Basement Membranes

Basement membranes are thin sheets of specialized extracellular matrices. They are found at the basal surfaces of epithelial and endothelial cells, and they surround all muscle cells, fat cells, the central nervous system, and peripheral nerves. Basement membranes compartmentalize tissues, serve as macromolecular filters, provide sites for cell adhesion, and harbor signaling cues that mediate cell proliferation, migration, and differentiation. All basement membranes contain laminin, type IV collagen, nidogen, and sulfated proteoglycans such as perlecan, agrin, and collagen XVIII. Laminin and collagen IV can self-polymerize into networks that are linked by nidogen and proteoglycans. Cells recognize basement membranes and in some cases facilitate their assembly using both integrin and non-integrin receptors such as dystroglycan, DDR1, and Lutheran/BCAM. A number of human genetic diseases, including junctional epidermolysis bullosa, congenital muscular dystrophy, and Alport syndrome, are caused by mutations that affect basement membrane components. This chapter discusses these and other aspects of basement membranes.