EVOLUTIONARY RELATIONSHIP BETWEEN HUMAN AND MOUSE IMMUNOGLOBULIN KAPPA-LIGHT CHAIN VARIABLE REGION GENES

Similar to the Igh-V multigene family, the human or mouse Igk-V repertoire is a distorted continuum of homologous genes that may be grouped into families displaying > 80% nucleic acid sequence similarity among their members. Systematic interspecies sequence comparisons reveal that most human Igk-V gene families exhibit clear homology to mouse Igk-V families (sequence similarity generally > 74%). A hypothetical phylogenetic tree of Igk-V genes predicts that a minimum of seven Igk-V genes/families predate mammalian radiation. In two cases, several interrelated mouse Igk-V families exhibit phylogenetic equidistance with just one human Igk-V family, implying a more pronounced divergence for the elevated number of Igk-V gene families in the mouse. Mouse-human Igk-V comparisons, moreover, illustrate how expansion, contraction, and perhaps deletion of Igk-V gene families shape the Igk-V repertoire during mammalian evolution.