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Aims Arrhythmogenic cardiomyopathy (ACM) is an inherited cardiac disorder that is characterized by progressive loss of myocardium that is replaced by fibro-fatty cells, arrhythmias, and sudden cardiac death. While myocardial degeneration and fibro-fatty replacement occur in specific locations, the underlying molecular changes remain poorly characterized. Here, we aim to delineate local changes in gene expression to identify new genes and pathways that are relevant for specific remodelling processes occurring during ACM. Methods and results Using Tomo-Seq, genome-wide transcriptional profiling with high spatial resolution, we created transmural epicardial-to-endocardial gene expression atlases of explanted ACM hearts to gain molecular insights into disease-driving processes. This enabled us to link gene expression profiles to the different regional remodelling responses and allowed us to identify genes that are potentially relevant for disease progression. In doing so, we identified distinct gene expression profiles marking regions of cardiomyocyte degeneration and fibro-fatty remodelling and revealed Zinc finger and BTB domain-containing protein 11 (ZBTB11) to be specifically enriched at sites of active fibro-fatty replacement of myocardium. Immunohistochemistry indicated ZBTB11 to be induced in cardiomyocytes flanking fibro-fatty areas, which could be confirmed in multiple cardiomyopathy patients. Forced overexpression of ZBTB11 induced autophagy and cell death-related gene programmes in human cardiomyocytes, leading to increased apoptosis. Conclusion Our study shows the power of Tomo-Seq to unveil new molecular mechanisms in human cardiomyopathy and uncovers ZBTB11 as a novel driver of cardiomyocyte loss.

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Previous studies have described that tumor organoids can capture the diversity of defined human carcinoma types. Here, we describe conditions for long-term culture of human mucosal organoids. Using this protocol, a panel of 31 head and neck squamous cell carcinoma (HNSCC)–derived organoid lines was established. This panel recapitulates genetic and molecular characteristics previously described for HNSCC. Organoids retain their tumorigenic potential upon xenotransplantation. We observe differential responses to a panel of drugs including cisplatin, carboplatin, cetuximab, and radiotherapy in vitro. Additionally, drug screens reveal selective sensitivity to targeted drugs that are not normally used in the treatment of patients with HNSCC. These observations may inspire a personalized approach to the management of HNSCC and expand the repertoire of HNSCC drugs.Significance:This work describes the culture of organoids derived from HNSCC and corresponding normal epithelium. These tumoroids recapitulate the disease genetically, histologically, and functionally. In vitro drug screening of tumoroids reveals responses to therapies both currently used in the treatment of HNSCC and those not (yet) used in clinical practice.See related commentary by Hill and D'Andrea, p. 828.This article is highlighted in the In This Issue feature, p. 813

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Movie S5 from Oral Mucosal Organoids as a Potential Platform for Personalized Cancer Therapy

Supplementary Figures including legends, Supplementary Tables

Supplementary Table from Differential Survival and Therapy Benefit of Patients with Breast Cancer Are Characterized by Distinct Epithelial and Immune Cell Microenvironments

Supplementary Data from Differential Survival and Therapy Benefit of Patients with Breast Cancer Are Characterized by Distinct Epithelial and Immune Cell Microenvironments

Purpose:Extensive work in preclinical models has shown that microenvironmental cells influence many aspects of cancer cell behavior, including metastatic potential and their sensitivity to therapeutics. In the human setting, this behavior is mainly correlated with the presence of immune cells. Here, in addition to T cells, B cells, macrophages, and mast cells, we identified the relevance of nonimmune cell types for breast cancer survival and therapy benefit, including fibroblasts, myoepithelial cells, muscle cells, endothelial cells, and seven distinct epithelial cell types.Experimental Design:Using single-cell sequencing data, we generated reference profiles for all these cell types. We used these reference profiles in deconvolution algorithms to optimally detangle the cellular composition of more than 3,500 primary breast tumors of patients that were enrolled in the SCAN-B and MATADOR clinical trials, and for which bulk mRNA sequencing data were available.Results:This large data set enables us to identify and subsequently validate the cellular composition of microenvironments that distinguish differential survival and treatment benefit for different treatment regimens in patients with primary breast cancer. In addition to immune cells, we have identified that survival and therapy benefit are characterized by various contributions of distinct epithelial cell types.Conclusions:From our study, we conclude that differential survival and therapy benefit of patients with breast cancer are characterized by distinct microenvironments that include specific populations of immune and epithelial cells.

