Establishment of paternal methylation imprint at the imprinting control region.

The insulator model explains the workings of the and imprinted domain in the soma, where insulation of the promoter from its enhancers occurs by CTCF in the maternally inherited unmethylated chromosome but not the paternally inherited methylated allele. The molecular mechanism that targets paternal methylation imprint establishment to the imprinting control region (ICR) in the male germline is unknown. We tested the function of prospermatogonia-specific broad low-level transcription in this process using mouse genetics.