RESUMEN
Mammalian blastocyst formation involves the specification of the trophectoderm followed by the differentiation of the inner cell mass into embryonic epiblast and extra-embryonic primitive endoderm (PrE). During this time, the embryo maintains a window of plasticity and can redirect its cellular fate when challenged experimentally. In this context, we found that the PrE alone was sufficient to regenerate a complete blastocyst and continue post-implantation development. We identify an in vitro population similar to the early PrE in vivo that exhibits the same embryonic and extra-embryonic potency and can form complete stem cell-based embryo models, termed blastoids. Commitment in the PrE is suppressed by JAK/STAT signaling, collaborating with OCT4 and the sustained expression of a subset of pluripotency-related transcription factors that safeguard an enhancer landscape permissive for multi-lineage differentiation. Our observations support the notion that transcription factor persistence underlies plasticity in regulative development and highlight the importance of the PrE in perturbed development.
Asunto(s)
Blastocisto , Diferenciación Celular , Endodermo , Animales , Endodermo/metabolismo , Endodermo/citología , Ratones , Blastocisto/metabolismo , Blastocisto/citología , Linaje de la Célula , Factor 3 de Transcripción de Unión a Octámeros/metabolismo , Factor 3 de Transcripción de Unión a Octámeros/genética , Transducción de Señal , Desarrollo Embrionario , Quinasas Janus/metabolismo , Regulación del Desarrollo de la Expresión Génica , Factores de Transcripción STAT/metabolismo , Factores de Transcripción/metabolismo , Femenino , Embrión de Mamíferos/metabolismo , Embrión de Mamíferos/citologíaRESUMEN
In early mammalian development, cleavage stage blastomeres and inner cell mass (ICM) cells co-express embryonic and extra-embryonic transcriptional determinants. Using a protein-based double reporter we identify an embryonic stem cell (ESC) population that co-expresses the extra-embryonic factor GATA6 alongside the embryonic factor SOX2. Based on single cell transcriptomics, we find this population resembles the unsegregated ICM, exhibiting enhanced differentiation potential for endoderm while maintaining epiblast competence. To relate transcription factor binding in these cells to future fate, we describe a complete enhancer set in both ESCs and naive extra-embryonic endoderm stem cells and assess SOX2 and GATA6 binding at these elements in the ICM-like ESC sub-population. Both factors support cooperative recognition in these lineages, with GATA6 bound alongside SOX2 on a fraction of pluripotency enhancers and SOX2 alongside GATA6 more extensively on endoderm enhancers, suggesting that cooperative binding between these antagonistic factors both supports self-renewal and prepares progenitor cells for later differentiation.
Asunto(s)
Regulación del Desarrollo de la Expresión Génica , Factores de Transcripción , Animales , Linaje de la Célula/genética , Factores de Transcripción/genética , Factores de Transcripción/metabolismo , Diferenciación Celular/genética , Estratos Germinativos , Endodermo , Blastocisto , Mamíferos/metabolismoRESUMEN
Modified parental histones are segregated symmetrically to daughter DNA strands during replication and can be inherited through mitosis. How this may sustain the epigenome and cell identity remains unknown. Here we show that transmission of histone-based information during DNA replication maintains epigenome fidelity and embryonic stem cell plasticity. Asymmetric segregation of parental histones H3-H4 in MCM2-2A mutants compromised mitotic inheritance of histone modifications and globally altered the epigenome. This included widespread spurious deposition of repressive modifications, suggesting elevated epigenetic noise. Moreover, H3K9me3 loss at repeats caused derepression and H3K27me3 redistribution across bivalent promoters correlated with misexpression of developmental genes. MCM2-2A mutation challenged dynamic transitions in cellular states across the cell cycle, enhancing naïve pluripotency and reducing lineage priming in G1. Furthermore, developmental competence was diminished, correlating with impaired exit from pluripotency. Collectively, this argues that epigenetic inheritance of histone modifications maintains a correctly balanced and dynamic chromatin landscape able to support mammalian cell differentiation.
Asunto(s)
Epigenoma , Histonas , Animales , Histonas/genética , Cromatina/genética , Células Madre Embrionarias , Mitosis , MamíferosRESUMEN
High-resolution maps of embryonic development suggest that acquisition of cell identity is not limited to canonical germ layers but proceeds via alternative routes. Despite evidence that visceral organs are formed via embryonic and extra-embryonic trajectories, the production of organ-specific cell types in vitro focuses on the embryonic one. Here we resolve these differentiation routes using massively parallel single-cell RNA sequencing to generate datasets from FOXA2Venus reporter mouse embryos and embryonic stem cell differentiation towards endoderm. To relate cell types in these datasets, we develop a single-parameter computational approach and identify an intermediate en route from extra-embryonic identity to embryonic endoderm, which we localize spatially in embryos at embryonic day 7.5. While there is little evidence for this cell type in embryonic stem cell differentiation, by following the extra-embryonic trajectory starting with naïve extra-embryonic endoderm stem cells we can generate embryonic gut spheroids. Exploiting developmental plasticity therefore offers alternatives to pluripotent cells and opens alternative avenues for in vitro differentiation.
