Background

In recent years the Illumina HumanMethylation450 (HM450) BeadChip has provided a user-friendly platform to profile DNA methylation in human samples. However, HM450 lacked coverage of distal regulatory elements. Illumina have now released the MethylationEPIC (EPIC) BeadChip, with new content specifically designed to target these regions. We have used HM450 and whole-genome bisulphite sequencing (WGBS) to perform a critical evaluation of the new EPIC array platform.

Results

EPIC covers over 850,000 CpG sites, including >90 % of the CpGs from the HM450 and an additional 413,743 CpGs. Even though the additional probes improve the coverage of regulatory elements, including 58 % of FANTOM5 enhancers, only 7 % distal and 27 % proximal ENCODE regulatory elements are represented. Detailed comparisons of regulatory elements from EPIC and WGBS show that a single EPIC probe is not always informative for those distal regulatory elements showing variable methylation across the region. However, overall data from the EPIC array at single loci are highly reproducible across technical and biological replicates and demonstrate high correlation with HM450 and WGBS data. We show that the HM450 and EPIC arrays distinguish differentially methylated probes, but the absolute agreement depends on the threshold set for each platform. Finally, we provide an annotated list of probes whose signal could be affected by cross-hybridisation or underlying genetic variation.

Conclusion

The EPIC array is a significant improvement over the HM450 array, with increased genome coverage of regulatory regions and high reproducibility and reliability, providing a valuable tool for high-throughput human methylome analyses from diverse clinical samples.

Pidsley R, Zotenko E, Peters T J, et al. Critical evaluation of the Illumina MethylationEPIC BeadChip microarray for whole-genome DNA methylation profiling[J]. Genome biology, 2016, 17(1): 1-17.

1.   Workflow Selection

In the current version, multiple functions are integrated in the work flow "WGBS Pipeline Accuracy Analysis".

2.   Customized Parameter

1). "Project name"

Give your analysis a name, it will serve as the recognizable name “Job Name” in “My Jobs - Results”.

· Data

1). "Data From": "DRS", "Local", "Web"

Location of data to be analyzed.

Web = Only upload the data temporarily for analysis;

DRS = Data stored in the Data Repository Storage already;

If "Local" OR "Web" is selected in "Data From", you need to fill in the corresponding ID here.

· Script

· Others (Under development)

row = chromosome location;