Tissue distribution of products of the mouse decay-accelerating factor (DAF) genes. Exploitation of a Daf1 knock-out mouse and site-specific monoclonal antibodies

Decay-accelerating factor (DAF) is a membrane regulator of C3 activation th at protects self cells from autologous complement attack. In humans, DAF is uniformly expressed as a glycosylphosphatidylinositol (GPI)-anchored molec ule. In mice, both GPI-anchored and transmembrane-anchored DAF proteins are produced, each of which can be derived from two different genes (Daf1 and Daf2). In this report, we describe a Daf1 gene knock-out mouse arising as t he first product of a strategy for targeting one or both Daf genes. As part of the work, we characterize recently described monoclonal antibodies agai nst murine DAF protein using deletion mutants synthesized in yeast, and the n employ the monoclonal antibodies in conjunction with wild-type and the Da f1 knock-out mice to determine the tissue distribution of the mouse Daf1 an d Daf2 gene products. To enhance the immunohistochemical detection of murin e DAF protein, we utilized the sensitive tyramide fluorescence method. In w ild-type mice, we found strong DAF labelling of glomeruli, airway and gut e pithelium, the spleen, vascular endothelium throughout all tissues, and sem iniferous tubules of the testis. In Daf1 knock-out mice, DAF labelling was ablated in most tissues, but strong labelling of the testis and splenic den dritic cells remained. In both sites, reverse transcription-polymerase chai n reaction analyses identified both GPI and transmembrane forms of Daf2 gen e-derived protein. The results have relevance for studies of in vivo murine DAF function and of murine DAF structure.