27 kDa extracellular matrix protein revealed by a monoclonal antibody raised against rat testis

In search of unique components of the seminiferous tubule extracellular mat rix, monoclonal antibodies were raised against an isolated seminiferous tub ule extracellular matrix, and the monoclonal antibody 12G11 was cloned. By immunofluorescence microscopy in eight kinds of rat tissues (testis, lung, liver, small intestine, cardiac muscle, skeletal muscle, kidney, and brain) , 12G11 antigen existed only in the testis. Immunoelectron microscopy revea led that the antigen is localized in the basement membrane of the seminifer ous tubule and in the basement membranes of myoid cells. For a biochemical analysis, eight kinds of rat extracellular matrices were isolated and solub ilized with 8 M urea and 2% beta -mercaptoethanol. Immunoblot analysis of t hese samples in 0.8% agarose gel also showed that the antigen was specific for the testis, and in a two high-molecular weight aggregates. These aggreg ates seemed to contain type TV collagen and laminin chains. The antigen of 12G11 antibody was shown to be 27 kDa by 10% SDS-PAGE followed by immunoblo tting. From these data, the existence of a testis specific 27 kDa basement membrane protein, which associate with type IV collagen and laminin, was su ggested. Anat Rec 260:402-409, 2000. (C) 2000 Wiley-Liss, Inc.