Analysis on the mechanisms of growth, differentiation, and survival of megakaryocytic cells

点击翻译按钮获取中文摘要

1.To explore activation mechanism of FLT3 TKD mutation, we analysed critical tyrosine residues for the constitutive activation and downstream signaling of the mutant by generating a series of single Tyr→Phe substitution mutant of all 22 cytoplasmic tyrosine residues of murine FLT3 TKD-mutant (mFLT3Asp838Val). Tyr845Phe, Tyr892Phe and Tyr922Phe substitutions suppressed the phosphorylation of mFLT3Asp838Val itself, the activation of Erk1/2,STAT3 and STAT5, and the factor-independent cell proliferation and survival. In contrast, these three Tyr→Phe mutations partially suppressed but maintained the ligand-dependent activation and anti-apoptotic activity of wild-type FLT3, suggesting that these tyrosine residues were more critical for the constitutive activation and signaling of mFLT3Asp838Val.2.We examined the expression of cell cycle regulatory molecules during Notch- and HOXB4-induced self-renewal of hematopoietic stem cells, and found that both molecules induce the expression of c-myc. … More In addition, we determined that HOXB4 activated the c-my promoter through the element between -195 and -161 bp. We also proved that the induction of c-myc activity alone was sufficient for enhancing self-renewal of hematopoietic stem cells in the presence of appropriate cytokines using Myc/ERT, which reveals c-myc activity in response to 4-hydroxytamoxifen. These results indicated that Notch and HOXB4 induce self-renewal of hematopoietic stem cells through the induction of c-myc.3.We generated knock out mice for Anamorsin. Anamorsin^<-/-> mice are embryonic lethal due to the failure of definitive hematopoiesis in the fetal liver, Although the number of hematopoietic stem/progenitor cells in the fetal liver did not decrease in these mice, myeloid and particularly erythroid colony formation was severely disrupted. Also, Anamorsin^<-/-> erythroid cells initiated apoptosis during terminal maturation. As for the mechanism of Anamorsin-mediated cell survival, a microarray analysis revealed that the expression of Bcl-xL and Jak2 was severely impaired in the fetal liver of Anamorsin^<-/-> mice. Less