title: Isolation of novel olfactory receptor genes in marmosets (Callithrix): insights into pseudogene formation and evidence for functional degeneracy in non-human primates.
abstract: Nineteen olfactory receptor (OR) genes were isolated from three OR subfamilies in two species of marmoset (Callithrix). Olfactory receptor 912-93 has high sequence similarity among marmosets and between marmosets and humans, suggesting strong conservation of function. All of the remaining seventeen OR genes identified from subfamilies 3A and 1E were pseudogenes. Following pseudogene formation, marmoset OR genes in both 1E and 3A subfamilies underwent duplications, indel events and a high rate of nucleotide substitution. These results provide a contrast to previous studies, and show that in spite of the keen olfactory sense of marmosets, they harbour many OR pseudogenes. A high rate of in vitro recombination using Pfu polymerase but not Taq polymerase was confirmed. The rapid molecular evolution of OR pseudogenes suggests that they do not provide a useful source of sequence variation for conversion to intact OR genes over evolutionary timescales. The overall pattern of OR evolution in marmosets is comparable to the 'birth-and-death' model of gene family evolution. An unbiased view on the evolutionary timing of the reduction of the functional olfactory repertoire in humans must await more data.
authors.affiliation: Department of Biological Anthropology, University of Oxford, Oxford, UK.
authors.forename: Alaine
authors.initials: A
authors.lastname: Whinnett
authors.forename: Nicholas I
authors.initials: NI
authors.lastname: Mundy
mesh_terms: D000818:Animals; D002144:Callithrix / Q000235:genetics*; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D004259:DNA-Directed DNA Polymerase / Q000378:metabolism; D019143:Evolution, Molecular; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics; D010802:Phylogeny; D016133:Polymerase Chain Reaction / Q000379:methods; D011110:Polymorphism, Genetic; D011544:Pseudogenes / Q000235:genetics; D018035:Receptors, Odorant / Q000235:genetics*; D017422:Sequence Analysis, DNA; D019914:Taq Polymerase / Q000378:metabolism
chemical_list: D018035:Receptors, Odorant; D004247:DNA; C072146:Pfu DNA polymerase; D019914:Taq Polymerase; D004259:DNA-Directed DNA Polymerase