Asymmetric DNA methylation of CpG dyads is a feature of secondary DMRs associated with the Dlk1/Gtl2 imprinting cluster in mouse

Table 2 Average levels of DNA methylation on the paternal and maternal alleles are significantly different at the Gtl2- and IG-DMRs

	Genomic DNA sample	Grouped			Ungrouped
	Genomic DNA sample	% methylation, paternal alleles	% methylation, maternal alleles	P value	% methylation, paternal alleles	% methylation, maternal alleles	P value
Gtl2-DMR, 5′, BxC	7.5 d.p.c. embryo	82.2% (217/264)	11.7% (25/214)	0.0001	83.4% (257/308)	9.2% (32/346)	<0.0001
	14.5 d.p.c. embryo	82.5% (235/285)	1.5% (2/132)	0.0024	84.8% (279/329)	0.9% (2/220)	0.0001
	5 d.p.p. liver	69.7% (92/132)	8% (14/176)	0.0024	69.7% (92/132)	6.4% (14/220)	0.0014
	adult liver	78.3% (155/198)	15.4% (23/149)	0.0021	78.3% (155/198)	9.7% (23/237)	0.0004
IG-DMR, BxC	7.5 d.p.c. embryo	94.2% (912/968)	1.5% (2/132)	<0.01	94.5% (1621/1716)	1.1% (2/176)	<0.01
	14.5 d.p.c. embryo	96.9% (597/616)	11.1% (39/352)	0.0002	97.6% (816/836)	9.8% (39/396)	<0.0001
	5 d.p.p. liver	96.8% (852/880)	17.4% (45/258)	0.0003	97.6% (1159/1188)	16.8% (58/346)	<0.0001
	adult liver	97.2% (599/616)	13.6% (24/176)	<0.01	97.7% (1333/1364)	13.6% (24/176)	<0.01

Percent methylation and number of sites analyzed on the paternal and maternal alleles in DNA derived from 7.5 and 14.5 d.p.c. embryos and 5 d.p.p. and adult liver. Grouped data were derived when subclones from the same PCR with identical DNA methylation patterns and sequences were grouped as a single sample, as illustrated in Figs. 2, 4. Ungrouped data were derived when subclones from the same PCR with identical DNA methylation patterns and sequences were treated as independent samples. P values were calculated using a Mann–Whitney U test

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