Project description:T-cell Acute Lymphoblastic Leukaemia (T-ALL) can be classified into a number of subfamilies, including those that overexpress TAL1/LMO, TLX1/3 and HOXA transcription factors. Whilst it has been previously shown in mouse models that TAL1/LMO transcription factors induce thymocyte self-renewal, whether this is the case for other transcription factor subclasses is currently unknown. To address this, we have studied vav-Nup98-HoxD13-transgenic (NHD13-Tg) mice, a model of HOXA-driven T-ALL, which overexpress HOXA transcription factors throughout haematopoiesis and display features of myelodysplastic syndrome in the bone marrow along with T-cell developmental abnormalities in the thymus and subsequent development of T-ALL in approximately 15% of mice. Thymocytes from preleukemic NHD13-Tg mice could engraft long-term in serial transplantation assays, demonstrating that NHD13-Tg thymocytes have acquired self-renewal capacity. Transcriptome analysis showed that NHD13-Tg thymocytes exhibited a Stem Cell like transcriptional program which closely resembled that of Lmo2 transgenic thymocytes, including Lmo2 itself and the critical Lmo2 cofactor Lyl1, suggesting a common mechanism of thymocyte self-renewal in these models. To determine whether Lmo2/Lyl1 are required for NHD13-induced thymocyte self-renewal, NHD13-Tg mice were crossed with Lyl1 knockout mice to generate NHD13-Tg mice lacking Lyl1. This showed that Lyl1 is essential for expression of the stem cell-like gene expression program in NHD13-Tg thymocytes and for thymocyte self-renewal. Surprisingly however, absence of Lyl1 accelerated the onset of T-ALL in NHD13-Tg mice. These studies demonstrate that Lyl1 is essential for self-renewal of NHD13-Tg thymocytes, suggesting that Lmo2 and Lyl1 may mediate thymocyte self-renewal induced by a variety of T-cell oncogenes. However, whilst Lyl1-induced thymocyte self-renewal is essential for Lmo2-driven T-cell leukemia, NHD13 can also promote T-ALL via an alternative pathway.
Project description:Analysis of Lin-c-Kit+Sca-1- haematopoietic stem cells (HSCs) expressing the Nup98-HoxD13 (NHD13) fusion gene. NHD13 induces myelodysplastic syndrome (MDS) in mice. Results provide insight into the molecular basis of the myelodysplastic phenotype WT mouse HSCs were compared to an NHD13 mutant sequenced in triplicate on a HiSeq 2000
Project description:Analysis of Lin-c-Kit+Sca-1- haematopoietic stem cells (HSCs) expressing the Nup98-HoxD13 (NHD13) fusion gene. NHD13 induces myelodysplastic syndrome (MDS) in mice. Results provide insight into the molecular basis of the myelodysplastic phenotype
Project description:To determine the requirement for Lyl1 in Lmo2-driven T-ALL, microarray data was perepared from sorted CD4-CD8 double negative thymocytes of wild-type, Lmo2 transgenic and Lmo2-transgenic, Lyl1 knockout mice.
Project description:To determine the requirement for Lyl1 in Lmo2-driven T-ALL, microarray data was perepared from sorted CD4-CD8 double negative thymocytes of wild-type, Lmo2 transgenic and Lmo2-transgenic, Lyl1 knockout mice. Total RNA obtained from sorted CD4-CD8 double-negative thymocytes
Project description:Lmo2 is an oncogenic transcription factor that is a frequent target of chromosomal abnormalities in this T-cell acute lymphoblastic leukemia (T-ALL). In transgenic mouse models, overexpression of Lmo2 causes thymocyte self-renewal leading to T-cell leukemia with long latency. However, the requirement of Lmo2 for maintenance of overt leukemia is poorly understood. We found that Lyl1, a critical cofactor for Lmo2-induced leukemia, is frequently lost in cell lines derived from Lmo2-transgenic mice, raising the possibility that Lmo2 function is dispensable at this stage. To study this, we developed a Tetracycline-repressible knock-in mouse model (Vav-TRE-Lmo2), which expresses Lmo2 throughout the haematopoietic system. This led to specific effects on T-cell development and the development of T-cell leukemia with long latency, preceded by the presence of self-renewing T-cells in the thymus. Repression of Lmo2 overcame the Lmo2-induced thymocyte developmental block at the preleukemic stage and led to elimination of Lmo2-induced thymocyte self-renewal in vivo. In contrast, Lmo2 function was dispensable for the majority of overt Lmo2-induced T-cell leukemias as well as leukemia-derived cell lines, implying an evolution of oncogene addiction in the majority of T-cell leukemias. Lmo2-dependence in T-ALL was associated with an immature gene expression profile, but could not be predicted by immunophenotype or assessment of Notch pathway activation. Thus, Lmo2 can give rise to both Lmo2-depenent and –independent T-cell leukemias. The Vav-TRE-Lmo2 model should be useful to determine the molecular features associated with Lmo2-dependence, as well as the critical components of the Lmo2-induced self-renewal pathways in T-ALL.