Supplementary Figure from Differential Survival and Therapy Benefit of Patients with Breast Cancer Are Characterized by Distinct Epithelial and Immune Cell Microenvironments

XLSX file - 9K, Different inference of diversity depending on the loci analyzed.

XLSX file - 32K, Shannon and Simpson's index for each tumor and each probe based on BAC, CEP, BAC/CEP and unique counts.

XLSX file - 32K, Shannon and Simpson's index for each tumor and each probe based on BAC, CEP, BAC/CEP and unique counts.

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XLSX file - 86K, Shannon and Simpson's index for each cell type based on BAC, CEP, BAC/CEP and unique counts.

XLSX file - 1151K, BAC and CEP counts for each cell phenotype in the paired metastatic tumor (left) and paired primary and lymph node metastasis (right) series.

PDF file - 3207K, Representative examples of box plots depicting BAC/CEP ratios for the indicated chromosomal regions in two different metastatic sites (A and B) within the same patient (S1); Representative examples of kernel density and Whittaker plots (S2); Distribution of genomic variability (S3); Genetic differences between adjacent cells (S4).

XLSX file - 14K, Clinical information of the paired metastasis and primary tumors (PR) and lymph node (LN) metastasis series.

XLSX file - 107K, Shannon and Simpson's index for each cell type based on BAC, CEP, BAC/CEP and unique counts.

Cancer homeostasis depends on a balance between activated oncogenic pathways driving tumorigenesis and engagement of stress-response programs that counteract the inherent toxicity of such aberrant signaling. While inhibition of oncogenic signaling pathways has been explored extensively, there is increasing evidence that overactivation of the same pathways can also disrupt cancer homeostasis and cause lethality. We show here that inhibition of Protein Phosphatase 2A (PP2A) hyperactivates multiple oncogenic pathways and engages stress responses in colon cancer cells. Genetic and compound screens identify combined inhibition of PP2A and WEE1 as synergistic in multiple cancer models by collapsing DNA replication and triggering premature mitosis followed by cell death. This combination also suppressed the growth of patient-derived tumorsin vivo. Remarkably, acquired resistance to this drug combination suppressed the ability of colon cancer cells to form tumorsin vivo. Our data suggest that paradoxical activation of oncogenic signaling can result in tumor suppressive resistance.

Regulation of chromatin states involves the dynamic interplay between different histone modifications to control gene expression. Recent advances have enabled mapping of histone marks in single cells, but most methods are constrained to profile only one histone mark per cell. Here, we present an integrated experimental and computational framework, scChIX-seq (single-cell chromatin immunocleavage and unmixing sequencing), to map several histone marks in single cells. scChIX-seq multiplexes two histone marks together in single cells, then computationally deconvolves the signal using training data from respective histone mark profiles. This framework learns the cell-type-specific correlation structure between histone marks, and therefore does not require a priori assumptions of their genomic distributions. Using scChIX-seq, we demonstrate multimodal analysis of histone marks in single cells across a range of mark combinations. Modeling dynamics of in vitro macrophage differentiation enables integrated analysis of chromatin velocity. Overall, scChIX-seq unlocks systematic interrogation of the interplay between histone modifications in single cells.

In a human cell thousands of replication forks simultaneously coordinate the duplication of the entire genome. The rate at which this process occurs, might depend on the epigenetic state of the genome and vary between, or even within, cell types. To accurately measure DNA replication speeds, we developed a technology to detect recently replicated DNA using single-cell sequencing. Replication speed is not constant but increases during S-phase of the cell cycle. Using genetic and pharmacological perturbations we are able to alter this acceleration of replication and conclude that DNA damage inflicted by the process of transcription limits the speed of replication during early S-phase. In late S-phase, during which less transcription occurs, replication accelerates and approaches its maximum speed.

The developmental role of histone H3K9 methylation (H3K9me), which typifies heterochromatin, remains unclear. In Caenorhabditis elegans, loss of H3K9me leads to a highly divergent upregulation of genes with tissue and developmental-stage specificity. During development H3K9me is lost from differentiated cell type-specific genes and gained at genes expressed in earlier developmental stages or other tissues. The continuous deposition of H3K9me2 by the SETDB1 homolog MET-2 after terminal differentiation is necessary to maintain repression. In differentiated tissues, H3K9me ensures silencing by restricting the activity of a defined set of transcription factors at promoters and enhancers. Increased chromatin accessibility following the loss of H3K9me is neither sufficient nor necessary to drive transcription. Increased ATAC-seq signal and gene expression correlate at a subset of loci positioned away from the nuclear envelope, while derepressed genes at the nuclear periphery remain poorly accessible despite being transcribed. In conclusion, H3K9me deposition can confer tissue-specific gene expression and maintain the integrity of terminally differentiated muscle by restricting transcription factor activity., Nature Cell Biology, 23, ISSN:1465-7392, ISSN:1476-4679

