Fig. 2

Comparative genome analysis of Trem genes in vertebrates. a Synteny block including Trem and their neighbor genes. The arrows represent the genes and their transcriptional orientations annotated in the Ensembl genome data for each species. Gray and black arrows indicate ITIM-containing Trem and other Trem genes, respectively. This figure is not drawn to scale. b Neighbor-joining tree of vertebrate Trem genes based on extracellular Ig domains. Numbers at the nodes represent the bootstrap confidence level in percentage. Only bootstrap values over 40 are indicated. Hs; human (Homo sapiens), Mm; mouse (Mus musculus), Oc; rabbit (Oryctolagus cuniculus), Cf; dog (Canis lupus familiaris), Ec; horse (Equus caballus), Bt; cow (Bos taurus), Ss; pig (Sus scrofa), Md; opossum (Monodelphis domestica), Gg; chicken (Gallus gallus), Xt; frog (Xenopus tropicalis). c Evolutionary model of murine paired Trem genes. Firstly, ancestral paired Trem gene and Treml7 rose from common ancestral gene that encored two ITIMs in its CPR. After brunching to murine linage, ancestral paired Trem gene containing ITIMs were duplicated, and the one of them evolved murine Treml6 gene. Another duplicated gene was translocated between Trem1 and Foxp4 genes and lost ITIMs. Finally, the common ancestor of Trem5 and Trem4 genes was duplicated, and evolved murine Trem5 and Trem4