Molecular Biology and Evolution, Vol 8, 563-578, Copyright © 1991 by Society for Molecular Biology and Evolution
ZF Zhu, V Vincek, F Figueroa, C Schonbach and J Klein
The DRB family of human class II major histocompatibility complex (Mhc)
loci is unusual in that individuals differ in the number and combination of
genes (haplotypes) they carry. Indications are that both the allelic and
haplotype polymorphisms of the DRB loci predate speciation. Searching for
the evolutionary origins of these polymorphisms, we have sequenced five DRB
clones isolated from a cDNA library of a pigtail macaque (Macaca
nemestrina) B lymphocyte line. The clones represent five different genes
which we designate Mane-DRB*01- Mane-DRB*05. The genes appears to be
approximately equidistant from each other, so that allelic relationships
between them cannot be established on the basis of the sequence data alone.
If positions coding for the peptide-binding region of the class II beta
chains are eliminated from sequence comparisons, the Mane-DRB genes appear
to be most closely related to the human (HLA) DRB1 genes of the DRw52
group. We interpret this finding to indicate that the ancestral gene of the
DRw52 group of human DRB1 alleles separated from the rest of the HLA- DRB1
alleles before the separation of the Old World monkeys (Cercopithecoidea)
from the apes (Hominoidea) in the early Oligocene. After this separation,
the ancestral DRB1 gene of the DRw52 group duplicated in the Old World
monkey lineage to give rise to genes at three loci at least, while in the
ape lineage this gene may have remained single and diverged into a number
of alleles instead. These findings suggest that some of the polymorphism
currently present at the DRB1 locus is greater than 35 Myr old.
ORIGINAL ARTICLE
Mhc-DRB genes of the pigtail macaque (Macaca nemestrina): implications for the evolution of human DRB genes
Max-Planck-Institut fur Biologie, Abteilung Immungenetik, Tubingen, Germany.
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