Biology subjects

Boroviak, T. E.

Publications and source records attributed to Boroviak, T. E..

5 recordsLinked to original sources

bioRxiv2026

WNT/β-catenin increases 3D chromatin mobility and reorganisation during posterior cell state transitions

Chromatin mobility, the exploration of 3D conformations by the chromatin fibre, is implicated in transcription and DNA repair, and is thought to decrease progressively as cells differentiate. Here, combining live-cell 3D single-nucleosome tracking with genomic approaches, we show that chromatin mobility instead changes in a cell-type-specific manner, increasing as pluripotent cells acquire posterior fates. This is accompanied by 3D genome reorganisation, including loss of Polycomb-associated interactions and emergence of CDX2-associated interactions. Withdrawal of posteriorising WNT/{beta}-catenin signalling rapidly reduces chromatin mobility and partially restores Polycomb-associated chromatin interactions, while Cdx1/2/4-null cells fail to acquire these WNT/{beta}-catenin-dependent changes. Together, our findings establish chromatin mobility as a regulated property of cell state, with WNT/{beta}-catenin signalling and CDX factors acting as mediators that fine-tune the sampling of 3D chromatin interactions during cell state transitions.

cell biology↗

bioRxiv2022

Requirement for STAT3 and its target, TFCP2L1 in self-renewal of naïve pluripotent stem cells in vivo and in vitro

We previously demonstrated gradual loss of epiblast during diapause in embryos lacking components of the LIF/IL6 receptor. Here we explore requirement for the downstream signalling transducer and activator of transcription, STAT3 and its target, TFCP2L1, in maintenance of naive pluripotency. Unlike conventional markers, such as NANOG, which remains high in epiblast until implantation, both STAT3 and TFCP2L1 proteins decline during blastocyst expansion, but intensify in the embryonic region after induction of diapause, as observed visually and confirmed using our novel image analysis tool, consistent with our previous transcriptional expression data. Embryos lacking STAT3 or TFCP2L1, underwent catastrophic loss of most of the inner cell mass during the first few days of diapause, implicating involvement of signals in addition to LIF/IL6 for sustaining naive pluripotency in vivo. By blocking MEK/ERK signalling from the morula stage we could derive embryonic stem cells with high efficiency from STAT3 null embryos, but not those lacking TFCP2L1, suggesting a hitherto unknown additional role for this essential STAT3 target in transition from embryo to embryonic stem cells in vitro. Summary StatementInducing diapause in mouse embryos demonstrates that STAT3 and TFCP2L1 are essential for self-renewal of the epiblast, but only TFCP2L1 is required for derivation of embryonic stem cells.

developmental biology↗

bioRxiv2022

Origin and segregation of the human germline

Human germline-soma segregation occurs during weeks 2-3 in gastrulating embryos. While direct studies are hindered, here we investigate the dynamics of human primordial germ cell (PGCs) specification using in vitro models with temporally resolved single-cell transcriptomics and in-depth characterisation to in vivo datasets from human and non-human primates, including a 3D marmoset reference atlas. We elucidate the molecular signature for the transient gain of competence for germ cell fate during peri-implantation epiblast development. Further, we show that both the PGCs and amnion arise from transcriptionally similar TFAP2A positive progenitors at the posterior end of the embryo. Notably, genetic loss of function experiments show that TFAP2A is crucial for initiating the PGC fate without detectably affecting the amnion, and its subsequently replaced by TFAP2C as an essential component of the genetic network for PGC fate. Accordingly, amniotic cells continue to emerge from the progenitors in the posterior epiblast, but importantly, this is also a source of nascent PGCs.

developmental biology↗

bioRxiv2022

Plakoglobin is a mechanoresponsive regulator of naïve pluripotency

Biomechanical cues are instrumental in guiding embryonic development and cell differentiation. Understanding how these physical stimuli translate into transcriptional programs could provide insight into mechanisms underlying mammalian pre-implantation development. Here, we explore this by exerting microenvironmental control over mouse embryonic stem cells (ESCs). Microfluidic encapsulation of ESCs in agarose microgels stabilized the naive pluripotency network and specifically induced expression of Plakoglobin (Jup), a vertebrate homologue of {beta}-catenin. Indeed, overexpression of Plakoglobin was sufficient to fully re-establish the naive pluripotency gene regulatory network under metastable pluripotency conditions, as confirmed by single-cell transcriptome profiling. Finally, we found that in the epiblast, Plakoglobin was exclusively expressed at the blastocyst stage in human and mouse embryos - further strengthening the link between Plakoglobin and naive pluripotency in vivo. Our work reveals Plakoglobin as a mechanosensitive regulator of naive pluripotency and provides a paradigm to interrogate the effects of volumetric confinement on cell-fate transitions. HighlightsO_LI3D agarose spheres stabilize the naive pluripotency network in mouse ESCs. C_LIO_LIVolumetric confinement induces expression of Plakoglobin, a vertebrate homologue of {beta}-catenin. C_LIO_LIPlakoglobin expression in the epiblast is specific to pre-implantation human and mouse embryos. C_LIO_LIPlakoglobin overexpression maintains naive pluripotency independently of {beta}-catenin. C_LI

developmental biology↗

bioRxiv2020

Oct4 regulates embryonic pluripotency via metabolic mechanisms and Stat3 signalling.

OCT4 is a fundamental component of the molecular circuitry governing pluripotency in vivo and in vitro. To determine how OCT4 protects the pluripotent lineage from differentiation into trophoblast, we used single cell transcriptomics and quantitative immunofluorescence on blastocysts and established differentially expressed genes and pathways between control and OCT4 null cells. Activation of most pluripotency-associated transcription factors in the early mouse inner cell mass appears independent of OCT4, whereas JAK/STAT signalling requires OCT4, via activation of IL6ST. Single cell deconvolution, diffusion component and trajectory inference dissected the process of differentiation of OCT4 null cells by activating specific gene-network and transcription factors. Downregulation of glycolytic and oxidative metabolism was observed. CHIPseq analysis suggests OCT4 directly targets rate-limiting glycolytic enzymes. Concomitant with significant disruption of the STAT3 pathway, oxidative respiration is significantly diminished in OCT4 null cells. Upregulation of the lysosomal pathway detected in OCT4 null embryos is likely attributable to aberrant metabolism. Highlights and noveltyO_LIMajor pluripotency-associated transcription factors are activated in OCT4-deficient early mouse ICM cells, coincident with ectopic expression of trophectoderm markers C_LIO_LIJAK/STAT signalling is defective in OCT4 null embryos C_LIO_LIOCT4 promotes expression of KATS enzymes by means of glycolytic production of Acetyl CoA to secure chromatin accessibility for acquisition of epiblast identity C_LIO_LIOCT4 regulates the metabolic and biophysical processes required for establishment of embryonic pluripotency C_LI

developmental biology↗