Table 1.

Abbreviations used frequently in this paper

Term	Meaning	Description
GEO	Gene Expression Omnibus	Public database containing all methylation array data analyzed in this paper.
GSE	Study accession number	Unique identifier for a study record in GEO that includes a platform, set of sample records and supplemental matrices containing assay data.
GSM	Sample accession number	Unique identifier for a sample record that includes sample-specific metadata and may also include supplemental sample datasets.
CpG	Cytosine-guanine dinucleotide	Dinucleotide sequence, or locus, consisting of a cytosine followed by a guanine.
DNAm	DNA methylation	The presence of a nucleotide-bound methyl group, typically at the 5’ cytosine position in a CpG locus.
HM450K	HumanMethylome 450K	Popular array platform, manufactured by Illumina, that uses BeadArray technology to probe DNAm at roughly 480 000 CpG loci.