Assignment of porcine CD97 gene to the 1/2q21→q22 region of the pig chromosome 2 with somatic cell hybrids

CD97 is a member of a novel subfamily of leukocyte proteins that are characterized by the presence of tandemly repeated extracellular epidermal growth factor (EGF)-like domains and a seven-span transmembrane region, known as EGF-TM7. To date, the EGF-TM7 group comprises CD97, EGF module-containing mucin-like hormone receptor (EMR) EMR1, EMR2, EMR3, and ETL in human, and CD97, F4/80 (EMR1) and EMR4 in the mouse (Kwakkenbos et al., 2002; McKnight et al., 1998; Stacey et al., 2002; Stacey et al., 2001). CD97 is induced rapidly on the surface of most leukocytes upon activation. So far, CD97 is the only EGF-TM7 family member of which a ligand has been identified. CD97 binds to its cellular ligand CD55 (decay accelerating factor), which protects several cell types from complement-mediated damage (Hannan et al., 1996). The functional consequences of CD97CD55 binding are largely unknown, but previous data imply that CD97-CD55 interactions play a role in cellular activation, migration, and adhesion under inflammatory conditions (Visser et al., 2002). The CD97 structural gene is mapped to the 19p13.2→ p13.12 region on human chromosome 19. We have recently cloned the pig homologue of the CD97 antigen. Sequence comparison indicates that pig CD97 shares many structural features with human, cattle and mouse CD97 (Perez de la Lastra et al., 2003). To date, this is the first member of the EGF-TM7 family identified in the pig.