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Comparison of the canine and human olfactory receptor gene repertoires

Pascale Quignon1, Ewen Kirkness2, Edouard Cadieu1, Nizar Touleimat1, Richard Guyon1, Corinne Renier13, Christophe Hitte1, Catherine André1, Claire Fraser2 and Francis Galibert1*

Author Affiliations

1 UMR 6061 CNRS Génétique et Développement, Faculté de Médecine, 2 Avenue du Professeur Léon Bernard, 35043 Rennes Cedex, France

2 The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, MD 20850, USA

3 Current address: Stanford University School of Medicine, Center for Narcolepsy, 701B Welch Road, Palo Alto, CA 94305-5742, USA

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Genome Biology 2003, 4:R80  doi:10.1186/gb-2003-4-12-r80

Published: 28 November 2003



Olfactory receptors (ORs), the first dedicated molecules with which odorants physically interact to arouse an olfactory sensation, constitute the largest gene family in vertebrates, including around 900 genes in human and 1,500 in the mouse. Whereas dogs, like many other mammals, have a much keener olfactory potential than humans, only 21 canine OR genes have been described to date.


In this study, 817 novel canine OR sequences were identified, and 640 have been characterized. Of the 661 characterized OR sequences, representing half of the canine repertoire, 18% are predicted to be pseudogenes, compared with 63% in human and 20% in mouse. Phylogenetic analysis of 403 canine OR sequences identified 51 families, and radiation-hybrid mapping of 562 showed that they are distributed on 24 dog chromosomes, in 37 distinct regions. Most of these regions constitute clusters of 2 to 124 closely linked genes. The two largest clusters (124 and 109 OR genes) are located on canine chromosomes 18 and 21. They are orthologous to human clusters located on human chromosomes 11q11-q13 and HSA11p15, containing 174 and 115 ORs respectively.


This study shows a strongly conserved genomic distribution of OR genes between dog and human, suggesting that OR genes evolved from a common mammalian ancestral repertoire by successive duplications. In addition, the dog repertoire appears to have expanded relative to that of humans, leading to the emergence of specific canine OR genes.