RESUMEN
RUNX1 encodes a DNA binding subunit of the core-binding transcription factors and is frequently mutated in acute leukemia, therapy-related leukemia, myelodysplastic syndrome, and chronic myelomonocytic leukemia. Mutations in RUNX1 are thought to confer upon hematopoietic stem cells (HSCs) a pre-leukemic state, but the fundamental properties of Runx1 deficient pre-leukemic HSCs are not well defined. Here we show that Runx1 deficiency decreases both apoptosis and proliferation, but only minimally impacts the frequency of long term repopulating HSCs (LT-HSCs). It has been variously reported that Runx1 loss increases LT-HSC numbers, decreases LT-HSC numbers, or causes age-related HSC exhaustion. We attempt to resolve these discrepancies by showing that Runx1 deficiency alters the expression of several key HSC markers, and that the number of functional LT-HSCs varies depending on the criteria used to score them. Finally, we identify genes and pathways, including the cell cycle and p53 pathways that are dysregulated in Runx1 deficient HSCs.
Asunto(s)
Apoptosis , Biomarcadores/metabolismo , Proliferación Celular , Subunidad alfa 2 del Factor de Unión al Sitio Principal/fisiología , Células Madre Hematopoyéticas/citología , Células Madre Hematopoyéticas/metabolismo , Animales , Western Blotting , Ciclo Celular , Feto/citología , Feto/metabolismo , Citometría de Flujo , Perfilación de la Expresión Génica , Integrasas/metabolismo , Hígado/citología , Hígado/metabolismo , Ratones , Ratones Endogámicos C57BL , Ratones Noqueados , Análisis de Secuencia por Matrices de OligonucleótidosRESUMEN
Chromosomal translocations that disrupt transcriptional regulators are frequently involved in the etiology of leukemia. To gain an understanding of the normal and pathologic roles of these transcriptional regulators, both gain- and loss-of-function mutations have been examined in the context of steady-state hematopoiesis. These studies have identified a remarkable number of genes whose loss-of-function phenotype includes a perturbation of hematopoietic stem cell (HSC) proliferation. As more of these models are generated and analyzed using commonly available tools, the regulatory pathways that control HSC quiescence and proliferation are becoming clearer. An emerging theme is that leukemia-associated transcriptional regulators coordinate the balance of proliferation and quiescence within the HSC pool by modulating the number and frequency of cells transiting the cell cycle. Uncoupling proliferation from differentiation by the aberrant generation of chimeric oncogenes that retain some, but not all of the attributes of the original transcription factor is likely to be an important step during leukemogenesis.
Asunto(s)
Células Madre Hematopoyéticas/patología , Leucemia/patología , Animales , Ciclo Celular , Proliferación Celular , Homeostasis , Humanos , Mutación/genéticaRESUMEN
AML1/ETO is the chimeric protein resulting from the t(8;21) in acute myeloid leukemia. The Nervy homology 2 (NHR2) domain in ETO mediates oligomerization and AML1/ETO's interactions with ETO, MTGR1, and MTG16, and with the corepressor molecules mSin3A and HDAC1 and HDAC3. We solved the NHR2 domain structure and found it to be an alpha-helical tetramer. We show that oligomerization contributes to AML1/ETO's inhibition of granulocyte differentiation, is essential for its ability to enhance the clonogenic potential of primary mouse bone marrow cells, and affects AML1/ETO's activity on several endogenous genes. Oligomerization is also required for AML1/ETO's interactions with ETO, MTGR1, and MTG16, but not with other corepressor molecules.