Description

In mouse, the ceacam1 gene exists in two allelic forms, ceacam1a and ceacam1b, and the ceacam1 alleles expressed largely determine mouse susceptibility to MHV. Mouse strains expressing ceacam1a (such as C57BL/6, BALB/c, and C3H) are highly susceptible, while strains homozygous for ceacam1b (such as SJL) are resistant to infection. ceacam1a transcripts are alternatively spliced, yielding four distinct variants in the mouse. These splice variants encode either two or four extracellular immunoglobulin-like (Ig-like) domains linked by a transmembrane domain to a short (10 amino acids) or long (73 amino acids) cytoplasmic tail. The MHV binding site resides within the N-terminal IgV-like domain, D1 . This domain is present in all four isoforms of CEACAM1a, and thus all serve as functional receptors for MHV. Mouse CEACAM1 shares 56% and 70% aa identity with human and rat CEACAM1, respectively. The human and mouse CEACAM1 genes have highly conserved structures, similar patterns of mRNA splicing, and similar patterns of expression in different tissues.