Pluripotent stem cell models of early mammalian development.

Pluripotent stem cells derived from the early mammalian embryo offer a convenient model system for studying cell fate decisions in embryogenesis. The last 10 years have seen a boom in the popularity of two-dimensional micropatterns and three-dimensional stem cell culture systems as a way to recreate the architecture and interactions of particular cell populations during development. These methods enable the controlled exploration of cellular organization and patterning during development, using cell lines instead of embryos. They have established a new class of in vitro model system for pre-implantation and peri-implantation embryogenesis, ranging from models of the blastocyst stage, through gastrulation and toward early organogenesis. This review aims to set these systems in context and to highlight the strengths and suitability of each approach in modelling early mammalian development.This work was supported by the European Research Council (Advanced Grant to A.M.A., number 834580) and the Leverhulme Trust (RPG-2018-356). N.M. holds the Constance Work Junior Research Fellowship at Newnham College, Cambridge

Biomedical and societal impacts of in vitro embryo models of mammalian development.

In recent years, a diverse array of in vitro cell-derived models of mammalian development have been described that hold immense potential for exploring fundamental questions in developmental biology, particularly in the case of the human embryo where ethical and technical limitations restrict research. These models open up new avenues toward biomedical advances in in vitro fertilization, clinical research, and drug screening with potential to impact wider society across many diverse fields. These technologies raise challenging questions with profound ethical, regulatory, and social implications that deserve due consideration. Here, we discuss the potential impacts of embryo-like models, and their biomedical potential and current limitations

A genome–wide screen to identify genes controlling the rate of entry into mitosis in fission yeast

We have carried out a haploinsufficiency (HI) screen in fission yeast using heterozygous deletion diploid mutants of a genome-wide set of cell cycle genes to identify genes encoding products whose level determines the rate of progression through the cell cycle. Cell size at division was used as a measure of advancement or delay of the G2-M transition of rod-shaped fission yeast cells. We found that 13 mutants were significantly longer or shorter (greater than 10%) than control cells at cell division. These included mutants of the cdc2, cdc25, wee1 and pom1 genes, which have previously been shown to play a role in the timing of entry into mitosis, and which validate this approach. Seven of these genes are involved in regulation of the G2-M transition, 5 for nuclear transport and one for nucleotide metabolism. In addition we identified 4 more genes that were 8–10% longer or shorter than the control that also had roles in regulation of the G2-M transition or in nuclear transport. The genes identified here are all conserved in human cells, suggesting that this dataset will be useful as a basis for further studies to identify ratelimiting steps for progression through the cell cycle in other eukaryotes

Single-cell and spatial transcriptomics reveal somitogenesis in gastruloids.

Gastruloids are three-dimensional aggregates of embryonic stem cells that display key features of mammalian development after implantation, including germ-layer specification and axial organization1-3. To date, the expression pattern of only a small number of genes in gastruloids has been explored with microscopy, and the extent to which genome-wide expression patterns in gastruloids mimic those in embryos is unclear. Here we compare mouse gastruloids with mouse embryos using single-cell RNA sequencing and spatial transcriptomics. We identify various embryonic cell types that were not previously known to be present in gastruloids, and show that key regulators of somitogenesis are expressed similarly between embryos and gastruloids. Using live imaging, we show that the somitogenesis clock is active in gastruloids and has dynamics that resemble those in vivo. Because gastruloids can be grown in large quantities, we performed a small screen that revealed how reduced FGF signalling induces a short-tail phenotype in embryos. Finally, we demonstrate that embedding in Matrigel induces gastruloids to generate somites with the correct rostral-caudal patterning, which appear sequentially in an anterior-to-posterior direction over time. This study thus shows the power of gastruloids as a model system for exploring development and somitogenesis in vitro in a high-throughput manner.This work was supported by an European Research Council Advanced grant (ERC-AdG 742225-IntScOmics), a Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) TOP award (NWOCW 714.016.001), and the Foundation for Fundamental Research on Matter, financially supported by NWO (FOM-14NOISE01) to S.C.v.d.B., A.A., V.v.B., M.B., J.V. and A.v.O., a BBSRC (No. BB/M023370/1 and BB/P003184/1), Newton Trust (INT16.24b) and MRC (MR/R017190/1) grant to A.M.A., a Newnham College Cambridge Junior Research Fellowship to N.M., and a studentship from the Engineering and Physical Sciences Research Council (EPSRC) to P.B.J.. The Cambridge Stem Cell Institute is supported by core funding from the Wellcome Trust and Medical Research Council; J. N. was funded by the University of Cambridge, and K.F.S. by core funding from the Hubrecht Institute. This work is part of the Oncode Institute which is partly financed by the Dutch Cancer Society

