Methylation levels at VMRs are influenced by heritable and non-heritable factors.

(A) Cell count corrected heritability [17] for VMRs in five cell types. Shared VMRs found in >1 cell type show significantly higher heritability, suggesting these are mostly under genetic control. (B) Methylation differences found within 426 pairs of monozygotic twins. CpGs that lie within VMRs show significantly increased MZ twin divergence compared to other CpGs, which is consistent with an environmental influence on methylation levels at VMRs.