Features of Methylation and Gene Expression in the Promoter-Associated CpG Islands Using Human Methylome Data

Table 1

Summary of the CpG islands (CGIs) or CpG clusters (CGCs) identified by different algorithms in the human genome.

Method*	Whole genome CGIs					Promoter-associated CGIs
	# CGIs	Length (bp)	GC content (%)	CpG O/E**		# CGIs	Proportion (%)	# genes	CGIs/gene	Length (bp)	GC content (%)	CpG O/E**
TJ-CGIs	37, 729	1089	60.6	0.717		13,207	35.0	12, 521	1.05	1477	62.2	0.759
CGCs-15	37, 184	605	68.7	0.855		14,419	38.8	11, 292	1.28	694	70.1	0.885
CGCs-20	25, 454	727	70.3	0.853		12,115	47.6	10, 245	1.18	767	70.6	0.885
UCSC-CGIs	27, 639	763	66.1	0.862		12,297	44.5	11, 744	1.05	964	69.3	0.862

*The methods/algorithms for screening CpG islands or CpG clusters are described in Section 2.
**CpG O/E: the ratio of the observed versus expected number of CpG dinucleotides in a sequence.