Project description:We have uncovered that BEND3 is a heterochromatin-associated protein that functions as a transcription repressor. Expression of BEND3 correlates with the state of pluripotency, with a significant decline in BEND3 levels in differentiated cells. Cells lacking BEND3 show defects in cell cycle progression with failure to enter S-phase. BEND3 affects the transcription of cellular genes that modulate chromatin organization and cellular differentiation and that downregulation of BEND3 is critical for cellular differentiation.
Project description:Recent evidence suggests that lncRNAs play an integral regulatory role in numerous functions, including determination of cellular identity. We determined global expression (RNA-seq) and genome wide profiles (ChIP-seq) of histone post-translational modifications and p53 binding in human embryonic stem cells (hESCs) undergoing differentiation to define a high-confidence set of 40 lncRNAs, which are p53 transcriptional targets. We focused on lncRNAs, highly expressed in pluripotent hESCs and repressed by p53 during differentiation, to identify lncPRESS1 as a p53-regulated transcript that maintains hESC pluripotency in concert with core pluripotency factors. RNA-seq of hESCs depleted of lncPRESS1 revealed that lncPRESS1 controls a gene network that promotes pluripotency. Further, we found that lncPRESS1 physically interacts with SIRT6 to prevent SIRT6 chromatin localization and maintain high levels of histone H3K56 and H3K9 acetylation at promoters of pluripotency genes. In summary, we describe a novel pluripotency-specific lncRNA that safeguards the hESC state by disrupting SIRT6 activity
Project description:We have uncovered that BEND3 is a heterochromatin-associated protein that functions as a transcription repressor. Expression of BEND3 correlates with the state of pluripotency, with a significant decline in BEND3 levels in differentiated cells. Cells lacking BEND3 show defects in cell cycle progression with failure to enter S-phase. BEND3 affects the transcription of cellular genes that modulate chromatin organization and cellular differentiation and that downregulation of BEND3 is critical for cellular differentiation.
Project description:Tight control of cell fate choices is crucial for normal development. Here we show that lamin A/C plays a key role in chromatin organization in embryonic stem cells (ESCs), which safeguards naïve pluripotency and ensures proper cell fate choices during cardiogenesis. We find major changes in chromatin compaction and localization of cardiac genes already in Lmna−/−ESCs resulting in precocious activation of a transcriptional program promoting cardiomyocyte versus endothelial cell fate, accompanied by premature cardiomyocyte differentiation, cell cycle withdrawal, and abnormal contractility. Gata4 is activated by lamin A/C loss and Gata4 silencing or haploinsufficiency rescues the aberrant cardiovascular cell fate choices induced by lamin A/C deficiency. Importantly, we observe divergent functions of lamin A/C in naïve pluripotent stem cells and cardiomyocytes, which has distinct contributions to the transcriptional alterations of patients with LMNA-associated cardiomyopathy. Thus, disruption of lamin A/C-dependent chromatin architecture in ESCs is a primary event in LMNA loss-of-function cardiomyopathy.
Project description:Embryonic stem (ES) cells express pluripotency-associated genes and repress differentiation-inducible genes. The activities of these genes are coordinately reversed during differentiation. The changes in the transcriptome upon conditional KAP1 knockout in ES cells overlapped with the changes during embryoid body formation. KAP1 repressed differentiation-inducible genes and derepressed pluripotency-associated genes in ES cells. KAP1 formed complexes with polycomb repressive complexes 1 (PRC1) through an interaction that was mediated by the KAP1 coiled-coil region. KAP1 and PRC1 bound cooperatively at the promoters of differentiation-inducible genes and repressed their transcription. In contrast, KAP1 bound the transcribed and flanking sequences of pluripotency-associated genes, did not enhance PRC1 binding, and derepressed their transcription. KAP1 had opposite effects on differentiation-inducible and pluripotency-associated gene transcription both in ES cells and in differentiating embryoid bodies. The region of KAP1 that mediated the interaction with PRC1 was required for KAP1 enhancement of PRC1 binding and for KAP1 repression of transcription at differentiation-inducible promoters. This region of KAP1 was not required for KAP1 suppression of PRC1 binding or for KAP1 derepression of transcription at pluripotency-associated promoters. The opposite effects of KAP1 on transcription of differentiation-inducible versus pluripotency-associated genes contributed to the reciprocal changes in their transcription during differentiation. Analysis of the transcript levels in mouse embryonic stem cells before and after conditional KAP fl/fl knockout
