Maintenance of pluripotency signature in the entire ectoderm enables potential for neural crest formation [bulk_RNASeq]
Ontology highlight
ABSTRACT: The ability of the pluripotent epiblast to contribute progeny to all three germ layers is thought to be lost after gastrulation. The later-forming neural crest (NC) rises from ectoderm and it remains poorly understood how its exceptionally high stem-cell potential to generate mesodermal- and endodermal-like cells is obtained. We monitored transcriptional changes from gastrulation to neurulation using single-cell-Multiplex-Spatial-Transcriptomics (scMST) complemented with RNA-sequencing. Here we show maintenance of pluripotency-signature (Nanog/Oct4-PouV/Klf4-positive) in undecided pan-ectodermal stem-cells spanning the entire ectoderm late during neurulation with ectodermal patterning completed only at the end of neurulation when the pluripotency-signature becomes restricted to NC, challenging our understanding of gastrulation. Furthermore, broad ectodermal pluripotency-signature is found at all axial levels unrelated to the NC lineage the cells later commit to, suggesting a general role in stemness enhancement and proposing a mechanism by which the NC acquires its ability to form derivatives beyond “ectodermal-capacity” in chick and mouse embryos.
Project description:The ability of the pluripotent epiblast to contribute progeny to all three germ layers is thought to be lost after gastrulation. The later-forming neural crest (NC) rises from ectoderm and it remains poorly understood how its exceptionally high stem-cell potential to generate mesodermal- and endodermal-like cells is obtained. We monitored transcriptional changes from gastrulation to neurulation using single-cell-Multiplex-Spatial-Transcriptomics (scMST) complemented with RNA-sequencing. Here we show maintenance of pluripotency-signature (Nanog/Oct4-PouV/Klf4-positive) in undecided pan-ectodermal stem-cells spanning the entire ectoderm late during neurulation with ectodermal patterning completed only at the end of neurulation when the pluripotency-signature becomes restricted to NC, challenging our understanding of gastrulation. Furthermore, broad ectodermal pluripotency-signature is found at all axial levels unrelated to the NC lineage the cells later commit to, suggesting a general role in stemness enhancement and proposing a mechanism by which the NC acquires its ability to form derivatives beyond “ectodermal-capacity” in chick and mouse embryos.
Project description:The ability of the pluripotent epiblast to contribute progeny to all three germ layers is thought to be lost after gastrulation. The later-forming neural crest (NC) rises from ectoderm and it remains poorly understood how its exceptionally high stem-cell potential to generate mesodermal- and endodermal-like cells is obtained. We monitored transcriptional changes from gastrulation to neurulation using single-cell-Multiplex-Spatial-Transcriptomics (scMST) complemented with RNA-sequencing. Unexpectedly, we find maintenance of undecided Nanog/Oct4-PouV/Klf4-positive pluripotent-like pan-ectodermal stem-cells spanning the entire ectoderm late in the neurulation process with ectodermal patterning completed only at the end of neurulation when pluripotency becomes restricted to NC, challenging our understanding of gastrulation. Furthermore, broad ectodermal pluripotency is found at all axial levels unrelated to the NC lineage the cells later commit to, suggesting a general role in stemness enhancement and proposing a mechanism by which the NC acquires its ability to form derivatives beyond “ectodermal-capacity” in chick and mouse embryos.
Project description:During primary neurulation, the separation of a single-layered ectodermal sheet into the surface ectoderm (SE) and neural tube specifies SE and neural ectoderm (NE) cell fates. The mechanisms underlying fate specification in conjunction with neural tube closure are poorly understood. Here, by comparing expression profiles between SE and NE lineages, we observed that uncommitted progenitor cells, expressing stem cell markers, are present in the neural plate border/neural fold prior to neural tube closure. To identify what type of signaling pathways and transcriptional factors are involved in the fate specification between SE and NE cells during neurulation.