3D gastruloids, aggregates of embryonic stem cells that recapitulate key aspects of gastrula-stage embryos, have emerged as a powerful tool to study the early stages of mammalian post-implantation development in vitro. Owing to their tractable nature and the relative ease by which they can be generated in large numbers, 3D gastruloids provide an unparalleled opportunity to study normal and pathological embryogenesis from a bottom-up perspective and in a high-throughput manner. Here, we review how gastruloid models can be exploited to deepen our understanding of mammalian development. In addition, we discuss current limitations, potential clinical applications, and ethical implications of this emerging model system.

Data de publicació electrònica: 27-06-2022 Most methods for single-cell transcriptome sequencing amplify the termini of polyadenylated transcripts, capturing only a small fraction of the total cellular transcriptome. This precludes the detection of many long non-coding, short non-coding and non-polyadenylated protein-coding transcripts and hinders alternative splicing analysis. We, therefore, developed VASA-seq to detect the total transcriptome in single cells, which is enabled by fragmenting and tailing all RNA molecules subsequent to cell lysis. The method is compatible with both plate-based formats and droplet microfluidics. We applied VASA-seq to more than 30,000 single cells in the developing mouse embryo during gastrulation and early organogenesis. Analyzing the dynamics of the total single-cell transcriptome, we discovered cell type markers, many based on non-coding RNA, and performed in vivo cell cycle analysis via detection of non-polyadenylated histone genes. RNA velocity characterization was improved, accurately retracing blood maturation trajectories. Moreover, our VASA-seq data provide a comprehensive analysis of alternative splicing during mammalian development, which highlighted substantial rearrangements during blood development and heart morphogenesis. This work was supported by a European Research Council (ERC) Advanced Grant (ERC-AdG 742225-IntScOmics), a Nederlandse Organisatie voor Wetenschappelijk Onderzoek (NWO) TOP award (NWO-CW 714.016.001) and the Wellcome Trust (WT108438/C/15/Z). This work is part of the Oncode Institute, which is partly financed by the Dutch Cancer Society. J.D.J. received scholarship support from the Biotechnology and Biological Sciences Research Council (BBSRC), T.N.K. from AstraZeneca, A.L.E. from the Cambridge Trusts and the EU H2020 Marie Curie ITN MMBio and T.S.K. from an EU H2020 Marie Skłodowska-Curie Actions Individual Fellowship (MSCA-IF 750772). F.H. is an H2020 ERC Advanced Investigator (69566). M.H. was supported by a core grant from the Wellcome Trust and by funding from the Evergrande Center for Immunologic Diseases. J.N. was funded by the Wellcome Trust (03151/Z/16/Z). For the purpose of open access, the author has applied a CC BY public copyright license to any Author Accepted Manuscript version arising from this submission. A.Y. was funded by the BBSRC (RG83885), and the mice used in the study are associated with the Wellcome Trust Strategic Grant (105031). Parts of the illustrations were designed using BioRender.

In recent years, single-cell transcriptome sequencing has revolutionized biology, allowing for the unbiased characterization of cellular subpopulations. However, most methods amplify the termini of polyadenylated transcripts capturing only a small fraction of the total cellular transcriptome. This precludes the detection of many long non-coding, short non-coding and non-polyadenylated protein-coding transcripts. Additionally, most workflows do not sequence the full transcript hindering the analysis of alternative splicing. We therefore developed VASAseq to detect the total transcriptome in single cells. VASA-seq is compatible with both platebased formats and droplet microfluidics. We applied VASA-seq to over 30,000 single cells in the developing mouse embryo during gastrulation and early organogenesis. The dynamics of the total single-cell transcriptome result in the discovery of novel cell type markers, many based on non-coding RNA, an in vivo cell cycle analysis and an improved RNA velocity characterization. Moreover, it provides the first comprehensive analysis of alternative splicing during mammalian development.

