Genome-wide analysis of natural selection in human repetitive DNA elements

摘要

BackgroundFrom previous studies on coding sequences,population differentiation in the modern human genome has been indicated to be affected by natural selection acting at gene level. Repetitive DNA elements account for more than half content of the human genome, most of which locate outside the exons of genes. Therefore, it remains to be elucidated whether these elements are among the candidate target of natural selection during the evolution of modern human populations.ResultsUsing fixation index (FST), population differentiation has been assessed for 1.28 million SNPs from HapMap Phase Ⅱ data, all of which reside within repetitive DNA elements.Different spectra of population differentiation have been observed in repetitive DNA elements through comparing with SNPs residing outside these elements. Population differentiation at SNPs with low minor allele frequencies (MAF) is significantly reduced in Alu elements,suggesting potential negative selection in the elements (Figure 1). In addition, population differentiation is increased in Alu and ERV elements at SNPs with intermediate MAF,showing positive selection effects on these elements.