Project description:Erythro-myeloid progenitors (EMP) and their progeny were labeled with YFP in mouse embryos using genetic fate mapping (constitutive Csf1r-iCre;Rosa26-eYFP or inducible Csf1r-MeriCreMer;Rosa26-eYFP injected at embryonic day E8.5 with 4-hydroxytamoxifen). EMP-derived progenitors (Lin- Kit+ YFP+) were sorted by FACS for single-cell transcriptomic analysis using the MARS-Seq approach. The purpose was to uncover heterogeneity and differentiation trajectories of EMP by comparing their transcriptional status at different developmental timepoints (E9.5, E10.5 and E12.5) and across niches (yolk sac and fetal liver).
Project description:Hematopoietic stem cell (HSC)-independent lymphopoiesis has been elucidated in murine embryos. However, our understanding regarding human embryonic counterparts remains limited. Here, we unveiled the presence of human yolk sac-derived lymphoid-biased progenitors (YSLPs) expressing CD34, IL7R, LTB and IRF8 at Carnegie Stage 10, much earlier than the first HSCs emergence. The number and lymphopoietic potential of these progenitors were both significantly higher in yolk sac than embryo proper at this early stage. Importantly, single-cell/bulk culture and CITE-seq have elucidated the tendency of YSLP differentiating into innate lymphoid cells and dendritic cells. Notably, lymphoid progenitors in fetal liver before and after HSCs seeding displayed distinct transcriptional features, with the former closely resembling those of YSLPs.
Project description:Hematopoietic stem cell (HSC)-independent lymphopoiesis has been elucidated in murine embryos. However, our understanding regarding human embryonic counterparts remains limited. Here, we unveiled the presence of human yolk sac-derived lymphoid-biased progenitors (YSLPs) expressing CD34, IL7R, LTB and IRF8 at Carnegie Stage 10, much earlier than the first HSCs emergence. The number and lymphopoietic potential of these progenitors were both significantly higher in yolk sac than embryo proper at this early stage. Importantly, single-cell/bulk culture and CITE-seq have elucidated the tendency of YSLP differentiating into innate lymphoid cells and dendritic cells. Notably, lymphoid progenitors in fetal liver before and after HSCs seeding displayed distinct transcriptional features, with the former closely resembling those of YSLPs.
Project description:The human yolk sac (YS) is an extra-embryonic tissue critical for early prenatal life development. It is the first site of haematopoiesis where progenitors differentiate from endoderm within blood islands of the yolk sac contributing initially to primitive erythropoiesis and in subsequent waves to erythro-myeloid and lymphoid differentiation.
Project description:The human yolk sac (YS) is an extra-embryonic tissue critical for early prenatal life development. It is the first site of haematopoiesis where progenitors differentiate from endoderm within blood islands of the yolk sac contributing initially to primitive erythropoiesis and in subsequent waves to erythro-myeloid and lymphoid differentiation.
Project description:Investigating the blood, immune and stromal cells present in a human fetal embryo in a world first single cell transcriptomic atlas. The embryo was dissected into 12 coronal sections, yolk sac, and yolk sac stalk. Live single cells sorted, with cell suspension then undergoing 10x chromium 5 prime scRNA-seq. This accession contains the yolk sac and yolk sac stalk data from this embryo. A matched accession contains the coronal section data. Lane "WS_wEMB12142156" (from yolk sac) was excluded from downstream analysis due to low fraction reads in cells post-CellRanger QC. Termination procedure for this embryo was medical. The F158_[features...barcodes...matrix].[tsv...mtx].gz files attached to this accession represent raw count data from all the 10x lanes in this accession combined, and as output from CellRanger filtered matrices (CellRanger version 6.0.1 using human reference genome GRCh38-2020-A). One set of count matrices relates to the yolk sac data, and one set of count matrices relates to the yolk sac stalk data.
Project description:The human definitive yolk sac is an important organ supporting the early developing embryo through nutrient supply and by facilitating the establishment of the embryonic circulatory system. However, the molecular and cellular biology of the human yolk sac remains largely obscure due to the lack of suitable in vitro models. Here, we show that human induced pluripotent stem cells (hiPSCs) co-cultured with various types of stromal cells as spheroids self-organize into yolk sac-like organoids without the addition of exogenous factors. Yolk sac-like organoids recapitulated a yolk sac specific cellular complement and structures as well as the functional ability to generate definitive hematopoietic progenitor cells (HPCs). Furthermore, sequential hemato-vascular ontogenesis could be observed during organoid formation. Notably, our organoid system can be performed in a scalable, autologous, and xeno-free condition, thereby providing an important model of human definitive yolk sac development and allows for efficient bulk generation of hiPSC-derived HPCs.
Project description:GW182 (Tnrc6a) is a key component of RISC (miRNA-Induced Silencing Complex) that plays a critical role in miRNA-mediated gene silencing. Here, we show that GW182 is expressed in the yolk sac endoderm, and that gene-trap disruption of GW182 leads to growth arrest of yolk sac endoderm, impaired hematopoiesis and embryonic lethality. To investigate roles of GW182 in the yolk sac endoderm, we assessed changes in mRNA expression in the yolk sac of E9.5 GW182gt/gt embryos using microarrays (Affymetrix).
Project description:GW182 (Tnrc6a) is a key component of RISC (miRNA-Induced Silencing Complex) that plays a critical role in miRNA-mediated gene silencing. Here, we show that GW182 is expressed in the yolk sac endoderm, and that gene-trap disruption of GW182 leads to growth arrest of yolk sac endoderm, impaired hematopoiesis and embryonic lethality. To investigate roles of GW182 in the yolk sac endoderm, we assessed changes in mRNA expression in the yolk sac of E9.5 GW182gt/gt embryos using microarrays (Affymetrix). Yolk sac of wild type littermates and GW182gt/gt embryos at E9.5 was collected for total RNA isolation using Trizol (Invitrogen). RNAs were purified according to the manufacturer’s protocol before subjected to Mouse Gene 1.0 ST Whole Genome Array (Affymetrix) for mRNA expression profiling. Experiments were performed in triplicate. Differentially expressed mRNAs were identified using a two-sample t-test (P<0.05 considered significant).
Project description:Hematopoietic cells arise from spatiotemporally restricted domains in the developing embryo. Although studies of non-mammalian animal and in vitro embryonic stem cell models suggest a close relationship among cardiac, endocardial, and hematopoietic lineages, it remains unknown whether the mammalian heart tube serves as a hemogenic organ akin to the dorsal aorta. Here, we examined the hemogenic activity of the developing endocardium. Mouse heart explants generated myeloid and erythroid colonies in the absence of circulation. Hemogenic activity arose from a subset of endocardial cells in the outflow cushion and atria earlier than in the aorta-gonad-mesonephros region, and was transient and definitive in nature. Interestingly, key cardiac transcription factors, Nkx2-5 and Isl1, were expressed in and required for the hemogenic activity of the endocardium. Together, these data suggest that a subset of endocardial and yolk sac endothelial cells expressing cardiac markers serve as a de novo source for transient definitive hematopoietic progenitors. Two independent biological duplicates of freshly isolated mouse tissues (caudal half, heart tube, yolk sac) were sorted for CD31+/CD41-/CD45- cells.