Summary The mechanisms responsible for maintaining genomic methylation imprints in mouse embryos are not understood. We generated a knockout mouse in the Zfp57 locus encoding a KRAB zinc finger protein. Loss of just the zygotic function of Zfp57 causes partial neonatal lethality, while eliminating both maternal and zygotic functions of Zfp57 results in a highly penetrant embryonic lethality. In oocytes, absence of Zfp57 results in failure to establish maternal methylation imprints at the Snrpn imprinted region. Intriguingly, methylation imprints are re-acquired specifically at the maternally derived Snrpn imprinted region when the zygotic Zfp57 is present in embryos. This suggests that there may be DNA methylation-independent memory for genomic imprints. Zfp57 is also required for the post-fertilization maintenance of maternal and paternal methylation imprints at multiple imprinted domains. The effects on genomic imprinting are consistent with the maternal-zygotic lethality of Zfp57 mutants.

Background: ZFP57 is a maternal-zygotic effect gene that maintains genomic imprinting in mouse embryos. Results: KAP1 facilitates the interaction between ZFP57 and DNA methyltransferases. The KRAB box of ZFP57 is required for maintaining DNA methylation imprint in ES cells. Conclusion: ZFP57 recruits DNA methyltransferases and maintains DNA methylation imprint through KRAB box-mediated interaction.Significance: This work implies that ZFP57 recruits DNA methyltransferases via KAP1 to maintain DNA methylation imprint.