Polycomb enables primitive endoderm lineage priming in embryonic stem cells.

Robert S Illingworth,Fabian V Roske,Jurriaan J Hölzenspies,Joshua M Brickman,Wendy A Bickmore

doi:10.7554/elife.14926

Robert S Illingworth, Fabian V Roske + Show 3 more

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https://doi.org/10.7554/elife.14926

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Abstract

Mouse embryonic stem cells (ESCs), like the blastocyst from which they are derived, contain precursors of the epiblast (Epi) and primitive endoderm (PrEn) lineages. While transient in vivo, these precursor populations readily interconvert in vitro. We show that altered transcription is the driver of these coordinated changes, known as lineage priming, in a process that exploits novel polycomb activities. We find that intragenic levels of the polycomb mark H3K27me3 anti-correlate with changes in transcription, irrespective of the gene's developmental trajectory or identity as a polycomb target. In contrast, promoter proximal H3K27me3 is markedly higher for PrEn priming genes. Consequently, depletion of this modification stimulates the degree to which ESCs are primed towards PrEn when challenged to differentiate, but has little effect on gene expression in self-renewing ESC culture. These observations link polycomb with dynamic changes in transcription and stalled lineage commitment, allowing cells to explore alternative choices prior to a definitive decision.

Highlights

Embryonic stem cells (ESCs) derived from the ICM of the early mammalian blastocyst are characterised by their capacity to differentiate into all cell types of the future organism and by their ability to transmit this property through successive self-renewing cell divisions
To identify a definitive set of genes correlated with lineage priming in ESCs we isolated SSEA1+ (S+) HV reporter ESCs by fluorescence activated cell sorting (FACS) based on the level of HV expression
As previous analysis suggested that the primitive endoderm (PrEn)-primed population (HV+S+) exhibited small but detectable increases in expression of endoderm markers, we first defined the set of genes showing differential expression between the undifferentiated Epi-primed fraction (HV-S+; Figure 1A; green gate) and spontaneously differentiated endoderm cells (HV+S-; Figure 1A; yellow gate) using analysis of variance (ANOVA; false discover rate (FDR) of 0.05 and a fold change of > 1.5; Figure 1B)

Summary

Introduction

Embryonic stem cells (ESCs) derived from the ICM of the early mammalian blastocyst are characterised by their capacity to differentiate into all cell types of the future organism (pluripotency) and by their ability to transmit this property through successive self-renewing cell divisions. Like the peri-implantation ICM from which they are derived, ESCs are heterogeneous and consist of at least two morphologically indistinguishable cell types, representing primed progenitors of the epiblast and endoderm lineages (Singh et al, 2007; Canham et al, 2010; Lanner and Rossant, 2010; Morgani et al, 2013). In vivo these progenitors exist very transiently prior to implantation, at which point cells rapidly become committed to adopt embryonic or extra-embryonic fates. The Epi-primed pluripotent population shows an equivalent enhanced capacity to differentiate towards epiblast lineages and contributes to the epiblast in vivo (Canham et al, 2010; Morgani et al, 2013)

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