# Description

This track displays regions of the reference genome that have exceptionally high sequence depth, inferred from alignments of short-read sequences from the 1000 Genomes Project. These regions may be caused by collapsed repetitive sequences in the reference genome assembly; they also have high read depth in assays such as ChIP-seq, and may trigger false positive calls from peak-calling algorithms. Excluding these regions from analysis of short-read alignments should reduce such false positive calls.

# Methods

Pickrell et al. downloaded sequencing reads for 57 Yoruba individuals from the 1000 Genomes Project's low-coverage pilot data, mapped them to the Mar. 2006 human genome assembly (NCBI36/hg18), computed the read depth for every base in the genome, and compiled a distribution of read depths. They then identified contiguous regions where read depth exceeded thresholds corresponding to the top 0.001, 0.005, 0.01, 0.05 and 0.1 of the per-base read depths, merging regions which fall within 50 bases of each other. The regions are available for download from http://eqtl.uchicago.edu/Masking/ (see the readme file).

# Credits

Thanks to Joseph Pickrell at the University of Chicago for these data.

# References

Pickrell JK, Gaffney DJ, Gilad Y, Pritchard JK. False positive peaks in ChIP-seq and other sequencing-based functional assays caused by unannotated high copy number regions. Bioinformatics. 2011 Aug 1;27(15):2144-6. Epub 2011 Jun 19.