ChIP-seq peak calling from replicates

[ttnguyen]

Hi,
Are there any advice or software to do peak calling for histone modification ChIP-seq data having two replicates with two corresponding control libraries? Thanks a lot.

[emilyjia2000]

I have similar data, which is technique replicate, I am thinking merge the two replicates before peak calling. any suggestions?

Thanks

[mudshark]

the easiest way is to do the peak calling on each data set and retain the common peaks. however, histone modificiations might not necessarily give a peak-like pattern rather extended regions of enrichment. this could be more difficult to analyze.

[emilyjia2000]

Hi, shark,
How do judge if the peaks are common or not between the two replicates? I am asking because very few peaks could be exactly same, some of them could be overlapped more or less between two replicates.
Thanks

[mudshark]

that should depend on the nature of your target. for sequence specific transcription factors I would consider common peaks to be located (peak center) within 200 bp. for histone modifications this is more difficult to define.

in case you have similar amount of reads in all your samples you could also do a simple enrichment statistic on windowed data (100 bp windows e.g.). as I already said histone modifications might have extended regions of enrichment and peak calling is not the best way to look for those.