MEDIPS was developed for analyzing data derived from methylated DNA immunoprecipitation (MeDIP) experiments followed by sequencing (MeDIP-seq). Nevertheless, several functionalities may be applied to other types of sequencing data (e.g. differential coverage or testing the saturation of ChIP-seq data). MEDIPS addresses several aspects in the context of MeDIP-seq data analysis including basic data processing, several quality controls, normalization, and identification of differential coverage.
As a quality check for the enrichment of CpG rich DNA fragments obtained by the immunoprecipitation step of a MeDIP experiment, this function provides the functionality to calculate CpG enrichment values. The main idea is to check, how strong the regions are enriched for CpGs compared to the reference genome. For this, the function counts the number of Cs, the number of Gs, the number CpGs, and the total number of bases within the stated reference genome. Subsequently, the function calculates the relative frequency of CpGs and the observed/expected ratio of CpGs present in the reference genome. Additionally, the function calculates the same for the DNA sequences underlying the given regions. The final enrichment values result by dividing the relative frequency of CpGs (or the observed/expected value, respectively) of the regions by the relative frequency of CpGs (or the observed/expected value, respectively) of the reference genome.
The function calculates the local densities of a defined sequence pattern (e.g. CpGs) and returns a COUPLING SET object which is necessary for normalizing MeDIP data.
Reads the input file and calculates the short read coverage (counts) for the specified regions of interest(ROI). After reading of the input file, the MEDIPS ROI SET contains information about the input file name, the dependent organism, the chromosomes included in the input file, the length of the included chromosomes (automatically loaded), the number of regions, and a GRange object of the ROIs.
Reads the input file and calculates genome wide short read coverage (counts) at the specified window size. After reading of the input file, the MEDIPS SET contains information about the input file name, the dependent organism, the chromosomes included in the input file, the length of the included chromosomes (automatically loaded), and the number of regions.
The function allows for exporting the calculated methylation values (counts or rpkm) or sequence pattern densities from a MEDIPS or COUPLING SET into a wiggle (WIG) file. The wiggle file will contain values for all genomic windows of the genome/coupling vector and can be used for data visualization using appropriate genome browsers. Either a MEDIPS SET (parameter MSet) or a COUPLING SET (parameter CSet) has to be given.
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