Sometimes a cigar is just a cigar

Abstract

In this issue of Blood, Connolly and colleagues describe an elegant approach to studying the significance of specific molecular interactions in vivo. The authors have "knocked-in" amutant form of the protease, urokinase-type plasminogen activator (uPA), into the murineuPAlocus, to create a mouse strain (PlauGFDhu/GFDhu) where the interaction between endogenous uPA and its receptor (uPAR) is selectively disrupted, while leaving other functions of both uPA and uPAR intact. Their findings suggest that the primary role of uPAR in vivo is to promote fibrinolysis within tissues through localization of uPA, and that many of the previously described activities of uPAR may be secondary to this process.