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Hendrich, B.

Publications and source records attributed to Hendrich, B..

12 recordsLinked to original sources

BCOR mutations establish a persistent culture-adaptive state in human induced pluripotent stem cells

Human induced pluripotent stem cells (hiPSCs) are widely used for disease modelling and regenerative medicine, yet their utility depends on maintaining molecular integrity during long-term culture. BCOR (BCL6 Co-Repressor) mutations are among the most recurrent culture-acquired alterations in hiPSCs, but their functional consequences remain poorly understood. Here, we show that hiPSC BCOR mutations are predominantly truncating indels enriched in exon 7, defining a mutational landscape distinct from that observed in cancer. Multi-omics profiling reveals that BCOR loss drives widespread chromatin, transcriptomic and proteomic remodelling, with coordinated activation of developmental, pluripotency-associated and mitochondrial metabolism programmes. To facilitate routine surveillance, we develop a cost-effective TaqMan qPCR assay that accurately identifies BCOR-mutant hiPSCs across independent cell lines. Finally, we demonstrate that correction of BCOR mutation by CRISPR-Cas9 only partially restores the wildtype molecular state, highlighting the importance of early detection and monitoring of adaptive mutations in hiPSC cultures.

cell biology↗

Chromatin remodelling enables enhancer resetting to facilitate the ERK transcriptional response

During development, cellular identity is ultimately determined by transcriptional output: lineage-specific genes must be activated, while genes associated with alternative fates must be repressed. This process depends on the activity of chromatin remodelling complexes, which regulate the accessibility of transcription factors to chromatin regulatory elements. In addition, cellular identity is shaped by exposure to intercellular signals. Understanding the mechanisms by which extracellular signals are translated into changes in the transcriptional program is essential for understanding cell fate decisions during development, as well as in disease conditions such as cancer. Here we describe a rapid and widespread enhancer resetting event in response to ERK signalling in mouse ES cells. This process occurs in two distinct phases: an immediate, genome-wide alteration in transcription factor binding dynamics at regulatory regions which is dependent on the release of paused RNA Polymerase II, followed by the re-establishment of a context appropriate, stable chromatin state. We demonstrate that the chromatin remodelling complex NuRD is required for this reestablishment phase and for the appropriate transcriptional response to ERK signalling. We propose that enhancer resetting places genomic regulatory regions in a state which is permissive to the exchange of transcription factors in order to establish a new, stable enhancer topology enabling rapid yet precise transcriptional response to extracellular signals.

molecular biology↗

Protein-protein interactions drive differences in the spatiotemporal dynamics of transcription factors NANOG and SOX2 in naïve pluripotent cells

Maintenance of naive pluripotency requires core transcription factors (TFs) like SOX2 and auxiliary TFs like NANOG, yet molecular mechanisms governing their intra-nuclear dynamics and DNA binding interactions remain unclear. Here, using high-density 3D single-molecule light-field microscopy combined with novel spatiotemporal analysis pipelines, we track SOX2 and NANOG dynamics in live cells. Despite lower protein abundance, NANOG displays a similar chromatin-bound fraction to SOX2. This arises partially because, while both TFs undergo frequent transient non-specific binding interactions ([~]0.5-0.7s), NANOG exhibits more stable specific binding ([~]25s vs [~]16s). Both TFs also assemble into phase-separated domains of [~]400 nm containing both freely diffusing and chromatin-bound proteins, which further influences their dynamics. Strikingly, NANOGs protein-protein interaction domain markedly increases chromatin residence time (>5-fold) and the size of these phase-separated domains. Our work uncovers how NANOG and SOX2 stabilise gene regulatory networks that maintain naive pluripotency while providing quantitative pipelines for dissecting spatiotemporal TF dynamics.

cell biology↗

The chromatin remodeller CHD4 controls both nucleosome integrity and transcription factor binding to promote activity of active regulatory elements and to prevent activation of silent enhancers

