Project description:Human oncogenes involved in the development of hematological malignancies have been widely used to model experimental leukemia. Here, we used the fli1 promoter in zebrafish to target the expression of oncogenic HRAS to endothelial cells, including the hemogenic endothelium and observed the development of a myelo-erythroid proliferative disease. In larvae, the pathological phenotype is characterized by some disruption of the vascular system with prominent expansion of the caudal hematopoietic tissue, increase of expression of stem cell markers and myelo-erythroid specific genes and production of a large number of l-plastin leukocytes. In mosaic juveniles, increased number of hematopoietic blasts and arrest of myeloid maturation was found in kidney marrow. Peripheral blood showed delays of erythrocyte maturation and increased number of circulating myeloid progenitors. We found that the abnormal phenotype is associated with a down regulation of the Notch pathway as shown by the decrease of expression of Notch target genes, whereas overexpressing an activated form of Notch together with the oncogene prevents the expansion of the myelo-erythroid compartment. This study identifies the downregulation of the Notch pathway following an oncogenic event in the hemogenic endothelium as an important step in the pathogenesis of myelo-erythroid diseases and describes a number of potential effectors of this transformation. Methods: mRNA profiles of transgenic zebrafish overexpressing the oncogene HRAS in endothelial cells (Tg(fli1ep:GAL4FF)ubs3; Tg(UAS:eGFP-HRASV12)io006); or expressing activate Notch in endothelial cells (Tg(fli1ep:GAL4FF)ubs3; tg(UAS:NICD)kca3) were generated by deep sequencing using Illumina HiSeq 2000. The sequence reads that passed quality filters were analyzed using the CLC bio Assembly Cell software (version 3.2) and the Ensembl (release 63) predicted cDNAs for the Zv9 genome assembly. qRTM-bM-^@M-^SPCR validation was performed using TaqMan and SYBR Green assays.
Project description:Human oncogenes involved in the development of hematological malignancies have been widely used to model experimental leukemia. Here, we used the fli1 promoter in zebrafish to target the expression of oncogenic HRAS to endothelial cells, including the hemogenic endothelium and observed the development of a myelo-erythroid proliferative disease. In larvae, the pathological phenotype is characterized by some disruption of the vascular system with prominent expansion of the caudal hematopoietic tissue, increase of expression of stem cell markers and myelo-erythroid specific genes and production of a large number of l-plastin leukocytes. In mosaic juveniles, increased number of hematopoietic blasts and arrest of myeloid maturation was found in kidney marrow. Peripheral blood showed delays of erythrocyte maturation and increased number of circulating myeloid progenitors. We found that the abnormal phenotype is associated with a down regulation of the Notch pathway as shown by the decrease of expression of Notch target genes, whereas overexpressing an activated form of Notch together with the oncogene prevents the expansion of the myelo-erythroid compartment. This study identifies the downregulation of the Notch pathway following an oncogenic event in the hemogenic endothelium as an important step in the pathogenesis of myelo-erythroid diseases and describes a number of potential effectors of this transformation.
Project description:Classical embryological studies revealed that during mid-embryogenesis vertebrates show similar morphologies. This âphylotypic stageâ has recently received support from transcriptome analyses, which have also detected similar stages in nematodes and arthropods. A conserved stage in these three phyla has led us to ask if all animals pass through a universal definitive stage as a consequence of ancestral constraints on animal development. Previous work has suggested that HOX genes may comprise such a âzootypicâ stage, however this hypothetical stage has hitherto resisted systematic analysis. We have examined the embryonic development of ten different animals each of a fundamentally different phylum, including a segmented worm, a flatworm, a roundworm, a water bear, a fruitfly, a sea urchin, a zebrafish, a sea anemone, a sponge, and a comb jelly. For each species, we collected the embryonic transcriptomes at ~100 different developmental stages and analyzed their gene expression profiles. We found dynamic gene expression across all of the species that is structured in a stage like manner. Strikingly, we found that animal embryology contains two dominant modules of zygotic expression in terms of their protein domain composition: one involving proliferation, and a second involving differentiation. The switch between these two modules involves induction of the zootype; which in addition to homeobox containing genes, also involves Wnt and Notch signaling as well as forkhead domain transcription factors. Our results provide a systematic characterization of animal universality and identify the points of embryological constraints and flexibility. 106 single embryo samples
Project description:In this study, we interrogated the role of DNA methylation in HSPC generation by taking advantage of dnmt1 knockout/knockdown embryos in zebrafish. First, we generated a comprehensive DNA methylation landscape of EHT, which revealed gradually hypermethylated regions associated with vasculogenesis. Taking advantage of dnmt1-deficient embryos, we showed that the decreased DNA methylation blocked HSPC emergence. Mechanistically, we demonstrated that the decreased DNA methylation increased the expression of arterial genes and Notch signaling, thus contributing to defects in the EHT in dnmt1-deficient embryos. Herein, we identified that DNA methylation, as epigenetic regulator, participates in the negative modulation of Notch signaling through inhibiting transcription during HSPC generation in zebrafish.
Project description:Classical embryological studies revealed that during mid-embryogenesis vertebrates show similar morphologies. This “phylotypic stage” has recently received support from transcriptome analyses, which have also detected similar stages in nematodes and arthropods. A conserved stage in these three phyla has led us to ask if all animals pass through a universal definitive stage as a consequence of ancestral constraints on animal development. Previous work has suggested that HOX genes may comprise such a ‘zootypic’ stage, however this hypothetical stage has hitherto resisted systematic analysis. We have examined the embryonic development of ten different animals each of a fundamentally different phylum, including a segmented worm, a flatworm, a roundworm, a water bear, a fruitfly, a sea urchin, a zebrafish, a sea anemone, a sponge, and a comb jelly. For each species, we collected the embryonic transcriptomes at ~100 different developmental stages and analyzed their gene expression profiles. We found dynamic gene expression across all of the species that is structured in a stage like manner. Strikingly, we found that animal embryology contains two dominant modules of zygotic expression in terms of their protein domain composition: one involving proliferation, and a second involving differentiation. The switch between these two modules involves induction of the zootype; which in addition to homeobox containing genes, also involves Wnt and Notch signaling as well as forkhead domain transcription factors. Our results provide a systematic characterization of animal universality and identify the points of embryological constraints and flexibility.