Project description:Mouse embryonic development is a canonical model system for studying mammalian cell fate acquisition. Recently, single-cell atlases comprehensively charted embryonic transcriptional landscapes, yet inference of the coordinated dynamics of cells over such atlases remains challenging. Here we introduce a temporal model for mouse gastrulation, consisting of data from 153 individually sampled embryos spanning 36 hours of molecular diversification. Using new algorithms and precise timing we infer differentiation flows and lineage specification dynamics over the embryonic transcriptional manifold. Rapid transcriptional bifurcations characterize the commitment of early specialized node and blood cells. However, for most lineages, we observe combinatorial multi-furcation dynamics rather than hierarchical transcriptional transitions. In the mesoderm, dozens of transcription factors combinatorially regulate multi-furcations, as we exemplify using time-matched chimeric embryos of Foxc1/Foxc2 mutants. Our study rejects the notion of differentiation being governed by a series of binary choices, providing an alternative quantitative model for cell fate acquisition.
Project description:Mouse embryonic development is a canonical model system for studying mammalian cell fate acquisition. Recently, single-cell atlases comprehensively charted embryonic transcriptional landscapes, yet inference of the coordinated dynamics of cells over such atlases remains challenging. Here, we introduce a temporal model for mouse gastrulation, consisting of data from 153 individually sampled embryos spanning 36 h of molecular diversification. Using algorithms and precise timing, we infer differentiation flows and lineage specification dynamics over the embryonic transcriptional manifold. Rapid transcriptional bifurcations characterize the commitment of early specialized node and blood cells. However, for most lineages, we observe combinatorial multi-furcation dynamics rather than hierarchical transcriptional transitions. In the mesoderm, dozens of transcription factors combinatorially regulate multifurcations, as we exemplify using time-matched chimeric embryos of Foxc1/Foxc2 mutants. Our study rejects the notion of differentiation being governed by a series of binary choices, providing an alternative quantitative model for cell fate acquisition.
Project description:The blueprint of lineage segregation of early mouse embryo is established during gastrulation in which progenitors of various cell fates are regionalized and patterned in specific embryo locations. Despite the central importance of this period of mammalian development, we currently lack a comprehensive understanding of the underlying developmental trajectories and molecular processes, principally because research efforts either employed in vitro systems, focused on small numbers of genes, or limited the number of developmental stages or cell types that were studied. Here, we study the regulatory landscape of gastrulation by combining single-cell RNA-seq (A total of ~35,000 single cells isolated at E6.5, E6.75, E7.0, E7.25, E7.5) and geographical position sequencing (Geo-seq) technique, and we report a de novo identification of spatial signatures and a method to enable retrospective locating of single cells to their origins. Our work provides insights into the exit from pluripotency and priming for differentiation, and the emergence of regulatory networks associated with cell fate decisions. Finally, we reconstruct the spatio-temporal roadmap of gastrula mouse embryo in single-cell resolution. This result uncovers the cell migration trajectories and molecular processes associated with lineage segregation.
Project description:We investigated marmoset gastrulation using SpaTial Embryo Profiling (STEP) to generate 3D-transcriptomes based on the physical location of samples within the implanted embryo. Samples were isolated from unfixed tissues using laser-capture-microdissection and subjected to single-cell full-lengths transcriptome profiling using a modified version of Smart-Seq2.
Project description:Here, we constructed monkey blastoids resembling blastocysts in morphology and transcriptomics using naïve ESCs and optimized protocol. The synthetic blastoids could develop to embryonic disk stage with the structure of yolk sac, chorionic cavity, amnion cavity, primitive streak, connecting stalk along the rostral–caudal axis by in-vitro prolonged culture (IVC). Primordial germ cells, gastrulating cells, visceral endoderm/yolk-sac endoderm, three germ layers and haemato-endothelial progenitors were identified in the monkey blastoid IVC embryo by single-cell transcriptomics or immunostaining. Besides, pregnancies with early gestation sacs were achieved by transferring monkey blastoids to surrogates. Our results revealed the in-vitro gastrulation and in-vivo early pregnancy of primate synthetic embryos, providing a powerful system to dissect primate embryonic development with less ethical concerns and restrict access.
Project description:Single-cell RNA sequencing offers snapshots of whole transcriptomes but obscures the temporal RNA dynamics. Here we present single-cell metabolically labeled new RNA tagging sequencing (scNT-Seq), a method for massively parallel analysis of newly-transcribed and pre-existing mRNAs from the same cell. This droplet microfluidics-based method enables high-throughput chemical conversion on barcoded beads, efficiently marking newly-transcribed mRNAs with T-to-C substitutions. With scNT-Seq, we jointly profiled new and old transcriptomes in ~55,000 single cells. These data revealed time-resolved transcription factor activities and cell state trajectories at single-cell level in response to neuronal activation. We further determined rates of RNA biogenesis and decay to uncover RNA regulatory strategies during stepwise conversion between pluripotent and rare totipotent two-cell-embryo-like (2C-like) stem cell states. Finally, integrating scNT-Seq with genetic perturbation identifies DNA methylcytosine dioxygenases as an epigenetic barrier into 2C-like cell state. Time-resolved single-cell transcriptomic analysis thus opens new lines of inquiry regarding cell-type-specific RNA regulatory mechanisms.
Project description:To glean an appreciation of the holistic genetic activity in the gastrulating mouse embryo, we performed a genome-wide spatial transcriptome analysis (Stereo-seq), using a low-cell number sequencing protocol on laser microdissected samples of epiblast cells with retained positional address. The 3D transcriptome reveals that (i) the epiblast is partitioned into transcription domains corresponding to regions of epiblast where cells are endowed specifically with ectoderm and mesendoderm potency, (ii) novel lineage markers are identified as genes expressed in epiblast domains populated by cells displaying different lineage fates, (iii) functionally related gene regulatory circuitry and signaling pathways are acting in concert in the transcriptional domains, and (iv) the spatial information provides reference zipcodes for mapping the prospective address of cell samples from different embryos and stem cell lines. The quantified expression data can also be visualized as â3D digitized whole mount in situ hybridizationâ of all the expressed transcripts in the epiblast. (i) By using laser-microdissection, we carried out transcriptome profiling on embryo sections at a high resolution of ~20 cells per sample with the spatial information preserved. We then constructed a comprehensive spatial transcriptome map in the mid-gastrulation embryo that is visualized in a 3D embryonic model based on the sequencing data. Embryo position (A/L/P/R) and section (1-11) descriptors: A stands for laser capture microdissected samples from the anterior epiblast of the embryo; P for posterior; L for the left lateral epiblast of the embryo; R for the right lateral. The section is collected from distal to proximal, and the section 1 to 11 is the cryosection order, covering the whole embryonic part of a late mid-streak embryo. Section 1 is the most distal section and 11 is the most proximal section. (ii) Additional samples are RNA-seq data of 70 single cells from E7.0 mouse embryo. These 70 samples were randomly picked from the anterior or posterior embryonic half.