Ultrastructural colocalization of nidogen-1 and nidogen-2 with laminin-1 in murine kidney basement membranes

Nidogen-1, a key component of basement membranes, is considered to function as a link between laminin and collagen type IV networks. Recently a new member of the nidogen family, nidogen-2, has been characterized. Preliminary immunohistochemical data indicated that nidogen-1 and nidogen-2 show a similar tissue distribution at the light microscopic level. We have now localized nidogen-1 and nidogen-2, as well as their corresponding mRNAs, at the light and electron microscopic levels in adult mouse kidney, by in situ hybridization and immunogold histochemistry, as well as carrying out double labeling with laminin-1. Both nidogen-1 and nidogen-2 mRNAs are found not only in mesenchymal cells of embryonic tissues, but also in all epithelial and endothelial cells in adult mouse kidney. Both nidogens are ubiquitous basement membrane components in the mouse kidney, being found in glomerular, tubular, and capillary compartments and Bowman's capsule. Furthermore, a substantial fraction of nidogen-1 and nidogen-2 colocalizes with laminin-1. The results indicate that nidogen-1 and nidogen-2 could well substitute for one another in some of their biological activities in kidney, for example, stabilizing basement membrane networks in vivo.