Novel cis-regulatory function in ICR-mediated imprinted repression of H19

► Sequence outside of CTCF sites at the ICR is required for imprinted H19 repression. ► Hypermethylation of the paternal H19 ICR is insufficient for full H19 repression. ► H19 ICR size and CpG density play a major role in paternal H19 repression.