Asunto(s)
Endodermo , Transcriptoma , Animales , Diferenciación Celular/genética , Células Madre Embrionarias , Femenino , Regulación del Desarrollo de la Expresión Génica , Estratos Germinativos , Ratones , EmbarazoRESUMEN
Embryonic stem cells (ESCs) are derived from the pre-implantation mammalian blastocyst. At this point in time, the newly formed embryo is concerned with the generation and expansion of both the embryonic lineages required to build the embryo and the extra-embryonic lineages that support development. When used in grafting experiments, embryonic cells from early developmental stages can contribute to both embryonic and extra-embryonic lineages, but it is generally accepted that ESCs can give rise to only embryonic lineages. As a result, they are referred to as pluripotent, rather than totipotent. Here, we consider the experimental potential of various ESC populations and a number of recently identified in vitro culture systems producing states beyond pluripotency and reminiscent of those observed during pre-implantation development. We also consider the nature of totipotency and the extent to which cell populations in these culture systems exhibit this property.
Asunto(s)
Blastocisto/metabolismo , Linaje de la Célula , Células Madre Embrionarias Humanas/metabolismo , Células Madre Totipotentes/metabolismo , Animales , Blastocisto/citología , Células Madre Embrionarias Humanas/citología , Humanos , Células Madre Totipotentes/citologíaRESUMEN
Components of the KDM7 family of histone demethylases are implicated in neuronal development and one member, PHF8, is often found to be mutated in cases of X-linked mental retardation. However, how PHF8 regulates neurodevelopmental processes and contributes to the disease is still largely unknown. Here, we show that the catalytic activity of a PHF8 homolog in Caenorhabditis elegans, JMJD-1.2, is required non-cell-autonomously for proper axon guidance. Loss of JMJD-1.2 dysregulates transcription of the Hedgehog-related genes wrt-8 and grl-16, the overexpression of which is sufficient to induce the axonal defects. Deficiency of either wrt-8 or grl-16, or reduced expression of homologs of genes promoting Hedgehog signaling, restores correct axon guidance in jmjd-1.2 mutants. Genetic and overexpression data indicate that Hedgehog-related genes act on axon guidance through actin remodelers. Thus, our study highlights a novel function of jmjd-1.2 in axon guidance that might be relevant for the onset of X-linked mental retardation and provides compelling evidence of a conserved function of the Hedgehog pathway in C. elegans axon migration.
Asunto(s)
Orientación del Axón , Axones/metabolismo , Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/metabolismo , Regulación del Desarrollo de la Expresión Génica , Proteínas Hedgehog/metabolismo , Histona Demetilasas con Dominio de Jumonji/metabolismo , Actinas/metabolismo , Animales , Animales Modificados Genéticamente , Sistemas CRISPR-Cas , Modelos Animales de Enfermedad , Epigénesis Genética , Histona Demetilasas/metabolismo , Neuronas/metabolismo , Interferencia de ARN , Transducción de SeñalRESUMEN
PURPOSE OF THE STUDY: Primary congenital glaucoma (PCG OMIM 231300) can be caused by pathogenic sequence variations in cytochrome P450, subfamily 1, polypeptide 1 (CYP1B1). The purpose of this study was to investigate the contribution of sequence variations in CYP1B1 in a cohort of individuals with PCG residing in Denmark. METHODS: The study included 37 unrelated individuals with PCG. Individuals were investigated for CYP1B1 mutations by Sanger sequencing of polymerase chain reaction products using BigDye terminators and capillary electrophoresis. RESULTS: A total of 12 mutations were identified and 5 of these were novel. Six were missense mutations; 4 were truncating mutations (2 nonsense and 2 frameshift); 1 was an in-frame deletion and 1 was an in-frame duplication. Mutations in CYP1B1 could fully explain the PCG phenotype in 7 individuals (18%). Five individuals were compound heterozygous or presumed compound heterozygous, 1 was homozygous and 1 was apparently homozygous. Three individuals were heterozygous for sequence variations in CYP1B1 thought to be pathogenic-one of these was p.(Tyr81Asn). Several known sequence variations with presumably no functional effect were found in the cohort. CONCLUSIONS: In this study, we identified 12 CYP1B1 mutations, 5 of which were novel. The frequency of CYP1B1 mutations in this cohort was comparable with other populations. We also detected an individual heterozygous for p.(Tyr81Asn) mutation, previously suggested to cause autosomal dominant primary open-angle glaucoma.
