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Open Access Research article

Alu repeats increase local recombination rates

David J Witherspoon1*, W Scott Watkins1, Yuhua Zhang1, Jinchuan Xing1, Whitney L Tolpinrud2, Dale J Hedges3, Mark A Batzer4 and Lynn B Jorde1

Author Affiliations

1 Dept. of Human Genetics, University of Utah Health Sciences Center, Salt Lake City, Utah, 84112, USA

2 Yale School of Medicine, New Haven, Connecticut, 06510, USA

3 Miami Institute for Human Genomics, Miller School of Medicine, University of Miami, Miami, 33124, USA

4 Dept. of Biological Sciences, Louisiana State University, Baton Rouge, Louisiana, 70803, USA

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BMC Genomics 2009, 10:530  doi:10.1186/1471-2164-10-530

Published: 16 November 2009

Abstract

Background

Recombination rates vary widely across the human genome, but little of that variation is correlated with known DNA sequence features. The genome contains more than one million Alu mobile element insertions, and these insertions have been implicated in non-homologous recombination, modulation of DNA methylation, and transcriptional regulation. If individual Alu insertions have even modest effects on local recombination rates, they could collectively have a significant impact on the pattern of linkage disequilibrium in the human genome and on the evolution of the Alu family itself.

Results

We carried out sequencing, SNP identification, and SNP genotyping around 19 AluY insertion loci in 347 individuals sampled from diverse populations, then used the SNP genotypes to estimate local recombination rates around the AluY loci. The loci and SNPs were chosen so as to minimize other factors (such as SNP ascertainment bias and SNP density) that could influence recombination rate estimates. We detected a significant increase in recombination rate within ~2 kb of the AluY insertions in our African population sample. To test this observation against a larger set of AluY insertions, we applied our locus- and SNP-selection design and analyses to the HapMap Phase II data. In that data set, we observed a significantly increased recombination rate near AluY insertions in both the CEU and YRI populations.

Conclusion

We show that the presence of a fixed AluY insertion is significantly predictive of an elevated local recombination rate within 2 kb of the insertion, independent of other known predictors. The magnitude of this effect, approximately a 6% increase, is comparable to the effects of some recombinogenic DNA sequence motifs identified via their association with recombination hot spots.