| Hematopoietic stem cells have been identified not only working in bone marrow but also circulating in peripheral blood for a long time. They circuited silently in the blood stream,inside and outside bone marrow until they could substitute bone marrow to reconstitute hematopoiesis in patients with myeloablative treatment. With development of leukopheresis equipment,this technique,now called peripheral blood stem cell transplantation(PBSCT),has been primarily performed in treating malignant hematologic diseases and now widely applied in the treatment of some solid tumors and autoimmune disorders. The advantages of PBSCT are fairly pronounced with quick reconstruction of hematopoiesis,lower incidence of infection and fatal bleeding and no anesthesia and pain caused by extraction of marrow.In spite of successful application in clinical practice,few knowledge of peripheral blood stem cell has been learned. What's difference between peripheral blood and bone marrow-derived stem cells? How do peripheral blood stem cells go out and home to bone marrow? The answers will not only benefit the transplantation but also facilitate the research of stem cell since recent studies have suggest that hematopoietic stem cells are,in addition to their hematopoietic potential,able to differentiate into nonhematopoietic cell types such as hepatocytes,cardiac muscle cells,vascular endothelial cells,and even neuronal cells.Up to now,no unique phenotype of hematopoietic stem cells can be found so that many researchers recognize hematopoietic stem cells as a group of cells containing all age hierarchies of stem cells. This group of cells has a common cell surface antigen,CD34,by which they can be isolated.There have been some findings of qualitative as well as quantitative differences in CD34+ cells,which have been shown to differ in surfacephenotype,metabolic activity,and cycling status. CD34+cells are rare in both bone marrow and peripheral blood,even though in mobilized peripheral blood,which frustrated comparison of then" cytogenetics until two groups of researchers published their papers respectively. They overcame the limited starting material by mixing CD34+ from different individuals to identify genes differentially expressed between bone marrow-derived and G-CSF-mobilized peripheral blood (GMPB) CD34+ cells by microarray.Here SMART (Switching Mechanism At 5' end of RNA Template) cDNA technology was applied to generate high yields of high-quality,double-stranded cDNA from as little as nanograms of total or poly A+ RNA. It facilitated the comparison of two groups of CD34+ cells from the same healthy donor,one of which came from bone marrow and the other from GMPB,when cDNA microarray containing about 3600 genes and subtractive suppression hybridization (SSH) were employed.One hundred clones were randomly picked from the subtractive library of SSH. Nineteen clones examined by differential screening were confirmed to be differentially expressed genes in GMPB CD34+ cells. Sequence analysis revealed that 13 of the 19 clones matched previously described genes in the GenBank database. Nine of the 13 genes were included in the up-regulated genes of GMPB CD34+ cells detected by microarray. Three sequences from the 19 clones were novel ESTs after compared with GenBank and human EST database. Another 3 sequences of the 19 clones did not match any previously reported genes but had homologous ESTs from other tissues in human EST database.There were 47 up-regulated known genes in GMPB CD34+ cells after scanned with microarray and SSH. These genes were grouped into 8 functional classifications. Sixteen up-regulated genes of transcription including RNA polymerase II and transcription factors showed that more GMPB CD34+ cells stayed at interphase since the polymerase was depressed at M phase.Four Zn finger and 2 homoebox highly expressed genes were alsoinvolved in transcription activity. And splicing next to transcription rendered 2 related genes increased expression.The gene of protein tyrosine phosphatase wi...
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