Loss of PRC2 subunits primes lineage choice during exit of pluripotency

Abstract

Polycomb Repressive Complex 2 (PRC2) is crucial for the coordinated expression of genes during early embryonic development, catalyzing histone H3 lysine 27 trimethylation. Two distinct PRC2 complexes, PRC2.1 and PRC2.2, contain respectively MTF2 and JARID2 in embryonic stem cells (ESCs). In this study, we explored their roles in lineage specification and commitment, using single-cell transcriptomics and mouse embryoid bodies derived from Mtf2 and Jarid2 null ESCs. We observe that the loss of Mtf2 results in enhanced and faster differentiation towards cell fates from all germ layers, while the Jarid2 null cells are predominantly directed towards early differentiating precursors, with reduced efficiency towards mesendodermal lineages. These effects are caused by derepression of developmental regulators that are poised for activation in pluripotent cells and gain H3K4me3 at their promoters in the absence of PRC2 repression. Upon lineage commitment, the differentiation trajectories are relatively similar to those of wild-type cells. Together, our results uncover a major role for MTF2-containing PRC2.1 in balancing poised lineage-specific gene activation, whereas the contribution of JARID2-containing PRC2 is more selective in nature compared to MTF2. These data explain how PRC2 imposes thresholds for lineage choice during the exit of pluripotency.

Evolutionary adaptation of the Polycomb repressive complex 2

“…These results demonstrate that the efficient recruitment of PRC2 requires the associated factors of both PRC2 subcomplexes, suggesting a certain redundancy and synergism between PRC2.1 and PRC2.2. Nonetheless, recent work demonstrated that PRC2.1- and PRC2.2-associated factors have unique roles in chromatin binding and mouse ES cell differentiation [ 38 – 41 ]. In mESCs, PRC2.1 chromatin recruitment is mainly mediated by the DNA binding function of MTF2, while PRC2.2 chromatin recruitment is mediated by the affinity of JARID2 for the PRC1-associated histone mark H2AK119ub [ 38 ].…”

“…Consistent with this hypothesis, the removal of MTF2 or JARID2 in mESCs leads to the derepression of a distinct set of genes upon differentiation and consequently to altered lineage choices. MTF2 is associated with genes that remain repressed during differentiation [ 39 ] and its loss leads to enhanced commitment to all germ layers [ 41 ]. Conversely, JARID2-sensitive genes were active in mESCs and became newly repressed upon differentiation [ 39 ].…”

“…Conversely, JARID2-sensitive genes were active in mESCs and became newly repressed upon differentiation [ 39 ]. JARID2-deleted cells possess a more selective differentiation process towards early differentiated precursors and have a reduced efficiency towards mesendodermal lineages [ 41 ]. Thus, this recent work suggests that each of the PRC2 subcomplexes has a unique function, which cannot be reproduced by alternative complex assemblies.…”

De Novo Polycomb Recruitment and Repressive Domain Formation

“…In contrast, the ablation of PRC2 in mouse embryos causes severe defects during gastrulation, and organisms succumb around the seventh embryonic day when the cell executes fate decisions [ 12 , 13 , 14 , 15 ]. This behavior reflects the essential role of Polycomb in maintaining and rewiring the transcriptional repression network that sustains pluripotency and posterior lineage specification [ 16 , 17 ]. Similarly, alterations in Polycomb activity affect the culture of mouse embryonic stem cells (mESC) as the lack of PRC1 causes proliferation to cease and the loss of typical mESC morphology [ 18 , 19 ], whereas PRC2 deficiency allows self-renewal but no cell differentiation in vitro [ 16 , 20 , 21 , 22 ].…”

Vertebrate Cell Differentiation, Evolution, and Diseases: The Vertebrate-Specific Developmental Potential Guardians VENTX/NANOG and POU5/OCT4 Enter the Stage

“…FGF/MAPK signaling activity is required for the induction of both ectoderm and mesendoderm lineages, as well as for further lineage-restricted decisions (e.g., neural and neural crest cell fate; axial/paraxial mesodermal fate) [ 81 , 89 , 90 , 91 ]. Recently, several studies point out the fundamental function of chromatin organization and poised enhancers, which represent distal regulatory elements that control the expression of major developmental genes, during the process of embryonic cell commitment and the establishment of stable epigenetic memory, which signs the exit from pluripotency state at the onset of gastrulation [ 68 , 69 , 70 , 92 , 93 , 94 ].…”