition Paracrine signal
initiates transition Benefits for
development? Benefits for
Adulthood?
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