Early mammalian development is accompanied by a profound global remodeling of chromatin-based regulation. The Zdbf2 locus provides a valuable model to uncover the effect of dynamic chromatin transition, as it is polycomb silenced in embryonic stem cells (ESCs) and only becomes activated after Long isoform of Zdbf2 (Liz) transcription-dependent de novo DNA methylation during differentiation. Here we show that four enhancers contribute to the Liz-to-Zdbf2 promoter switch, concomitantly with dynamic changes in chromatin architecture. CTCF plays a key role in partitioning the locus in ESCs, when Liz is active and Zdbf2 is silenced. The partition is relieved when Zdbf2 becomes DNA methylated and active. Mutant ESCs that lack the partition fail to properly activate Zdbf2. Notably, the CTCF-based regulation occurs independently of the polycomb and DNA methylation pathways, suggesting a multi-layered regulatory framework that ensures proper epigenetic programming of a developmentally important gene.
Overall design
Circular chromosome conformation capture followed by sequencing (4C-seq) in mouse ESCs and EpiLCs in WT and mutant backgrounds
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