Project description:By tracing the VE-cadherin expression in the newborn bone marrow hematopoietic LSK (lineage minus/Sca-positive/Kit-positive) cells, we demonstrated that the late foetal/newborn BM hemogenic endothelial cells produce a small cohort of hematopoietic stem and progenitor cells (HSPCs) capable of circulating and colonizing the secondary haematopoietic organs. Phenotypic and functional analyses disclosed that BM endothelium-derived HSPCs are mainly Multipotent Progenitors (MPPs) and a few Hematopoietic Stem Cells. We used microarrays to detail the global programme of gene expression underlying the endothelial origin of LSK cells in the newborn bone marrow.
Project description:Embryonic Endothelial Evolution towards First Hematopoietic Stem Cells Revealed by Single-Cell Transcriptomic and Functional Analyses
Project description:<p><strong>BACKGROUND:</strong> Hematopoietic stem cell transplantation is a curative procedure for a variety of conditions. Despite major advances, a plethora of adverse clinical outcomes can develop post-transplantation including graft-versus-host disease and infections, which remain the major causes of morbidity and mortality. There is increasing evidence that the gastrointestinal microbiota is associated with clinical outcomes post-hematopoietic stem cell transplantation. Herein, we investigated the longitudinal dynamics of the gut microbiota and metabolome and potential associations to clinical outcomes in pediatric hematopoietic stem cell transplantation at a single centre.</p><p><strong>RESULTS:</strong> On admission (baseline), the majority of patients presented with a different gut microbial composition in comparison to healthy control children with a significantly lower alpha diversity. A further, marked decrease in alpha diversity was observed immediately post-transplantation and in most microbial diversity, and composition did not return to baseline status while hospitalized. Longitudinal trajectories identified continuous fluctuations in microbial composition, with the dominance of a single taxon in a significant proportion of patients. Using pam clustering, three clusters were observed in the dataset. Cluster 1 was common pre-transplantation, characterized by a higher abundance of <em>Clostridium XIVa</em>, <em>Bacteroides</em> and <em>Lachnospiraceae</em>; cluster 2 and cluster 3 were more common post-transplantation with higher abundance of <em>Streptococcus</em> and <em>Staphylococcus</em> in the former whilst <em>Enterococcus</em>, <em>Enterobacteriaceae</em> and <em>Escherichia</em> predominated in the latter. Cluster 3 was also associated with a higher risk of viraemia. Likewise, further multivariate analysis reveals <em>Enterobacteriaceae</em>, viraemia, use of total parenteral nutrition and various antimicrobials contributing towards cluster 3, <em>Streptococcaceae</em>, <em>Staphylococcaceae</em>, <em>Neisseriaceae</em>, vancomycin and metronidazole contributing towards cluster 2. <em>Lachnospiraceae</em>, <em>Ruminococcaceae</em>, <em>Bifidobacteriaceae</em> and not being on total parenteral nutrition contributed to cluster 1. Untargeted metabolomic analyses revealed changes that paralleled fluctuations in microbiota composition; importantly, low fecal butyrate was associated with higher risk of viraemia.</p><p><strong>CONCLUSIONS:</strong> These findings highlight the frequent shifts and dominations in the gut microbiota of pediatric patients undergoing hematopoietic stem cell transplantation. The study reveals associations between the fecal microbiota, metabolome and viraemia. To identify and explore the potential of microbial biomarkers that may predict risk of complications post-HSCT, larger multi-centre studies investigating longitudinal microbial profiling in pediatric hematopoietic stem cell transplantation are warranted.</p>
Project description:Find the casual relationship between gene expression network and cellular phenotype at single cell resolution. We collected donated human pre-implatation embryos, and the embryonic stem cells derived from them, isolate individual cells, prepared single cell cDNAs, and sequenced them by HiSeq2000. Then we analyzed the expression of known RefSeq genes. We get transcriptome of 124 individual cells from human pre-implantation embryos and human embryonic stem cells by applying single cell RNA-seq technique we recently developed[1][2][3][4]. We did in-depth bioinformatic analysis to these data and found very dynamic expression of protein-coding genes. [1] Tang, F. et al. (2010a) Tracing the Derivation of Embryonic Stem Cells from the Inner Cell Mass by Single-Cell RNA-Seq Analysis. Cell Stem Cell 6, 468-478. [2] Tang, F. et al. (2010b) RNA-Seq analysis to capture the transcriptome landscape of a single cell. Nat Protocols 5, 516-535. [3] Tang, F. et al. (2009) mRNA-Seq whole-transcriptome analysis of a single cell. Nat Meth 6, 377-382. [4] Tang, F. et al. (2011) Development and applications of single-cell transcriptome analysis. Nat Meth 8, S6-S11.
Project description:There are no described quality assurance mechanisms for newly formed stem cells. We observed intimate interactions between macrophages and blood stem cells in zebrafish embryos. Stressed stem cells were marked by surface Calreticulin, which stimulates macrophage interaction as an eat me signal. Macrophage-stem cell interactions either lead to removal of cytoplasmic material and stem cell proliferation or resulted in complete stem cell engulfment. Calreticulin knock down or embryonic macrophage depletion reduced the number of stem cell clones into adulthood. Our work supports a model in which embryonic macrophages determine hematopoietic clonality by monitoring stem cell quality.
Project description:In the past decades, the paradigm of three germ layers formed by gastrulation has been modified by data suggesting an existence of neuromesodermal progenitors (NMPs) that arise during gastrulation and contribute to both spinal cord and adjacent paraxial mesoderm1-5. However, there lacks direct genetic lineage tracing evidence and functional assessment of NMPs in vivo. Here, we develop a dual recombinases-mediated genetic system to specifically trace and genetically ablate Brachyury+Sox2+ NMPs. Genetic lineage tracing results and single-cell RNA sequencing analysis show that NMPs contain three distinct uni-potent and bi-potent progenitor populations for progressive differentiation into neural and mesodermal fates. Genetic ablation of NMPs by diphtheria toxin reveals a critical role of NMPs in tail formation. This study provides in vivo genetic evidence for heterogeneity of NMPs in their cell fate determination and their functional role in developing embryos.