Biology subjects

Mansfield, W.

Publications and source records attributed to Mansfield, W..

4 recordsLinked to original sources

bioRxiv2024

STAT3 signalling enhances tissue expansion during postimplantation mouse development

STAT3 signalling has been studied extensively in the context of self-renewal and differentiation of mouse embryonic stem cells. Zygotic STAT3 is required for normal postimplantation development. On an outbred genetic background, Stat3 null embryos consistently lagged behind their littermates, beginning with significant reduction of epiblast cells at implantation. Remarkably, mutants closely resemble non-affected embryos from the previous day at all postimplantation stages examined. We pinpoint this phenotype to loss of the serine-phosphorylated form of STAT3 which predominates in postimplantation embryonic tissues. Bulk RNA-sequencing analysis of isolated mouse epiblasts confirmed Stat3 null embryos exhibited developmental delay transcriptionally. Single cell RNA sequencing of mid gestation chimaeras containing STAT3 null embryonic stem cells revealed exclusion of mutant cells exclusively from the erythroid lineage. Although Stat3 null embryonic stem cells can differentiate into erythroid and hematopoietic lineages in vitro, they are out-competed when mixed with wild type cells. Combined with the reduced size of STAT3 null epiblasts after implantation, our results implicate a role for STAT3 in cell proliferation affecting temporal control of embryonic progression and rapid differentiation. For the purpose of Open Access, the author has applied a CC BY public copyright licence to any Author Accepted Manuscript version arising from this submission.

developmental biology↗

bioRxiv2020

De novo DNA methylation suppresses aberrant fate determination during pluripotency transition

Genome remethylation is essential for mammalian development but specific reasons are unclear. Here we examined embryonic stem (ES) cell fate in the absence of de novo DNA methyltransferases. We observed that ES cells deficient for both Dnmt3a and Dnmt3b are rapidly eliminated from chimaeras. On further investigation we found that in vivo and in vitro the formative pluripotency transition is derailed towards production of trophoblast. This aberrant trajectory is associated with failure to suppress activation of Ascl2. Ascl2 encodes a bHLH transcription factor expressed in placenta. Misexpression of Ascl2 in ES cells provokes transdifferentiation to trophoblast-like cells. Conversely, Ascl2 deletion rescues formative transition of Dnmt3a/b mutants and improves contribution to chimaeric epiblast. Thus, de novo DNA methylation safeguards against ectopic activation of Ascl2. However, Dnmt3a/b-deficient cells remain defective in ongoing embryogenesis. We surmise that multiple developmental transitions may be secured by DNA methylation silencing potentially disruptive genes. SIGNIFICANCE STATEMENTMammalian DNA is widely modified by methylation of cytosine residues. This modification is added to DNA during early development. If methylation is prevented, the embryo dies by mid-gestation with multiple abnormalities. In this study we found that stem cells lacking the DNA methylation enzymes do not differentiate efficiently into cell types of the embryo and are diverted into producing placental cells. This switch in cell fate is driven by a transcription factor, Ascl2, which should only be produced in placenta. In the absence of DNA methylation, the Ascl2 gene is mis-expressed. Removing Ascl2 redirects embryonic fate but not full differentiation potential, suggesting that methylation acts at multiple developmental transitions to restrict activation of disruptive genes.

developmental biology↗

bioRxiv2020

Capture of mouse and human stem cells with features of formative pluripotency

Pluripotent cells emerge via a naive founder population in the blastocyst, acquire capacity for germline and soma formation, and then undergo lineage priming. Mouse embryonic stem (ES) cells and epiblast stem cells (EpiSCs) represent the initial naive and final primed phases of pluripotency, respectively. Here we investigate the intermediate formative stage. Using minimal exposure to specification cues, we expand stem cells from formative mouse epiblast. Unlike ES cells or EpiSCs, formative stem (FS) cells respond directly to germ cell induction. They colonise chimaeras including the germline. Transcriptome analyses show retained pre-gastrulation epiblast identity. Gain of signal responsiveness and chromatin accessibility relative to ES cells reflect lineage capacitation. FS cells show distinct transcription factor dependencies from EpiSCs, relying critically on Otx2. Finally, FS cell culture conditions applied to human naive cells or embryos support expansion of similar stem cells, consistent with a conserved attractor state on the trajectory of mammalian pluripotency.

developmental biology↗

bioRxiv2019

StemBond hydrogels optimise the mechanical microenvironment for embryonic stem cells

Studies of mechanical signalling are typically performed by comparing cells cultured on soft and stiff hydrogel-based substrates. However, it is challenging to independently and robustly control both substrate stiffness and tethering of extracellular matrix (ECM) to substrates, making ECM tethering a potentially confounding variable in mechanical signalling investigations. Moreover, poor ECM tethering can lead to weak cell attachment. To address this, we developed StemBond hydrogels, a hydrogel formulation in which ECM tethering is stable and can be varied independently of stiffness. We show that soft StemBond hydrogels provide an optimal format for culturing embryonic stem (ES) cells. We find that soft StemBond substrates improve the homogeneity of ES cell populations, boost their self-renewal, and increase the efficiency of cellular reprogramming. Our findings underline how soft microenvironments impact mechanosensitive signalling pathways regulating self-renewal and differentiation, indicating that optimising the complete mechanical microenvironment will offer greater control over stem cell fate specification.

cell biology↗