title: Chromosomal dynamics of nucleolar organizer regions (NORs) in the house mouse: micro-evolutionary insights.
abstract: Variation in the number and chromosomal location of nucleolar organizer regions (NORs) was studied in the house mouse, Mus musculus (2n=40). From an origin in Western Asia, this species colonized the Middle East, Europe and Asia. This expansion was accompanied by diversification into five subspecies. NOR diversity was revealed by fluorescence in situ hybridization using 18S and 28S probes on specimens spanning Asia to Western Europe. The results showed that the house mouse genome possessed a large number of NOR-bearing autosomes and a surprisingly high rate of polymorphism for the presence/absence of rRNA genes on all these chromosomes. All NOR sites were adjacent to the centromere except for two that were telomeric. Subspecific differentiation established from the NOR frequency data was concordant with the overall pattern of radiation proposed from molecular studies, but highlighted several discrepancies that need to be further addressed. NOR diversity in M. musculus consisted of a large number of polymorphic NORs that were common to at least two subspecies, and a smaller number of NORs that were unique to one subspecies. The most parsimonious scenario argues in favor of a subspecific differentiation by lineage sorting of ancestral NOR polymorphisms; only the unique NORs would have appeared by inter-chromosomal transposition, except for the two telomeric ones that may have originated by hybridization with another species. Such a scenario provides an alternative view from the one prevailing in most systematic and phylogenetic analyses that NORs have a high transposition rate due to concerted evolution of rRNA genes.
authors.affiliation: Institut des Sciences de l'Evolution, Université Montpellier 2, Montpellier cedex, France. janice.britton-davidian@univ-montp2.fr
authors.forename: J
authors.initials: J
authors.lastname: Britton-Davidian
authors.forename: B
authors.initials: B
authors.lastname: Cazaux
authors.forename: J
authors.initials: J
authors.lastname: Catalan
mesh_terms: D000818:Animals; D033481:Chromosomes, Mammalian / Q000235:genetics / Q000378:metabolism*; D019143:Evolution, Molecular; D020459:Genes, rRNA; D014644:Genetic Variation; D017404:In Situ Hybridization, Fluorescence; D051379:Mice / Q000235:genetics*; D009697:Nucleolus Organizer Region; D010802:Phylogeny; D011110:Polymorphism, Genetic
references.citation: Mol Ecol. 2008 Dec;17(24):5349-63
references.pmid: 19121002
references.citation: Mol Biol Evol. 1987 Nov;4(6):594-601
references.pmid: 3444415
references.citation: Chromosome Res. 2004;12(4):383-95
references.pmid: 15241017
references.citation: Genetics. 2007 Feb;175(2):477-85
references.pmid: 17322354
references.citation: Genomics. 2006 Nov;88(5):564-71
references.pmid: 16765020
references.citation: J Vet Med Sci. 2007 Dec;69(12):1277-9
references.pmid: 18176025
references.citation: Genetica. 2010 Mar;138(3):343-354
references.pmid: 19921441
references.citation: Cytogenet Genome Res. 2009;126(4):359-67
references.pmid: 20110675
references.citation: Genomics. 2003 Dec;82(6):637-43
references.pmid: 14611805
references.citation: Proc Natl Acad Sci U S A. 2008 Sep 23;105(38):14477-81
references.pmid: 18787123
references.citation: J Vet Med Sci. 2008 Sep;70(9):997-1000
references.pmid: 18840979
references.citation: Mol Ecol. 2008 Jan;17(2):627-41
references.pmid: 18179435
references.citation: Genetics. 1998 Oct;150(2):835-61
references.pmid: 9755213
references.citation: C R Biol. 2002 Feb;325(2):89-97
references.pmid: 11980180
references.citation: Evolution. 1998 Apr;52(2):592-603
references.pmid: 28568333
references.citation: Mol Biol Evol. 2004 Aug;21(8):1595-601
references.pmid: 15155800
references.citation: Genomics. 2001 May 1;73(3):255-63
references.pmid: 11350117
references.citation: Chromosome Res. 2004;12(3):225-37
references.pmid: 15125636
references.citation: Cytogenet Cell Genet. 1980;26(2-4):158-64
references.pmid: 6156053
references.citation: Plant Cell. 2006 Mar;18(3):529-44
references.pmid: 16461583
references.citation: Genetica. 2010 Oct;138(9-10):951-7
references.pmid: 20680404
references.citation: Mamm Genome. 1996 Dec;7(12):886-9
references.pmid: 8995758
references.citation: Cytogenet Genome Res. 2008;122(1):41-54
references.pmid: 18931485
references.citation: Mol Biol Evol. 1986 Mar;3(2):126-37
references.pmid: 2895411
references.citation: Cytogenet Genome Res. 2008;120(3-4):351-7
references.pmid: 18504364
references.citation: Chromosome Res. 2008;16(4):595-607
references.pmid: 18431681
references.citation: Heredity (Edinb). 2002 Aug;89(2):154-8
references.pmid: 12136419
references.citation: Cytogenet Genome Res. 2002;98(1):75-7
references.pmid: 12584445
references.citation: Mol Biol Evol. 1990 May;7(3):271-82
references.pmid: 1694258
references.citation: Mol Ecol. 2011 Dec;20(24):5248-64
references.pmid: 22066696
references.citation: Heredity (Edinb). 2009 Jul;103(1):54-61
references.pmid: 19384343
references.citation: Chromosome Res. 1999;7(6):481-92
references.pmid: 10560971
references.citation: Genome Biol. 2007;8(5):R80
references.pmid: 17501990
references.citation: Comput Appl Biosci. 1996 Aug;12(4):357-8
references.pmid: 8902363
references.citation: Chromosome Res. 2006;14(8):845-57
references.pmid: 17195054
references.citation: BMC Evol Biol. 2011 May 13;11:124
references.pmid: 21569527