Differential expression of mouse α5(IV) and α6(IV) collagen genes in epithelial basement membranes

We first completed the primary structure of the mouse α5(IV) and α6(IV) chains, from which synthetic peptides were produced and α chain-specific monoclonal antibodies were raised. Expression of collagen IV genes in various basement membranes underlying specific organ epithelia was analyzed by immunohistochemical staining using these monoclonal antibodies and other antibodies from human and bovine sequences. It was possible to predict the presence of the three collagen IV molecules: [α1(IV)]₂ α2(IV), α3-(IV)α4(IV)α5(IV), and [α5(IV)]₂α6(IV). In skin basement membrane two of the three forms, [α1(IV)]₂α2(IV) and [α5(IV)]₂α6(IV), were detected. The α3(IV)α4(IV)α5(IV) molecule was observed as the major form in glomerulus, alveolus, and choroid plexus, where basement membranes function as filtering units. The molecular form [α5(IV)]₂α6(IV) was present in basement membranes in tubular organs such as the epididymis, where the tubes need to expand in diameter. Thus, the distribution of the basement membranes with different molecular composition is consistent with tissue-specific function.