RESUMEN
The blueprint of the mammalian body plan is laid out during gastrulation, when a trilaminar embryo is formed. This process entails a burst of proliferation, the ingression of embryonic epiblast cells at the primitive streak, and their priming toward primitive streak fates. How these different events are coordinated remains unknown. Here, we developed and characterized a 3D culture of self-renewing mouse embryonic cells that captures the main transcriptional and architectural features of the early gastrulating mouse epiblast. Using this system in combination with microfabrication and in vivo experiments, we found that proliferation-induced crowding triggers delamination of cells that express high levels of the apical polarity protein aPKC. Upon delamination, cells become more sensitive to Wnt signaling and upregulate the expression of primitive streak markers such as Brachyury. This mechanistic coupling between ingression and differentiation ensures that the right cell types become specified at the right place during embryonic development.
Asunto(s)
Diferenciación Celular , Gastrulación , Estratos Germinativos , Animales , Ratones , Estratos Germinativos/citología , Estratos Germinativos/metabolismo , Proteínas de Dominio T Box/metabolismo , Proteínas de Dominio T Box/genética , Células Madre Pluripotentes/citología , Células Madre Pluripotentes/metabolismo , Línea Primitiva/citología , Línea Primitiva/metabolismo , Proteínas Fetales/metabolismo , Proteínas Fetales/genética , Vía de Señalización Wnt , Proliferación Celular , Regulación del Desarrollo de la Expresión Génica , Embrión de Mamíferos/citología , Embrión de Mamíferos/metabolismoRESUMEN
Polarized cells rely on a polarized cytoskeleton to function. Yet, how cortical polarity cues induce cytoskeleton polarization remains elusive. Here, we capitalized on recently established designed 2D protein arrays to ectopically engineer cortical polarity of virtually any protein of interest during mitosis in various cell types. This enables direct manipulation of polarity signaling and the identification of the cortical cues sufficient for cytoskeleton polarization. Using this assay, we dissected the logic of the Par complex pathway, a key regulator of cytoskeleton polarity during asymmetric cell division. We show that cortical clustering of any Par complex subunit is sufficient to trigger complex assembly and that the primary kinetic barrier to complex assembly is the relief of Par6 autoinhibition. Further, we found that inducing cortical Par complex polarity induces two hallmarks of asymmetric cell division in unpolarized mammalian cells: spindle orientation, occurring via Par3, and central spindle asymmetry, depending on aPKC activity.
Asunto(s)
Proteínas Adaptadoras Transductoras de Señales , Polaridad Celular , Técnicas Citológicas , Mitosis , Animales , Citoesqueleto/metabolismo , Mamíferos/metabolismo , Microtúbulos/metabolismo , Proteína Quinasa C/metabolismo , Proteínas Adaptadoras Transductoras de Señales/metabolismoRESUMEN
The Company of Biologists' 2022 workshop on 'Cell State Transitions: Approaches, Experimental Systems and Models' brought together an international and interdisciplinary team of investigators spanning the fields of cell and developmental biology, stem cell biology, physics, mathematics and engineering to tackle the question of how cells precisely navigate between distinct identities and do so in a dynamic manner. This second edition of the workshop was organized after a successful virtual workshop on the same topic that took place in 2021.
Asunto(s)
Células Madre , Congresos como Asunto , Biología Celular , Biología EvolutivaRESUMEN
Studying human embryo development is technically and ethically challenging. An improved protocol to generate human embryo-like structures (blastoids) from human pluripotent stem cells (PSCs) (Kagawa et al., 2021) offers innovative opportunities to dissect the mechanisms of human embryogenesis.
Asunto(s)
Células Madre Pluripotentes , Embrión de Mamíferos , Desarrollo Embrionario , HumanosRESUMEN
In our 20th anniversary year, we reflect on how fields have changed since our first issue and here look to the future. In this collection of Voices, our writers speculate on the future: in terms of philosophy, cell states, cell processes, and then how to model cell systems.