Asunto(s)
Citocromo P-450 CYP1B1/genética , ADN/genética , Glaucoma de Ángulo Abierto/genética , Presión Intraocular , Mutación , Citocromo P-450 CYP1B1/metabolismo , Análisis Mutacional de ADN , Dinamarca/epidemiología , Femenino , Glaucoma de Ángulo Abierto/congénito , Glaucoma de Ángulo Abierto/epidemiología , Humanos , Incidencia , Masculino , Mutación Missense , Fenotipo , Reacción en Cadena de la PolimerasaRESUMEN
The dynamic regulation of histone modifications is important for modulating transcriptional programs during development. Aberrant H3K4 methylation is associated with neurological disorders, but how the levels and the recognition of this modification affect specific neuronal processes is unclear. Here, we show that RBR-2, the sole homolog of the KDM5 family of H3K4me3/2 demethylases in Caenorhabditis elegans, ensures correct axon guidance by controlling the expression of the actin regulator wsp-1. Loss of rbr-2 results in increased levels of H3K4me3 at the transcriptional start site of wsp-1, with concomitant higher wsp-1 expression responsible for defective axon guidance. In agreement, overexpression of WSP-1 mimics rbr-2 loss, and its depletion restores normal axon guidance in rbr-2 mutants. NURF-1, an H3K4me3-binding protein and member of the chromatin-remodeling complex NURF, is required for promoting aberrant wsp-1 transcription in rbr-2 mutants and its ablation restores wild-type expression of wsp-1 and axon guidance. Thus, our results establish a precise role for epigenetic regulation in neuronal development by demonstrating a functional link between RBR-2 activity, H3K4me3 levels, the NURF complex and the expression of WSP-1.
Asunto(s)
Actinas/metabolismo , Axones/fisiología , Proteínas de Caenorhabditis elegans/fisiología , Proteínas Cromosómicas no Histona/fisiología , Regulación del Desarrollo de la Expresión Génica , Histonas/metabolismo , Proteína 2 de Unión a Retinoblastoma/fisiología , Alelos , Animales , Tipificación del Cuerpo , Caenorhabditis elegans , Catálisis , Cromatina/metabolismo , Epigénesis Genética , Histona Demetilasas/metabolismo , Lisina/metabolismo , Metilación , Microscopía Fluorescente , Mutación , Neuronas/metabolismo , Estructura Terciaria de Proteína , Transducción de Señal , TransgenesRESUMEN
Oxygen (O2) and carbon dioxide (CO2) provoke distinct olfactory behaviors via specialized sensory neurons across metazoa. In the nematode C. elegans, the BAG sensory neurons are specialized to sense changes in both O2 and CO2 levels in the environment. The precise functionality of these neurons is specified by the coexpression of a membrane-bound receptor-type guanylyl cyclase GCY-9 that is required for responses to CO2 upshifts and the soluble guanylyl cyclases GCY-31 and GCY-33 that mediate responses to downshifts in O2. Expression of these gas-sensing molecules in the BAG neurons is partially, although not completely, controlled by ETS-5, an ETS-domain-containing transcription factor, and EGL-13, a Sox transcription factor. We report here the identification of EGL-46, a zinc-finger transcription factor, which regulates BAG gas-sensing fate in partially parallel pathways to ETS-5 and EGL-13. Thereby, three conserved transcription factors collaborate to ensure neuron type-specific identity features of the BAG gas-sensing neurons.
Asunto(s)
Proteínas de Caenorhabditis elegans/metabolismo , Caenorhabditis elegans/genética , Células Quimiorreceptoras/metabolismo , Neurogénesis , Factores de Transcripción/metabolismo , Animales , Caenorhabditis elegans/crecimiento & desarrollo , Caenorhabditis elegans/metabolismo , Proteínas de Caenorhabditis elegans/genética , Dióxido de Carbono/farmacología , Células Quimiorreceptoras/efectos de los fármacos , Guanilato Ciclasa/genética , Guanilato Ciclasa/metabolismo , Oxígeno/farmacología , Factores de Transcripción/genéticaRESUMEN
Animals harbor specialized neuronal systems that are used for sensing and coordinating responses to changes in oxygen (O2) and carbon dioxide (CO2). In Caenorhabditis elegans, the O2/CO2 sensory system comprises functionally and morphologically distinct sensory neurons that mediate rapid behavioral responses to exquisite changes in O2 or CO2 levels via different sensory receptors. How the diversification of the O2- and CO2-sensing neurons is established is poorly understood. We show here that the molecular identity of both the BAG (O2/CO2-sensing) and the URX (O2-sensing) neurons is controlled by the phylogenetically conserved SoxD transcription factor homolog EGL-13. egl-13 mutant animals fail to fully express the distinct terminal gene batteries of the BAG and URX neurons and, as such, are unable to mount behavioral responses to changes in O2 and CO2. We found that the expression of egl-13 is regulated in the BAG and URX neurons by two conserved transcription factors-ETS-5(Ets factor) in the BAG neurons and AHR-1(bHLH factor) in the URX neurons. In addition, we found that EGL-13 acts in partially parallel pathways with both ETS-5 and AHR-1 to direct BAG and URX neuronal fate respectively. Finally, we found that EGL-13 is sufficient to induce O2- and CO2-sensing cell fates in some cellular contexts. Thus, the same core regulatory factor, egl-13, is required and sufficient to specify the distinct fates of O2- and CO2-sensing neurons in C. elegans. These findings extend our understanding of mechanisms of neuronal diversification and the regulation of molecular factors that may be conserved in higher organisms.