Chromatin organisation and transcriptional regulation are tightly coordinated processes that are essential for maintaining cellular identity and function. ATP-dependent chromatin remodelling proteins play critical roles in control of genome structure and in regulating transcription across eukaryotes. Their essential nature, however, has made it difficult to define exactly how these functions are mediated. The chromatin remodeller CHD4 has been shown to be capable of sliding nucleosomes in vitro, and to regulate chromatin accessibility and gene expression in vivo. Using an inducible depletion system, here we identify a second mechanism of action for CHD4 in actively restricting the residence time of transcription factors on chromatin. Together these activities result in distinct, context-dependent outcomes: at highly accessible regulatory elements, CHD4 limits transcription factor binding to maintain regulatory function, while at low-accessibility euchromatic regions, it prevents transcription factor engagement and sustains chromatin compaction, thereby silencing cryptic enhancers. Collectively, these mechanisms enable CHD4 to reduce transcriptional noise while preserving the responsiveness of active regulatory networks.

molecular biology↗

HP1β and densely packed chromatin form separate microdomains in mouse ES cells, which are reconfigured upon exit from naive pluripotency

Heterochromatin proteins play a key role in establishing local chromatin structure to control the transcription of target genes. Here we uncover a surprising segregation between regions of high DNA- and high heterochromatin protein 1{beta} (HP1{beta})-density in mouse ES cells. DNA-low/HP1{beta}-high foci retain freely diffusing HP1{beta}, and form via condensation through a multitude of weak interactions on top of HP1{beta} that is bound stably to chromatin. DNA-high/HP1{beta}-low foci exclude freely diffusing HP1{beta} and display reduced chromatin mobility, suggesting a higher degree of chromatin self-interaction and a more repressive environment. Finally, the two types of environments are intertwined in DNA-high/HP1{beta}-high foci, where HP1{beta} maintains heterochromatin in a more compact yet dynamic chromatin state. During the exit from naive pluripotency HP1{beta} is lost from regions of high DNA density as cells transition through the formative state, which might facilitate the reconfiguration of genome structure accompanying a change in cell state that we observed previously. Subsequently, as cells enter primed pluripotency, canonical heterochromatin is established.

molecular biology↗

The Nucleosome Remodelling and Deacetylation complex coordinates the transcriptional response to lineage commitment in pluripotent cells

As cells exit the pluripotent state and begin to commit to a specific lineage they must activate genes appropriate for that lineage while silencing genes associated with pluripotency and preventing activation of lineage-inappropriate genes. The Nucleosome Remodelling and Deacetylation (NuRD) complex is essential for pluripotent cells to successfully undergo lineage commitment. NuRD controls nucleosome density at regulatory sequences to facilitate transcriptional responses, and also has been shown to prevent unscheduled transcription (transcriptional noise) in undifferentiated pluripotent cells. How these activities combine to ensure cells engage a gene expression program suitable for successful lineage commitment has not been determined. Here we show that while NuRD is not required to silence all genes, its activity is important to restrict expression of genes primed for activation upon exit from the pluripotent state, and that NuRD activity facilitates their subsequent transcriptional activation. We further show that NuRD coordinates gene expression changes, which acts to maintain a barrier between different stable states. Thus NuRD-mediated chromatin remodelling serves multiple functions, including reducing transcriptional noise, priming genes for activation and coordinating the transcriptional response to facilitate lineage commitment.

developmental biology↗

Enhancer-promoter interactions are reconfigured through the formation of long-range multiway chromatin hubs as mouse ES cells exit pluripotency

