Unknown,Transcriptomics,Genomics,Proteomics

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Analysis of differential gene expression in Cebpa-positive and Cebpa-negative hematopoietic stem cells using a Cebpa-Cre EYFP reporter mouse model

ABSTRACT: C/EBPalpha is a transcription factor critically involved in myeloid development and indispensable for formation of granulocytes. To track the cellular fate of stem and progenitor (LSK) cells, which express C/EBPalpha, we developed a mouse model expressing Cre recombinase from the Cebpa promoter and an inducible EYFP allele. We show that Cebpa/EYFP+ cells represent a significant subset of LSK cells, which predominantly give rise to myeloid cells in steady state hematopoiesis. C/EBPalpha induced a robust myeloid gene expression signature and downregulated E2A-induced regulators of early lymphoid development. In addition, Cebpa/EYFP+ cells comprise a fraction of early thymic progenitors (ETP) with robust myeloid potential. However, Cebpa/EYFP+ LSK and ETP cells retained the ability to develop into erythroid and T-lymphoid lineages, respectively. These findings support an instructive, but argue against a lineage restrictive role of C/EBPalpha in multipotent hematopoietic and thymic progenitors. We performed global gene expression profiling of double-sorted Cebpa/EYFP+ and Cebpa/EYFP- LSK cells of pooled Cebpa Cre/wt R26 EYFP reporter mice to identify differentially regulated genes in Cebpa+ versus Cebpa- LSK cells. RNA was isolated from three biological replicates of Cebpa/EYFP+ LSK cells and two biological replicates of Cebpa/EYFP- LSK cells. To determine if the identified genes were truly dependent on Cebpa expression, we also performed global gene expression profilling of Cebpa/EYFP+ and Cebpa/EYFP- fetal liver LSK cells of Cebpa Cre/fl R26 EYFP mice. Induction of Cebpa/Cre expression in these mice leads to Cre-mediated recombination of the floxed wt Cebpa allele resulting in a complete Cebpa knock-out. In this case, RNA was isolated from two biological replicates of either Cebpa/EYFP+ and Cebpa/EYFP- LSK cells. In addition, we included one biological replicate of Cebpa/EYFP+ and Cebpa/EYFP- fetal liver LSK cells of Cebpa Cre/wt R26 EYFP mice to determine the correlation of differentially regulated genes in bone marrow and fetal liver LSK cells.

ORGANISM(S): Mus musculus

SUBMITTER: Albert Wölfler

PROVIDER: E-GEOD-23800 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:The CCAAT enhancer binding protein alpha (C/EBPalpha) transcription factor plays a key role in the regulation of growth and differentiation of the granulocytic lineage in the hematopoietic system and CEBPA (encoding C/EBPalpha) is often mutated or deregulated in AML patients. Consistently, mice lacking C/EBPalpha have no mature neutrophils and die within a few hours. However, homozygous knockin mice in which wild type Cebpa has been replaced with a mutant allele (BRM2), which abolish the growth-repressing ability of C/EBPalpha, are viable, but at 8 weeks of age they display myeloid dysplasia with absence of neutrophil granulocytes. Strikingly, in older CebpaBRM2/BRM2 knockin mice the myeloid dysplastic phenotype progress into other myeloid malignancies such as myeloid proliferative syndrome and acute myeloid leukemia-like malignancy. This strongly suggests that secondary mutations in other loci must occur when developing leukemia in the CebpaBRM2/BRM2. In order to identify genes that cooperate with Cebpa mutations in the development of leukemia in CebpaBRM2/BRM2 mice a so-called retroviral insertion mutagenesis screen was performed. Inbred newborn CebpaBRM2/BRM2 and wildtype mice were injected with SRS19-6 retrovirus, which incorporated into the genome and resulted in activation of oncogenes and leukemic progression. When leukemia was evident the mice were euthanized and analyzed. As expected the CebpaBRM2/BRM2 mice had a shorter latency than wildtype mice (186 vs. 276 days). The mice had enlarged spleen, thymus, and/or lymph nodes and were thoroughly investigated by histology, flow cytometry and southern in order to determine the leukemic phenotypes. Most of the CebpaBRM2/BRM2 mice developed an AML-like phenotype, whereas T cell leukemias were most prominent in wildtype mice, showing that mutating Cebpa specifically directs leukemic progression towards a myeloid direction. Genomic instability was analyzed by CGH. Finally, the retroviral insertion loci were identified through a splinkerette-aided PCR strategy. This led to the identification of several novel putative and previously unexplored oncogenes, which might collaborate with mutated Cebpa in the development of AML. Keywords: Disease state analysis

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Analysis of differential gene expression in Cebpa-positive and Cebpa-negative hematopoietic stem cells using a Cebpa-Cre EYFP reporter mouse model

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