Cross-referencing methylation status with CTCF occupancy. (A) shows that an antibody against 5-methylcytidine immunopurifies only the methylated paternal H19 ICR allele if the maternally inherited allele is of the wild type. Conversely, when the mutated H19 ICR allele is inherited maternally (labeled 142* and unable to interact with CTCF in vivo while displaying massive de novo methylation; Pant et al. 2003), both alleles are brought down as determined by using PCR primers spanning CTCF target site #3 and a diagnostic EcoRV site (Pant et al. 2003). (B,C) Scatterplot analyses comparing CTCF in vivo occupancy/insulator strength vs. single CpG methylation (B, using an antibody against methylated cytidine) and clustered (C, using an antibody against MBD2) CpG methylation states in mouse fetal liver.