Project description:Pluripotency is the capacity of early embryonic cells to make all the future lineages of the organism, and the existence of a pluripotent population of cells is important to both germ cell function and the pool of progenitor cells that enable vertebrate development to proceed over time through the process of gastrulation. Oct4, a class V POU transcription factor, is required for maintenance of pluripotency in embryonic stem cells (ESCs) and induction of pluripotency via transcription factor reprogramming. Homologues of Oct4 have been identified in other gnathostomes and classified into two different paralogues: POU5F1 and POU5F3. Here we provide evidence that these proteins are probably derived from a single POUV gene through ancient whole genome duplication events. To approach this issue, we compared the functional conservation and divergence of different POUV proteins in their capacity to support naïve pluripotency in mouse ESCs. We found a strong correlation between POU5F1 activity in naïve pluripotency and the regulation of germ cell specification programs. In contrast, POU5F3 exhibited reduced capacity to support naïve ESCs and its activity in ESCs correlated with the expression of genes associated with pre-gastrulation stages, or primed pluripotency. We detected evidence of this functional segregation as early as Sarcopterygian ancestors, based on the activities of coelacanth POUV proteins. Furthermore, we were able to identify earlier POUV homologues in lamprey and shark, indicating that the earliest point at which mammalian-level pluripotency of both POUV paralogues emerged is between the osteichthyan-chondrichthyan split and the gnathostome-cyclostome split.Taken together, our work highlights the evolutionary history of POUV activities across jawed vertebrates, suggesting that evolutionary pressure has facilitated maintenance of both paralogues over long periods of evolutionary history. In species with both paralogues, subfunctionalization of these proteins appears conserved. However, in many branches of vertebrate evolution, one of these paralogues is lost, suggesting a high level of plasticity in function and precarious balance between retaining both proteins and the overall levels of POUV activity in different developmental systems. While the conserved subfunctionalization of POUV activities evolved at some point just before the appearance of tetrapods, the additional divergent activities of this protein family appear to have evolved independently in each vertebrate lineage after gnathostome radiation.
Project description:Pluripotency is the capacity of early embryonic cells to make all the future lineages of the organism, and the existence of a pluripotent population of cells is important to both germ cell function and the pool of progenitor cells that enable vertebrate development to proceed over time through the process of gastrulation. Oct4, a class V POU transcription factor, is required for maintenance of pluripotency in embryonic stem cells (ESCs) and induction of pluripotency via transcription factor reprogramming. Homologues of Oct4 have been identified in other gnathostomes and classified into two different paralogues: POU5F1 and POU5F3. Here we provide evidence that these proteins are probably derived from a single POUV gene through ancient whole genome duplication events. To approach this issue, we compared the functional conservation and divergence of different POUV proteins in their capacity to support naïve pluripotency in mouse ESCs. We found a strong correlation between POU5F1 activity in naïve pluripotency and the regulation of germ cell specification programs. In contrast, POU5F3 exhibited reduced capacity to support naïve ESCs and its activity in ESCs correlated with the expression of genes associated with pre-gastrulation stages, or primed pluripotency. We detected evidence of this functional segregation as early as Sarcopterygian ancestors, based on the activities of coelacanth POUV proteins. Furthermore, we were able to identify earlier POUV homologues in lamprey and shark, indicating that the earliest point at which mammalian-level pluripotency of both POUV paralogues emerged is between the osteichthyan-chondrichthyan split and the gnathostome-cyclostome split.Taken together, our work highlights the evolutionary history of POUV activities across jawed vertebrates, suggesting that evolutionary pressure has facilitated maintenance of both paralogues over long periods of evolutionary history. In species with both paralogues, subfunctionalization of these proteins appears conserved. However, in many branches of vertebrate evolution, one of these paralogues is lost, suggesting a high level of plasticity in function and precarious balance between retaining both proteins and the overall levels of POUV activity in different developmental systems. While the conserved subfunctionalization of POUV activities evolved at some point just before the appearance of tetrapods, the additional divergent activities of this protein family appear to have evolved independently in each vertebrate lineage after gnathostome radiation.
Project description:During primary neurulation, the separation of a single-layered ectodermal sheet into the surface ectoderm (SE) and neural tube specifies SE and neural ectoderm (NE) cell fates. The mechanisms underlying fate specification in conjunction with neural tube closure are poorly understood. Here, by comparing expression profiles between SE and NE lineages, we observed that uncommitted progenitor cells, expressing stem cell markers, are present in the neural plate border/neural fold prior to neural tube closure.
