Background CpG dinucleotide-rich genomic DNA areas, known as CpG islands (CGIs), can be methylated at their cytosine residues mainly because an epigenetic mark that is stably inherited during cell mitosis. size, and a reduced CpG percentage. Practical analysis of the genes associated with autosomal IRDM-CGIs showed that many of them are involved in DNA binding and development. Conclusions Our results display that several specific practical and structural features characterize common IRDM-CGIs. They may symbolize a specific subset of CGIs that are more prone to becoming differentially methylated for his or her intrinsic characteristics. cell culture. In particular, we focused on DM-CGIs found in culture replicas of the same cell collection. Although culture conditions, including medium composition, heat, CO2%, and cell-cell relationships, are standardized TSA and the cell micro-environment is definitely expected to become the same across TSA replicas, it is likely that marginal changes happen by opportunity. In light of these considerations, we analyzed the variance in CGI methylation between replicas of 35 cell lines. We used publicly available data provided by the Encyclopedia of DNA Elements (ENCODE) consortium . As expected, we found that most CGIs showed related DNA methylation ideals between the two replicas. We focused our attention within the minority of CGIs with different DNA methylation levels between the two replicas. The CGIs showing this behaviour inside a cell collection were found differentially methylated also in additional cell lines more frequently than expected by opportunity. Furthermore, we found that several Fgfr2 practical and structural specific features characterize these CGIs. Results Evaluation of CpG island methylation and calculation of the correlation between replicas For CpG island definition and localization, we used the UCSC Genome Internet browser CpG island track (Cpg Island Ext track). CpG methylation data from 35 cell lines produced by the ENCODE consortium  were downloaded from your UCSC Genome Internet browser (http://genome.ucsc.edu, HAIB Methyl RRBS track) . Data for two replicas are available for each cell collection within this repository. To compare different cell lines, we restricted our analysis to CGIs in which methylation data were present in both replicas only. In order to define a reliable methylation level for any CGI we regarded as its CpGs having a go through protection??10 only. These cell lines belonged to three organizations: cancer transformed cells (n?=?10), EBV transformed cells (n?=?5) and normal untransformed cells (n?=?20). Additional file 1: Table S1 shows the list of the cells used and their features. To estimate the level of DNA methylation of each CGI, we determined the mean methylation ideals of all CpGs located within a CGI. Recognition of inter replicas differentially methylated CpG islands As expected, we observed a good correlation between the two replicas for each cell type using the Pearson correlation (mean?=?0.97). To identify CGIs that were differentially methylated between two replicas of the same cell collection, we have sequentially applied two methods: Quantitative Differentially Methylated Region (QDMR) and TSA Hypergeometric Centered Approach (HBA). The first is a quantitative method that identifies differentially methylated areas using an entropy-based algorithm  (observe Methods). HBA is definitely a method able to test the statistical need for possible variations in the methylation amounts between two reproductions of a specific genomic area. QDMR is specially sensitive towards the total difference in the methylation degree of two reproductions regarded as while HBA is specially sensitive towards the examine coverage and the quantity of CpGs within the CGI regarded as (see Strategies). We thought as Inter Reproductions Differentially Methylated CpG Islands (IRDM-CGIs), the CGIs which were categorized by both methods as differentially methylated. Such conservative approach has the advantage to take simultaneously into account the read coverage and the CpG content of the considered CGI, and the difference in the methylation values measured in the two replicas. By using sequentially these two methods we observed an average of 439.5 IRDM-CGIs per cell line (range, 109-913). No statistically significant differences were noted in the number of IRDM-CGIs between cancer, EBV and normal cell lines using Welchs one-way analysis of means test (p?=?0.262). IRDM-CGIs are similar across different cell lines Since we expected that the same CGI be methylated to the same extent in two replicas of.