Adult monozygotic twins discordant for intra-uterine growth have indistinguishable genome-wide DNA methylation profiles

Table 6 Genome-wide DNA methylation studies for birth weight

Study	Design	Sample	Tissue	Method	Significant loci	Remark
Einstein et al. [16]	Population based	5 IUGR and 5 AGA	CD34+ hematopoietic stem cells (cord blood)	HELP	56 loci (P < 0.00001)
Banister et al. [37]	Population based	89 IUGR and 117 AGA	Placenta	HM27	22 loci (number predetermined)
Fryer et al. [34]	Population based	12 newborns	Cord blood	HM27	304 loci (P < 0.05)	Samples were selected to give a range in LINE1 methylation values
Adkins et al. [36]	Population based	201 newborns	Cord blood	HM27	10 loci (P < 0.001)
Turan et al. [35]	Population based	48 newborns	Cord blood and placenta	HM27	23 loci	Regularized regression model fit was used (R² > 0.80)
Gordon et al. [38]	Twin design	18 MZ and 10 DZ^a	CBMCs, placenta and UVECs	HM27	7 loci in DZ CBMCs 1 loci in MZ UVECs (FDR <0.1)	Twins not selected for birth weight discordancy

^aMaximal 18 MZ and 10 DZ twins per tissue. AGA, appropriate for gestational age; CBMC, cord blood mononuclear cell; DZ, dizygotic twin; FDR, false discovery rate; HELP, HpaII tiny fragment Enrichment by Ligation-mediated PCR assay; HM27, HumanMethylation27 BeadChip; IUGR, intra-uterine growth retarded; MZ, monozygotic twins; UVEC, umbilical vascular endothelial cell.

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