Two CD1 genes map to the chicken MHC, indicating that CD1 genes are ancient and likely to have been present in the primordial MHC
- Jan Salomonsen†,‡,
- Maria Rathmann Sørensen†,‡,
- Denise A. Marston‡,§,
- Sally L. Rogers§,
- Trevor Collen§,
- Andrew van Hateren§,
- Adrian L. Smith§,
- Richard K. Beal§,
- Karsten Skjødt¶, and
- Jim Kaufman§,∥
- †Department of Pathobiology, Laboratory of Immunology, Royal Veterinary and Agricultural University, Stigbøjlen 7, DK-1870 Frederiksberg C, Denmark; §Division of Immunology and Pathology, Institute for Animal Health, Compton, Berks RG20 7NN, United Kingdom; and ¶Department of Immunology and Medical Microbiology, University of Southern Denmark, Winsløvparken 21, DK-5000 Odense C, Denmark
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Edited by Max D. Cooper, University of Alabama, Birmingham, AL, and approved April 6, 2005 (received for review December 10, 2004)
Abstract
CD1 molecules play an important role in the immune system, presenting lipid-containing antigens to T and NKT cells. CD1 genes have long been thought to be as ancient as MHC class I and II genes, based on various arguments, but thus far they have been described only in mammals. Here we describe two CD1 genes in chickens, demonstrating that the CD1 system was present in the last common ancestor of mammals and birds at least 300 million years ago. In phylogenetic analysis, these sequences cluster with CD1 sequences from other species but are not obviously like any particular CD1 isotype. Sequence analysis suggests that the expressed proteins bind hydrophobic molecules and are recycled through intracellular vesicles. RNA expression is strong in lymphoid tissues but weaker to undetectable in some nonlymphoid tissues. Flow cytometry confirms expression from one gene on B cells. Based on Southern blotting and cloning, only two such CD1 genes are detected, located ≈800 nucleotides apart and in the same transcriptional orientation. The sequence of one gene is nearly identical in six chicken lines. By mapping with a backcross family, this gene could not be separated from the chicken MHC on chromosome 16. Mining the draft chicken genome sequence shows that chicken has only these two CD1 genes located ≈50 kb from the classical class I genes. The unexpected location of these genes in the chicken MHC suggests the CD1 system was present in the primordial MHC and is thus ≈600 million years old.
Footnotes
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↵ ∥ To whom correspondence should be addressed. E-mail: jim.kaufman{at}bbsrc.ac.uk.
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↵ ‡ J.S., M.R.S., and D.A.M. contributed equally to this work.
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Author contributions: J.S., A.v.H., and J.K. designed research; J.S., M.R.S., D.A.M., S.L.R., A.v.H., A.L.S., R.K.B., K.S., and J.K. performed research; J.S., D.A.M., S.L.R., T.C., A.v.H., K.S., and J.K. analyzed data; and D.A.M. and J.K. wrote the paper.
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This paper was submitted directly (Track II) to the PNAS office.
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Data deposition: The sequences reported in this paper have been deposited in the GenBank database (accession nos. AY849318-AY849320).
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See Commentary on page 8399.
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↵ †† Miller, S., Dykes, D. & Polesky, H. (1988) Nucleic Acids Res. 16, 215 (abstr.).
- Copyright © 2005, The National Academy of Sciences
