Hi All,

New to this forum - so please correct me if this Q is misplaced.

Is it possible to do ChIP-seq QC on broad peaks (diffuse histone marks and pol2) with ChIPQC?

Maybe by using the PeakCaller="macs".

Found no documentation regarding this

Kind regards,

Linda

hi Linda,

I think the problem lies in the sample names.

Both sample sheets (from the RData objects) contain sample names starting with numerics. Internally names for R objects which start with a numeric have a "X" attached and this then causes problems in ChIPQC plotting functions.

The second "no_consensus" RData object has "#" in the sample names which will also be a problem.

 I would recommend replacing "#" with underscore and adding "Sample" infront of your numeric IDs i.e. 1 become Sample_1.

You can use also use the make.names() function to produce names which will work in ChIPQC. If i try make.names() on a few of your sample names then you can see where the problem is.

> make.names("12")
[1] "X12"
> make.names("7856_8#7")
[1] "X7856_8.7"

Thanks for your reply!

I have called peaks with MACS2 - and are now trying to figure out how obtain the QC metrics for h3k4me3, h3k27me3 and pol2 domains. I just keep getting the following error: 

> ChIPQCreport(samples)

Saving 7 x 7 in image

Error in `$<-.data.frame`(`*tmp*`, "SCALE_X", value = 1L) : 

  replacement has 1 row, data has 0

Calls: ChIPQCreport ... facet_train_layout -> facet_train_layout.wrap -> $<- -> $<-.data.frame

In addition: Warning message:

In max(panels$ROW) : no non-missing arguments to max; returning -Inf

Execution halted

Im not at all aware of what the error message is referring to - other than some data are missing - so was just wondering if it might had something to do with MACS2 .xls peak files missing the summit column? 

Cheers,

Linda

hi Linda,

ChIPQC can be used for Broad peaks. It is important to call peaks using an appropriate peak caller when working with more diffuse marks. Peak callers like Sicer or MACs2 can do a pretty good job with Pol2 and less diffuse histone marks.

For comparison there are some Pol2 and histone marks in the ChIPQC course run at BioC 2014 conference (at this link)

http://www.bioconductor.org/help/course-materials/2014/BioC2014/Bioc2014_ChIPQC_Practical.pdf

Hope that helps,

tom

Thomas Carroll
Head of Bioinformatics
MRC Clinical Sciences Centre, Faculty of Medicine,
Imperial College London,Hammersmith Hospital Campus
Du Cane Road,London,W12 0NN

hi Linda,

Could you share with tc.infomatics@gmail.com?

thank you.

tom

Have done (-: Thanks.

I only think That is a problem with the plotCC, no also the plotPeakProfile

Cheers,

Hi Tom,

Thanks for your help - all the plots are working now.

I have a question regarding the peak profiles of my controls. They all seems very much enriched ... also more than many of my ip samples  - however these "enrichments" is not spotted in the control pileup files from macs2 when inspecting the controls in IGV (of cause only on selected areas - those which are the most highly reproducible between replicates AND thus would be on the consensus peak list which ChIPQC generates when using consensus=TRUE). Any thoughts on this?

How is R calculating these "peaks"?

thank you so much and kind regards, Linda