DiffBind time course
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enricoferrero ▴ 660
@enricoferrero-6037
Last seen 2.5 years ago
Switzerland
Hi, Is there a way to use DiffBind to analyse time course data? I have sample and control replicates at five different time points and I would like to know which sites show differential binding over time. At the moment I'm doing multiple pairwise comparisons (i.e: sample at 24h vs control at 24h) and I'm trying to understand if it's possible at all and, if yes, what parameters I should pass to dba.contrast() and dba.analyze(). Thanks! -- Enrico Ferrero
DiffBind • 1.8k views
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Rory Stark ★ 5.2k
@rory-stark-5741
Last seen 17 days ago
Cambridge, UK
Hello Enrico- You can do some more advanced modelling using DiffBind, but to really get the full power of the GLMs, you probably want to extract the binding matrix and/or the edgeR/DESEq2 objects and run the appropriate RNA-seq package directly. Within DiffBind, you can use the "block" parameter in dba.contrast to indicate the metadata field that has the timepoint. So if the sample/control distinction is indicated as the Treatment and the timepoint info is in the Condition, you can say: > DBA = dba.contrast(DBA,categories=DBA_TREATMENT, block=DBA_CONDITION) > DBA = dba.analyze(DBA) # for default edgeR analysis This will model the data as [~Condition + Treatment] and give you the effects of the treatment consistent across timepoints. There are other models you may want to fit, (eg [~Condition * Treatment]); for this you would need to run edgeR (or DESeq/DESeq2) independently -- their respective vignettes give examples of analyzing time series data. -Rory On 09/08/2014 12:02, Enrico Ferrero <enricoferrero86 at="" gmail.com=""> wrote: > >--------------------------------------------------------------------- - > >Message: 1 >Date: Mon, 8 Sep 2014 12:01:57 +0100 >From: Enrico Ferrero <enricoferrero86 at="" gmail.com=""> >To: "bioconductor at r-project.org" <bioconductor at="" r-project.org=""> >Subject: [BioC] DiffBind time course >Message-ID: > <cao22hxcaqm_61p7uh4kskkm13yfn5g5hp7fzs32+cbgtnnpzdw at="" mail.gmail.com=""> >Content-Type: text/plain; charset=UTF-8 > >Hi, > >Is there a way to use DiffBind to analyse time course data? >I have sample and control replicates at five different time points and >I would like to know which sites show differential binding over time. > >At the moment I'm doing multiple pairwise comparisons (i.e: sample at >24h vs control at 24h) and I'm trying to understand if it's possible >at all and, if yes, what parameters I should pass to dba.contrast() >and dba.analyze(). > >Thanks! > >-- >Enrico Ferrero
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Hi Rory, Many thanks for the explanation. At first sight, using a blocking factor should probably do the job - I hadn't though about it. For future reference, how and at what step I can extract the binding matrix or edgeR/DESeq2 objects to continue the analysis with those packages? Thanks! Best, On 9 September 2014 14:43, Rory Stark <rory.stark at="" cruk.cam.ac.uk=""> wrote: > Hello Enrico- > > You can do some more advanced modelling using DiffBind, but to really get > the full power of the GLMs, you probably want to extract the binding > matrix and/or the edgeR/DESEq2 objects and run the appropriate RNA- seq > package directly. > > Within DiffBind, you can use the "block" parameter in dba.contrast to > indicate the metadata field that has the timepoint. So if the > sample/control distinction is indicated as the Treatment and the timepoint > info is in the Condition, you can say: > >> DBA = dba.contrast(DBA,categories=DBA_TREATMENT, block=DBA_CONDITION) >> DBA = dba.analyze(DBA) # for default edgeR analysis > > This will model the data as [~Condition + Treatment] and give you the > effects of the treatment consistent across timepoints. There are other > models you may want to fit, (eg [~Condition * Treatment]); for this you > would need to run edgeR (or DESeq/DESeq2) independently -- their > respective vignettes give examples of analyzing time series data. > > -Rory > > On 09/08/2014 12:02, Enrico Ferrero <enricoferrero86 at="" gmail.com=""> wrote: > >> >>-------------------------------------------------------------------- -- >> >>Message: 1 >>Date: Mon, 8 Sep 2014 12:01:57 +0100 >>From: Enrico Ferrero <enricoferrero86 at="" gmail.com=""> >>To: "bioconductor at r-project.org" <bioconductor at="" r-project.org=""> >>Subject: [BioC] DiffBind time course >>Message-ID: >> <cao22hxcaqm_61p7uh4kskkm13yfn5g5hp7fzs32+cbgtnnpzdw at="" mail.gmail.com=""> >>Content-Type: text/plain; charset=UTF-8 >> >>Hi, >> >>Is there a way to use DiffBind to analyse time course data? >>I have sample and control replicates at five different time points and >>I would like to know which sites show differential binding over time. >> >>At the moment I'm doing multiple pairwise comparisons (i.e: sample at >>24h vs control at 24h) and I'm trying to understand if it's possible >>at all and, if yes, what parameters I should pass to dba.contrast() >>and dba.analyze(). >> >>Thanks! >> >>-- >>Enrico Ferrero > -- Enrico Ferrero
