Humanization of a tandem repeat in IG-DMR causes stochastic restoration of paternal imprinting at mouse Dlk1-Dio3 domain.

The Dlk1-Dio3 imprinted domain, regulated by an intergenic differentially methylated region (IG-DMR), is important for mammalian embryonic development. Although previous studies have reported that DNA methylation of a tandem repeated array sequence in paternal IG-DMR (IG-DMR-Rep) plays an essential role in the maintenance of DNA methylation in mice, the function of a tandem repeated array sequence in human IG-DMR (hRep) is unknown. Here, we generated mice with a human tandem repeated sequence, which replaced the mouse IG-DMR-Rep. Mice that transmitted the humanized allele paternally exhibited variable methylation status at the IG-DMR and were stochastically rescued from the lethality of IG-DMR-Rep deficiency, suggesting that hRep plays a role in human IG-DMR for the regulation of imprinted expression. Moreover, chromatin immunoprecipitation analysis showed that TRIM28 was enriched in hypermethylated paternal hRep without ZFP57. Our results suggest that hRep contributes to the maintenance of human IG-DMR methylation imprints via the recruitment of TRIM28.