The role of mitochondria dynamics and its molecular regulators remains largely unknown during naïve-to-primed pluripotent cell interconversion. Here we report that mitochondrial MTCH2 is a regulator of mitochondrial fusion, essential for the naïve-to-primed interconversion of murine embryonic stem cells (ESCs). During this interconversion, wild-type ESCs elongate their mitochondria and slightly alter their glutamine utilization. In contrast, MTCH2-/- ESCs fail to elongate their mitochondria and to alter their metabolism, maintaining high levels of histone acetylation and expression of naïve pluripotency markers. Importantly, enforced mitochondria elongation by the pro-fusion protein Mitofusin (MFN) 2 or by a dominant negative form of the pro-fission protein dynamin-related protein (DRP) 1 is sufficient to drive the exit from naïve pluripotency of both MTCH2-/- and wild-type ESCs. Taken together, our data indicate that mitochondria elongation, governed by MTCH2, plays a critical role and constitutes an early driving force in the naïve-to-primed pluripotency interconversion of murine ESCs. Overall design: Examination of WT and MTCH2 KO ESC and EpiLC mouse embryonic stem cells transcriptome
MTCH2-mediated mitochondrial fusion drives exit from naïve pluripotency in embryonic stem cells.
Specimen part, Subject
View SamplesRecent reports have proposed a new paradigm for obtaining mature somatic cell types from fibroblasts without going through a pluripotent state, by briefly expressing canonical iPSC reprogramming factors Oct4, Sox2, Klf4 and c-Myc (abbreviated as OSKM), in cells expanded in lineage differentiation promoting conditions. Here we apply genetic lineage tracing for endogenous Nanog, Oct4 and X chromosome reactivation during OSKM induced trans-differentiation, as these molecular events mark final stages for acquisition of induced pluripotency. Remarkably, the vast majority of reprogrammed cardiomyocytes or neural stem cells derived from mouse fibroblasts via OSKM mediated trans-differentiation were attained after transient acquisition of pluripotency, and followed by rapid differentiation. Our findings underscore a molecular and functional coupling between inducing pluripotency and obtaining “trans-differentiated” somatic cells via OSKM induction, and have implications on defining molecular trajectories assumed during different cell reprogramming methods. Overall design: poly RNA-Seq was measured before, during and after conversion of mouse embryonic fibroblasts to neural stem cells using OSKM trans-differentiation method.
Transient acquisition of pluripotency during somatic cell transdifferentiation with iPSC reprogramming factors.
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The H3K27 demethylase Utx regulates somatic and germ cell epigenetic reprogramming.
Specimen part
View SamplesPluripotency can be induced in somatic cells by ectopic expression of defined transcription factors, however the identity of epigenetic regulators driving the progression of cellular reprogramming requires further investigation. Here we uncover a non-redundant role for the JmjC-domain-containing protein histone H3 methylated Lys 27 (H3K27) demethylase Utx, as a critical regulator for the induction, but not for the maintenance, of primed and nave pluripotency in mice and in humans. Utx depletion results in aberrant H3K27me3 repressive chromatin demethylation dynamics, which subsequently hampers the reactivation of pluripotency promoting genes during reprogramming. Remarkably, Utx deficient primordial germ cells (PGCs) display a cell autonomous aberrant epigenetic reprogramming in vivo during their embryonic maturation, resulting in the lack of functional contribution to the germ-line lineage.
The H3K27 demethylase Utx regulates somatic and germ cell epigenetic reprogramming.
Specimen part
View SamplesHow cells acquire their fate is a fundamental question in both developmental and regenerative biology. Multipotent progenitors undergo gradual cell fate restriction in response to temporal and positional cues from the microenvironment, the nature of which is far from being clear. In the case of the lymphatic system, venous endothelial cells are thought to give rise to lymphatic vessels, through a process of trans-differentiation. Upon expression of a set of transcription factors, venous cells acquire a lymphatic fate, and bud out to generate the lymphatic vasculature. In this work we challenge this view and show that while lymphatic endothelial cells (LECs) do arise in the Cardinal Vein (CV), they do so from a previously uncharacterized pool of multipotent angioblasts. Using lymphatic-specific transgenic zebrafish, in combination with endothelial photoconvertible reporters, and long-term live imaging, we demonstrate that these multipotent angioblasts can generate not only lymphatic, but also arterious, and venous fates. We further reveal that the underlying endoderm serves as a source of Wnt5b, which acts as a lymphatic inductive signal, promoting the angioblast-to-lymphatic transition. Moreover, Wnt5b induced lymphatic specification in human embryonic stem cells- derived vascular progenitors, suggesting that this process is evolutionary conserved. Our results uncover a novel mechanism of lymphatic vessel formation, whereby multipotent angioblasts and not venous endothelial cells give rise to the lymphatic endothelium, and provide the first characterization of their inductive niche. More broadly, our findings highlight the CV as a plastic and heterogeneous structure containing different cell populations, analogous to the hematopoietic niche in the aortic floor. Overall design: Following Kaede photoconversion of dorsal or ventral halves of the PCV in Tg(fli1:gal4;uasKaede) embryos at 24 hpf, 6Â embryos per group were used for FACS isolation of Kaede photconverted (red) ECs.
