Figure 4

The protein phylogenetic (ME) trees of all 17 ancestral (pre-WGD) vertebrate tetraspanin lineages. The bony vertebrate ortholog lineages and the ohnolog patterns are highlighted as shown in panel A. Red-filled rectangles are used to mark each ancestral lineage in panel J and K. #1, a distant tetraspanin, only found in ray-finned fish otocephala; #2, found in ray-finned fishes, xenopus and reptiles, probably an independent duplicate of TSPAN4; #3, a tetraspanin pseudogene from mouse; #4, a divergent tetraspanin found in all bony vertebrates, originated by retrotransposition; #5, mammalian ROM1, the true ortholog of bony vertebrate ROM1, but too divergent to cluster with other ROM1; #6, mammal TSPAN16, the true ortholog of teleost TSPAN16, but too divergent to cluster with other TSPAN16; #7, a divergent lineage, its position is not determined; #8 and #9, no synteny shared between TSPAN33 and TSPAN33-like, but since they were separated before the radiation of bony vertebrates, here we treated them as an ohnolog pair; #10, found in reptiles and mammals, as a result of tandem duplication of CD81, becoming too divergent to cluster with CD81; #11, only found in ray-finned fish otocephala, as a result of independent duplication of CD9, becoming too divergent to cluster with CD9; #12, has weak support for its clustering with tetrapod CD37 and sharing no synteny, so its identity is questionable.