Genomic imprinting: CTCF protects the boundaries.
Lewis A., Murrell A.
The DNA-binding protein CTCF, which acts as a chromatin 'insulator', regulates imprinting of the mammalian Igf2 and H19 genes in a methylation-sensitive manner. It has now been shown that CTCF is also required for protection against de novo methylation of the differentially methylated domain of H19 in the female germline.