Project description:Primitive erythropoiesis in the mouse yolk sac is followed by definitive erythropoiesis resulting in adult erythrocytes. In comparison to definitive erythropoiesis little is known about the genes that control the embryonic erythroid program. The purpose of this study was to generate a profile of mouse embryonic yolk sac erythroid cells and identify novel regulatory genes differentially expressed in erythroid compared to non-erythroid (epithelial cells). The identification of these genes will contribute to a greater understanding of how the primitive erythroid program is controlled. This work will have clinical implications for treating sickle cell anemia and β-thalassemia. Activating genes in adult erythroid cells that increase embryonic or fetal globin gene expression may be a therapeutic approach to treat individuals with these disorders. Keywords: Comparison between mouse embryonic day 9.5 yolk sac microdissected primitive erythroid precursors and epithelial cells
Project description:Primitive erythropoiesis in the mouse yolk sac is followed by definitive erythropoiesis resulting in adult erythrocytes. In comparison to definitive erythropoiesis little is known about the genes that control the embryonic erythroid program. The purpose of this study was to generate a profile of mouse embryonic yolk sac erythroid cells and identify novel regulatory genes differentially expressed in erythroid compared to non-erythroid (epithelial cells). The identification of these genes will contribute to a greater understanding of how the primitive erythroid program is controlled. This work will have clinical implications for treating sickle cell anemia and β-thalassemia. Activating genes in adult erythroid cells that increase embryonic or fetal globin gene expression may be a therapeutic approach to treat individuals with these disorders. Experiment Overall Design: Embryonic day 9.5 (E9.5) yolk sacs were dissected from the embryos of timed-pregnant FVB/N mice. These tissues were frozen in OCT media and 8-micron frozen sections were obtained. Laser capture microdissection (LCM) was used to isolate primitive erythroid precursors and epithelial cells from these E9.5 yolk sac frozen sections using 2 to 4 yolk sacs from 2 different litters per biological replicate. Paired erythroid and epithelial samples were collected from the same microscope slides. Total RNA was isolated from 4 different pairs of erythroid and epithelial samples and hybridized to Affymetrix 430 A 2.0 microarrays.
Project description:KLF2 is a Krüppel-like zinc-finger transcription factor required for blood vessel, lung, T-cell, and erythroid development. KLF2-/- mice die by embryonic day 14.5 (E14.5), due to hemorrhaging and heart failure. Embryonic -like globin gene expression is reduced in KLF2-/- embryos compared to wildtype (WT), and E10.5 erythroid cells exhibit abnormal morphology. Other KLF2 target genes were identified by comparing E9.5 KLF2-/- and WT yolk sac erythroid cells, using laser capture microdissection and microarray assays. One hundred and ninety-six genes exhibited significant differences in expression; eighty-nine of these are downregulated in KLF2-/- compared to WT. Genes involved in cell migration, differentiation and development are over-represented in the KLF2-regulated gene list. Previously identified erythroid-enriched regulatory genes such as reelin, adenylate cyclase 7, cytotoxic T lymphocyte-associated protein 2 alpha, and CD24a antigen are downregulated in KLF2-/- compared to WT. SOX2, a pluripotency factor in ES cells, is also a KLF2 target in embryonic erythroid cells. We investigated whether reelin, which has an established role in neuronal migration and proliferation, has a role in embryonic erythropoiesis. Luciferase reporter assays demonstrated that KLF2 directly transactivates the reelin promoter, but reelin mutant mice have no apparent abnormalities in embryonic erythroid morphology or globin gene expression. Timed-pregnant KLF2+/- females were anesthetized and sacrificed. E9.5 yolk sacs were dissected from the embryo, cryoprotected in 20% sucrose in PBS and frozen in OCT media. A small portion of the embryo tail was used for PCR genotyping. Eight micron KLF2-/- frozen yolk sac sections were obtained and laser capture microdissection (LCM) was used to isolate primitive erythroid precursors. For each biological replicate, 2 to 4 yolk sacs from 2 different litters were used. Total RNA was isolated from 4 different KLF2-/- erythroid samples and hybridized to Affymetrix 430 A 2.0 microarrays
Project description:This study aimed at exploring the physiological function of mammalian HYPB by means of knockout mouse model. Homogenous disruption of mouse Hypb gene leads to embryonic lethality at E10.5-E11.5. Severe vascular defects were observed in the Hypb-/- embryos, yolk sac and placenta.In the mutant embryo and yolk sac, disorganized and abnormally dilated capillaries cannot be remodeled into large blood vessels or intricate networks. Thus, our results suggest that the mammalian HYPB HMT plays an important role in embryonic vascularization. Keywords: knockout, mouse embryo development, angiogenesis, yolk sac, E9.0, E10.5
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: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: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.
Project description:Background Vasculogenesis in amniotes is often viewed as two spatially and temporally distinct processes, occurring in the yolk sac and in the embryo. However, the spatial origins of the cells that form the primary intra-embryonic vasculature remain uncertain. In particular, do they obtain their haemato-endothelial cell fate in situ, or do they migrate from elsewhere? Recently developed imaging techniques, together with new Tal1 and existing Flk1 reporter mouse lines, have allowed us to investigate this question directly, by visualising cell trajectories live and in three dimensions. Results We describe the pathways that cells follow to form the primary embryonic circulatory system in the mouse embryo. In particular, we show that Tal1-positive cells migrate from within the yolk sac, at its distal border, to contribute to the endocardium, dorsal aortae and head vasculature. Other Tal1 positive cells, similarly activated within the yolk sac, contribute to the yolk sac vasculature. Using single-cell transcriptomics and our imaging, we identify VEGF and Apela as potential chemo-attractants that may regulate the migration into the embryo. The dorsal aortae and head vasculature are known sites of secondary haematopoiesis; given the common origins that we observe, we investigate whether this is also the case for the endocardium. We discover cells budding from the wall of the endocardium with high Tal1 expression and diminished Flk1 expression, indicative of an endothelial to haematopoietic transition. Conclusions In contrast to the view that the yolk sac and embryonic circulatory systems form by two separate processes, our results indicate that Tal1-positive cells from the yolk sac contribute to both vascular systems. It may be that initial Tal1 activation in these cells is through a common mechanism.