The embryo instructs the allocation of cell states to spatially regulate functions. In the blastocyst, patterning of trophoblast (TR) cells ensures successful implantation and placental development. Here, we defined an optimal set of molecules secreted by the epiblast (inducers) that captures in vitro stable, highly self-renewing mouse trophectoderm stem cells (TESCs) resembling the blastocyst stage. When exposed to suboptimal inducers, these stem cells fluctuate to form interconvertible subpopulations with reduced self-renewal and facilitated differentiation, resembling peri-implantation cells, known as TR stem cells (TSCs). TESCs have enhanced capacity to form blastoids that implant more efficiently in utero due to inducers maintaining not only local TR proliferation and self-renewal, but also WNT6/7B secretion that stimulates uterine decidualization. Overall, the epiblast maintains sustained growth and decidualization potential of abutting TR cells, while, as known, distancing imposed by the blastocyst cavity differentiates TR cells for uterus adhesion, thus patterning the essential functions of implantation.

Significance Barrett’s esophagus (BE), the premalignant condition of esophageal adenocarcinoma, is categorized into different stages which correlate with the risk of developing carcinoma. We performed single-cell DNA-sequencing experiments with fresh biopsies, which revealed the appearance of a specific T > C and T > G mutational signature, known as COSMIC signature SBS17, in BE cells that are chromosomally unstable. The SBS17-specific mutations were, however, not detected in chromosomally stable BE cells. Additionally, we performed single-cell RNA sequencing experiments which identified seven genes that facilitate the distinction between different BE stages on histological sections., Barrett’s esophagus (BE) is categorized, based on morphological appearance, into different stages, which correlate with the risk of developing esophageal adenocarcinoma. More advanced stages are more likely to acquire chromosomal instabilities, but stage-specific markers remain elusive. Here, we performed single-cell DNA-sequencing experiments (scDNAseq) with fresh BE biopsies. Dysplastic BE cells frequently contained chromosomal instability (CIN) regions, and these CIN cells carried mutations corresponding to the COSMIC mutational signature SBS17, which were not present in biopsy-matched chromosomally stable (CS) cells or patient-matched nondiseased control cells. CS cells were predominantly found in nondysplastic BE biopsies. The single-base substitution (SBS) signatures of all CS BE cells analyzed were indistinguishable from those of nondiseased esophageal or gastric cells. Single-cell RNA-sequencing (scRNAseq) experiments with BE biopsies identified two sets of marker genes which facilitate the distinction between columnar BE epithelium and nondysplastic/dysplastic stages. Moreover, histological validation confirmed a correlation between increased CLDN2 expression and the presence of dysplastic BE stages. Our scDNAseq and scRNAseq datasets, which are a useful resource for the community, provide insight into the mutational landscape and gene expression pattern at different stages of BE development.

The hematopoietic niche is a supportive microenvironment comprised of distinct cell types, including specialized vascular endothelial cells that directly interact with hematopoietic stem and progenitor cells (HSPCs). The molecular factors that specify niche endothelial cells and orchestrate HSPC homeostasis remain largely unknown. Using multi-dimensional gene expression and chromatin accessibility analyses, we define a conserved gene expression signature and cis-regulatory landscape unique to sinusoidal endothelial cells in the HSPC niche. Using enhancer mutagenesis and transcription factor overexpression, we elucidate a transcriptional code involving members of the Ets, Sox and Nuclear Hormone Receptor families that is sufficient to induce ectopic niche endothelial cells that associate with mesenchymal stromal cells and support the recruitment, maintenance and division of HSPCs in vivo. These studies set forth an approach for generating synthetic HSPC niches, in vitro or in vivo, and for effective therapies to modulate the endogenous niche.

In recent years, single-cell transcriptome sequencing has revolutionized biology, allowing for the unbiased characterization of cellular subpopulations. However, most methods amplify the termini of polyadenylated transcripts capturing only a small fraction of the total cellular transcriptome. This precludes the detection of many long non-coding, short non-coding and non-polyadenylated protein-coding transcripts. Additionally, most workflows do not sequence the full transcript hindering the analysis of alternative splicing. We therefore developed VASA-seq to detect the total transcriptome in single cells. VASA-seq is compatible with both plate-based formats and droplet microfluidics. We applied VASA-seq to over 30,000 single cells in the developing mouse embryo during gastrulation and early organogenesis. The dynamics of the total single-cell transcriptome result in the discovery of novel cell type markers many based on non-coding RNA, an in vivo cell cycle analysis and an improved RNA velocity characterization. Moreover, it provides the first comprehensive analysis of alternative splicing during mammalian development.

