Biology subjects

Murre, C.

Publications and source records attributed to Murre, C..

14 recordsLinked to original sources

bioRxiv2026

A hierarchy of spatial confinements governs chromatin dynamics and genomic encounters

Antibody diversity is generated through stochastic rearrangement of the immunoglobulin heavy chain locus (Igh) involving the recombination of variable (VH), diversity (DH) and joining (JH) gene segments. How coding elements within the Igh locus locate one another in the complex nuclear environment is not understood. Here, we sought to identify the molecular mechanisms and physical principles that govern VH-DHJH genomic encounters. We found that transcription imposed a local confinement that stabilized interactions between spatially proximal genomic elements. The loop anchor CTCF modestly constrained population-average chromatin motion, whereas cohesin-mediated loops established large-scale confinement and reinforced self-similarity of VH-DHJH motion across spatial and temporal scales. Quantitative scaling arguments for first-passage times revealed that encounter frequencies between remote VH-DHJH genomic regions are governed by the interplay of diffusivity and spatial proximity. Together, these findings show that the hierarchy of confinements imposed by transcription and loop extrusion provides the balance between stability and mobility required to regulate genomic encounter frequencies.

biophysics↗

bioRxiv2026

CTCF-mediated cis-regulatory chromatin insulation enforces a central B-cell tolerance checkpoint

The generation of a diverse and self-tolerant B cell repertoire is essential for adaptive immunity and is achieved through V(D)J recombination. In mice, Ig{kappa} is the dominant light chain, whereas Ig{lambda} rearrangement typically occurs in response to nonproductive or autoreactive Ig{kappa} recombination, a process termed receptor editing. Recombination at the RS element deletes the Ig{kappa} constant exon, silencing the locus and enabling Ig{lambda} expression. However, the epigenetic regulatory framework that orchestrates and governs receptor editing remains poorly defined. Here, we identify a CTCF-binding insulator element (CBE) within the 3' Ig{kappa} super-enhancer (3'-SE{kappa}) that regulates receptor editing and directs the {kappa}-to-{lambda} switch required for Ig{lambda} B-cell development. Mechanistically, loss of this CBE activates an insulated enhancer within the 3'-SE{kappa}, causing aberrant V{kappa} rearrangements and altered chromatin interactions through disrupted loop extrusion dynamics. Notably, loss of this CBE in mice leads to increased autoantibody production by ten weeks of age, demonstrating that CBE-mediated chromatin architecture shapes B cell fate by constraining autoreactive potential. Collectively, our findings define a novel CTCF-dependent cis-regulatory insulation checkpoint that connects chromatin loop extrusion to antigen-driven receptor editing, thereby enforcing B-cell tolerance.

immunology↗

bioRxiv2025

Interlinked roles for HEB and Id3 in fetal gamma-delta T cell commitment and functional programming

T cells expressing the {gamma}{delta} T cell receptor (TCR) develop in a stepwise process initiating at the {beta}/{gamma}{delta} T cell branchpoint followed by maturation and acquisition of effector functions, including the ability to produce interleukin-17 (IL-17) as {gamma}{delta}T17 cells. Previous studies linked TCR signal strength and fate choices to the transcriptional regulator HEB (Tcf12) and its antagonist, Id3, but how these factors regulate different stages of {gamma}{delta} T cell development has not been determined. We found that immature fetal {gamma}{delta}TCR+ cells from conditional Tcf12 knockout (HEB cKO) mice were defective in activating the {gamma}{delta}T17 program at an early stage, whereas Id3 deficient (Id3-KO) mice displayed a partial block in {gamma}{delta}T17 maturation and a defect in IL-17 production. We also found that HEB cKO mice failed to upregulate Id3 during {gamma}{delta}T17 development, whereas HEB overexpression elevated the levels of Id3 in collaboration with TCR signaling. Moreover, Egr2 and HEB were bound to several of the same regulatory sites on the Id3 gene locus in the context of early T cell development. Therefore, our findings reveal an interlinked sequence of events during which HEB and TCR signaling synergize to upregulate Id3, which enables maturation and acquisition of the {gamma}{delta}T17 effector program. One Sentence SummaryThe transcription factor HEB synergizes with TCR signaling to upregulate Id3, which is required for the maturation of fetal IL-17-producing {gamma}{delta} T cells.

