DMRcaller: Call Differentially Methylated Regions (DMRs) between two...
In DMRcaller: Differentially Methylated Regions caller

Description Details Author(s) See Also Examples

Uses bisulfite sequencing data in two conditions and identifies differentially methylated regions between the conditions in CG and non-CG context. The input is the CX report files produced by Bismark and the output is a list of DMRs stored as GRanges objects.

The most important functions in the DMRcaller are:

readBismark: reads the Bismark CX report files in a GRanges object.
readBismarkPool: Reads multiple CX report files and pools them together.
saveBismark: saves the methylation data stored in a GRanges object into a Bismark CX report file.
poolMethylationDatasets: pools together multiple methylation datasets.
poolTwoMethylationDatasets: pools together two methylation datasets.
computeMethylationDataCoverage: Computes the coverage for the bisulfite sequencing data.
plotMethylationDataCoverage: Plots the coverage for the bisulfite sequencing data.
computeMethylationDataSpatialCorrelation: Computes the correlation between methylation levels as a function of the distances between the Cytosines.
plotMethylationDataSpatialCorrelation: Plots the correlation of methylation levels for Cytosines located at a certain distance apart.
computeMethylationProfile: Computes the low resolution profiles for the bisulfite sequencing data at certain locations.
plotMethylationProfile: Plots the low resolution profiles for the bisulfite sequencing data at certain locations.
plotMethylationProfileFromData: Plots the low resolution profiles for the loaded bisulfite sequencing data.
computeDMRs: Computes the differentially methylated regions between two conditions.
filterDMRs: Filters a list of (potential) differentially methylated regions.
mergeDMRsIteratively: Merge DMRs iteratively.
analyseReadsInsideRegionsForCondition: Analyse reads inside regions for condition.
plotLocalMethylationProfile: Plots the methylation profile at one locus for the bisulfite sequencing data.
computeOverlapProfile: Computes the distribution of a set of subregions on a large region.
plotOverlapProfile: Plots the distribution of a set of subregions on a large region.
getWholeChromosomes: Computes the GRanges objects with each chromosome as an element from the methylationData.
joinReplicates: Merges two GRanges objects with single reads columns. It is necessary to start the analysis of DMRs with biological replicates.
computeDMRsReplicates: Computes the differentially methylated regions between two conditions with multiple biological replicates.

Nicolae Radu Zabet n.r.zabet@gen.cam.ac.uk, Jonathan Michael Foonlan Tsang jmft2@cam.ac.uk Alessandro Pio Greco apgrec@essex.ac.uk

Maintainer: Nicolae Radu Zabet n.r.zabet@gen.cam.ac.uk

See vignette("rd", package = "DMRcaller") for an overview of the package.

## Not run: 
# load the methylation data
data(methylationDataList)

#plot the low resolution profile at 5 Kb resolution
par(mar=c(4, 4, 3, 1)+0.1)
plotMethylationProfileFromData(methylationDataList[["WT"]],
                               methylationDataList[["met1-3"]],
                               conditionsNames=c("WT", "met1-3"),
                               windowSize = 5000, autoscale = TRUE,
                               context = c("CG", "CHG", "CHH"),
                               labels = LETTERS)

# compute low resolution profile in 10 Kb windows in CG context
lowResProfileWTCG <- computeMethylationProfile(methylationDataList[["WT"]],
                     region, windowSize = 10000, context = "CG")

lowResProfileMet13CG <- computeMethylationProfile(
                     methylationDataList[["met1-3"]], region,
                     windowSize = 10000, context = "CG")

lowResProfileCG <- GRangesList("WT" = lowResProfileWTCG,
                   "met1-3" = lowResProfileMet13CG)

# compute low resolution profile in 10 Kb windows in CHG context
lowResProfileWTCHG <- computeMethylationProfile(methylationDataList[["WT"]],
                     region, windowSize = 10000, context = "CHG")

lowResProfileMet13CHG <- computeMethylationProfile(
                     methylationDataList[["met1-3"]], region,
                     windowSize = 10000, context = "CHG")

lowResProfileCHG <- GRangesList("WT" = lowResProfileWTCHG,
                   "met1-3" = lowResProfileMet13CHG)

# plot the low resolution profile
par(mar=c(4, 4, 3, 1)+0.1)
par(mfrow=c(2,1))
plotMethylationProfile(lowResProfileCG, autoscale = FALSE,
                       labels = LETTERS[1],
                       title="CG methylation on Chromosome 3",
                       col=c("#D55E00","#E69F00"),  pch = c(1,0),
                       lty = c(4,1))
plotMethylationProfile(lowResProfileCHG, autoscale = FALSE,
                       labels = LETTERS[2],
                       title="CHG methylation on Chromosome 3",
                       col=c("#0072B2", "#56B4E9"),  pch = c(16,2),
                       lty = c(3,2))

# plot the coverage in all three contexts
plotMethylationDataCoverage(methylationDataList[["WT"]],
                           methylationDataList[["met1-3"]],
                           breaks = 1:15, regions = NULL,
                           conditionsNames = c("WT","met1-3"),
                           context = c("CG", "CHG", "CHH"),
                           proportion = TRUE, labels = LETTERS, col = NULL,
                           pch = c(1,0,16,2,15,17), lty = c(4,1,3,2,6,5),
                           contextPerRow = FALSE)