Project description:In gastrulation, distinct progenitor cell populations are induced and sorted into the three germ layers ectoderm, mesoderm and endoderm. In order to identify genes involved in germ layer specification and morphogenesis, we identified genes differentially expressed between ectodermal and mesendodermal progenitor cells. To do so, we first generated highly enriched pools of ectodermal and mesendodermal progenitor cells. Mesendodermal cells were generated by over-expressing the Nodal signal Cyclops in wild type embryos and ectodermal cells were taken from mz-one-eyed-pinhead (oep) mutant embryos. We then compared the transcriptome of ectodermal versus mesendodermal cells taken from embryos at 7 hours post fertilization (hpf). In wild type embryos at this stage (70% epiboly), the first ectodermal and mesendodermal progenitor cells have already been sorted into their respective germ layers and ingression of mesendodermal progenitors is still ongoing.
Project description:The epiblast of vertebrate embryos is comprised of neural and non-neural ectoderm, with the border territory at their intersection harbouring neural crest and cranial placode progenitors. Here we profile avian epiblast cells as a function of time using single-cell RNA-seq to define transcriptional changes in the emerging ‘neural plate border’. The results reveal gradual establishment of heterogeneous neural plate border signatures, including novel genes that we validate by fluorescent in situ hybridization. Developmental trajectory analysis shows that segregation of neural plate border lineages only commences at early neurulation, rather than at gastrulation as previously predicted. We find that cells expressing the prospective neural crest marker Pax7 contribute to multiple lineages, and a subset of premigratory neural crest cells shares a transcriptional signature with their border precursors. Together, our results suggest that cells at the neural plate border remain heterogeneous until early neurulation, at which time progenitors become progressively allocated toward defined lineages.
Project description:During vertebrate neurulation, the embryonic ectoderm is patterned into lineage progenitors for neural plate, neural crest, placodes and epidermis. Here, we use Xenopus laevis embryos to analyze the spatial and temporal transcriptome of distinct ectodermal domains in the course of neurulation, during the establishment of cell lineages. In order to define the transcriptome of small groups of cells from a single germ layer, and to retain spatial information, dorsal and ventral ectoderm was subdivided along the anterior-posterior and medial-lateral axes by microdissections. Principal Component Analysis on the transcriptomes of these ectoderm fragments primarily identifies embryonic axes and temporal dynamics. This provides a genetic code to define positional information of any ectoderm sample along the anterior-posterior and dorsal-ventral axes, directly from its transcriptome. In parallel, we use Non-Negative Matrix Factorization to predict enhanced gene expression maps onto early and mid-neurula embryos, and specific signatures for each ectoderm area. The clustering of spatial and temporal datasets allowed detection of multiple biologically relevant groups (e.g. Wnt signaling, neural crest development, sensory placode specification, ciliogenesis, germ layer specification). We provide an interactive network interface, EctoMap, for exploring synexpression relationships among genes expressed in the neurula, and suggest several strategies to use this comprehensive dataset to address questions in developmental biology as well as stem cell or cancer research.
Project description:In recent years, several studies have shed light into the processes that regulate epidermal specification and homeostasis. We previously showed that a broad-spectrum γ–secretase inhibitor DAPT promoted early keratinocyte specification in human embryonic stem cells triggered to undergo ectoderm specification. Here, we show that DAPT accelerates human embryonic stem cell differentiation and induces expression of the ectoderm protein AP2. Furthermore, we utilize RNA sequencing to identify several candidate regulators of ectoderm specification including those involved in epithelial and epidermal development in human embryonic stem cells. Genes associated with transcriptional regulation and growth factor activity are significantly enriched upon DAPT treatment during specification of human embryonic stem cells to the ectoderm lineage. The human ectoderm cell signature identified in this study contains several genes expressed in ectodermal and epithelial tissues. Importantly, these genes are also associated with skin disorders and ectodermal defects, providing a platform for understanding the biology of human epidermal keratinocyte development under diseased and homeostatic conditions. 6 samples were analyzed, 3 replicates of ETOH treated H1 HESCs and 3 replicates of DAPT treated H1 HESCs