Stress granules are phase separated assemblies formed around mRNAs whose identities remain elusive. The techniques available to identify the RNA content of stress granules rely on their physical purification, and are therefore not suitable for single cells and tissues displaying cell heterogeneity. Here, we adapted TRIBE (Target of RNA-binding proteins Identified by Editing) to detect stress granule RNAs by fusing a stress granule RNA-binding protein (FMR1) to the catalytic domain of an RNA-editing enzyme (ADAR). RNAs colocalized with this fusion are edited, producing mutations that are detectable by sequencing. We first optimized the expression of this fusion protein so that RNA editing preferentially occurs in stress granules. We then show that this purification-free method can reliably identify stress granule RNAs in bulk and single S2 cells, and in Drosophila tissues, such as 398 neuronal stress granule mRNAs encoding ATP binding, cell cycle and transcription factors. This new method opens the possibility to identify the RNA content of stress granules as well other RNA based assemblies in single cells derived from tissues.

Recent advances have enabled mapping of histone modifications in single cells1–12, but current methods are constrained to profile only one histone modification per cell. Here we present an integrated experimental and computational framework, scChIX (single-cell chromatin immunocleavage and unmixing), to map multiple histone modifications in single cells. scChIX multiplexes two histone modification profiles together in single cells, then computationally deconvolves the signal using training data from respective histone modification profiles. We first validate this method using purified blood cells and show that although the two repressive marks, H3K27me3 and H3K9me3, are generally mutually exclusive, the transitions between the two regions can vary between cell types. Next we apply scChIX to a heterogenous cell population from mouse bone marrow to generate linked maps of active (H3K4me1) and repressive (H3K27me3) chromatin landscapes in single cells, where coordinates in the active modification map correspond to coordinates in the repressive map. Linked analysis reveals that immunoglobulin genes in the Igkv region are in a repressed chromatin state in pro-B cells, but become activated in B cells. Overall, scChIX unlocks systematic interrogation of the interplay between histone modifications in single cells.

SUMMARYPost-translational histone modifications modulate chromatin packing to regulate gene expression. How chromatin states, at euchromatic and heterochromatic regions, underlie cell fate decisions in single cells is relatively unexplored. We develop sort assisted single-cell chromatin immunocleavage (sortChIC) and map active (H3K4me1 and H3K4me3) and repressive (H3K27me3 and H3K9me3) histone modifications in hematopoietic stem and progenitor cells (HSPCs), and mature blood cells in the mouse bone marrow. During differentiation, HSPCs acquire distinct active chromatin states that depend on the specific cell fate, mediated by cell type-specifying transcription factors. By contrast, most regions that gain or lose repressive marks during differentiation do so independent of cell fate. Joint profiling of H3K4me1 and H3K9me3 demonstrates that cell types within the myeloid lineage have distinct active chromatin but share similar myeloid-specific heterochromatin-repressed states. This suggests hierarchical chromatin regulation during hematopoiesis: heterochromatin dynamics define differentiation trajectories and lineages, while euchromatin dynamics establish cell types within lineages.

Gastruloids are aggregates of Pluripotent Stem Cells (PSCs) which, when exposed to differentiation medium and plated within defined conditions, undergo trilineage differentiation to all three germ layers (mesoderm, ectoderm and endoderm) with constitutive cell types organised spatiotemporally along 3 axes (Becarri et. al. 2018). They also undergo morphological shape changes including axial elongation through convergent extension cell movements. The gastruloid method has been well-established using mouse Embryonic Stem Cells (mESCs) and mouse induced PSCs (iPSCs) (van den Brink et. al., 2014; Turner et. al. 2016a; Turner et. al. 2016b; Bailie-Johnson et. al. 2015; Turner et. al. 2017a; Turner et. al. 2017b, Beccari et. al., 2018, See method in Girgin et. al., 2018). Here, we describe a new method to generate equivalent gastruloids from human pluripotent stem cells (hPSCs). hPSCs are able to generate axially elongated human gastruloids with evidence of spatially organised germ layers and comparable features to their mouse counterparts (Moris et. al., 2020).

