entactiin

Entactin, also known as nidogen, is a basement membrane glycoprotein that acts as a key linker within the extracellular matrix. In vertebrates, two closely related isoforms are encoded: nidogen-1 (entactin-1) and nidogen-2 (entactin-2). These high-molecular-weight proteins are secreted by various cell types and incorporated into basement membranes across tissues.

Entactin's primary role is to connect major basement membrane networks by binding to laminin and to type IV collagen. Through these interactions, it helps assemble and stabilize the basement membrane, contributing to barrier function, cell adhesion, and tissue morphogenesis. Its presence supports normal development and tissue remodeling in multiple organs.

Expression patterns of nidogen isoforms are widespread, with enrichment in the basement membranes of kidney, lung, skin, brain, and vascular tissues, among others. While there is a level of redundancy between the two isoforms, genetic studies in model organisms indicate that loss of both nidogen-1 and nidogen-2 can lead to severe defects in basement membranes and, in some cases, embryonic or perinatal lethality, whereas single-isoform deficiencies tend to produce milder phenotypes.

Clinical relevance in humans is still being explored. Variations in NID1 or NID2 have been investigated for associations with developmental and basement membrane-related disorders, though such conditions are considered rare. In research and diagnostics, entactin serves as a histological marker for basement membranes due to its abundant localization in these structures.

See also: basement membrane, laminin, collagen IV, nidogen-related proteins.