LIMS support is available for the Infinium MethylationEPIC BeadChip and the Infinium Mouse Methylation BeadChip.
Background subtraction is required when you compare data run on different types of scanners because of technical disparities. Background subtraction has a much smaller effect when you scan chips on the same scanner, and might not be necessary. Analyze a subset of data with and without subtraction, and choose the subset of data you prefer based on your results.
The array density is much higher in the Infinium HumanMethylation450 BeadChip. There are a large number of CpGs for which multiple transcripts are listed and for which the CpG site can fall into different annotation categories. Consequently, the task of calculating TSS distances would be a large bioinformatic undertaking, and the numbers would have to be modified every time the genome was updated. Additionally, the column "UCSC_RefGene_Group" has content about the location of the CpG relative to specific regions and features of the associated genes, which is in many ways richer than the simple distance relative to transcriptional start site.
FFPE samples are NOT recommended for the standard protocol. FFPE samples are already highly degraded, with a high level of crosslinking, so conversion does not occur effectively. However, you can run FFPE samples on the Infinium HumanMethylation450 BeadChip using the FFPE automated or FFPE manual protocol along with the Infinium FFPE DNA Restoration Solution kit.
Illumina has not extensively tested any of the commercially available standards, and does not currently recommend any of them. In-house, Illumina uses standards generated in our own laboratory. Our methods for generating the standards are described in the following article:
This is a two-color assay.
For the Infinium HumanMethyation27 BeadChip assay, which is based on Infinium I Assay designs, the color incorporated depends upon the base preceding the CpG locus being queried. This can be either green or red.
The Infinium HumanMethylation450 BeadChip assay includes Infinium I and Infinium II study designs. In the latter case, a single base extension from the 3' end of the probe sequence (which is one base upstream of the query base) will result in either a red or green signal depending on whether the query site was unmethylated or methylated.
Yes. Illumina recommends the following of-the-shelf bisulfite conversion kits from Zymo Research.
SNPs were included on the BeadChip so investigators could generate a DNA fingerprintof their samples as an added level of quality control. Please find further information in the Infinium HD Methylation Assay Protocol Guide. SNP assays on the BeadChip are not mentioned in the assay guide and only briefly described in the GenomeStudio Methylation Module. Follow this method to confirm the identity of samples from the same individual:
Samples from the same individual:
Samples from different persons:
The scatterplots differ because the beta values calculated from SNP assays will cluster, much as they do in a standard genotyping theta graph. Samples from the same individual have the SNP results fall along the identity line in a scatter plot, whereas samples from different persons scatter into the 9 different possible spots, based on their genotypes.
What you are seeing are histograms of the beta values in bins of 0.02 steps and categorized by Infinium design type. The difference in beta value ranges between the Infinium I and Infinium II assay design types cause the double peaks. In general, the beta peaks at the extremes of Infinium I probes tend to be further out than the beta peaks for Infinium II.
The beta beak differences do not affect the final analysis of the project. Individual CpG assays are not intended to be compared directly with other CpG assays, as each probe (or probe set for Infinium I designs) has different binding characteristics and behaves differently than any other probe or probe set. Rather, each assay is compared between two samples or sample groups (ie, in determining a relative rather than an absolute methylation value). For the Infinium HumanMethylation450K, Infinium Mouse Methylation, and Infinium MethylationEPIC array, we expect technical replicates to show > 98% correlation, and often observe > 99% correlation.
Similar to the Infinium genotyping assay, Illumina recommends DNA that is sized ≥ 2kb, which can be assessed on an agarose gel.
If you use at least 250–1000 ng DNA for the bisulfite conversion, requantification is not necessary. It is critical to quantify the input DNA concentration with PicoGreen to make sure that you add sufficient DNA to the bisulfite conversion reaction. Bisulfite conversion renders DNA less complementary, therefore much of the DNA are denatured and more difficult to quantitate accurately.
Download the manifest file for the array from the Product Files page of the BeadChip support pages.
See the Merging Gene Expression and Methylation Data technical note.
For information, see the Infinium Methylation Coverage Technical Note.
Illumina has not validated the array for 5-hMc. However, publications have used the Infinium HumanMethylation450K array for 5-hMc analysis and it is possible that this protocol will works on the Infinium MethylationEPIC array.
For more information, see Nazor, Kristopher L., et al. "Application of a low cost array-based technique—TAB-Array—for quantifying and mapping both 5mC and 5hmC at single base resolution in human pluripotent stem cells." Genomics 104.5 (2014): 358-367.