Enhancers are genomic DNA sequences that bind transcription factors, chromatin regulators and non-coding transcripts to modulate the expression of target genes. They have been found to act from different locations relative to a gene and to modulate the activity of promoters up to [~]1 Mb away. Here we report the first 3D genome structures of single mouse ES cells as they are induced to exit pluripotency, transition through a formative stage and undergo neuroectodermal differentiation. In order to directly study how interactions between enhancers and promoters are reconfigured genome wide we have determined 3D structures of haploid cells using single cell Hi-C, where we can unambiguously map the contacts to particular chromosomes. We find that there is a remarkable reorganisation of 3D genome structure where inter-chromosomal intermingling increases dramatically in the formative state. This intermingling is associated with the formation of a large number of multiway hubs that bring together enhancers and promoters with similar chromatin states from typically 5-8 distant chromosomal sites that are often separated by many Mb from each other. Genes important for pluripotency exit establish contacts with emerging enhancers within multiway chromatin hubs as cells enter the formative state, consistent with these structural changes playing an important role in establishing new cell identities. Furthermore, we find that different multiway chromatin hubs, and thus different enhancer-promoter interactions, are formed in different individual cells. Our results suggest that studying genome structure in single cells will be important to identify key changes in enhancer-promoter interactions that occur as cells undergo developmental transitions.

developmental biology↗

Live-cell 3D single-molecule tracking reveals how NuRD modulates enhancer dynamics

Enhancer-promoter dynamics are crucial for the spatiotemporal control of gene expression, but it remains unclear whether these dynamics are controlled by chromatin regulators, such as the nucleosome remodelling and deacetylase (NuRD) complex. The NuRD complex binds to all active enhancers to modulate transcription and here we use Hi-C experiments to show that it blurs TAD boundaries and increases the proximity of intermediate-range (~1 Mb) genomic sequences and enhancer-promoter interactions. To understand whether NuRD alters the dynamics of 3D genome structure, we developed an approach to segment and extract key biophysical parameters from 3D single-molecule trajectories of the NuRD complex determined using live-cell imaging. Unexpectedly, this revealed that the intact NuRD complex decompacts chromatin structure and makes NuRD-bound enhancers move faster, increasing the overall volume of the nucleus that these key regulatory regions explore. Interestingly, we also uncovered a rare fast-diffusing state of NuRD bound enhancers that exhibits directed motion. The NuRD complex reduces the amount of time that enhancers remain in this fast-diffusing state, which we propose might otherwise re-organise enhancer-promoter proximity. Thus, we uncover an intimate connection between a chromatin remodeller and the spatial dynamics of the local regions of the genome to which it binds.

cell biology↗

Differential regulation of lineage commitment in human and mouse primed pluripotent stem cells by NuRD

Differentiation of mammalian pluripotent cells involves large-scale changes in transcription and, among the molecules that orchestrate these changes, chromatin remodellers are essential to initiate, establish and maintain a new gene regulatory network. The NuRD complex is a highly conserved chromatin remodeller which fine-tunes gene expression in embryonic stem cells. While the function of NuRD in mouse pluripotent cells has been well defined, no study yet has defined NuRD function in human pluripotent cells. We investigated the structure and function of NuRD in human induced pluripotent stem cells (hiPSCs). Using immunoprecipitation followed by mass-spectrometry in hiPSCs and in naive or primed mouse pluripotent stem cells, we find that NuRD structure and biochemical interactors are generally conserved. Using RNA sequencing, we find that, whereas in mouse primed stem cells and in mouse naive ES cells, NuRD is required for an appropriate level of transcriptional response to differentiation signals, hiPSCs require NuRD to initiate these responses. This difference indicates that mouse and human cells interpret and respond to induction of differentiation differently. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=109 SRC="FIGDIR/small/935544v1_ufig1.gif" ALT="Figure 1"> View larger version (21K): org.highwire.dtl.DTLVardef@1f68187org.highwire.dtl.DTLVardef@b1e9f3org.highwire.dtl.DTLVardef@766e9forg.highwire.dtl.DTLVardef@158c57b_HPS_FORMAT_FIGEXP M_FIG NuRD acts like a conductor in an orchestra. A. In the presence of NuRD (pink blob figure, centre) differentiation occurs in an ordered fashion in both mouse (left) and human (right) ES cells. Gene expression changes in both cell types are tightly controlled with down-regulation of pluripotency genes and up-regulation of lineage appropriate genes. This is akin to a group of musicians producing musical notes in the right order and at the right amplitude to create a coherent piece of music. B. Loss of "the conductor" NuRD results in increased transcriptional noise in both systems, indicated here as a low-level blanket of sound in both systems. Consequences of MBD3/NuRD loss differs between human and mouse ES cells. In mouse ES cells, differentiation cues lead to some down-regulation of pluripotency genes and incomplete progression along a lineage appropriate pathway. This is like musicians who know that they should be making music but who lose their way without a conductors influence. In human iPS cells the background level of noise without NuRD results in a lack of order to gene expression changes in response to differentiation. The noise from these "musicians" would be truly awful. C_FIG

