Cell Adhesion and Cell Sorting Cell IdentityMorphogenesis ? Cell Biology Cell Division/Death Cell Adhesion Cell Movement Cell Shape

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

Getting cells inside Cell Movements Relevant for Gastrulation Spreading tissues out Making tissues longer Convergence/extension Moving cells around

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 M. prolifera H. panicea M. prolifera Cell Adhesion Can Also Control Cell Sorting

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

Amphibian Gastrulation Normally Results From Precisely Controlled Cellular Movements

Townes and Holtfreter, 1955 “Gastrulation” By Cell Sorting in Dissociated Embryos!

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

More P-cadherin Less P-cadherin Minus calcium LOW HIGH

Townes and Holtfreter, 1955

Cell Sorting in the Embryonic Mesoderm in Drosophila 1) A/P and D/V info to specify cell identity 2) Cell sorting to make contiguous tissues

Cell Sorting in the Neural Crest and in Somite Derivatives (Muscle) (Vertebrae) (Dermis)

Functional Classes of Cell Adhesion Molecules (CAMs) Cell-cell vs. Cell-ECM Junctional vs. non-junctional Homophillic vs. heterophillic Calcium dependent vs. independent

adherens junction apical baso-lateral ECM (collagen, fibronectin, laminin, etc.) Types of Cell Adhesion

Epithelium Mesenchyme

Integrins -Primarily Cell-ECM (but sometimes Cell-Cell) -Calcium Dependent -Heterodimeric--different dimers can have different ligands

Ig-CAMs -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??? N-CAM Forms

Cadherins -Cell-cell -Primarily homophillic -Calcium Dependent

Cell Adhesion Molecules and Signaling Sensing Cell- Cell Contact Activation by Cleavage Modulation of Growth Factor Response Sensing Mechanical Strain (Tension, Substrate Rigidity, Flow) PMID:

The Notch Pathway: Cell-cell adhesion as a signal

Anti-N-cad Cleavage and “Shedding” of N-Cadherin Ectodomain by ADAM10 Reiss et al. EMBO 2005

N-Cad CTF inhibits CREB-dependent Txn Blocking Secretase Activates CREB-depd Txn N-Cad CTF Binds CBP Marambaud et al. Cell 2003 Regulation of Transcription by N-Cadherin Intracellular Domain

How are Cell Adhesion and CAMs Regulated? Production (transcription, splicing, RNA stability, translation) Post-Translational Modification (phosphorylation, glycosylation) Subcellular Localization (Cell Surface Localization, Endocytosis) Protein-Protein Interaction (adhesion complex members) Connection to the cytoskeleton Proteolytic Cleavage

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!! 61 kb just for transcription unit! Alternative splicing can create a larger repertoire of CAM binding specificities

What Do Cell Adhesion and CAMs Regulate? Cell Proliferation (contact inhibition) Cell Death Cell Shape Cell Migration Cell Identity Cell Sorting Tissue Type (epithelial vs. mesenchymal) Tissue Organization/Shape

The Fat/Ds Cadherins Regulate Tissue Size Via the Hippo Pathway PMID:

Cell-ECM and Cell-Cell Adhesion is Essential for Cell Migration Proper strength of adhesion is critical for migration: too much can be as bad as too little

The Epithelial-to-Mesenchymal Transition (EMT) Takeichi…Uemura 2000 Gastrulation Neural Crest Emmigration Nieto, 2002

Gastrulation (EMT) MET EMT Somite Development

wt flamingo gain of function Uemura and colleagues Dsh Flamingo Apical Basal PCP Cell Adhesion Regulates Planar Cell Polarity Classical cadherins are important for Apical-Basal Polarity Cadherins are also important for Planar Cell Polarity

Planar Cell Polarity and the Mammalian Organ of Corti (Inner Ear) Stereocillia Bundles Mouse flamingo-

Origins of Multicellularity: Adhesion is not just for animals Bacterial Biofilms Candida Hyphae Fungi Dictyostelium Plants

Social Development in Dictyostelium Migration as single cells Motile aggregate (slug) Morphogenesis and “fruiting body” formation

Choanoflagellate Sponge Origins of Multicellularity: Evolution of adhesion Single and multi-cellular phases “Polarized Epithelia” Catenins No Cadherins Unicellular Cadherin families No “Classical” Cadherin Catenins Multicellular Classical Cadherins Par proteins Sponge genome Aug 2010 PMID: Diploblasts (no mesoderm) Increased Diversity of Cell Junctions

EMT and Cancer Progression and Metastasis Lose E-cad E-cad can be re-expressed

Transition from Adenoma to Carcinoma is correlated with loss of E-cadherin * Note: Carcinomas had lost E-cad expression E-cad supresses, and Dominant Negative E-cad enhances, tumor progression and metastasis Pancreatic Cancer Model (Increased wt E-cad) (Increased DN E-cad) *

Somatic mutations Germline mutations E-cadherin is a Tumor Suppressor Gene

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