immunology↗

bioRxiv2024

Helical Coiled Nucleosome Chromosome Architectures during Cell Cycle Progression

Recent studies showed an interphase chromosome architecture, --- a specific coiled nucleosome structure, --- derived from cryo-preserved EM tomograms, and dispersed throughout the nucleus. The images were computationally processed to fill in the missing wedges of data caused by incomplete tomographic tilts. The resulting structures increased z-resolution enabling an extension of the proposed architecture to that of mitotic chromosomes. Here we provide additional insights and details into the coiled nucleosome chromosome architectures. We build on the defined chromosomes time-dependent structures in an effort to probe their dynamics. Variants of the coiled chromosome structures, possibly further defining specific regions, are discussed. We propose, based on generalized specific uncoiling of mitotic chromosomes in telophase, large-scale re-organization of interphase chromosomes. Chromosome territories, organized as micron-sized small patches, are constructed, satisfying complex volume considerations. Finally, we unveiled the structures of replicated coiled chromosomes, still attached to centromeres, as part of chromosome architecture. Significance StatementThis study places all 46 sequenced human chromosomes, --- correctly filled with nucleosomes and in micron sized chromosome territories -- into 10micron (average sized) nuclei. The chromosome architecture used a helical nucleosome coiled structure discerned from cryo-EM tomography, as was recently published (https://doi.org/10.1073/pnas.2119101119). This chromosome architecture was further modeled to dynamic structures, structure variations and chromosome replication centromere complications. Finally, this chromosome architecture was modified to allow seamless transition through the cell cycle.

cell biology↗

bioRxiv2023

Active maintenance of CD8+ T cell naivety through regulation of global genome architecture

The differentiation of naive CD8+ cytotoxic T lymphocytes (CTLs) into effector and memory states results in large scale changes in transcriptional and phenotypic profiles. Little is known about how large-scale changes in genome organisation reflect or underpin these transcriptional programs. We utilised Hi-C to map changes in the spatial organisation of long-range genome contacts within naive, effector and memory virus-specific CD8+ T cells. We observed that the architecture of the naive CD8+ T cell genome was distinct from effector and memory genome configurations with extensive changes within discrete functional chromatin domains. However, deletion of the BACH2 or SATB1 transcription factors was sufficient to remodel the naive chromatin architecture and engage transcriptional programs characteristic of differentiated cells. This suggests that the chromatin architecture within naive CD8+ T cells is preconfigured to undergo autonomous remodelling upon activation, with key transcription factors restraining differentiation by actively enforcing the unique naive chromatin state. One Sentence SummaryCD8+ T cell naivety is actively maintained by transcription factors that enforce a distinct, naive chromatin architecture. HighlightsO_LICD8+ T cell differentiation states are underscored by distinct chromatin looping architectures. C_LIO_LIChromatin loops juxtapose CTL state appropriate enhancers, transcription factors and genes. C_LIO_LIEffector and memory CTLs have similar genome architectures, explaining rapid memory recall. C_LIO_LICTL differentiation is restrained by BACH2 and SATB1, which enforce a naive loop architecture. C_LI

immunology↗

bioRxiv2021

A Proposed Unified Mitotic Chromosome Architecture

A molecular architecture is proposed for an example mitotic chromosome, human Chromosome 10. This architecture is built on a previously described interphase chromosome structure based on Cryo-EM cellular tomography (1), thus unifying chromosome structure throughout the complete mitotic cycle. The basic organizational principle, for mitotic chromosomes, is specific coiling of the 11-nm nucleosome fiber into large scale approximately 200 nm structures (a Slinky (2, motif cited in 3) in interphase, and then further modification and subsequent additional coiling for the final structure. The final mitotic chromosome architecture accounts for the dimensional values as well as the well known cytological configurations. In addition, proof is experimentally provided, by digital PCR technology, that G1 T-cell nuclei are diploid, thus one DNA molecule per chromosome. Many nucleosome linker DNA sequences, the promotors and enhancers, are suggestive of optimal exposure on the surfaces of the large-scale coils. Significance StatementThe significance of this proposed mitotic chromosome architecture is that a specific, sequenced chromosome, human Chromosome 10, can be built into a specific architecture that accounts for the dimensional values and cytological descriptions, a first time result. Since this molecular architecture is an extension of the interphase chromosome structure, a coiling of the 11-nm nucleosome fiber with further coiling, a unifying molecular structure motif is present throughout the entire mitotic cycle, interphase through mitosis.

cell biology↗

bioRxiv2021

A Proposed Unified Interphase Nucleus Chromosome Structure: Preliminary Preponderance of Evidence

