Nidogens are highly conserved proteins present in vertebrate and invertebrate basement membranes. Nidogens connect the Laminin and Collagen IV networks and integrate other proteins into the membrane. In mammals, two Nidogen proteins, Nidogen and Nidogen-2, interact at comparable levels with Collagen I, IV and Perlecan, serving to stabilize basement membranes and playing a major role in embryogenesis. The two isoforms have a similar shape, consisting of three globular domains, and co-localize in vessel walls and other basement membrane zones. Nidogen-2 is a cell adhesion protein glycosylated at nitrogen and oxygen sites, and is widely distributed in basement membranes in heart, placenta, bone and, to a lesser extent, in pancreas, kidney and skeletal muscle.