Sequence similarity searches were performed using the NCBI BLAST tools [49] and Ensembl BLAST/SSAHA search programs [50] . For the identification of CEACAM genes not yet annotated in the dog genome, sequences from human and mouse CEACAM and PSG cDNAs were run against the WGS databases or whole genome sequences. Multiple sequence alignments were performed and phylogenetic trees were constructed with Clus-talW [51] using default parameters.