Expansion of functionally defined mouse hematopoietic stem and progenitor cells by a short isoform of RUNX1/AML1.
ABSTRACT Self-renewal activity is essential for the maintenance and regeneration of the hematopoietic system. The search for molecules capable of promoting self-renewal and expanding hematopoietic stem cells (HSCs) has met with limited success. Here, we show that a short isoform (AML1a) of RUNX1/AML1 has such activities. Enforced AML1a expression expanded functionally defined HSCs, with an efficiency that was at least 20 times greater than that of the control in vivo and by 18-fold within 7 days ex vivo. The ex vivo-expanded HSCs could repopulate hosts after secondary transplantations. Moreover, AML1a expression resulted in vigorous and long-term (> 10(6)-fold at 4 weeks) ex vivo expansion of progenitor cell populations capable of differentiating into multilineages. Gene expression analysis revealed that AML1a expression was associated with up-regulation of genes, including Hoxa9, Meis1, Stat1, and Ski. shRNA-mediated silencing of these genes attenuated AML1a-mediated activities. Overall, these findings establish AML1a as an isoform-specific molecule that can influence several transcriptional regulators associated with HSCs, leading to enhanced self-renewal activity and hematopoietic stem/progenitor cell expansion ex vivo and in vivo. Therefore, the abilities of AML1a may have implications for HSC transplantation and transfusion medicine, given that the effects also can be obtained by cell-penetrating AML1a protein.
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ABSTRACT: The initial steps involved in the pathogenesis of acute leukemia are poorly understood. The TEL-AML1 fusion gene usually arises before birth, producing a persistent and covert preleukemic clone that may convert to precursor B cell leukemia following the accumulation of secondary genetic "hits". Here we show that TEL-AML1 can induce persistent self-renewing pro-B cells in mice. TEL-AML1+ cells nevertheless differentiate terminally in the long term, providing a "window" period that may allow secondary genetic "hits" to accumulate and lead to leukemia. TEL-AML1-mediated self-renewal is associated with a transcriptional program shared with embryonic stem cells (ESCs), within which Mybl2, Tgif2, Pim2 and Hmgb3 are critical and sufficient components to establish self-renewing pro-B cells. We further show that TEL-AML1 increases the number of leukemia-initiating cells that are generated in collaboration with additional genetic "hits", thus providing an overall basis for the development of novel therapeutic and preventive measures targeting the TEL-AML1-associated transcriptional program.Stem Cells 11/2012; · 7.70 Impact Factor
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ABSTRACT: Patients in the chronic phase (CP) of chronic myelogenous leukemia (CML) have been treated successfully following the advent of ABL kinase inhibitors, but once they progress to the blast crisis (BC) phase the prognosis becomes dismal. Although mechanisms underlying the progression are largely unknown, recent studies revealed the presence of alterations of key molecules for hematopoiesis, such as AML1/RUNX1. Our analysis of 13 BC cases revealed that three cases had AML1 mutations and the transcript levels of wild-type (wt.) AML1 were elevated in BC compared with CP. Functional analysis of representative AML1 mutants using mouse hematopoietic cells revealed the possible contribution of some, but not all, mutants for the BC-phenotype. Specifically, K83Q and R139G, but neither R80C nor D171N mutants, conferred upon BCR-ABL-expressing cells a growth advantage over BCR-ABL-alone control cells in cytokine-free culture, and the cells thus grown killed mice upon intravenous transfer. Unexpectedly, wt.AML1 behaved similarly to K83Q and R139G mutants. In a bone marrow transplantation assay, K83Q and wt.AML1s induced the emergence of blast-like cells. The overall findings suggest the roles of altered functions of AML1 imposed by some, but not all, mutants, and the elevated expression of wt.AML1 for the disease progression of CML.PLoS ONE 01/2013; 8(9):e74864. · 3.73 Impact Factor
- Blood 06/2013; 121(26):5252-3. · 9.06 Impact Factor