Lymphatic vessels arise from specialized angioblasts within a venous niche.
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Corrigendum: Deterministic direct reprogramming of somatic cells to pluripotency.
Specimen part
View SamplesSomatic cells can be directly reprogrammed to pluripotency by exogenous expression of transcription factors, classically Oct4, Sox2, Klf4 and c-Myc. While distinct types of somatic cells can be reprogramed with varying efficiencies and by different modified reprogramming protocols, induced pluripotent stem cell (iPSC) induction remains inefficient and stochastic where a fraction of the cells converts into iPSCs. The nature of rate limiting barrier(s) preventing majority of cells to convert into iPSCs remains elusive. Here we show that neutralizing Mbd3, a core member of the Mbd3/NURD co-repressor and chromatin-remodeling complex, results in deterministic and synchronized reprogramming of multiple differentiated cell types to pluripotency. 100% of Mbd3 depleted mouse and human somatic cells convert into iPSCs after seven days of reprogramming factor induction. Our findings delineate a critical pathway blocking the reestablishment of pluripotency, and offer a novel platform for future dissection of epigenetic dynamics leading to iPSC formation at high resolution.
Deterministic direct reprogramming of somatic cells to pluripotency.
Specimen part
View SamplesThis SuperSeries is composed of the SubSeries listed below.
Derivation of novel human ground state naive pluripotent stem cells.
Specimen part, Cell line
View SamplesMouse embryonic stem (ES) cells are isolated from the inner cell mass of blastocysts, and can be preserved in vitro in a naive inner-cell-mass-like configuration by providing exogenous stimulation with leukaemia inhibitory factor (LIF) and small molecule inhibition of ERK1/ERK2 and GSK3b signalling (termed 2i/LIF conditions). Hallmarks of naive pluripotency include driving Oct4 (also known as Pou5f1) transcription by its distal enhancer, retaining a pre-inactivation X chromosome state, global reduction in DNA methylation and in H3K27me3 repressive chromatin mark deposition on developmental regulatory gene promoters.Upon withdrawal of 2i/LIF, nave mouse ES cells can drift towards a primed pluripotent state resembling that of the post-implantation epiblast. Although human ES cells share several molecular features with naive mouse ES cells, they also share a variety of epigenetic properties with primed murine epiblast stem cells (EpiSCs). These include use of the proximal enhancer element to maintain OCT4 expression, pronounced tendency for X chromosome inactivation in most female human ES cells, increase in DNA methylation and prominent deposition of H3K27me3 and bivalency acquisition on lineage regulatory genes. The feasibility for establishing human ground state naive pluripotency in vitro with equivalent molecular and functional features to those characterized in rodent ES cells remains to be defined. Here we establish defined conditions that facilitate the derivation of genetically unmodified human naive pluripotent stem cells from already established primed human ES cells, from somatic cells through induced pluripotent stem (iPS) cell reprogramming or directly from blastocysts. The novel naive pluripotent cells validated herein retain molecular characteristics and functional properties that are highly similar to mouse naive ES cells, and distinct from conventional primed human pluripotent cells. This includes competence in the generation of cross-species chimaeric embryos that underwent organogenesis following microinjection of human naive iPS cells into mouse morulas. Collectively, our findings establish new avenues for regenerative medicine, patient-specific iPS cell disease modelling and the study of early human development in vitro and in vivo.
Derivation of novel human ground state naive pluripotent stem cells.
Specimen part
View SamplesNaïve and primed pluripotent states retain distinct molecular properties, yet limited knowledge exists on how their state transitions are regulated. Here we identify Mettl3, an N6-Methyladenosine (m6A) transferase, as a regulator for terminating murine naïve pluripotency. Mettl3 knockout pre-implantation epiblasts and naïve embryonic stem cells (ESCs) are depleted for m6A in mRNAs and yet, are viable. However, they fail to adequately terminate their naïve state, and subsequently undergo aberrant and restricted lineage priming at the post-implantation stage, leading to early embryonic lethality. m6A predominantly and directly reduces mRNA stability, including that of key naïve pluripotency promoting transcripts. This study highlights a critical role for an mRNA epigenetic modification in vivo, and identifies regulatory modules that functionally influence naïve and primed pluripotency in an opposing manner. Overall design: 3'' polyA RNA-sequencing (equivalent to Digital Gene Expression) measured in mouse Embryonic Stem Cells (ESCs) and mouse Embriod bodies (EBs) 0,4 & 8 hours after treatment with Actinomycin which halts transcription. Measured in both WT and Mettl3-KO cells.
Stem cells. m6A mRNA methylation facilitates resolution of naïve pluripotency toward differentiation.
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