Journal Article

Extrachromosomal amplification mechanisms in a glioma with amplified sequences from multiple chromosome loci

Anne Gibaud, Nicolas Vogt, Nabila-Sandra Hadj-Hamou, Jean-Philippe Meyniel, Philippe Hupé, Michelle Debatisse and Bernard Malfoy

in Human Molecular Genetics

Volume 19, issue 7, pages 1276-1285
Published in print April 2010 | ISSN: 0964-6906
Published online January 2010 | e-ISSN: 1460-2083 | DOI: http://dx.doi.org/10.1093/hmg/ddq004
Extrachromosomal amplification mechanisms in a glioma with amplified sequences from multiple chromosome loci

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Accumulation of extrachromosomal DNA molecules (double minute) is often responsible for gene amplification in cancers, but the mechanisms leading to their formation are still largely unknown. By using quantitative PCR, chromosome walking, in situ hybridization on metaphase chromosomes and whole genome analysis, we studied a glioma containing four extrachromosomally amplified loci (7p11, 1q32.1, 5p15 and 9p2). Complex extrachromosomal DNA molecules were formed by the fusion of several syntenic or non-syntenic DNA fragments from 7p11, 5p15 to 9p2. Fragments ranged from a few base pairs to megabase pairs. Scars of the amplification process remained at the original locus in the form of deletions or chromosome rearrangements. Chromosome fragmentation, due to replication stress, could explain this complex situation. In contrast, at 1q32.1, the initial extrachromosomal DNA molecule resulted from the circularization of a single fragment associated with an intrachromosomal deletion including, but larger than, the amplified sequence. The nature of the sequences involved in these rearrangements suggests that a V(D)J-like illegitimate recombination contributes to its formation.

Journal Article.  5367 words.  Illustrated.

Subjects: Genetics and Genomics

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