Molecular cloning of murine decay accelerating factor by immunoscreening.

Although the cDNA of human decay accelerating factor (DAF) which restricts complement activation on homologous cell membranes was cloned in 1987, all trials to detect the cDNA of mouse DAF by cross-hybridization were unsuccessful. However, by immunoscreening with a rabbit antiserum against purified mouse DAF, we successfully cloned the cDNA. It contains four typical short consensus repeats (SCR) similar to that in human and guinea pig DAF. The base sequence showed 63.7 and 63.8% identity to that of human and guinea pig DAF respectively. The deduced amino acid sequence identity to human and guinea pig DAF was 47.2 and 46.5% respectively. Mouse complement receptor related gene Y (Crry)/p65 function is comparable to DAF. SCR3 and SCR4 of mouse DAF showed 50% identity to SCR2 and SCR3 of Crry/p65 respectively. Identification of the mouse DAF gene should open a new approach for determining the actual in vivo role of DAF by analyzing autoimmune mice as well as generating DAF gene knockout mice using embryonic stem cells.