Project description:LMO2 regulates gene expression facilitating the formation of multipartite DNA-binding complexes. In B cells, LMO2 is specifically up-regulated in the Germinal Center (GC) reaction and is expressed in GC-derived non-Hodgkin’s lymphomas. LMO2 is one of the most powerful prognostic indicators in DLBCL patients. However, its function in GC B cells and DLBCL is currently unknown. In the present study we characterized the LMO2 transcriptome and interactome in DLBCL cells. LMO2 regulates genes implicated in kinetochore function, chromosome assembly and mitosis. Overexpression of LMO2 in DLBCL cell lines results in centrosome amplification. In DLBCL, the LMO2 complex contains some of the traditional partners such as LDB1, E2A, HEB, Lyl1, ETO2 and SP1, but not TAL1 or GATA proteins. Furthermore, we identified novel LMO2 interacting partners: ELK1, NFATc1 and LEF-1 proteins. Reporter assays revealed that LMO2 increases transcriptional activity of NFATc1 and decreases transcriptional activity of LEF-1 proteins. Overall, our studies identified a novel LMO2 transcriptome and interactome in DLBCL and provide a platform for future elucidation of LMO2 function in GC B-cells and DLBCL pathogenesis. RCK8 DLBCL cell lines were stably transfected with control plasmid or plasmid+LMO2
Project description:LMO2 regulates gene expression facilitating the formation of multipartite DNA-binding complexes. In B cells, LMO2 is specifically up-regulated in the Germinal Center (GC) reaction and is expressed in GC-derived non-Hodgkin’s lymphomas. LMO2 is one of the most powerful prognostic indicators in DLBCL patients. However, its function in GC B cells and DLBCL is currently unknown. In the present study we characterized the LMO2 transcriptome and interactome in DLBCL cells. LMO2 regulates genes implicated in kinetochore function, chromosome assembly and mitosis. Overexpression of LMO2 in DLBCL cell lines results in centrosome amplification. In DLBCL, the LMO2 complex contains some of the traditional partners such as LDB1, E2A, HEB, Lyl1, ETO2 and SP1, but not TAL1 or GATA proteins. Furthermore, we identified novel LMO2 interacting partners: ELK1, NFATc1 and LEF-1 proteins. Reporter assays revealed that LMO2 increases transcriptional activity of NFATc1 and decreases transcriptional activity of LEF-1 proteins. Overall, our studies identified a novel LMO2 transcriptome and interactome in DLBCL and provide a platform for future elucidation of LMO2 function in GC B-cells and DLBCL pathogenesis.
Project description:In t(8;21) leukemic cells, the leukemogenic fusion protein AML1-ETO is stabilized and functions through the AML1-ETO-containing transcription factor complex (AETFC). Destabilization of AETFC thus provides a strategy to target AML1-ETO. In this study, we found that AETFC can be destabilized by a specific mechanism involving a direct repression of the core component LYL1 by C/EBPalpha at transcriptional level. We performed a ChIP-seq analysis of the genome-wide occupancy of C/EBPalpha and identifeid a -1 kb C/EBPalpha-binding site in the LYL1 locus that mediate this repression. As LYL1 acts as a linker between the AML1-ETO-E and LMO2-LDB1 parts of AETFC, depletion of LYL1 causes a destabilization of AETFC, which increases susceptibility of the leukemic cells to differentiation. Our results have provided a novel mechanism by which C/EBPalpha can directly destabilize AETFC, and have identified LYL1 as a new therapeutic target for treatment of t(8;21) leukemia.