Project description:Pluripotency can be maintained in the naïve state through manipulation of ERK and WNT signalling (2i), shielding embryonic stem cells (ESCs) from inductive cues. Alternatively, inhibiting CDK8/19 (CDK8/19i), a repressor of the Mediator co-activator complex, directly stimulates super-enhancer activity, and was recently shown to stabilize cells in a functional state that resembles naïve pluripotency. Naïve ESCs exhibit important epigenetic, transcriptional and metabolic features. However, our understanding on how these regulatory layers are inter-connected to promote the naive state is in progress. To fill this gap, here we used mass spectrometry to describe the dynamic molecular events (i.e. phosphoproteome, proteome and metabolome) executed by 2i and CDK8/19i, as they transition cell identity into naïve pluripotency. We observed rapid proteomic reprogramming, revealing widespread commonalities, and some important differences, between these two approaches, suggesting a largely over-lapping mechanism. CDK8/19i acts directly on the control of the transcriptional machinery, which elicits a rapid and direct activation of key identity genes including those that maintain the naïve program. Additional molecular changes in 2i are achieved by phosphorylation of critical downstream effectors that reinforce the naïve transcriptional circuitry while repressing factors from the more-differentiated formative and primed states. Comparing transcriptomic and proteomic changes, we found that post-transcriptional de-repression is a major feature of naïve pluripotency conferred by both 2i and CDK8/19i, and this may support the enhanced mitochondrial capacity of naive cells. Furthermore, at the level of metabolome, while 2i- and CDK8/19i-treated cells share similar aspects in one-carbon metabolism and beta-oxidation, in other regards they are divergent, a feature which may explain their differences in DNA methylation. These datasets provide a valuable resource for exploring the molecular mechanisms underlying pluripotency and cell identity transitions.
Project description:Embryonic stem (ES) cells express pluripotency-associated genes and repress differentiation-inducible genes. The activities of these genes are coordinately reversed during differentiation. The changes in the transcriptome upon conditional KAP1 knockout in ES cells overlapped with the changes during embryoid body formation. KAP1 repressed differentiation-inducible genes and derepressed pluripotency-associated genes in ES cells. KAP1 formed complexes with polycomb repressive complexes 1 (PRC1) through an interaction that was mediated by the KAP1 coiled-coil region. KAP1 and PRC1 bound cooperatively at the promoters of differentiation-inducible genes and repressed their transcription. In contrast, KAP1 bound the transcribed and flanking sequences of pluripotency-associated genes, did not enhance PRC1 binding, and derepressed their transcription. KAP1 had opposite effects on differentiation-inducible and pluripotency-associated gene transcription both in ES cells and in differentiating embryoid bodies. The region of KAP1 that mediated the interaction with PRC1 was required for KAP1 enhancement of PRC1 binding and for KAP1 repression of transcription at differentiation-inducible promoters. This region of KAP1 was not required for KAP1 suppression of PRC1 binding or for KAP1 derepression of transcription at pluripotency-associated promoters. The opposite effects of KAP1 on transcription of differentiation-inducible versus pluripotency-associated genes contributed to the reciprocal changes in their transcription during differentiation. Analysis of the regions occupied by KAP1(TRIM28/TIF1beta) and by Ring1b(Rnf2) in mouse embryonic stem cells before and after conditional KAP fl/fl and Ring1b fl/fl knockout
Project description:Tight control of cell fate choices is crucial for normal development. Here we show that lamin A/C plays a key role in chromatin organization in embryonic stem cells (ESCs), which safeguards naïve pluripotency and ensures proper cell fate choices during cardiogenesis. We find major changes in chromatin compaction and localization of cardiac genes already in Lmna−/−ESCs resulting in precocious activation of a transcriptional program promoting cardiomyocyte versus endothelial cell fate, accompanied by premature cardiomyocyte differentiation, cell cycle withdrawal, and abnormal contractility. Gata4 is activated by lamin A/C loss and Gata4 silencing or haploinsufficiency rescues the aberrant cardiovascular cell fate choices induced by lamin A/C deficiency. Importantly, we observe divergent functions of lamin A/C in naïve pluripotent stem cells and cardiomyocytes, which has distinct contributions to the transcriptional alterations of patients with LMNA-associated cardiomyopathy. Thus, disruption of lamin A/C-dependent chromatin architecture in ESCs is a primary event in LMNA loss-of-function cardiomyopathy.