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:Hematopoietic stem cells (HSCs) are derived from hemogenic endothelial cells (HECs) during embryogenesis. The HSC-primed HECs are peak at embryonic day (E) 10 and have been efficiently captured by the marker combination CD41-CD43-CD45-CD31+CD201+Kit+CD44+ (PK44) in the aorta-gonad-mesonephros (AGM) region of mouse embryos most recently. In the present study, we investigated the spatiotemporal and functional heterogeneity of PK44 cells around the time of emergence of HSCs. First, PK44 cells in E10 AGM region could be further divided into three molecularly different populations showing endothelial- or hematopoietic-biased characteristics. Specifically, with the combination of Kit, the expression of CD93 or CD146 could divide PK44 cells into endothelial- and hematopoietic-feature biased populations, which was further functionally validated at single cell level. Next, PK44 population could also be detected in the yolk sac, showing a developmental dynamics and functional diversification similar to those in the AGM region. Importantly, PK44 cells in the yolk sac demonstrated an unambiguous multi-lineage reconstitution capacity after in vitro incubation. Regardless of the functional similarity, PK44 cells in the yolk sac displayed transcriptional features different to those in the AGM region. Taken together, our work delineated the spatiotemporal characteristics of HECs represented by PK44, and revealed a previously unknown HSC competence of HECs in the yolk sac. These findings provided a fundamental basis for in-depth studying the different origins and molecular programs of HSC generation in the future.
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:During ontogeny, HSCs or progenitors are generated from endothelial cells through the process known as endothelial-to-hematopoietic transition (EHT). After EHT, hematopoietic cells form cell aggregates, called hematopoietic clusters. To obtain mechanistic insight into HSC specification, we compared the gene expression profiles of hematopoietic clusters between caudal half region and yolk sac.
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:Etv2 transgene was expressed from ROSA26 locus by removing floxed STOP cassette by Tie-2 Cre transgene.VE-Cad+/CD45+ cells were sorted from control or tie-2-Etv2 E10.5 embryosYS(yolk sac) and compared for gene expression in duplicate. This study will reveal the effect of Etv2 transgene in E10.5 mouse embryo yolk sac. The effect of Etv2 overexpression in relevant mouse tissue will be important to understand its effect in comparison with in ES cells. Genes aberrantly regulated by Etv2 overexpression will help to understand the caveat when using Etv2 to induce endothelial and hematopoietic cells in vitro. Sample ID YS- ; (VECAD+CD45+;YS;Control) YS+12; (VECAD+CD45+;YS;Tg) YS+22 ; (VECAD+CD45+;YS;Tg)
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:CIRHIN is a transcription co-factor, shows postive effect on Hiv-1 LTR enhancer element(NF-κB site); and Cirh1a null is preimplantation lethal, but highly expressed in the early mice embryo (E6.0-E12.5). We hypothesis that Cirh1a's effect on gene transcription of early embryo can be detected with Cirh1a down regulated in Cirh1a+/- state. Result shows that Cirh1a+/- has significant effect on early mice embryo gene transcription, Differentially expressed genes (DEGs) detected are mainly involved in cell proliferation/differenciation, cell cycle progress, embryo development and multi-orgnaogenesis. Littermate embryos (E8.5) were dissected into RNAlater reagent for total RNA extraction, and yolk sac was used for genotyping PCR. Littermate embryos (E9.5) were dissected into RNAlater reagent for total RNA extraction, and yolk sac was used for genotyping PCR. Liver buds from littermate embryos (E11.5) were dissected into RNAlater reagent for total RNA extraction, and yolk sac was used for genotyping PCR. Liver buds from littermate embryos were dissected into RNAlater reagent for total RNA extraction, and yolk sac was used for genotyping PCR.