Asunto(s)
Biología Celular , Biología Evolutiva , Publicaciones Periódicas como Asunto/estadística & datos numéricos , Humanos , Factores de TiempoRESUMEN
Human embryogenesis entails complex signalling interactions between embryonic and extra-embryonic cells. However, how extra-embryonic cells direct morphogenesis within the human embryo remains largely unknown due to a lack of relevant stem cell models. Here, we have established conditions to differentiate human pluripotent stem cells (hPSCs) into yolk sac-like cells (YSLCs) that resemble the post-implantation human hypoblast molecularly and functionally. YSLCs induce the expression of pluripotency and anterior ectoderm markers in human embryonic stem cells (hESCs) at the expense of mesoderm and endoderm markers. This activity is mediated by the release of BMP and WNT signalling pathway inhibitors, and, therefore, resembles the functioning of the anterior visceral endoderm signalling centre of the mouse embryo, which establishes the anterior-posterior axis. Our results implicate the yolk sac in epiblast cell fate specification in the human embryo and propose YSLCs as a tool for studying post-implantation human embryo development in vitro.
Asunto(s)
Estratos Germinativos/crecimiento & desarrollo , Células Madre Pluripotentes/metabolismo , Saco Vitelino/crecimiento & desarrollo , Animales , Línea Celular , Ectodermo/crecimiento & desarrollo , Desarrollo Embrionario , Humanos , RatonesRESUMEN
Following implantation, the human embryo undergoes major morphogenetic transformations that establish the future body plan. While the molecular events underpinning this process are established in mice, they remain unknown in humans. Here we characterise key events of human embryo morphogenesis, in the period between implantation and gastrulation, using single-cell analyses and functional studies. First, the embryonic epiblast cells transition through different pluripotent states and act as a source of FGF signals that ensure proliferation of both embryonic and extra-embryonic tissues. In a subset of embryos, we identify a group of asymmetrically positioned extra-embryonic hypoblast cells expressing inhibitors of BMP, NODAL and WNT signalling pathways. We suggest that this group of cells can act as the anterior singalling centre to pattern the epiblast. These results provide insights into pluripotency state transitions, the role of FGF signalling and the specification of anterior-posterior axis during human embryo development.
Asunto(s)
Implantación del Embrión/genética , Desarrollo Embrionario , Gastrulación/genética , Regulación del Desarrollo de la Expresión Génica/genética , Estratos Germinativos/metabolismo , Análisis de la Célula Individual/métodos , Vía de Señalización Wnt , Proteína Morfogenética Ósea 1/antagonistas & inhibidores , Linaje de la Célula , Células Cultivadas , Implantación del Embrión/fisiología , Embrión de Mamíferos , Factores de Crecimiento de Fibroblastos/metabolismo , Gastrulación/fisiología , Estratos Germinativos/citología , Humanos , Procesamiento de Imagen Asistido por Computador , Familia de Multigenes , Proteína Nodal/antagonistas & inhibidores , RNA-Seq , Análisis Espacio-TemporalRESUMEN
Over the past year, Cell Stem Cell has introduced early-career researchers impacted by the COVID-19 pandemic and subsequent closures to our readers. One year since our first introductions, we've invited several participants to reflect on their experiences and key issues. In this Story, Marta Shahbazi discusses the meaning of identity while balancing running a lab with motherhood.
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COVID-19 , Pandemias , Femenino , Humanos , Madres , Investigadores , SARS-CoV-2RESUMEN
Mammalian embryogenesis is a paradigm of regulative development as mouse embryos show plasticity in the regulation of cell fate, cell number, and tissue morphogenesis. However, the mechanisms behind embryo plasticity remain largely unknown. Here, we determine how mouse embryos respond to an increase in cell numbers to regulate the timing and mechanism of embryonic morphogenesis, leading to the formation of the pro-amniotic cavity. Using embryos and embryonic stem cell aggregates of different size, we show that while pro-amniotic cavity formation in normal-sized embryos is achieved through basement membrane-induced polarization and exocytosis, cavity formation of increased-size embryos is delayed and achieved through apoptosis of cells that lack contact with the basement membrane. Importantly, blocking apoptosis, both genetically and pharmacologically, alters pro-amniotic cavity formation but does not affect size regulation in enlarged embryos. We conclude that the regulation of embryonic size and morphogenesis, albeit concomitant, have distinct molecular underpinnings.