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You can get the binding matrix after the call to dba.count, but you should make sure to set the "score" to either DBA_SCORE_READS or DBA_SCORE_READS_MINUS. If you've already counted and don't want to do it again, you can change the score and then retrieve the binding matrix: > DBA = dba.count(DBA,peaks=NULL,score=DBA_SCORE_READS) > bindingMatrix = dba.peakset(DBA, bRetrieve=TRUE) This will return the binding matrix as a GRanges object, with the read counts in the metadata. It may be easier to work with a dataframe: > bindingMatrix = dba.peakset(DBA, bRetrieve=TRUE, DataType=DBA_DATA_FRAME) In which case the count matrix is: > counts = bindingMatrix[,4:ncol(bindingMatrix)] As for retrieving the actual edgeR and DESeq object, the final section int he vignette describes where they are after a call to dba.analyze(). Cheers- Rory On 09/09/2014 15:29, "Enrico Ferrero" <enricoferrero86 at="" gmail.com=""> wrote: >Hi Rory, > >Many thanks for the explanation. At first sight, using a blocking >factor should probably do the job - I hadn't though about it. >For future reference, how and at what step I can extract the binding >matrix or edgeR/DESeq2 objects to continue the analysis with those >packages? > >Thanks! >Best, > > >On 9 September 2014 14:43, Rory Stark <rory.stark at="" cruk.cam.ac.uk=""> wrote: >> Hello Enrico- >> >> You can do some more advanced modelling using DiffBind, but to really >>get >> the full power of the GLMs, you probably want to extract the binding >> matrix and/or the edgeR/DESEq2 objects and run the appropriate RNA- seq >> package directly. >> >> Within DiffBind, you can use the "block" parameter in dba.contrast to >> indicate the metadata field that has the timepoint. So if the >> sample/control distinction is indicated as the Treatment and the >>timepoint >> info is in the Condition, you can say: >> >>> DBA = dba.contrast(DBA,categories=DBA_TREATMENT, block=DBA_CONDITION) >>> DBA = dba.analyze(DBA) # for default edgeR analysis >> >> This will model the data as [~Condition + Treatment] and give you the >> effects of the treatment consistent across timepoints. There are other >> models you may want to fit, (eg [~Condition * Treatment]); for this you >> would need to run edgeR (or DESeq/DESeq2) independently -- their >> respective vignettes give examples of analyzing time series data. >> >> -Rory >> >> On 09/08/2014 12:02, Enrico Ferrero <enricoferrero86 at="" gmail.com=""> wrote: >> >>> >>>------------------------------------------------------------------- --- >>> >>>Message: 1 >>>Date: Mon, 8 Sep 2014 12:01:57 +0100 >>>From: Enrico Ferrero <enricoferrero86 at="" gmail.com=""> >>>To: "bioconductor at r-project.org" <bioconductor at="" r-project.org=""> >>>Subject: [BioC] DiffBind time course >>>Message-ID: >>> >>><cao22hxcaqm_61p7uh4kskkm13yfn5g5hp7fzs32+cbgtnnpzdw at="" mail.gmail.com=""> >>>Content-Type: text/plain; charset=UTF-8 >>> >>>Hi, >>> >>>Is there a way to use DiffBind to analyse time course data? >>>I have sample and control replicates at five different time points and >>>I would like to know which sites show differential binding over time. >>> >>>At the moment I'm doing multiple pairwise comparisons (i.e: sample at >>>24h vs control at 24h) and I'm trying to understand if it's possible >>>at all and, if yes, what parameters I should pass to dba.contrast() >>>and dba.analyze(). >>> >>>Thanks! >>> >>>-- >>>Enrico Ferrero >> > > > >-- >Enrico Ferrero
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Dear Rory, 

Thank you for this response, I have found it to be very useful in an analysis I am doing, however I have a quick question:

This will model the data as [~Condition + Treatment] and give you the effects of the treatment consistent across timepoints.

I may have misinterpreted this, but if I performed this analysis with a block, that would show me the differences between my conditions any time-point? So if I found eg 600 sites when performing that analysis across a time-course, would I be expecting to see at least those 600 sites if I did a pair-wise comparison from one time-point in that analysis? I have performed that same analysis and see far fewer sites in a pairwise comparison than what I was seeing for the [condition + treatment].

Sorry if I have misinterpreted, and any clarification would be greatly appreciated. 

Kind regards, 
Andrew

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