A functional crosstalk between the H3K9 methylation writers and their reader HP1 in safeguarding embryonic stem cell identity

Histone H3 lysine 9 (H3K9) methylation, as a hallmark of heterochromatin, has a central role in cell lineage and fate determination. Although evidence of a cooperation between H3K9 methylation writers and their readers has started to emerge, their actual interplay remains elusive. Here, we show that loss of H3K9 methylation readers, the Hp1 family, causes reduced expression of H3K9 methyltransferases, and that this subsequently leads to the exit of embryonic stem cells (ESCs) from pluripotency and a reciprocal gain of lineagespecific characteristics. Importantly, the phenotypes of Hp1-null ESCs can be rescued by ectopic expression of Setdb1, Nanog, and Oct4. Furthermore, Setdb1 ablation results in loss of ESC identity, which is accompanied by a reduction in the expression of Hp1 genes. Together, our data support a model in which the safeguarding of ESC identity involves the cooperation between the H3K9 methylation writers and their readers.

Automated summary

The interaction between H3K9 methylation writers and readers is crucial for maintaining the identity of embryonic stem cells.