Lineage-specific diversification of killer cell Ig-like receptors in the owl monkey,a New World primate |
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Authors: | Luis F Cadavid Cheng-Man Lun |
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Institution: | (1) Department of Biology and Institute of Genetics, Universidad Nacional de Colombia, Cr. 30 # 4508, Bogotá, Distrito Capital, Colombia;(2) Department of Biology, The University of New Mexico, Albuquerque, NM 87131-0001, USA |
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Abstract: | Killer cell Ig-like receptors (KIRs) modulate the cytotoxic effects of natural killer cells. In primates, the KIRs are highly
diverse as a consequence of variation in gene content, alternative domain composition, and loci polymorphism. We analyzed
a bacterial artificial chromosome (BAC) clone draft sequence spanning the owl monkey KIR cluster. The draft sequence had seven
ordered yet unconnected contigs containing six full-length and two partial gene models, flanked by the LILRB and FcAR framework
genes. Gene models were predicted to encode KIRs with inhibitory, activating, or dual functionality. Four gene models encoded
three Ig domain receptors, while three others encoded molecules with four Ig domains. The additional domain resulted from
an insertion in tandem of a 2,101 bp fragment containing the last 289 bp of intron 2, exon 3, and intron 3, resulting in molecules
with two D0 domains. Re-screening of the owl monkey BAC library and sequencing of partial cDNAs from an owl monkey yielded
five additional KIRs, four of which encoded receptors with short cytoplasmic domains with premature stop codons due to either
a single nucleotide substitution or deletion or the absence of exon 8. Phylogenetic analysis by domains showed that owl monkey
KIRs were monophyletic, clustering independently from other primate KIR lineages. Retroelements found in introns, however,
were shared by KIRs from different primate lineages. This suggests that the owl monkey inherited a KIR cluster with a rich
history of exon shuffling upon which positive selection for ligand binding operated to diversify the receptors in a lineage-specific
fashion.
Nucleotide sequence data reported are available in the GenBank database under accession numbers FJ154791–5. |
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Keywords: | KIR Aotus Evolution |
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