# plot the correlation of methylation levels as a function of distance
plotMethylationDataSpatialCorrelation(methylationDataList[["WT"]],
                           distances = c(1,5,10,15), regions = NULL,
                           conditionsNames = c("WT","met1-3"),
                           context = c("CG"),
                           labels = LETTERS, col = NULL,
                           pch = c(1,0,16,2,15,17), lty = c(4,1,3,2,6,5),
                           contextPerRow = FALSE)

# the regions where to compute the DMRs
regions <- GRanges(seqnames = Rle("Chr3"), ranges = IRanges(1,1E6))

# compute the DMRs in CG context with noise_filter method
DMRsNoiseFilterCG <- computeDMRs(methylationDataList[["WT"]],
                     methylationDataList[["met1-3"]], regions = regions,
                     context = "CG", method = "noise_filter",
                     windowSize = 100, kernelFunction = "triangular",
                     test = "score", pValueThreshold = 0.01,
                     minCytosinesCount = 4, minProportionDifference = 0.4,
                     minGap = 200, minSize = 50, minReadsPerCytosine = 4,
                     cores = 1)

# compute the DMRs in CG context with neighbourhood method
DMRsNeighbourhoodCG <- computeDMRs(methylationDataList[["WT"]],
                       methylationDataList[["met1-3"]], regions = regions,
                       context = "CG", method = "neighbourhood",
                       test = "score", pValueThreshold = 0.01,
                       minCytosinesCount = 4, minProportionDifference = 0.4,
                       minGap = 200, minSize = 50, minReadsPerCytosine = 4,
                       cores = 1)

# compute the DMRs in CG context with bins method
DMRsBinsCG <- computeDMRs(methylationDataList[["WT"]],
               methylationDataList[["met1-3"]], regions = regions,
               context = "CG", method = "bins", binSize = 100,
               test = "score", pValueThreshold = 0.01, minCytosinesCount = 4,
               minProportionDifference = 0.4, minGap = 200, minSize = 50,
               minReadsPerCytosine = 4, cores = 1)

# load the gene annotation data
data(GEs)

#select the genes
genes <- GEs[which(GEs$type == "gene")]

# the regions where to compute the DMRs
genes <- genes[overlapsAny(genes, regions)]

# filter genes that are differntially methylated in the two conditions
DMRsGenesCG <- filterDMRs(methylationDataList[["WT"]],
               methylationDataList[["met1-3"]], potentialDMRs = genes,
               context = "CG", test = "score", pValueThreshold = 0.01,
               minCytosinesCount = 4, minProportionDifference = 0.4,
               minReadsPerCytosine = 3, cores = 1)

#merge the DMRs
DMRsNoiseFilterCGLarger <- mergeDMRsIteratively(DMRsNoiseFilterCG,
                           minGap = 500, respectSigns = TRUE,
                           methylationDataList[["WT"]],
                           methylationDataList[["met1-3"]],
                           context = "CG", minProportionDifference=0.4,
                           minReadsPerCytosine = 1, pValueThreshold=0.01,
                           test="score",alternative = "two.sided")

#select the genes
genes <- GEs[which(GEs$type == "gene")]

# the coordinates of the area to be plotted
chr3Reg <- GRanges(seqnames = Rle("Chr3"), ranges = IRanges(510000,530000))

# load the DMRs in CG context
data(DMRsNoiseFilterCG)

DMRsCGlist <- list("noise filter"=DMRsNoiseFilterCG,
                   "neighbourhood"=DMRsNeighbourhoodCG,
                   "bins"=DMRsBinsCG,
                   "genes"=DMRsGenesCG)


# plot the CG methylation
par(mar=c(4, 4, 3, 1)+0.1)
par(mfrow=c(1,1))
plotLocalMethylationProfile(methylationDataList[["WT"]],
                           methylationDataList[["met1-3"]], chr3Reg,
                           DMRsCGlist, c("WT", "met1-3"), GEs,
                           windowSize=100, main="CG methylation")


hotspotsHypo <- computeOverlapProfile(
               DMRsNoiseFilterCG[(DMRsNoiseFilterCG$regionType == "loss")],
               region, windowSize=2000, binary=TRUE, cores=1)

hotspotsHyper <- computeOverlapProfile(
               DMRsNoiseFilterCG[(DMRsNoiseFilterCG$regionType == "gain")],
               region, windowSize=2000, binary=TRUE, cores=1)

plotOverlapProfile(GRangesList("Chr3"=hotspotsHypo),
                   GRangesList("Chr3"=hotspotsHyper),
                   names=c("loss", "gain"), title="CG methylation")
# loading synthetic data
data("syntheticDataReplicates")

# creating condition vector
condition <- c("a", "a", "b", "b")

# computing DMRs using the neighbourhood method
DMRsReplicatesNeighbourhood <- computeDMRsReplicates(methylationData = methylationData,
                                                     condition = condition,
                                                     regions = NULL,
                                                     context = "CHH",
                                                     method = "neighbourhood",
                                                     test = "betareg",
                                                     pseudocountM = 1,
                                                     pseudocountN = 2,
                                                     pValueThreshold = 0.01,
                                                     minCytosinesCount = 4,
                                                     minProportionDifference = 0.4,
                                                     minGap = 200,
                                                     minSize = 50,
                                                     minReadsPerCytosine = 4,
                                                     cores = 1)

## End(Not run)