Matrilin-2, a large, oligomeric matrix protein, is expressed by a great variety of cells and forms fibrillar networks

Matrilin-2 is a member of the protein superfamily with von Willebrand facto r type A-like modules. Mouse matrilin-2 cDNA fragments were expressed in 29 3-EBNA cells, and the protein was purified, characterized, and used to immu nize rabbits. The affinity-purified antiserum detects matrilin-2 in dense a nd loose connective tissue structures, subepithelial connective tissue of t he skin and digestive tract, specialized cartilages, and blood vessel walls . In situ hybridization of S-35-labeled riboprobes localizes the matrilin-2 mRNA to fibroblasts of dermis, tendon, ligaments, perichondrium, and perio steum; connective tissue elements in the heart; smooth muscle cells; and ep ithelia and loose connective tissue cells of the alimentary canal and respi ratory tract. RNA blot hybridization and immunoblotting revealed both matri lin-2 mRNA and protein in cultures of a variety of cell types, confirming t he tissue distribution. Alternative splicing affects a module unique for ma trilin-2 in all of the above RNA sources. SDS-polyacrylamide gel electropho resis and electron microscopy reveals matrilin-2 from tissue extracts and c ell line cultures as a mixture of mono-, di-, tri-, and tetramers, Matrilin -2 is substituted with N-linked oligosaccharides but not with glycosaminogl ycans, Because of other, yet unidentified, cell-type dependent posttranslat ional modifications, the monomer is heterogeneous in size. Immunofluorescen ce showed that matrilin-2 functions by forming an extracellular, filamentou s network.