Cell Adhesion and Cell Sorting

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Cell Adhesion and Cell Sorting
Cell Identity
Morphogenesis
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Cells Can Have Different Degrees of Contact
(Adhesion) to Their Neighbors
Epithelia Tight adhesion, clear cell-cell
junctions, highly ordered Mesenchyme Loose
adhesion but still contiguous tissue Individual
cells
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Tissue Morphogenesis is Affected by Degree of
Cell-cell Contact
E.g. Cell behaviors during gastrulation
EpitheliumInvagination
MesenchymeInvolution
Single CellsIngression (Delamination, Emigration)
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Cell Adhesion Can Also Control Cell Sorting
H. panicea
M. prolifera
H. panicea
M. prolifera
Fernandez-Bisquets amd Burger
Dissociate sponge through silk sieve Allow cells
to reaggregate (requires calcium) Cells sort out
to make new sponges in species-specific manner
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Embryonic Cells Exhibit Spontaneous Cell Sorting
Ability
Townes and Holtfreter, 1955
Cells of a particular IDENTITY can have affinity
for one another
This affinity can cause them to sort out in
predictable ways
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Amphibian Gastrulation Normally Results From
Precisely Controlled Cellular Movements
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Gastrulation By Cell Sorting in Dissociated
Embryos!
Townes and Holtfreter, 1955
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Cell Sorting in the Embryonic Mesoderm in
Drosophila
1) A/P and D/V info to specify cell identity
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Differential Adhesion Hypothesis Cells
rearrange so as to maximize adhesive
interactions Weakly adhering cells will sort
outside or spread over strongly adhering
cells Requires differential cell adhesion and
cell motility
Malcolm S. Steinberg
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More P-cadherin
Less P-cadherin
Minus calcium
LOW HIGH
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Townes and Holtfreter, 1955
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Functional Classes of Cell Adhesion Molecules
(CAMs)

• Cell-cell vs. Cell-ECM
• Junctional vs. non-junctional
• Homophillic vs. heterophillic
• Calcium dependent vs. independent

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The Junctional Adhesion Complexes
apical
adherens junction
baso-lateral
ECM (collagen, fibronectin, laminin, etc.)
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Summary of Cell Adhesion
Epithelium Mesenchyme
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Families of Cell Adhesion Molecules (CAMs)
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Integrins
-Primarily Cell-ECM (but sometimes
Cell-Cell) -Calcium Dependent -Heterodimeric--diff
erent dimers can have different ligands
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Ig-CAMs
N-CAM Forms
-Cell-cell (but some bind ECM) -Immunoglobulin
like extracellular domains - Heterophillic or
homophillic -Calcium Independent -Many expressed
in nervous system -865 members in human genome???
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Cadherins
-Cell-cell -Primarily homophillic -Calcium
Dependent
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Classes of Cadherins
7 TM Planar polarity Spindle position Dendritic
morph.
FAT Planar polarity
Kinase
Desomosomal cadherins Protocadherins
http//www.zoo.utoronto.ca/utepass/cadherin.html
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How are Cell Adhesion and CAMs Regulated?
Production (transcription, splicing, RNA
stability, translation) Post-Translational
Modification (phosphorylation, glycosylation) Subc
ellular Localization (Cell Surface Localization,
Endocytosis) Protein-Protein Interaction
(adhesion complex members) Connection to the
cytoskeleton Degradation (extracellular
metalloproteases, lysosome)
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61 kb just for transcription unit!
12 x 48 x 33 x 2 38,016 possible splice
forms!!! RT-PCR and sequence 50 cDNA clones
49 different combinations of Exons 4, 6 and 9!!
Alternative splicing can create a larger
repertoire of CAM binding specificities
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Regulation of ß-Catenin by Tyrosine
Phosphorylation
EGFR
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Cleavage and Shedding of N-Cadherin Ectodomain
by ADAM10
Reiss et al. EMBO 2005
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What Do Cell Adhesion and CAMs Regulate?
Cell Proliferation (contact inhibition) Cell
Death Cell Shape Cell Migration Cell
Identity Tissue Type (epithelial vs.
mesenchymal) Tissue Shape Cell Sorting
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Cell-cell Contact and Competition Controls Cell
Proliferation and Cell Death
The Hippo/Salvadore/Warts pathway regulates
contact inhibition and cell competition during
development and also supresses uncontrolled
growth in adults (tumor suppression)
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What Do Cell Adhesion and CAMs Regulate?
Cell Proliferation (contact inhibition) Cell
Death Cell Shape Cell Migration Cell
Identity Tissue Type (epithelial vs.
mesenchymal) Tissue Shape Cell Sorting
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Cell-ECM and Cell-Cell Adhesion is Essential for
Cell Migration
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What Do Cell Adhesion and CAMs Regulate?
Cell Proliferation (contact inhibition) Cell
Death Cell Shape Cell Migration Cell Identity
(and sub-cellular identity) Tissue Type
(epithelial vs. mesenchymal) Tissue Shape Cell
Sorting
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Cell Adhesion Controls Cell Identity
Signaling Via CAMs
-CAMs can have or associate with intracellular
kinase or phosphatase domains e.g. Ret
(CAD-tyr kinase), LAR (IgCAM-tyr ppase) -IgCAMs
can be receptors for axon guidance factors -CAM
intracellular domains can regulate gene
expression? -CAMs are important for planar
cell polarity
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Regulation of Transcription by N-Cadherin
Intracellular Domain
Marambaud et al. Cell 2003
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Cell Adhesion Regulates Sub-Cellular Identity
Cell Polarity
PCP
Apical
Basal
Cadherins are also important for Planar Cell
Polarity
Classical cadherins are important for
Apical-Basal Polarity
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Planar Cell Polarity and the Mammalian Organ of
Corti (Inner Ear)
Stereocillia Bundles
Mouse flamingo-
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What Do Cell Adhesion and CAMs Regulate?
Cell Proliferation (contact inhibition) Cell
Death Cell Shape Cell Migration Cell
Identity Tissue Type (epithelial vs.
mesenchymal) Tissue Shape Cell Sorting
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The Epithelial-to-Mesenchymal Transition (EMT)
Gastrulation
Neural Crest Emmigration
TakeichiUemura 2000
Nieto, 2002
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Somite Development
Gastrulation (EMT)
Make up your mind already!
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What Do Cell Adhesion and CAMs Regulate?
Cell Proliferation (contact inhibition) Cell
Death Cell Shape Cell Migration Cell
Identity Tissue Type (epithelial vs.
mesenchymal) Tissue Shape Cell Sorting
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Townes and Holtfreter, 1955
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EMT and Cancer Progression and Metastasis
Lose E-cad
E-cad can be re-expressed
Thiery, 2002
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Conserved Pathways Regulate EMT in Development
and Cancer
Thiery, 2002
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Transition from Adenoma to Carcinoma
is correlated with loss of E-cadherin
E-cad supresses, and Dominant Negative E-cad
enhances, tumor progression and metastasis
Pancreatic Cancer Model

