1. ¹Department of Dermatology, University of Cologne, Cologne, Germany
2. ²Division A110 (A080), German Cancer Research Center, Heidelberg, Germany
3. ³School of Biological Science, University of Southampton, Southampton, UK

Correspondence: Dr Dirk Breitkreutz, Division A110 (A080), German Cancer Research Center, Im Neuenheimer Feld 280, Heidelberg 69120, Germany. E-mail: d.breitkreutz@dkfz.de

⁴These authors contributed equally to this work

Received 13 May 2006; Revised 11 July 2006; Accepted 28 July 2006; Published online 28 September 2006.

Abstract

Nidogens are considered as classical linkers joining laminin and collagen IV networks in basement membranes (BMs); however, recent genetic approaches have suggested that nidogens function in a tissue-specific and developmental context. Thus, in mice lacking both nidogen-1 and -2 heart and lung were severely affected, causing neonatal death. Furthermore, in various locations, extravasation of erythrocytes was observed implying microvascular defects. Mice expressing solely either isoform, had a functional BM, although nidogen-2 binds with lower affinity to the laminin 1 chain. Having previously blocked BM formation by interfering with nidogen-1 binding to laminin in skin-organotypic cocultures, here we investigated the roles of nidogen-1 and -2 in this model. For that purpose, human HaCaT cells were grown in three-dimensional cocultures on collagen matrices containing murine fibroblasts of varying nidogen deficiency. As with our experiments blocking laminin–nidogen interaction, lack of both nidogens completely prevented BM deposition and ultrastructural assembly of BM and hemidesmosomes, although other BM proteins remained detectable at comparable levels with no signs of degradation. Supplementation by recombinant nidogen-1 or -2 restored these structures, as shown by immunofluorescence and electron microscopy, confirming that in this system nidogen-2 is equivalent to nidogen-1, and both can promote the development of a functional BM zone.