ABSTRACT
Of all the social interactions between cells in a multicellular organism, the most fundamental are those that hold the cells together. The mechanisms of cohesion govern the architecture of the body, that is, its shape, its strength, and the arrangement of its different cell types. In epithelial tissues, such as the lining of the gut or the epidermal covering of the skin, cells are tightly bound together into sheets called epithelia. The extracellular matrix is less pronounced, consisting mainly of a thin mat called the basal lamina underlying the sheet. Cell–cell junctions come in many forms and can be regulated by a variety of mechanisms. The spacing between the cell membranes at an anchoring junction is precisely defined and depends on the structure of the participating cadherin molecules. Cadherins form specific homophilic attachments, explaining why there are so many different family members.