Asunto(s)
Embrión de Mamíferos/anatomía & histología , Morfogénesis , Amnios/embriología , Animales , Apoptosis , Agregación Celular , Embrión de Mamíferos/citología , Células Madre Embrionarias/citología , Células Madre Embrionarias/metabolismo , Femenino , Ratones Endogámicos C57BL , Ratones Endogámicos CBA , Tamaño de los Órganos , Factores de TiempoRESUMEN
Capecitabine-induced hand-foot syndrome (CiHFS) is a common dermatological adverse reaction affecting around 30% of patients with capecitabine-treated cancer, and the main cause of dose reductions and chemotherapy delays. To identify novel genetic factors associated with CiHFS in patients with cancer, we carried out an extreme-phenotype genomewide association study in 166 patients with breast and colorectal capecitabine-treated cancer with replication in a second cohort of 85 patients. We discovered and replicated a cluster of four highly correlated single-nucleotide polymorphisms associated with susceptibility to CiHFS at 20q13.33 locus (top hit = rs6129058, hazard ratio = 2.40, 95% confidence interval = 1.78-3.20; P = 1.2 × 10-8 ). Using circular chromosome conformation capture sequencing, we identified a chromatin contact between the locus containing the risk alleles and the promoter of CDH4, located 90 kilobases away. The risk haplotype was associated with decreased levels of CDH4 mRNA and the protein it encodes, R-cadherin (RCAD), which mainly localizes in the granular layer of the epidermis. In human keratinocytes, CDH4 downregulation resulted in reduced expression of involucrin, a protein of the cornified envelope, an essential structure for skin barrier function. Immunohistochemical analyses revealed that skin from patients with severe CiHFS exhibited low levels of RCAD and involucrin before capecitabine treatment. Our results uncover a novel mechanism underlying individual genetic susceptibility to CiHFS with implications for clinically relevant risk prediction.
Asunto(s)
Antimetabolitos Antineoplásicos/efectos adversos , Cadherinas/genética , Capecitabina/efectos adversos , Síndrome Mano-Pie/etiología , Síndrome Mano-Pie/genética , Polimorfismo de Nucleótido Simple/genética , Adulto , Anciano , Anciano de 80 o más Años , Antimetabolitos Antineoplásicos/uso terapéutico , Capecitabina/uso terapéutico , Línea Celular , Femenino , Predisposición Genética a la Enfermedad/genética , Haplotipos/genética , Humanos , Queratinocitos/efectos de los fármacos , Masculino , Persona de Mediana Edad , Neoplasias/tratamiento farmacológico , Neoplasias/genética , Regiones Promotoras Genéticas/genética , RiesgoRESUMEN
Pluripotent stem cells (PSCs) transition between cell states in vitro, reflecting developmental changes in the early embryo. PSCs can be stabilized in the naive state by blocking extracellular differentiation stimuli, particularly FGF-MEK signalling. Here, we report that multiple features of the naive state in human and mouse PSCs can be recapitulated without affecting FGF-MEK signalling or global DNA methylation. Mechanistically, chemical inhibition of CDK8 and CDK19 (hereafter CDK8/19) kinases removes their ability to repress the Mediator complex at enhancers. CDK8/19 inhibition therefore increases Mediator-driven recruitment of RNA polymerase II (RNA Pol II) to promoters and enhancers. This efficiently stabilizes the naive transcriptional program and confers resistance to enhancer perturbation by BRD4 inhibition. Moreover, naive pluripotency during embryonic development coincides with a reduction in CDK8/19. We conclude that global hyperactivation of enhancers drives naive pluripotency, and this can be achieved in vitro by inhibiting CDK8/19 kinase activity. These principles may apply to other contexts of cellular plasticity.
