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BACKGROUND: Hematopoietic stem cells have an ability of multi-directional differentiation and can be differentiated into megakayocytes in the presence of suitable hematopoietic growth factors and lineage special growth factors.Inducing of CD34+ stem cells to megakaryocytes in vitro involves many changes in gene expression, especially the signal transduction genes.OBJECTIVE: To study the expression of signal transduction genes after differentiation from stem cells into megakaryocytes.DESIGN: Open experiment.SETTING: Department of Tumor Immunology, Fujian Provincial Tumor Hospital.MATERIALS: 60-145 mL of cord blood was collected from normal labor fetuses under sterile conditions by using the blood-bag collective method. Patients and their relatives provided the confirmed consent. Reagents and equipments were detailed as follows: VarioMACS segregation apparatus, CD34+ Isolation Kit, SCGM serum-free medium, CD monoclonal antibodies, cytokines, human genome Oligo Set Version 2.1 from the CapitalBio Corporation, and LuxScan 10K/A bi-passage laser scanning apparatus. The researchers obtained consent from the local ethic committee.METHODS: This experiment was carried out in the Department of Tumor Immuonlogy, Fujian Provincial Tumor Hospital and the CaptialBio Corporation. from July 2005 to June 2006. RNA was extracted separately from CD34+ cells purified from cord blood and CD41+ cells induced from the same cord blood. The cDNA probes were synthesized by reverse transcription and purified. CD34+ cells before culturing and CD41+ cells after culturing were labeled with Cy3-dCTP and Cy5-dCTP respectively. Labeled DNA was dissolved in 30 μL hybridization fluid and hybridized at 42 ℃ over night MAIN OUTCOME MEASURES: The differential gene expression between haematopoietic stem cells and megakaryocytes involving cell signal transduction were detected by using DNA microarray analysis. According to the gene chip results,17 differentially expressed genes were selected for further analysis by RT-PCR.RESULTS: In this experiment, 3 522 differentially expressed genes were screened, including 1705 up-regulated genes and 1 817 down-regulated genes. In the 3 522 differentially expressed genes, there were 343 genes involved in cell signaling, 150 genes involved in transcription regulation, 21 genes involved in cell differentiation. The expression of the CD61 gene increased 369.83 fold, the expression of the CD41 gene increased 27.38 fold, and the expression of PF4 gene increased 24.06 folds; The expression of mitogen-activated protein kinases (MAPKs), G protein-coupled receptors (GPCRs) and members of RAS oncogene family increased mostly. The expression of the genes involved in STAT pathways, both SOCS1 and JAK2 were up-regulated, but STAT5A was down-regulated. As determined by the gene chip results, 17 differentially expressed genes were selected for further analysis by RT-PCR. GAPDH was used as the internal control, and RT-PCR results were in agreement and confirmed the finding from the gene chip expression results.CONCLUSION: Thrombopoeitin (TPO) and other hematopoietic growth factors may enhance the proliferation and differentiation of megakaryocytes derived from cord blood stem cells by GPCRs-Ras-MAPK pathway.