Journal Article

Large Multi-Chromosomal Duplications Encompass Many Members of the Olfactory Receptor Gene Family in the Human Genome

Barbara J. Trask, Hillary Massa, Veronique Brand-Arpon, Kin Chan, Cynthia Friedman, Oanh T. Nguyen, Evan Eichler, Ger van den Engh, Sylvie Rouquier, Hiroaki Shizuya and Dominique Giorgi

in Human Molecular Genetics

Volume 7, issue 13, pages 2007-2020
Published in print December 1998 | ISSN: 0964-6906
Published online December 1998 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/7.13.2007
Large Multi-Chromosomal Duplications Encompass Many Members of the Olfactory Receptor Gene Family in the Human Genome

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The human genome contains thousands of genes that encode a diverse repertoire of odorant receptors (ORs). We report here on the identification and chromosomal localization of 74 OR-containing genomic clones. Using fluorescence in situ hybridization (FISH), we demonstrate a striking homology among a set of ∼20 OR locations, illustrating a history of duplications that have distributed OR sequences across the genome. Half of the OR-containing BACs cloned from total genomic DNA and 86% of cosmids derived from chromosome 3 cross-hybridize to a subset of these locations, many to 17 of them. These paralogous regions are distributed on 13 chromosomes, and eight lie in terminal bands. By analyzing clones from an ∼250 kb clone-walk across one of these sites (3p13), we show that the homology among these sites is extensive (>150 kb) and encompasses both OR genes and intergenic genomic sequences. The FISH signals appear significantly larger at some sites than at the native location, indicating that portions of some duplicons have undergone local amplification/attrition. More restricted duplications involving pairs of other genomic locations are detected with 12% of the OR-BACs. Only a small subset of OR locations is sufficiently diverged from the others that clones derived from them behave as single-copy FISH probes. We estimate that duplications encompassing members of the OR gene family account for >0.1% of the human genome. A comparison of FISH signals at orthologous locations in other primates indicates that a portion of this OR ‘subgenome’ has been in flux during the divergence of primates, possibly as a mechanism for evolving the repertoire of olfactory receptors.

Journal Article.  10512 words.  Illustrated.

Subjects: Genetics and Genomics

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