developmental biology↗

MTA proteins act redundantly within the NuRD complex to ensure fidelity of ES cell lineage commitment

Multiprotein chromatin remodelling complexes show remarkable conservation of function amongst metazoans, even though components present in invertebrates are often present as multiple paralogous proteins in vertebrate complexes. In some cases these paralogues specify distinct biochemical and/or functional activities in vertebrate cells. Here we set out to define the biochemical and functional diversity encoded by one such group of proteins within the mammalian Nucleosome Remodelling and Deacetylation (NuRD) complex: Mta1, Mta2 and Mta3. We find that, in contrast to what has been described in somatic cells, MTA proteins are not mutually exclusive within ES cell NuRD and, despite subtle differences in chromatin binding and biochemical interactions, serve largely redundant functions. Nevertheless, ES cells lacking all three MTA proteins represent a complete NuRD null and are viable, allowing us to identify a previously undetected function for NuRD in maintaining differentiation trajectory during early stages of lineage commitment.

developmental biology↗

Transcriptional control by Sall4 in blastocysts facilitates lineage commitment of inner cell mass cells

The enhancer-binding zinc finger transcription factor Sall4 is essential for early mammalian postimplantation development and plays important roles in lineage commitment of embryonic stem cells. Enhancer binding by Sall4 results in transcriptional activation of some genes, but repression of others. Exactly how cells in preimplantation stage embryos use this transcriptional modulatory activity of Sall4 during early developmental transitions has not been determined. Using single cell gene expression analyses we show that Sall4 is required to maintain the gene regulatory network in inner cell mass (ICM) cells prior to lineage commitment. Although Sall4 is not required for ICM cells to adopt a correct epiblast or primitive endoderm gene expression profile, in the absence of Sall4 early ICM cells commit to either lineage at reduced frequency. We propose a model whereby Sall4 activity sets the stage for efficient progression from the uncommitted ICM progenitor state by modulating the gene regulatory network in early ICM cells.

developmental biology↗

The Nucleosome Remodelling and Deacetylation complex restricts Mediator access to enhancers to control transcription

A number of different chromatin remodelling complexes in mammalian cells are implicated in the control of gene expression. The genetic requirements for many such complex components have been described, and the biochemical activities of complex components characterised in vitro, yet the molecular mechanisms by which these biochemical activities impact transcriptional regulation in vivo remain ill-defined. Using an inducible system with fine temporal resolution, we show that the Nucleosome Remodelling and Deacetylation (NuRD) complex directly regulates chromatin architecture at enhancer regions in ES cells, in turn influencing the activity of RNA polymerase II via Mediator. Through this mechanism NuRD restricts Mediator access to enhancer chromatin during lineage commitment, thereby enabling appropriate transcriptional regulation. In contrast, acetylation levels of histone H3 lysine 27 are not immediately impacted by NuRD activity, correlating with transcriptional response only after expression levels have changed. These findings provide a detailed, molecular picture of genome-wide modulation of lineage-specific transcription by an abundant chromatin remodelling complex.

molecular biology↗