entactin

Entactin, historically named entactin and more commonly referred to today as nidogen, is a basement membrane glycoprotein that helps organize the extracellular matrix. In vertebrates there are two forms: entactin-1 (nidogen-1) and entactin-2 (nidogen-2), encoded by the NID1 and NID2 genes. Both are secreted components of basement membranes and are found in most tissues, where they contribute to the integrity of the basal lamina.

Entactins are large, modular glycoproteins that contain multiple globular and rod-like domains. They interact with several key basement membrane components, most notably laminin and type IV collagen, as well as heparan sulfate proteoglycans such as perlecan. Through these interactions, nidogens can bridge laminin networks to collagen IV networks, aiding in the assembly and stabilization of the basement membrane.

In tissue, entactin localizes to the basal laminae of epithelial and endothelial barriers and is particularly prominent in organs with specialized basement membranes, such as the kidney, skin, lungs, and vasculature. Its presence supports cell adhesion, polarity, and organized tissue morphogenesis, as well as remodeling during development and repair.

Genetic and functional studies in mice show that loss of either nidogen-1 or nidogen-2 alone yields relatively mild, tissue-specific effects, owing to partial redundancy. In contrast, simultaneous deficiency of both proteins leads to severe basement membrane defects, abnormal organ development, and perinatal lethality, underscoring entactin’s role in basement membrane integrity.

Clinical and research relevance: altered nidogen expression or distribution has been observed in certain diseases and tumor contexts, but entactin is not a common single-gene disease factor. It remains a focus of study for understanding basement membrane assembly and tissue remodeling.