Binding of Mouse Nidogen-2 to Basement Membrane Components and Cells and Its Expression in Embryonic and Adult Tissues Suggest Complementary Functions of the Two Nidogens

Gene Structure and Functional Analysis of the Mouse Nidogen-2 Gene: Nidogen-2 Is Not Essential for Basement Membrane Formation in Mice

“…The additional sequences of the cDNA represent repeats of coding (nt 4192 to 4255) and noncoding (nt 4358 to 4542) cDNA sequences. Our sequence analysis of EST-cDNA clone pEST-3.1 encoding mouse nidogen-2 sequences (see Materials and Methods) and an independent mouse nidogen-2 full-length cDNA sequence by Salmivirta et al (44) confirmed the genomic sequences in the corresponding amino acid positions and untranslated sequences.…”

“…These studies identify fibulin-5 as an essential determinant of elastic fiber organization (37,60). Despite the fact that nidogen-2 binds strongly to tropoelastin (46) and shows cell binding properties in vitro (21,44) our histological analyses have not revealed pathological changes in the elastic fiber organization and/or connection to adjacent cellular components. We cannot, however, exclude changes which may manifest in aged mice.…”

“…For some time, it was assumed that there is only one nidogen in the vertebrate genome until human and mouse nidogen-2 cDNAs were discovered (19,21). Both nidogen proteins have a similar modular structure, and the in vitro binding properties for major BM proteins have demonstrated a comparable binding to perlecan and collagen IV while the affinity of recombinant human and mouse nidogen-2 for mouse laminin ␥1 chain was 100-to 1,000-fold and 10-fold lower, respectively, compared to human and mouse nidogen-1 (21,44). To assess the in vivo roles of nidogens, nidogen-1 gene knockout mice have been generated and, unexpectedly, are viable and produce normal BM (35).…”

“…In vitro binding affinities of both nidogens for collagen IV and perlecan are nearly identical, whereas the binding affinities of human nidogen-2 to mouse laminin-1 and the corresponding high-affinity nidogen binding module, the laminin-type epidermal growth factor-like module ␥1III4 of the laminin ␥1 chain, is on the order of 2 to 3 magnitudes lower compared to human or mouse nidogen-1 (21). In contrast, mouse nidogen-2 binds to the ␥1III3-5 fragment of the laminin ␥1 chain, which contains the ␥1III4 module, with only about 10-fold lower affinity than mouse nidogen-1, and thus significantly (10-to 100-fold) better than human nidogen-2 (44). In vitro data have shown that recombinant nidogen-1 interacts through different binding sites with all three main BM components-laminin, collagen IV, and perlecan-and can mediate the formation of ternary complexes between laminin and collagen IV (11).…”

“…During embryonic development in mice, nidogen-1 can be detected in preimplantation embryos (7), and both nidogens share overlapping expression patterns at later developmental stages and in adult tissues (19,21,32,33,44). Enhanced localization in endothelial BM has been recognized as a distinguishing feature of nidogen-2 expression as opposed to a more ubiquitous and even distribution of nidogen-1 in BM.…”