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J Mol Evol

Title:		Exceptional LINE density at V1R loci: the Lyon repeat hypothesis revisited on autosomes
Author(s):		Kambere MB; Lane RP;
Address:		"Department of Molecular Biology and Biochemistry, Wesleyan University, Middletown, CT 06459, USA. mkambere@wesleyan.edu"
Journal Title:		J Mol Evol
Year:		2009
Volume:		20090120
Issue:		2
Page Number:		145 - 159
DOI:		10.1007/s00239-008-9195-0
ISSN/ISBN:		1432-1432 (Electronic) 0022-2844 (Linking)
Abstract:		"The mammalian olfactory system utilizes three large receptor families: the olfactory receptors (ORs) of the main nose and the vomeronasal type-1 and type-2 receptor genes (V1Rs and V2Rs) of the vomeronasal organ. We find that these loci are among the most long interspersed nuclear element (LINE)-dense regions of mammalian genomes. We investigate two evolutionary models to account for this cohabitation. First, we investigate an adaptive selection model, in which LINEs have contributed to expansions of mouse V1R repertoires. We find that even evolutionarily stable V1R loci are exceptionally LINE-rich compared to other genome loci, including loci containing other large gene clusters. Also, a more detailed analysis of specific V1R duplications does not reveal LINE patterns predicted by common LINE-mediated duplication mechanisms. Next, we investigate neutral models, in which LINEs were tolerated by, but not advantageous for, surrounding V1R genes. We find that V1R loci are exceptionally LINE-rich compared to other regions of similar AT base composition, and that duplicated V1R gene blocks are generally depleted of LINE elements, suggesting that these loci did not become densely populated with LINEs simply as a consequence of targeted integration or passive multiplication along with the genes. Finally, we show that individual LINE repeats of a given age at V1R, V2R, and OR loci exhibit a significantly longer average length than at other autosomal loci, suggesting a reduced tendency for these LINEs to be disrupted. We speculate that LINEs at V1R, V2R, and OR loci might be selectively retained because they contribute to allelic regulation of these three gene families"
Keywords:		"Algorithms Animals Cattle Chromosomes, Mammalian/genetics Cluster Analysis Dogs Dosage Compensation, Genetic *Evolution, Molecular Gene Duplication Long Interspersed Nucleotide Elements/*genetics Mammals/*genetics Mice *Models, Genetic Opossums Rats Recep;"
Notes:		"MedlineKambere, Marijo B Lane, Robert P eng R01-DC006267/DC/NIDCD NIH HHS/ Research Support, N.I.H., Extramural Germany 2009/01/21 J Mol Evol. 2009 Feb; 68(2):145-59. doi: 10.1007/s00239-008-9195-0. Epub 2009 Jan 20"