The evolution of African great ape subtelomeric heterochromatin and the fusion of human chromosome 2
- Mario Ventura1,2,7,
- Claudia R. Catacchio1,2,7,
- Saba Sajjadian1,
- Laura Vives1,
- Peter H. Sudmant1,
- Tomas Marques-Bonet3,4,
- Tina A. Graves5,
- Richard K. Wilson5 and
- Evan E. Eichler1,6,8
- 1Department of Genome Sciences, University of Washington School of Medicine, Seattle, Washington 98195, USA;
- 2Department of Genetics and Microbiology, University of Bari, Bari 70126, Italy;
- 3IBE, Institut de Biologia Evolutiva (UPF-CSIC), Universitat Pompeu Fabra, 08003 Barcelona, Catalonia, Spain;
- 4Institució Catalana de Recerca i Estudis Avançats (ICREA), 08010 Barcelona, Catalonia, Spain;
- 5Washington University Genome Sequencing Center, School of Medicine, St. Louis, Missouri 63108, USA;
- 6Howard Hughes Medical Institute, Seattle, Washington 98195, USA
Abstract
Chimpanzee and gorilla chromosomes differ from human chromosomes by the presence of large blocks of subterminal heterochromatin thought to be composed primarily of arrays of tandem satellite sequence. We explore their sequence composition and organization and show a complex organization composed of specific sets of segmental duplications that have hyperexpanded in concert with the formation of subterminal satellites. These regions are highly copy number polymorphic between and within species, and copy number differences involving hundreds of copies can be accurately estimated by assaying read-depth of next-generation sequencing data sets. Phylogenetic and comparative genomic analyses suggest that the structures have arisen largely independently in the two lineages with the exception of a few seed sequences present in the common ancestor of humans and African apes. We propose a model where an ancestral human-chimpanzee pericentric inversion and the ancestral chromosome 2 fusion both predisposed and protected the chimpanzee and human genomes, respectively, to the formation of subtelomeric heterochromatin. Our findings highlight the complex interplay between duplicated sequences and chromosomal rearrangements that rapidly alter the cytogenetic landscape in a short period of evolutionary time.
Footnotes
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↵7 These authors contributed equally to this paper.
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↵8 Corresponding author.
E-mail eee{at}gs.washington.edu.
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[Supplemental material is available for this article.]
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Article published online before print. Article, supplemental material, and publication date are at http://www.genome.org/cgi/doi/10.1101/gr.136556.111.
- Received December 16, 2011.
- Accepted March 6, 2012.
This article is distributed exclusively by Cold Spring Harbor Laboratory Press for the first six months after the full-issue publication date (see http://genome.cshlp.org/site/misc/terms.xhtml). After six months, it is available under a Creative Commons License (Attribution-NonCommercial 3.0 Unported License), as described at http://creativecommons.org/licenses/by-nc/3.0/.