Cellular cryo-electron tomography (CET) of the cell nucleus using Scanning Transmission Electron Microscopy (STEM) and the use of deconvolution (DC) processing technology has highlighted a large-scale, 100-300 nm interphase chromosome structure (LSS), that is present throughout the nucleus. This chromosome structure appears to coil the nucleosome 11-nm fiber into a defined hollow structure, analogous to a Slinky (S) (1, motif used in 2) helical spring. This S architecture can be used to build chromosome territories, extended to polytene chromosome structure, as well as to the structure of Lampbrush chromosomes. Significance StatementCryo-preservation of the nuclear interior allows a large scale interphase chromosome structure--present throughout the nucleus--to be seen for the first time. This structure can be proposed to be a defined coiled entity, a Slinky. This structure can be further used to explain polytene chromosome structure, an unknown chromosome architecture as well as for lampbrush chromosomes. In addition, this new structure can be further organized as chromosome territories, using all 46 human interphase chromosomes as an example, easily into a 10 micron diameter nucleus. Thus, interphase chromosomes can be unified into a flexible defined structure.

cell biology↗

bioRxiv2020

Direct observation of RAG recombinase recruitment to chromatin and the IgH locus in live pro-B cells

The RAG1 and RAG2 proteins introduce double-strand DNA breaks at antigen-receptor loci in developing lymphocytes to initiate V(D)J recombination. How RAG proteins find the correct target locus in a vast excess of non-specific chromatin is not known. Here we measured dynamics of RAG1/RAG2 interactions with chromatin in living pro-B cells. We found that the majority of RAG1 or RAG1/RAG2 complex is in a fast 3D diffusive state, and the residual slow diffusive (bound) fraction was determined by a non-core portion of RAG1, and the PHD domain of RAG2. The RAG proteins exhibited distinct dynamics at the IgH locus. In particular, RAG2 increased the probability of RAG1 binding to IgH, a property that likely explains its non-catalytic role in V(D)J recombination. Our observations reveal how RAG finds its targets in developing B cells. One Sentence SummarySingle-molecule imaging of the RAG recombinase reveals its search strategy for chromatin, H3K4me3 and antibody gene loci in living cells.

biophysics↗

bioRxiv2020

Molecular determinants and heterogeneity of tissue-resident memory CD8+ T lymphocytes revealed by single-cell RNA sequencing

During an immune response to microbial infection, CD8+ T cells give rise to distinct classes of cellular progeny that coordinately mediate clearance of the pathogen and provide long-lasting protection against reinfection, including a subset of non-circulating tissue-resident memory (TRM) cells that mediate potent protection within non-lymphoid tissues. Here, we utilized single-cell RNA-sequencing to examine the gene expression patterns of individual CD8+ T cells in the spleen and small intestine intraepithelial lymphocyte (siIEL) compartment throughout the course of their differentiation in response to viral infection. These analyses revealed previously unknown transcriptional heterogeneity within the siIEL CD8+ T cell population at several states of differentiation, representing functionally distinct TRM cell subsets as well as a subset of TRM cell precursors within the tissue early in infection. Taken together, these findings may inform strategies to optimize CD8+ T cell responses to protect against microbial infection and cancer. One sentence summaryHere, we applied single-cell RNA-sequencing to elucidate the gene expression patterns of individual CD8+ T cells differentiating throughout the course of infection in the spleen and small intestinal epithelium, which revealed previously unidentified molecular determinants of tissue-resident T cell differentiation as well as functional heterogeneity within the tissue-resident CD8+ T cell population.

immunology↗

bioRxiv2019

Upon microbial challenge human neutrophils undergo rapid changes in nuclear architecture to orchestrate an immediate inflammatory gene program

Differentiating neutrophils undergo large-scale changes in nuclear morphology. How such alterations in structure are established and modulated upon exposure to microbial agents is largely unknown. Here, we found that prior to encounter with bacteria, an armamentarium of inflammatory genes was positioned in a transcriptionally passive environment suppressing premature transcriptional activation. Upon microbial exposure, however, human neutrophils rapidly (<3 hours) repositioned the ensemble of pro-inflammatory genes towards the transcriptionally permissive compartment. We show that the repositioning of genes was closely associated with the swift recruitment of cohesin across the inflammatory enhancer landscape permitting an immediate transcriptional response upon bacterial exposure. These data reveal at the mechanistic level how upon microbial challenge human neutrophils undergo rapid changes in nuclear architecture to orchestrate an immediate inflammatory gene program.

genomics↗

bioRxiv2018

Antigen receptor locus dynamics is orchestrated near the sol-gel phase transition to enforce stepwise VDJ gene rearrangement

