The Polycomb group protein CBX6 is an essential regulator of embryonic stem cell identity

Polycomb group proteins are transcriptional repressors that control cell identity and development. In mammals, at least five different CBX proteins are believed to associate with the core Polycomb repressive complex 1 (PRC1). CBX6 and CBX7 are the most highly expressed CBX proteins in embryonic stem cells (ESCs), yet little is known about the function of CBX6 in these cells. Here we show that CBX6 is an essential regulator of ESC identity, since ablation of CBX6 function destabilizes the pluripotency network and triggers differentiation. At the molecular level, CBX6 is linked to the canonical PRC1 (cPRC1) complex; however, contrary to expectations, our results indicate that CBX6 also has a non-canonical PRC1 function. Taken together, our findings reveal that CBX6 is an essential component for ESC biology and contributes to the structural and functional complexity of the PRC1 complex. Overall design: List of ChIPseq samples (Cbx6/Cbx7/Ring1b) and RNAseq samples (control and Cbx6 knock-down)