The immunoglobulin κ locus of primates

Abstract

The immunoglobulin κ genes of nonhuman primates were studied by using sequence information and hybridization probes derived from the human κ gene regions. The following results were obtained: (1) V κ gene probes of the three major human κ subgroups hybridized to restriction nuclease digests of DNA from the chimpanzees Pan troglodytes (PTR) and Pan paniscus (PPA), the gorilla Gorilla gorilla (GGO), the orangutan Pongo pygmaeus (PPY), the macaque Macaca mulatta (MMU), the marmoset Callithrix geoffrei (CGE), and the bushbaby Galago demidovii (GDE), yielding patterns of decreasing similarity to the patterns of the human V κ multigene family. (2) The C κ gene segments of PTR, GGO, and PPY were 99.6, 97, and 93%, respectively, identical in sequence to the human C κ gene. A V κ gene in PTR, GGO, PPY, and MMU was 98, 96, 96, and 95%, respectively, identical to the most C κ proximal V κ gene, called B3. The other two J κC κ proximal V κ genes in human, B1 and B2, hybridize to restriction fragments of sizes identical to that of DNA from humans and great apes. (3) The long-range restriction maps of the human (HSA), PTR, and GGO κ loci as established by pulsed-field gel electrophoresis (PFGE) are quite homologous. According to the maps, however, and to hybridization studies with 11 duplication-differentiating probes, there is only one copy of the locus in PTR and GGO. This means that the duplication of large parts of the κ locus as found in humans occurred after the branch-point of human and great ape evolution. Despite the high similarity in structural details, the κ locus of the chimpanzee probably comprises only about half as many V κ genes as the human κ locus. (4) Comparative PFGE experiments indicate that a V κ-orphon region on the long arm of chromosome 2 (cos108) was translocated by a pericentric inversion that occurred after the separation of the GGO and PPY from the HSA and PTR clades.