Diverse antibody repertoires are generated through remote genomic interactions involving immunoglobulin variable (VH), diversity (DH) and joining (JH) gene segments. How such interactions are orchestrated remains unknown. We developed a novel strategy to track VH-DHJH motion and interactions in live B-lymphocytes. We found that VH and DHJH segments were trapped in configurations that only allowed constrained local motion, such that spatially proximal VH and DHJH segments remained in proximity, whereas spatially remote segments explored their immediate neighborhood while remaining remote. Comparison of experimental and simulated data revealed that such a highly constrained motion was imposed by a network of cross-linked chromatin chains characteristic of a gel phase, yet it was poised near the sol phase, a solution of independent chromatin chains. We propose that epigenetically induced gel droplets and the proximity to the sol-gel phase transition constitute the mechanism that orchestrates ordered VDJ rearrangement.

immunology↗

bioRxiv2018

An inter-chromosomal transcription hub activates the unfolded protein response in plasma cells

Previous studies have indicated that the transcription signature of antibody-secreting cells is closely associated with the induction of the unfolded protein response pathway (UPR). Here we have used genome-wide and single cell analyses to examine the folding patterns of plasma cell genomes. We found that plasma cells adopt a cartwheel configuration and undergo large-scale changes in chromatin folding at genomic regions associated with a plasma cell specific transcription signature. During plasma cell differentiation, Blimp1 assembles into an inter-chromosomal transcription hub with genes associated with the UPR, biosynthesis of the endoplasmic reticulum (ER) as well as a cluster of genes linked with Alzheimers disease. We suggest that the assembly of the Blimp1-UPR-ER transcription hub permits the coordinate activation of a wide spectrum of genes that collectively establish plasma cell identity.

immunology↗

bioRxiv2017

Id proteins suppress E2A-driven innate-like T cell development prior to TCR selection

Id proteins have been shown to promote the differentiation of conventional {beta} and {gamma}{delta}T cells, and to suppress the expansion of invariant Natural Killer T (iNKT) cells and innate-like {gamma}{delta}NKT within their respective cell lineages. However, it remains to be determined whether Id proteins regulate lineage specification in developing T cells that give rise to these distinct cell fates. Here we report that in the absence of Id2 and Id3 proteins, E2A prematurely activates genes critical for the iNKT cell lineage prior to TCR expression. Enhanced iNKT development in Id3-deficient mice lacking {gamma}{delta} NKT cells suggests that Id3 regulates the lineage competition between these populations. RNA-Seq analysis establishes E2A as the transcriptional regulator of both iNKT and {gamma}{delta}NKT development. In the absence of pre-TCR signaling, Id2/Id3 deletion gives rise to a large population of iNKT cells and a unique innate-like DP population, despite the block in conventional {beta} T cell development. The transcriptional profile of these unique DP cells reflects enrichment of innate-like signature genes, including PLZF (Zbtb16) and Granzyme A (Gzma). Results from these genetic models and genome-wide analyses suggest that Id proteins suppress E2A-driven innate-like T cell programs prior to TCR selection to enforce predominance of conventional T cells.

immunology↗

bioRxiv2017

Comprehensive characterization of neutrophil genome topology

Neutrophils are responsible for the first line of defense against invading pathogens. Their nuclei are uniquely structured as multiple lobes that establish a highly constrained nuclear environment. Here we found that neutrophil differentiation was not associated with large-scale changes in the number and sizes of topologically associating domains. However, neutrophil genomes were enriched for long-range genomic interactions that spanned multiple topologically associating domains. Population-based simulation of spherical and toroid genomes revealed declining radii of gyration for neutrophil chromosomes. We found that neutrophil genomes were highly enriched for heterochromatic genomic interactions across vast genomic distances, a process named super-contraction. Super-contraction involved genomic regions located in the heterochromatic compartment in both progenitors and neutrophils or genomic regions that switched from the euchromatic to the heterochromatic compartment during neutrophil differentiation. Super-contraction was accompanied by the repositioning of centromeres, pericentromeres and Long-Interspersed Nuclear Elements (LINEs) to the neutrophil nuclear lamina. We found that Lamin-B Receptor expression was required to attach centromeric and pericentromeric repeats but not LINE-1 elements to the lamina. Differentiating neutrophils also repositioned ribosomal DNA and mini-nucleoli to the lamina: a process that was closely associated with sharply reduced ribosomal RNA expression. We propose that large-scale chromatin reorganization involving super-contraction and recruitment of heterochromatin and nucleoli to the nuclear lamina facilitate the folding of the neutrophil genome into a confined geometry imposed by a multi-lobed nuclear architecture.

molecular biology↗