While measurement advances now allow extensive surveys of gene activity (large numbers of genes across many samples), interpretation of these data is often confounded by noise — expression counts can differ strongly across samples due to variation of both biological and experimental origin. Complimentary to perturbation approaches, we extract functionally related groups of genes by analyzing the standing variation within a sampled population. To distinguish biologically meaningful patterns from uninterpretable noise, we focus on correlated variation and develop a novel density-based clustering approach that takes advantage of a percolation transition generically arising in random, uncorrelated data. We apply our approach to two contrasting RNA sequencing data sets that sample individual variation — across single cells of fission yeast and whole animals of C. elegans worms — and demonstrate robust applicability and versatility in revealing correlated gene clusters of diverse biological origin, including cell cycle phase, development/reproduction, tissue-specific functions, and feeding history. Our technique exploits generic features of noisy high-dimensional data and is applicable, beyond gene expression, to feature-rich data that sample population-level variability in the presence of noise.Significance StatementGene expression largely determines the fate of each cell and ultimately the development and behavior of the whole organism. Whereas most of our knowledge on gene regulatory networks has been obtained from perturbation experiments (e.g. manipulating environmental conditions, genotype, or other physiological variables), here we develop an alternative approach based on the analysis of naturally occurring variations across individuals within a population. Using both single-cell and whole-animal RNA sequencing data, we demonstrate how a rich set of co-regulated gene modules can be uncovered from transcriptomic variability of individuals within unperturbed populations. To robustly extract interpretable clusters from the strong noise background, we devise a novel, versatile clustering approach based on network theory. With a foundation in the generic behavior of random networks near their percolation critical point, our method is broadly applicable, beyond gene expression, to any noisy, high-dimensional data that sample variation across individuals within a population.

Embryonic development is a crucial period in the life of a multicellular organism, during which limited sets of embryonic progenitors produce all cells in the adult body. Determining which fate these progenitors acquire in adult tissues requires the simultaneous measurement of clonal history and cell identity at single-cell resolution, which has been a major challenge. Clonal history has traditionally been investigated by microscopically tracking cells during development, monitoring the heritable expression of genetically encoded fluorescent proteins and, more recently, using next-generation sequencing technologies that exploit somatic mutations, microsatellite instability, transposon tagging, viral barcoding, CRISPR-Cas9 genome editing and Cre-loxP recombination. Single-cell transcriptomics provides a powerful platform for unbiased cell-type classification. Here we present ScarTrace, a single-cell sequencing strategy that enables the simultaneous quantification of clonal history and cell type for thousands of cells obtained from different organs of the adult zebrafish. Using ScarTrace, we show that a small set of multipotent embryonic progenitors generate all haematopoietic cells in the kidney marrow, and that many progenitors produce specific cell types in the eyes and brain. In addition, we study when embryonic progenitors commit to the left or right eye. ScarTrace reveals that epidermal and mesenchymal cells in the caudal fin arise from the same progenitors, and that osteoblast-restricted precursors can produce mesenchymal cells during regeneration. Furthermore, we identify resident immune cells in the fin with a distinct clonal origin from other blood cell types. We envision that similar approaches will have major applications in other experimental systems, in which the matching of embryonic clonal origin to adult cell type will ultimately allow reconstruction of how the adult body is built from a single cell.

Cell‐autonomous circadian oscillations strongly influence tissue physiology and pathophysiology of peripheral organs including the heart, in which the circadian clock is known to determine cardiac metabolism and the outcome of for instance ischemic stress. Human pluripotent stem cells represent a powerful tool to study developmental processes in vitro, but the extent to which human embryonic stem (ES) cell‐derived cardiomyocytes establish circadian rhythmicity in the absence of a systemic context is unknown. Here we demonstrate that while undifferentiated human ES cells do not possess an intrinsic functional clock, oscillatory expression of known core clock genes emerges spontaneously during directed cardiac differentiation. We identify a set of clock‐controlled output genes that contain an oscillatory network of stress‐related transcripts. Furthermore, we demonstrate that this network results in a time‐dependent functional response to doxorubicin, a frequently used anti‐cancer drug with known cardiotoxic side effects. Taken together, our data provide a framework from which the effect of oscillatory gene expression on cardiomyocyte physiology can be modeled in vitro, and demonstrate the influence of a functional clock on experimental outcome.

