Synthetic Analysis on the mechanisms of survival and differentiation of hematopoietic cells

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1. Although leukemogenic tyrosine kinases activate common downstream molecules, the phenotypes of leukemia caused by these LTKs are distinct. In this study, we analyzed its mechanism using F1P1L1-PDGFRα(F-PRα), a causative gene of hypereosinophilic syndrome/chronic eosinophilic leukemia. When introduced into c-Kit^<high>Sca-1^+ Lineage cells (KSLs), F- PRa but not TEL-PDGFRβ (T-PRβ) enhanced the development of Gr-1^<+>IL-5Rα^<+> eosinophil progenitors(EoPs). Also, F- PRα promoted eosinophil development from common myeloid progenitors (CMPs). Furthermore, when expressed in megakaryocyte/erythrocyte progenitors (MEPs) and common lymphoid progenitors (CLPs), F-PRα aberrantly developed EoPs from MEPs and CLPs. Regarding this mechanism, RT-PCR analysis revealed that F-PRα augmented the expression of C/EBPα and GATA-2, while it reduced PU. 1 expression. Furthermore, F-PRα and its downstream Ras enhanced GATA- 2 activity, while they inhibited PU.1 activity in luciferase assays.2. We previously cloned a novel anti-apoptotic gene, Anamorsin(AM). In this study, we generated transgenic(Tg) mice for AM. Although AM Tg mice did not develop any tumors spontaneously, marked splenomegaly due to the outgrowth of B cells was observed. In addition, we found that the expression of AM was a poor prognostic factor for the special subtype of diffuse large B-cell lymphoma using immunohistochemical staining.3. We developed a long-term culture system to produce B lymphocytes from human CD34_+ cells purified from umbilical cord blood using human mesenchymal stem cells (hMSC) as stroma. Using this cocultures, we could develop 1-5 x 10^<5> CD10_+ cells from 2000 CD34_+ cells. In this system, surface IgM_+ immature B cells began to appear after 4 weeks. In addition, we found that Activin A selectively suppressed B lymphocyte production.