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Hum Mol Genet. 2015 Jul 15;24(14):4061-77. doi: 10.1093/hmg/ddv146. Epub 2015 Apr 23.

Alu-mediated diverse and complex pathogenic copy-number variants within human chromosome 17 at p13.3.

Author information

1
Department of Molecular & Human Genetics.
2
Department of Molecular & Human Genetics, Texas Children's Hospital, Houston, TX 77030, USA and.
3
Department of Molecular & Human Genetics, Department of Biological Regulation, Weizmann Institute of Science, Rehovot, Israel.
4
Department of Molecular & Human Genetics, Department of Pediatrics and Human Genome Sequencing Center, Baylor College of Medicine, Houston, TX 77030, USA, Texas Children's Hospital, Houston, TX 77030, USA and jlupski@bcm.edu.

Abstract

Alu repetitive elements are known to be major contributors to genome instability by generating Alu-mediated copy-number variants (CNVs). Most of the reported Alu-mediated CNVs are simple deletions and duplications, and the mechanism underlying Alu-Alu-mediated rearrangement has been attributed to non-allelic homologous recombination (NAHR). Chromosome 17 at the p13.3 genomic region lacks extensive low-copy repeat architecture; however, it is highly enriched for Alu repetitive elements, with a fraction of 30% of total sequence annotated in the human reference genome, compared with the 10% genome-wide and 18% on chromosome 17. We conducted mechanistic studies of the 17p13.3 CNVs by performing high-density oligonucleotide array comparative genomic hybridization, specifically interrogating the 17p13.3 region with ∼150 bp per probe density; CNV breakpoint junctions were mapped to nucleotide resolution by polymerase chain reaction and Sanger sequencing. Studied rearrangements include 5 interstitial deletions, 14 tandem duplications, 7 terminal deletions and 13 complex genomic rearrangements (CGRs). Within the 17p13.3 region, Alu-Alu-mediated rearrangements were identified in 80% of the interstitial deletions, 46% of the tandem duplications and 50% of the CGRs, indicating that this mechanism was a major contributor for formation of breakpoint junctions. Our studies suggest that Alu repetitive elements facilitate formation of non-recurrent CNVs, CGRs and other structural aberrations of chromosome 17 at p13.3. The common observation of Alu-mediated rearrangement in CGRs and breakpoint junction sequences analysis further demonstrates that this type of mechanism is unlikely attributed to NAHR, but rather may be due to a recombination-coupled DNA replicative repair process.

PMID:
25908615
PMCID:
PMC4476451
DOI:
10.1093/hmg/ddv146
[Indexed for MEDLINE]
Free PMC Article

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