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Subtractive cloning of differentially expressed genes in chick heart/hemangioblast precursor cells

ABSTRACT: Genetic evidence has implicated several genes as being critical for heart development. However, the inducers of these genes as well as their other targets and the pathways they constitute, remain largely unknown. In the avian embryo, Cerberus (cCer) transcripts are detected in the anterior mesendoderm including the heart precursor cells and in the left lateral plate mesoderm. We have identified a promoter element of chick cCer able to drive EGFP expression into the heart and the hemangioblast precursor cells, allowing us to identify a population of cells that consistently exit from the anterior primitive streak region from as early as stage HH3+ and that later will populate the heart. In order to identify and study novel genes expressed and involved in the correct development and differentiation of the vertebrate H/HPC (Heart/ Hemangioblast Precursor Cells) lineages, a differential screening using Affymetrix GeneChip system technologies was performed. Remarkably, this screening led to the identification of more than 800 transcripts potentially expressed in these precursor lineages. We have identified unknown genes that are differentially expressed in the H/HPC precursor lineages. By developing a procedure to isolate the heart precursor cells using the cer2.5-EGFP construct, we were able to specifically isolate a population of H/HPC expressing already known cardiac markers, and a long list of still uncharacterized genes. From those, we defined by WISH that at least some of these in silico identified transcripts are in fact expressed in these cell populations and more importantly, functionally required for heart formation.More importantly, our study unveiled several uncharacterized genes that can now be used for further studies.

ORGANISM(S): Gallus gallus

PROVIDER: GSE23389 | GEO | 2010/08/04

SECONDARY ACCESSION(S): PRJNA131261

REPOSITORIES: GEO

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Project description:Genetic evidence has implicated several genes as being critical for heart development. However, the inducers of these genes as well as their other targets and the pathways they constitute, remain largely unknown. In the avian embryo, Cerberus (cCer) transcripts are detected in the anterior mesendoderm including the heart precursor cells and in the left lateral plate mesoderm. We have identified a promoter element of chick cCer able to drive EGFP expression into the heart and the hemangioblast precursor cells, allowing us to identify a population of cells that consistently exit from the anterior primitive streak region from as early as stage HH3+ and that later will populate the heart. In order to identify and study novel genes expressed and involved in the correct development and differentiation of the vertebrate H/HPC (Heart/ Hemangioblast Precursor Cells) lineages, a differential screening using Affymetrix GeneChip system technologies was performed. Remarkably, this screening led to the identification of more than 800 transcripts potentially expressed in these precursor lineages. We have identified unknown genes that are differentially expressed in the H/HPC precursor lineages. By developing a procedure to isolate the heart precursor cells using the cer2.5-EGFP construct, we were able to specifically isolate a population of H/HPC expressing already known cardiac markers, and a long list of still uncharacterized genes. From those, we defined by WISH that at least some of these in silico identified transcripts are in fact expressed in these cell populations and more importantly, functionally required for heart formation.More importantly, our study unveiled several uncharacterized genes that can now be used for further studies. Portions of chick embryos were selected and excised at early stages of development for RNA extraction and hybridization on Affymetrix microarrays. We sought to obtain homogeneous populations of embryos at early gastrula stage in order to increase the temporal resolution of expression profiles. To that end, we hand-selected and excised portions of the embryos according to morphological criteria and EGFP expression. Four GeneChip chicken arrays used for another study were added to the two arrays in this study to ensure a robust model for expression value computation (Note: The 4 samples chick_T2-1, chick_T2-2, chick_T2-3, chick_T2-4, were performed by another group and for a different array, and nothing has to do with our data. They were only run at the same time and used for normalization. Raw data unavailable.). The arrays were normalized to a baseline array with median CEL intensity by applying an Invariant Set Normalization Method. Normalized CEL intensities of the six arrays were used to obtain model-based gene expression indices (MBEI) based on a PM (Perfect Match)-only model. Processed data for all 6 samples can be found in supplementary file linked below.