Gastruloids are aggregates of mouse embryonic stem cells that can be used to study key aspects of mammalian post-implantation development in vitro1–4. Gastruloids generated with previously published protocols do not generate somite-like structures4–6. Here, we describe a modified version of the gastruloids culture protocol5,6 that results in gastruloids that do generate somite-like structures in vitro (van den Brink et al., Nature, 2020)7. Under these conditions, about 50% of the gastruloids generated form structures with features that are characteristic of somites7.This protocol takes 6 days, with relatively little hands-on time. The protocol starts with the aggregation of the cultured cells. Then, the Wnt-agonist Chiron is added 2 days (48h) later. The medium of the aggregates is replaced 3 days (72h) after aggregation. To induce somite-formation, gastruloids are embedded in Matrigel 4 days (96h) after aggregation. After 5 days (120h) of culture, gastruloids resemble E8.5 mouse embryos. At this timepoint they can be fixed (fixative is added on day 5 and washed away on day 6 after overnight incubation in PFA) to prepare them for staining or microscopy experiments.

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 (NWO-CW 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 Biotechnology and Biological Sciences Research Council (no. BB/P003184/1), Newton Trust (INT16.24b) and Medical Research Council (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 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. We thank A. Ebbing and M. Betist for the robotized tomo-seq protocol; G. Keller for the Brachyury-GFP cell line; J. Collignon for the Nodal-YFP line; K. Hadjantonakis for the TCF/LEF-mCherry line; S. van den Brink and E. R. Maandag for the E14-IB10 cells; J. Kress and A. Aulehla for the LfngT2AVenus mouse ES cell line; I. Misteli Guerreiro, J. Peterson-Maduro and J. Hoeksma for suggestions for in situ hybridization experiments; W. Thomas, Y. el Azhar, J. Juksar and J. Beumer for reagents and inhibitors; A. de Graaff and A. Stokkermans for help with multiphoton microscopy and analysis of the microscopy data; D. A. Turner for microscopy panels that were used for tomo-seq validation; J. Korving for help with the somite-size measurements in embryos; the Hubrecht FACS facility and R. van der Linden for FACS experiments; Single Cell Discoveries for 10x Genomics scRNA-seq; the Utrecht Sequencing facility for sequencing; and P. Zeller, H. Viñas Gaza, M. Vaninsberghe, V. Bhardwaj and all members of the van Oudenaarden, Sonnen and Martinez Arias laboratories for discussions.

Introduction/Background Ovarian cancer (OC) is a heterogeneous disease usually diagnosed at a late stage. Experimental in vitro models that faithfully capture the hallmarks and tumour heterogeneity of OC are limited and hard to establish. Methodology We present a protocol that enables efficient derivation and long-term expansion of OC organoids. Results Utilizing this protocol, we have established 56 organoid lines from 32 patients, representing all main subtypes of OC. OC organoids recapitulate histological and genomic features of the pertinent lesion from which they were derived, illustrating intra- and interpatient heterogeneity, and can be genetically modified. We show that OC organoids can be used for drug-screening assays and capture different tumour subtype responses to the gold standard platinum-based chemotherapy, including acquisition of chemoresistance in recurrent disease. Finally, OC organoids can be xenografted, enabling in vivo drug-sensitivity assays. Conclusion Taken together, this demonstrates their potential application for research and personalized medicine. Disclosure No competing interests. Applicable funding sources: EIF | Stand Up To Cancer (SU2C) [Clevers, Kopper, Balgobind, Begthel] KWF Kankerbestrijding (Dutch Cancer Society) - UU2015-7743 [de Witte, van Roosmalen, Witteveen, Zweemer, Kloosterman] Gieskes Strijbis Foundation (1816199) [Clevers, Witteveen, Kloosterman, Zweemer, Lohmussaar, Espejo Valle-Inclan, Hami, Bos, Snippert] Published in Nature Medicine. April 2019. dx.doi.org/10.1038/s41591-019-0422-6.

There were errors in J. Cell Sci. (2019) 132, [jcs231589][1] ([doi:10.1242/jcs.231589][2]). Labels for Spindly, MAD2 and ZW10 were incorrect in [Fig. 2][3]C. In Figs S1 and S2, a biological replicate of pMELT that had technical issues was inadvertently used. Replicate e2 has been replaced for

During germ cell development, cells undergo a drastic switch from mitosis to meiosis to form haploid germ cells. Sequencing and computational technologies now allow studying development at the single-cell level. Here we developed a multiplexed trajectory reconstruction to create a high-resolution developmental map of spermatogonia and prophase-I spermatocytes from testes of a Dazl-GFP reporter mouse. We identified three main transitions in the meiotic prophase-I: meiotic entry, the meiotic sex chromosome inactivation (MSCI), and concomitant pachytene activation. We validated the key features of these transitionsin vivousing single molecule FISH. Focusing on MSCI, we found that 34% of sex chromosomal genes are induced shortly before MSCI, that silencing time is diverse and correlates with specific gene functions. These highlight a previously underappreciated level of regulation of MSCI. Finally, we found that spermatozoal genes in pachytene are activated in a temporal pattern reflecting the future anatomic and functional order of the sperm cell. Altogether we highlighted how precise and sequential changes in gene expression regulate cellular states in meiotic prophase-I.

