Model for the evolution of gphβ/nt locus in vertebrates. Left panel: evolution of the ancestral locus with the first and second whole genome duplication (WGD). Right panel: resulting known genomic loci in sea lamprey Petromyzon marinus, elephant shark Callorhinchus milii and zebrafish Danio rerio. It is still to be established whether cyclostomes have been submitted to the two rounds of genome duplication or not. Duplicate loci resulting from WGD or the Fish Specific Genome Duplication (FSGD) are indicated by vertical brackets whereas horizontal brackets represent local gene duplications (LD). Crossed boxes represent genes that have been lost after duplication. Genes demonstrated to be gathered in a definite locus are linked by a horizontal bar. The origin of tshβ2 in Callorhinchus is uncertain, either resulting from the second round of WGD or from a local duplication of tshβ. A tshβ-type subunit gene is expected in lamprey but has not been characterized yet and is represented as an empty box. NTFt and NTFg are given symbols for ancestral NTs associated with TSH and GTH, respectively.
Dos Santos et al. BMC Evolutionary Biology 2011 11:332 doi:10.1186/1471-2148-11-332