In Drosophila, an example of position effect variegation in the fly eye. 

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#Unit 4. Cell Communication and Cell Signaling

Heterophilic Binding

A CAM on one cell can directly bind to a different class of CAM on an adjacent cell

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#Unit 4. Cell Communication and Cell Signaling

The formation of many cell-cell adhesions entails two types of molecular interactions:

1.Trans binding interactions 

2. Cis binding interactions

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#Unit 4. Cell Communication and Cell Signaling

Trans interactions (intercellular or adhesive interactions)

CAMs on one cell bind to CAMs on an adjacent cell. 

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#Unit 4. Cell Communication and Cell Signaling

In cis interactions (intracellular or lateral interactions)

monomeric CAMs on one cell bind to one or more CAMs in the same cell’s plasma membrane

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#Unit 4. Cell Communication and Cell Signaling

CAMs fall into one of four major families: 

Cadherins

Immunoglobulin (Ig) superfamily

Integrins

Selectins

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The adhesiveness of cadherins depends on the presence of extracellular Ca2+