Here we describe the LifeTime Initiative, which aims to track, understand and target human cells during the onset and progression of complex diseases, and to analyse their response to therapy at single-cell resolution. This mission will be implemented through the development, integration and application of single-cell multi-omics and imaging, artificial intelligence and patient-derived experimental disease models during the progression from health to disease. The analysis of large molecular and clinical datasets will identify molecular mechanisms, create predictive computational models of disease progression, and reveal new drug targets and therapies. The timely detection and interception of disease embedded in an ethical and patient-centred vision will be achieved through interactions across academia, hospitals, patient associations, health data management systems and industry. The application of this strategy to key medical challenges in cancer, neurological and neuropsychiatric disorders, and infectious, chronic inflammatory and cardiovascular diseases at the single-cell level will usher in cell-based interceptive medicine in Europe over the next decade.

During puberty, the mouse mammary gland develops into a highly branched epithelial network. Owing to the absence of exclusive stem cell markers, the location, multiplicity, dynamics and fate of mammary stem cells (MaSCs), which drive branching morphogenesis, are unknown. Here we show that morphogenesis is driven by proliferative terminal end buds that terminate or bifurcate witwh near equal probability, in a stochastic and time-invariant manner, leading to a heterogeneous epithelial network. We show that the majority of terminal end bud cells function as highly proliferative, lineage-committed MaSCs that are heterogeneous in their expression profile and short-term contribution to ductal extension. Yet, through cell rearrangements during terminal end bud bifurcation, each MaSC is able to contribute actively to long-term growth. Our study shows that the behaviour of MaSCs is not directly linked to a single expression profile. Instead, morphogenesis relies upon lineage-restricted heterogeneous MaSC populations that function as single equipotent pools in the long term.

Fermenting glucose in the presence of enough oxygen to support respiration, known as aerobic glycolysis, is believed to maximize growth rate. We observed increasing aerobic glycolysis during exponential growth, suggesting additional physiological roles for aerobic glycolysis. We investigated such roles in yeast batch cultures by quantifying O[subscript 2] consumption, CO[subscript 2] production, amino acids, mRNAs, proteins, posttranslational modifications, and stress sensitivity in the course of nine doublings at constant rate. During this course, the cells support a constant biomass-production rate with decreasing rates of respiration and ATP production but also decrease their stress resistance. As the respiration rate decreases, so do the levels of enzymes catalyzing rate-determining reactions of the tricarboxylic-acid cycle (providing NADH for respiration) and of mitochondrial folate-mediated NADPH production (required for oxidative defense). The findings demonstrate that exponential growth can represent not a single metabolic/physiological state but a continuum of changing states and that aerobic glycolysis can reduce the energy demands associated with respiratory metabolism and stress survival., National Institutes of Health (U.S.) (Grant DP1 CA174420), National Institutes of Health (U.S.) (Grant R01-GM068957), National Institutes of Health (U.S.) (Grant U54CA143874)

Early mammalian embryos form a blastocyst, a structure comprising embryonic cells surrounded by a trophoblast cyst able to implant into the mother’s uterus. Following subtle symmetry-breaking events (Zhang and Hiiragi, 2018), an axis forms in the blastocyst when the embryonic cells cluster on one inner side of the trophoblast globe and induce the directional proliferation and differentiation of trophoblasts (Gardner, 2000). Trophoblast stem cells (TSCs) are in vitro analogs of early trophoblasts (Tanaka et al., 1998). Here, we show that TSCs contain a range of plastic subpopulations reflecting aspects of trophoblasts states ranging from the blastocyst trophoblasts juxtaposing the embryo (polar trophoblasts) to post-implantation trophoblasts. However, when exposed to a specific combination of embryonic inductive signals, TSCs acquire properties of polar trophoblasts (gene expression, self-renewal) and a more homogeneous, epithelial phenotype. These lines of polar-like TSCs more efficiently form blastoids, which respond to the inner embryonic cells by spontaneously generating an embryonic-abembryonic axis. Altogether, the delineation of requirements and properties of the polar cells of the trophectoderm provides the ground to better recapitulate and dissect embryonic development in vitro.