Relationships of dog CEA gene family members. N domain exon nucleotide sequences from all CEACAM members of the human and dog CEA gene families (A) or dog CEACAM exons encoding IgC-like domains (B) were aligned and the results depicted as rooted dendrograms. Human and dog N domain exon sequences from CEACAM1-related genes are shown in blue and red, the ones from other CEACAM genes in black. The CEACAM1-like gene IgC type domain B, A1 and A2 type nucleotide sequences are depicted in magenta, dark and light green, respectively. Sequences from presumed pseudogenes are marked by shading. Note that the primordial N exon sequences are most closely related with their respective orthologous counterpart sequences (except for the primate-specific CEACAM21), while the human and canine CEACAM1-related N exon sequences cluster with that of members of the same species. Interestingly, CEACAM28 contains two CEACAM1 A2 type domains (A1, A2) which has not yet been observed for other CEA family members.