Asunto(s)
Diferenciación Celular , Quinasa 8 Dependiente de Ciclina/antagonistas & inhibidores , Quinasas Ciclina-Dependientes/antagonistas & inhibidores , Metilación de ADN , Elementos de Facilitación Genéticos , Células Madre Pluripotentes/citología , Animales , Quinasa 8 Dependiente de Ciclina/genética , Quinasa 8 Dependiente de Ciclina/metabolismo , Quinasas Ciclina-Dependientes/genética , Quinasas Ciclina-Dependientes/metabolismo , Femenino , Humanos , Ratones , Fosforilación , Células Madre Pluripotentes/metabolismo , Regiones Promotoras Genéticas , ARN Polimerasa II/genética , ARN Polimerasa II/metabolismo , Transducción de SeñalRESUMEN
Aneuploidy, the presence of an abnormal number of chromosomes, is a major cause of early pregnancy loss in humans. Yet, the developmental consequences of specific aneuploidies remain unexplored. Here, we determine the extent of post-implantation development of human embryos bearing common aneuploidies using a recently established culture platform. We show that while trisomy 15 and trisomy 21 embryos develop similarly to euploid embryos, monosomy 21 embryos exhibit high rates of developmental arrest, and trisomy 16 embryos display a hypo-proliferation of the trophoblast, the tissue that forms the placenta. Using human trophoblast stem cells, we show that this phenotype can be mechanistically ascribed to increased levels of the cell adhesion protein E-CADHERIN, which lead to premature differentiation and cell cycle arrest. We identify three cases of mosaicism in embryos diagnosed as full aneuploid by pre-implantation genetic testing. Our results present the first detailed analysis of post-implantation development of aneuploid human embryos.
Asunto(s)
Aneuploidia , Implantación del Embrión/genética , Embrión de Mamíferos , Desarrollo Embrionario , Antígenos CD/genética , Cadherinas/genética , Cadherinas/metabolismo , Adhesión Celular , Puntos de Control del Ciclo Celular , Linaje de la Célula , Segregación Cromosómica , Cromosomas Humanos Par 16 , Cromosomas Humanos Par 21 , Femenino , Genes erbB-1/genética , Pruebas Genéticas , Humanos , Monosomía , Mosaicismo , Embarazo , Células Madre , TrisomíaRESUMEN
Gene regulatory networks and tissue morphogenetic events drive the emergence of shape and function: the pillars of embryo development. Although model systems offer a window into the molecular biology of cell fate and tissue shape, mechanistic studies of our own development have so far been technically and ethically challenging. However, recent technical developments provide the tools to describe, manipulate and mimic human embryos in a dish, thus opening a new avenue to exploring human development. Here, I discuss the evidence that supports a role for the crosstalk between cell fate and tissue shape during early human embryogenesis. This is a critical developmental period, when the body plan is laid out and many pregnancies fail. Dissecting the basic mechanisms that coordinate cell fate and tissue shape will generate an integrated understanding of early embryogenesis and new strategies for therapeutic intervention in early pregnancy loss.
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Embrión de Mamíferos/metabolismo , Desarrollo Embrionario/genética , Aneuploidia , Proteínas de Ciclo Celular/genética , Proteínas de Ciclo Celular/metabolismo , Diferenciación Celular , Regulación del Desarrollo de la Expresión Génica , Redes Reguladoras de Genes , Humanos , Morfogénesis , Factores de Transcripción/genética , Factores de Transcripción/metabolismoRESUMEN
Embryonic development is orchestrated by robust and complex regulatory mechanisms acting at different scales of organization. In vivo studies are particularly challenging for mammals after implantation, owing to the small size and inaccessibility of the embryo. The generation of stem cell models of the embryo represents a powerful system with which to dissect this complexity. Control of geometry, modulation of the physical environment, and priming with chemical signals reveal the intrinsic capacity of embryonic stem cells to make patterns. Adding the stem cells for the extraembryonic lineages generates three-dimensional models that are more autonomous from the environment and recapitulate many features of the pre- and postimplantation mouse embryo, including gastrulation. Here, we review the principles of self-organization and how they set cells in motion to create an embryo.
