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Genetics, Vol. 177, 2507-2517, December 2007, Copyright © 2007
doi:10.1534/genetics.107.082313

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Genomic Instability Within Centromeres of Interspecific Marsupial Hybrids

Cushla J. Metcalfe*,1, Kira V. Bulazel*, Gianni C. Ferreri*, Elizabeth Schroeder-Reiter{dagger}, Gerhard Wanner{dagger}, Willem Rens{ddagger}, Craig Obergfell*, Mark D. B. Eldridge§ and Rachel J. O'Neill*,2

* Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut 06269, {ddagger} Cambridge Resource Centre for Comparative Genomics, Department of Clinical Veterinary Medicine, University of Cambridge, Cambridge CB2 1TN, United Kingdom, {dagger} Department Biologie I, Ludwig-Maximilians-Universität München, 80638 Munich, Germany and § Australian Museum, Sydney, New South Wales 2010, Australia

2 Corresponding author: Department of Molecular and Cell Biology, U-2131, 354 Mansfield Rd., Room 323, University of Connecticut, Storrs, CT 06269.
E-mail: rachel.oneill{at}uconn.edu

Several lines of evidence suggest that, within a lineage, particular genomic regions are subject to instability that can lead to specific types of chromosome rearrangements important in species incompatibility. Within family Macropodidae (kangaroos, wallabies, bettongs, and potoroos), which exhibit recent and extensive karyotypic evolution, rearrangements involve chiefly the centromere. We propose that centromeres are the primary target for destabilization in cases of genomic instability, such as interspecific hybridization, and participate in the formation of novel chromosome rearrangements. Here we use standard cytological staining, cross-species chromosome painting, DNA probe analyses, and scanning electron microscopy to examine four interspecific macropodid hybrids (Macropus rufogriseus x Macropus agilis). The parental complements share the same centric fusions relative to the presumed macropodid ancestral karyotype, but can be differentiated on the basis of heterochromatic content, M. rufogriseus having larger centromeres with large C-banding positive regions. All hybrids exhibited the same pattern of chromosomal instability and remodeling specifically within the centromeres derived from the maternal (M. rufogriseus) complement. This instability included amplification of a satellite repeat and a transposable element, changes in chromatin structure, and de novo whole-arm rearrangements. We discuss possible reasons and mechanisms for the centromeric instability and remodeling observed in all four macropodid hybrids.






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Copyright © 2007 by the Genetics Society of America.