Syntenic relationship of the carcinoembryonic antigen related cell adhesion molecule (CEACAM) gene loci in platypus, opossum, human, mouse, cattle and dog genomes. The syntenic chromosome regions from six mammalian species are shown except for platypus where only contig information is available. Arrowheads represent genes with their transcriptional orientation. CEACAM1-related genes are indicated in yellow or red when predominantly expressed in trophoblast cells, the orthologous CEACAM genes in blue and marker genes in black. Names of CEACAM1-like genes with immunoreceptor tyrosine-based inhibition motif/immunoreceptor tyrosine-based switch motif encoding exons are shown in red and with immunoreceptor tyrosine-based activation motif (ITAM) and ITAM-like motif-encoding exons in green and blue, respectively. Clockwise oriented arrows symbolize inversion events of the regions between the two CEACAM1-like gene clusters which have taken place independently in two different clades. Note that, in general, the genes in the same subcluster show the same transcriptional orientation, between the two subclusters opposite transcriptional orientation. The ancestral gene arrangement is unknown. Therefore, indication of species with inversion events is arbitrary; inversions relative to the human gene order are shown. The nucleotide numbering of the chromosomes starts at the telomere of the short arms. The scale indicated by dots is 1 Mbp unless interrupted by slanted lines. Note the inverse orientation of the opossum chromosome 4, cattle chromosome 18 and human chromosome 19 regions. C, CEACAM/Ceacam; chr, chromosome; P, PSG/Psg.