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Tipificación del Cuerpo , Desarrollo Embrionario , Células Madre Embrionarias/fisiología , Animales , Humanos , Ratones , Modelos BiológicosRESUMEN
The emergence of form and function during mammalian embryogenesis is a complex process that involves multiple regulatory levels. The foundations of the body plan are laid throughout the first days of post-implantation development as embryonic stem cells undergo symmetry breaking and initiate lineage specification, in a process that coincides with a global morphological reorganization of the embryo. Here, we review experimental models and how they have shaped our current understanding of the post-implantation mammalian embryo.
Asunto(s)
Linaje de la Célula , Investigaciones con Embriones , Embrión de Mamíferos/fisiología , Células Madre Embrionarias Humanas/fisiología , Morfogénesis , Células Madre Embrionarias de Ratones/fisiología , Investigación con Células Madre , Animales , Células Cultivadas , Investigaciones con Embriones/historia , Embrión de Mamíferos/citología , Embrión de Mamíferos/metabolismo , Regulación del Desarrollo de la Expresión Génica , Edad Gestacional , Historia del Siglo XX , Historia del Siglo XXI , Células Madre Embrionarias Humanas/metabolismo , Humanos , Ratones , Células Madre Embrionarias de Ratones/metabolismo , Transducción de Señal , Investigación con Células Madre/historiaRESUMEN
This corrects the article DOI: 10.1038/nature24675.
RESUMEN
The foundations of mammalian development lie in a cluster of embryonic epiblast stem cells. In response to extracellular matrix signalling, these cells undergo epithelialization and create an apical surface in contact with a cavity, a fundamental event for all subsequent development. Concomitantly, epiblast cells transit through distinct pluripotent states, before lineage commitment at gastrulation. These pluripotent states have been characterized at the molecular level, but their biological importance remains unclear. Here we show that exit from an unrestricted naive pluripotent state is required for epiblast epithelialization and generation of the pro-amniotic cavity in mouse embryos. Embryonic stem cells locked in the naive state are able to initiate polarization but fail to undergo lumenogenesis. Mechanistically, exit from naive pluripotency activates an Oct4-governed transcriptional program that results in expression of glycosylated sialomucin proteins and the vesicle tethering and fusion events of lumenogenesis. Similarly, exit of epiblasts from naive pluripotency in cultured human post-implantation embryos triggers amniotic cavity formation and developmental progression. Our results add tissue-level architecture as a new criterion for the characterization of different pluripotent states, and show the relevance of transitions between these states during development of the mammalian embryo.
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Embrión de Mamíferos/citología , Morfogénesis , Células Madre Pluripotentes/citología , Amnios/citología , Animales , Tipificación del Cuerpo , Colágeno , Combinación de Medicamentos , Femenino , Regulación del Desarrollo de la Expresión Génica , Estratos Germinativos/citología , Glicosilación , Células Madre Embrionarias Humanas/citología , Humanos , Laminina , Masculino , Ratones , Células Madre Embrionarias de Ratones/citología , Factor 3 de Transcripción de Unión a Octámeros/metabolismo , Proteoglicanos , Sialomucinas/metabolismo , Esferoides Celulares/citologíaRESUMEN
Establishment of cell polarity in the mammalian embryo is fundamental for the first cell fate decision that sets aside progenitor cells for both the new organism and the placenta. Yet the sequence of events and molecular mechanism that trigger this process remain unknown. Here, we show that de novo polarisation of the mouse embryo occurs in two distinct phases at the 8-cell stage. In the first phase, an apical actomyosin network is formed. This is a pre-requisite for the second phase, in which the Par complex localises to the apical domain, excluding actomyosin and forming a mature apical cap. Using a variety of approaches, we also show that phospholipase C-mediated PIP2 hydrolysis is necessary and sufficient to trigger the polarisation of actomyosin through the Rho-mediated recruitment of myosin II to the apical cortex. Together, these results reveal the molecular framework that triggers de novo polarisation of the mouse embryo.The molecular trigger that establishes cell polarity in the mammalian embryo is unclear. Here, the authors show that de novo polarisation of the mouse embryo at the 8-cell stage is directed by Phospholipase C and Protein kinase C and occurs in two phases: polarisation of actomyosin followed by the Par complex.