Reducing the environmental impact of surgery on a global scale: systematic review and co-prioritization with healthcare workers in 132 countries

Abstract Background Healthcare cannot achieve net-zero carbon without addressing operating theatres. The aim of this study was to prioritize feasible interventions to reduce the environmental impact of operating theatres. Methods This study adopted a four-phase Delphi consensus co-prioritization methodology. In phase 1, a systematic review of published interventions and global consultation of perioperative healthcare professionals were used to longlist interventions. In phase 2, iterative thematic analysis consolidated comparable interventions into a shortlist. In phase 3, the shortlist was co-prioritized based on patient and clinician views on acceptability, feasibility, and safety. In phase 4, ranked lists of interventions were presented by their relevance to high-income countries and low–middle-income countries. Results In phase 1, 43 interventions were identified, which had low uptake in practice according to 3042 professionals globally. In phase 2, a shortlist of 15 intervention domains was generated. In phase 3, interventions were deemed acceptable for more than 90 per cent of patients except for reducing general anaesthesia (84 per cent) and re-sterilization of ‘single-use’ consumables (86 per cent). In phase 4, the top three shortlisted interventions for high-income countries were: introducing recycling; reducing use of anaesthetic gases; and appropriate clinical waste processing. In phase 4, the top three shortlisted interventions for low–middle-income countries were: introducing reusable surgical devices; reducing use of consumables; and reducing the use of general anaesthesia. Conclusion This is a step toward environmentally sustainable operating environments with actionable interventions applicable to both high– and low–middle–income countries

In preprints: opportunities to unravel the earliest stages of human development using stem cell-based embryo models

Several exciting advances have enabled the derivation of stem cell-based embryo-like models (SCBEMs). Such models allow us to interrogate previously intractable questions in developmental biology and ask hypothesis-driven fundamental questions such as how the body plan forms, how tissue types interact and how transcriptomic, proteomic and metabolic states influence early human development. SCBEMs provide researchers with scalable, accessible and experimentally tractable systems when access to human embryos is limited or insufficient. SCBEM is an umbrella term, describing a diverse range of models produced through different protocols from self-organised stem cells. Crucially, none of the current models are ‘equivalent’ to human embryos; different SCBEM models represent specific aspects of development and to varying degrees. For example, SCBEMs may represent some, but not all, of the components of the early conceptus, whereas others model specific stages of development. Other SCBEMs might have the right cell types but in a disorganised, disproportionate or morphologically dysplastic state. Like any ‘toolbox’, human SCBEMs are powerful precisely because they represent a variety of ‘tools’ to ask a range of questions

Transition states and cell fate decisions in epigenetic landscapes.

Waddington's epigenetic landscape is an abstract metaphor frequently used to represent the relationship between gene activity and cell fates during development. Over the past few years, it has become a useful framework for interpreting results from single-cell transcriptomics experiments. It has led to the proposal that, during fate transitions, cells experience smooth, continuous progressions of global transcriptional activity, which can be captured by (pseudo)temporal dynamics. Here, focusing strictly on the fate decision events, we suggest an alternative view: that fate transitions occur in a discontinuous, stochastic manner whereby signals modulate the probability of the transition events.Kay Kendall Leukaemia FundThis is the author accepted manuscript. The final version is available from Nature Publishing Group via https://doi.org/10.1038/nrg.2016.9

Pluripotent stem cell models of early mammalian development

Pluripotent stem cells derived from the early mammalian embryo offer a convenient model system for studying cell fate decisions in embryogenesis. The last 10 years have seen a boom in the popularity of two-dimensional micropatterns and three-dimensional stem cell culture systems as a way to recreate the architecture and interactions of particular cell populations during development. These methods enable the controlled exploration of cellular organization and patterning during development, using cell lines instead of embryos. They have established a new class of in vitro model system for pre-implantation and peri-implantation embryogenesis, ranging from models of the blastocyst stage, through gastrulation and toward early organogenesis. This review aims to set these systems in context and to highlight the strengths and suitability of each approach in modelling early mammalian development.This work was supported by the European Research Council (advanced grant to AMA, number 834580) and the Leverhulme Trust (RPG-2018-356). NM holds the Constance Work Junior Research Fellowship at Newnham College, Cambridge