Project description:Signaling pathways controlling vasculogenesis and angiogenesis are still poorly understood. Zebrafish Ets1-related protein (Etsrp) which encodes an ETS domain transcription factor, evolutionary related to the mammalian ER71 protein subfamily, has been identified as a major regulator of vasculogenesis and myelopoiesis and functions at the hemangioblast stage affecting the formation of both lineages. In the absence of Etsrp, angioblasts do not migrate or differentiate while overexpression of Etsrp results in the expansion of vascular endothelial and myeloid lineages. To identify genes functioning downstream of Etsrp we performed microarray analysis of etsrp-overexpressing embryos. Etsrp RNA injected embryos and control uninjected embryos were frozen at the tailbud stage and analyzed for expression of more than 30,000 genes using Nimblegen expression arrays. Approximately 300 genes showed greater than two-fold induction in etsrp-overexpressing embryos. Scl, crl, egfl7, aqp8, fli1a, fli1b, lmo2, cdh5 were among the previously known hemangioblast or vasculature-specific genes which were strongly upregulated in Etsrp-overexpressing embryos. We isolated and characterized a number of genes that were novel or previously unassociated with the zebrafish vasculature formation. Eight of them which include angiotensin II type 2 receptor (agtr2), src homology 2 domain containing E (she), similar to mannose receptor C1 (mrc1), endothelial cell-specific adhesion molecule (esam), cdc42 guanine nucleotide exchange factor 9 (arhgef9), yes-related kinase (yrk), zinc finger protein, multitype 2b (zfpm2b/fog2b) and stabilin 2 (stab2) were specifically expressed in vascular endothelial cells during early embryonic development while keratin18 expression was localized to the myeloid cells among others. Identification of novel vasculature and myeloid-specific genes that are regulated by Etsrp will be important for dissecting molecular mechanisms that regulate vasculogenesis / angiogenesis and myelopoiesis.

Project description:Hemangioblasts are known as the common precursors for primitive hematopoietic and endothelial lineages. Their existence has been supported mainly by the observation that both cell types develop in close proximity and by in vitro differentiation and genetic studies. However, more compelling evidence will arise from tracking their cell fates using a lineage-specific marker. We report the identification of a hemangioblast-specific enhancer (Hb) located in the cis-regulatory region of chick Cerberus gene (cCer) that is able to direct the expression of enhanced green fluorescent protein (eGFP) to the precursors of yolk sac blood and endothelial cells in electroporated chick embryos. Moreover, we present the Hb-eGFP reporter as a powerful live imaging tool for visualizing hemangioblast cell fate and blood island morphogenesis. We hereby introduce the Hb enhancer as a valuable resource for genetically targeting the hemangioblast population as well as for studying the dynamics of vascular and blood cell development. We used microarray analysis of Hb-eGFP expressing cells to verify the expression of hemangioblast-specific genes in this cell population. In order to characterize the gene expression profile of the Hb-eGFP-positive population, we have isolated Hb-eGFP-positive cells and compared their expression profile with the control RFP-positive population. In brief, chicken embryos were electroporated at HH3 with Hb-eGFP and pCAGGS-RFP reporter constructs, observed under a fluorescence stereoscope and harvested at stage HH5-6 into three groups of four embryos each. Embryos were dissociated into single cell suspensions and the eGFP-positive and eGFP-negative/RFP-positive cell populations were sorted by Fluorescence Activated Cell Sorting (FACS). Cell populations were collected simultaneously into two different tubes, containing RNAlater (Ambion) and subsequently used for RNA extraction. Total RNA was isolated from triplicates of each population, evaluated for RNA integrity, reverse transcribed, amplified and hybridized against six Affymetrix Chicken Genome microarrays.

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Subtractive cloning of differentially expressed genes in chick heart/hemangioblast precursor cells

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