Detection of mouse osteopontin by western blotting

Several different antibodies to mouse and/or rat osteopontin have been developed, and some antisera raised against human osteopontin have been shown to react with mouse osteopontin. We have taken advantage of the lack of osteopontin protein in mice with a targeted disruption of the osteopontin gene to characterize the reactivity and the specificity of several of these antibodies with mouse osteopontin by Western blotting. Our results demonstrate that, with the exception of the rat monoclonal antibody MPIIIB10, which does not recognize mouse osteopontin on Western blots, all the tested reagents do react with mouse osteopontin, but their sensitivity varies widely, and in some cases there is significant cross-reactivity of the antibodies with other proteins found in mouse tissue extracts.