Project description:RISC-mediated control of selected chromatin regulators stabilizes ground state pluripotency of mouse embryonic stem cells (miRNA-Seq)
Project description:Pluripotency is established in E4.5 preimplantation epiblast. Embryonic stem cells (ESCs) represent the immortalization of pluripotency, however, they only partially resemble the gene expression signature of developmental ground-state. Induced PRAMEL7 expression, a protein highly expressed in the ICM but lowly expressed in ESCs, reprograms developmentally advanced ESC+serum into ground-state pluripotency by inducing a gene expression signature close to developmental ground-state. However, how PRAMEL7 reprograms gene expression remains elusive. Here we show that PRAMEL7 associates with Cullin2 (CUL2) and this interaction is required to establish ground-state gene expression. PRAMEL7 recruits CUL2 to chromatin and targets for proteasomal degradation regulators of repressive chromatin, including NuRD complex. PRAMEL7 antagonizes NuRD-mediated repression of genes implicated in pluripotency by decreasing NuRD stability and promoter association in a CUL2-dependent manner. Our data link proteasome degradation pathways to ground-state gene expression, offering insights to generate in vitro models to reproduce the in vivo ground-state pluripotency.
Project description:Deciphering the mechanisms that control the pluripotent ground state is key for understanding embryonic development. Nonetheless, the epigenetic regulation of ground-state mouse embryonic stem cells (mESCs) is not fully understood. Here, we identify the epigenetic protein MPP8 as being essential for ground-state pluripotency. Its depletion leads to cell cycle arrest and spontaneous differentiation. MPP8 has been suggested to repress LINE1 elements by recruiting the human silencing hub (HUSH) complex to H3K9me3-rich regions. Unexpectedly, we find that LINE1 elements are efficiently repressed by MPP8 lacking the chromodomain, while the unannotated C-terminus is essential for its function. Moreover, we show that SETDB1 recruits MPP8 to its genomic target loci, whereas transcriptional repression of LINE1 elements is maintained without retaining H3K9me3 levels. Taken together our findings demonstrate that MPP8 protects the DNA-hypomethylated pluripotent ground state through its association with the HUSH core complex, however, independently of detectable chromatin binding and maintenance of H3K9me3.
Project description:Understanding mechanisms of epigenetic regulation in embryonic stem cells (ESCs) is of fundamental importance for stem cell and developmental biology. Here we identify Spic, a member of the ETS family of transcription factors, as a specific marker of ground state pluripotency. We show that Spic is rapidly induced in ESCs cultured with GSK3-, MEK-inhibitors and LIF (2iL), and in response to MEK/ERK inhibition. ChIP-seq analysis demonstrated that Spic binds to enhancer elements that are associated with pluripotency genes. Interaction proteomics and genomic profiling confirmed that SPIC interacts with NANOG and stabilizes its binding to chromatin in 2iL-ESCs. Additional gain of function and loss of function experiments revealed that Spic controls genes involved in one carbon (1C) metabolism, Bhmt, Bhmt2, and Dmgdh, and the flux of SAM-to-SAH in 2iL-ESCs. By maintaining low levels of SAM, Spic controls the level of H3K4me3 and H3R17me2 histone methylation in ground state ESCs. Our data highlight the role of uncharacterized axillary transcription factors that link cellular metabolism to epigenetic regulation in ground state pluripotency.
Project description:Understanding mechanisms of epigenetic regulation in embryonic stem cells (ESCs) is of fundamental importance for stem cell and developmental biology. Here we identify Spic, a member of the ETS family of transcription factors, as a specific marker of ground state pluripotency. We show that Spic is rapidly induced in ESCs cultured with GSK3-, MEK-inhibitors and LIF (2iL), and in response to MEK/ERK inhibition. ChIP-seq analysis demonstrated that Spic binds to enhancer elements that are associated with pluripotency genes. Interaction proteomics and genomic profiling confirmed that SPIC interacts with NANOG and stabilizes its binding to chromatin in 2iL-ESCs. Additional gain of function and loss of function experiments revealed that Spic controls genes involved in one carbon (1C) metabolism, Bhmt, Bhmt2, and Dmgdh, and the flux of SAM-to-SAH in 2iL-ESCs. By maintaining low levels of SAM, Spic controls the level of H3K4me3 and H3R17me2 histone methylation in ground state ESCs. Our data highlight the role of uncharacterized axillary transcription factors that link cellular metabolism to epigenetic regulation in ground state pluripotency.
Project description:The self-renewing pluripotent state was first captured in mouse embryonic stem cells (mESCs) over two decades ago. The standard condition requires the presence of serum and LIF, which provide growth promoting signals for cell expansion. However, there are pro-differentiation signals which destabilize the undifferentiated state of mESCs. The dual inhibition (2i) of the pro-differentiation Mek/Erk and Gsk3/Tcf3 pathways in mESCs is sufficient to establish an enhanced pluripotent “ground state” which bears features resembling the pre-implantation mouse epiblast. Gsk3 inhibition alleviates the repression of Esrrb, a transcription factor that can substitute for Nanog function in mESCs. The molecular mechanism that is mediated by Mek inhibition is however not clear. In this study, we investigate the pathway through which Mek inhibition operates to maintain ground state pluripotency. We have found that in mESCs, Kruppel-like factor 2 (Klf2) is a protein target of the Mek/Erk pathway; and that Klf2 protein is phosphorylated by Erk2 and subsequently degraded through the proteosome. It is therefore by Mek-inhibition through PD0325901 or 2i that enables the stabilization and accumulation of Klf2 to sustain ground state pluripotency. Importantly, we found that Klf2-null mESCs, while viable under LIF/Serum conditions, cannot be maintained and eventually gradually die within a few passages. Our result thus demonstrates that Klf2 is an essential factor of ground state pluripotency. Collectively, our study defines the Mek/Klf2 axis that cooperates with the Gsk3/Esrrb pathway in mediating ground state pluripotency.