MECHANISMS FOR VARIABILITY IN A MEMBER OF THE SCAVENGER-RECEPTOR CYSTEINE-RICH SUPERFAMILY

This study reports a molecular analysis of pig WCl, a new member of th e scavenger-receptor cysteine-rich (SRCR) superfamily. The pig WCl con tains up to six extra-cellular SRCR domains, highly homologous to othe r members of the family. However, the striking feature of the WCl gene , as for its cattle and sheep homologues, is that it is present as a m ultigene family showing extensive sequence diversity, for both DNA and predicted protein sequence. The basis of this diversity was examined and was shown to be attributable to several different causes. These in cluded single base-pair changes within SRCR domains, the optional usag e of whole domains or exons, including a SRCR domain and the proximal ''hinge'' region, and alternative isoforms of the putative cytoplasmic tail. These results suggest that WCl may code for a new, though more primitive type of antigen recognition structure specific for gamma/del ta T cells.