Note Carcinomas had lost E-cad expression
(Increased wt E-cad)
(Increased DN E-cad)
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E-cadherin is a Tumor Suppressor Gene
Somatic mutations
Germline mutations
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Take Home Messages
Cell adhesion controls many aspects of cell
behavior during development, homeostasis and
disease It is therefore regulated at many levels
via diverse mechanisms Adhesive properties of
individual cells define and control
tissues Cells with a particular identity often
have affinity for one another, mediated by CAMs,
that defines a tissue The nature of cell-cell
contacts in a tissue, e.g. epithelial vs.
mesenchymal, dictates tissue morphogenesis
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Cone Cell Behavior Can be Described by a Surface
Tension Model
Like soap bubbles, cone cells configure so as to
maximize interactions with one another, and
minimize interactions with their surroundings
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Cadherins Determine Surface Tension
Model -DE-cadherin promotes adhesion b/w all
cells of system -DN-cadherin promotes additional
adhesion just b/w cone cells -Cone cells maximize
their interactions w/ one another and minimize
contacts with other cells -These forces determine
final arrangement of these cells
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Tissue Engineering
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Gonad Formation in Drosophila
SGP fusion
Germ Cell CD8-GFP EYA
Gonad compaction Germ cell ensheathment
germ cells
somatic gonadal precursors (SGPs)
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E-cadherin is Required for Germ Cell Migration
Jenkins et al., 2003
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E-cadherin is Required for Gonad Formation
Jenkins et al., 2003
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Increasing Germ Cell-Germ Cell Adhesion Blocks
Ensheathment
wt
Germ Cells SGPs
Increased E-cadherin in Germ Cells
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E-cadherin May be Important for Germline Stem
Cell Niche Formation
Male Embryo Stage 17 Late
Adult Testis
Stephanie LeBras
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E-cadherin is Required for Germline Stem Cell
Mainenance
Germ cells mutant for E-cad or ß-catenin
Song and Xie, 2002
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E-cadherin is required for proper
oocyte localization
Godt and Tepass, 1998 Gonzales-Reyes and St.
Johnston, 1998
E-Cad DNA
wt
E-cad- gc
E-cad- fc
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E-cadherin Again and Again
in Drosophila Gonad Development

• Germ cell migration
• Embryonic Gonad Formation
• Stem Cell Recruitment and Maintanence
• Oocyte Position in Egg Chamber
• Border Cell Migration
• Centripetal Follicle Cell Migration

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Examples of Cell Behavior During Morphogenesis
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Cadherins and the Neural Crest
E-Cad
N-Cad
Hatta and Takeichi