Comparison of human and mouse T-cell receptor variable gene segment subfamilies

Like the immunoglobulin Igh-V and Igk-V gene families, the human or mouse TCRV gene families may be grouped into subfamilies displaying > 75% nucleic acid sequence similarity among their members. Systematic interspecies sequence comparisons reveal that most mouse Tcr-V subfamilies exhibit clear homology to human TCRV subfamilies (> 60% amino acid sequence similarity). Homologous pairs of TCRV genes in mice and humans show higher sequence similarity than TCRV genes from different subfamilies within either species, indicating transspecies evolution of TCRV genes. Mouse and human homologues show conservation of their relative map order, particularly in the 3' region and a similar sequential and developmentally programmed expression. When the V regions from both species were analyzed together, local length differences and conserved residues in the loop regions were revealed, characteristic of each of the four TCRV families.