Browsing by Author "Kondo, Motonari"

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    Inflammation and the reciprocal production of granulocytes and lymphocytes in bone marrow.
    (J Exp Med, 2005-06-06) Ueda, Yoshihiro; Kondo, Motonari; Kelsoe, Garnett
    The coordinated production of leukocytes in bone marrow is crucial for innate and adaptive immunity. Inflammation alters normal leukocyte production by promoting granulopoiesis over lymphopoiesis, a response that supports the reactive neutrophilia that follows infection. Here we demonstrate that this specialization for granulopoiesis is determined by inflammation-induced reductions of growth and retention factors, most significantly stem cell factor and CXCL12, which act preferentially to inhibit lymphoid development. These hierarchical effects suggest that the normal equilibrium of leukocyte production in bone marrow is determined by lymphopoiesis' higher demand for specific growth factors and/or retention signals. Inflammation regulates this balance by reducing growth factors that have less impact on developing neutrophils than lymphocytes. We demonstrate that granulopoiesis and lymphopoiesis are coupled specifically in the bone marrow by development in a common niche and propose that the leukopoietic equilibrium is specified by limiting amounts of developmental resources.
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    Inflammation controls B lymphopoiesis by regulating chemokine CXCL12 expression.
    (J Exp Med, 2004-01-05) Ueda, Yoshihiro; Yang, Kaiyong; Foster, Sandra J; Kondo, Motonari; Kelsoe, Garnett
    Inflammation removes developing and mature lymphocytes from the bone marrow (BM) and induces the appearance of developing B cells in the spleen. BM granulocyte numbers increase after lymphocyte reductions to support a reactive granulocytosis. Here, we demonstrate that inflammation, acting primarily through tumor necrosis factor alpha (TNFalpha), mobilizes BM lymphocytes. Mobilization reflects a reduced CXCL12 message and protein in BM and changes to the BM environment that prevents homing by cells from naive donors. The effects of TNFalpha are potentiated by interleukin 1 beta (IL-1beta), which acts primarily to expand the BM granulocyte compartment. Our observations indicate that inflammation induces lymphocyte mobilization by suppressing CXCL12 retention signals in BM, which, in turn, increases the ability of IL-1beta to expand the BM granulocyte compartment. Consistent with this idea, lymphocyte mobilization and a modest expansion of BM granulocyte numbers follow injections of pertussis toxin. We propose that TNFalpha and IL-1beta transiently specialize the BM to support acute granulocytic responses and consequently promote extramedullary lymphopoiesis.
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    The Role of MEK in Leukemogenesis
    (2011) Chung, Eva

    Hematopoiesis is the continual process of blood cell generation that primarily occurs in the bone marrow of adult animals. Hematologic neoplasms can also occur in the bone marrow and often result from dysregulation of signal transduction pathways. One example is the activation of the Ras oncogene, which has been linked to a variety of different cancers, including hematologic neoplasms. Ras is located proximal to the cell membrane and can activate many downstream effector pathways, thus it is difficult to determine which downstream pathway is mediating oncogenic Ras function. My thesis work focused on the effect of inappropriate activation of MEK/ERK, a downstream Ras effector pathway, in the hematopoietic system.

    Using a retroviral transduction system, we expressed a constitutively active form of MEK1 in hematopoietic stem cells (HSCs). Mice transplanted with HSCs expressing active MEK developed a lethal myelodysplastic syndrome/myeloproliferative disease (MDS/MPN) characterized by the expansion of granulocytes/macrophages (GM) at the expense of lymphoid cell development. Transplantation of active MEK-induced MDS/MPNs into naïve mice did not result in further disease, suggesting that the MDS/MPN is not a frank leukemia.

    Bcl-2 is an anti-apoptotic molecule that has been shown to play a role in leukemia development and maintenance. Coupling expression of active MEK and Bcl-2 resulted in MDS/MPNs that were phenotypically identical and had very similar disease onset compared to active MEK-induced MDS/MPNs. However, transplantation of Bcl-2/active MEK-induced MDS/MPNs did not result in a myeloid disease; rather, it resulted in the development of T-acute lymphoblastic leukemia (T-ALL) that was marked by activated Notch signaling.

    These results led us to conclude that activation of MEK/ERK was sufficient to cause a pre-leukemic myeloid disease; however, additional oncogenic factors, such as Bcl-2 and Notch, were necessary for frank leukemia development. Moreover, additional oncogenic factors can alter the disease phenotype and disease course. Future analysis of the interplay between oncogenic factors will help shed light on disease development and aid in the development of more effective cancer treatments.