STAT5-Induced Self-Renewal and Impaired Myelopoiesis of Human Hematopoietic Stem/Progenitor Cells Involves Downmodulation of C/EBPα
| Autor: | Edo Vellenga, Malcolm A.S. Moore, Hein Schepers, Bart-Jan Wierenga, Jan Jacob Schuringa |
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| Rok vydání: | 2005 |
| Předmět: | |
| Zdroj: | Blood. 106:268-268 |
| ISSN: | 1528-0020 0006-4971 |
| DOI: | 10.1182/blood.v106.11.268.268 |
| Popis: | Previously, we demonstrated that enforced activation of STAT5 in human cord blood (CB)-derived stem/progenitor cells results in enhanced long-term stem cell self-renewal and impaired myelopoiesis (J.J.Schuringa et al, J.Exp.Med. 2004;200:623). Now, C/EBPα was identified as a critical transcription factor that is downregulated by STAT5. Affymetrix microarray analysis on STAT5A(1*6)-transduced CD34+ cells identified C/EBPα as the most prominently downregulated gene (−3.3 fold), and these data were confirmed by RT-PCR and Western blotting. To determine the cell-biological relevance of these observations, a 4-OHT-inducible C/EBPα-ER protein was co-expressed with the STAT5A(1*6) mutant in CB CD34+ cells by using a retroviral approach. Re-expression of C/EBPα in STAT5A(1*6) cells resulted in a marked restoration of myelopoiesis as determined by morphological analyses, FACS analyses for myeloid markers such as CD11b, CD14 and CD15, and RT-PCR for myeloid-restricted genes such as g-csfr. While enforced activation of STAT5A resulted in accelerated erythropoiesis, this was blocked when C/EBPα was re-introduced into STAT5A(1*6) cells. Similarly, the proliferative advantage imposed on CD34+ cells by STAT5A(1*6) depended on the downmodulation of C/EBP as reintroduction of C/EBPα in these cells induced a quick cell cycle arrest and the onset of myeloid differentiation. At the stem/progenitor cell level, LTC-IC frequencies were elevated from 0.5% to 11% by STAT5A(1*6) as compared to controls, but these elevated LTC-IC frequencies were strongly reduced when C/EBPα was reintroduced in STAT5A(1*6) cells. Enumeration of progenitors in methylcellulose assays revealed similar results, the number of CFCs was reduced over 10-fold when C/EBPα was expressed in STAT5A(1*6) cells. Also, secondary CAFCs and long-term cultures could only be generated from STAT5A(1*6) expressing cells, but not from cells that co-expressed STAT5A(1*6) and C/EBPα. Taken together, these data indicate that STAT5-induced self-renewal and impaired myelopoiesis involves downmodulation of C/EBPα. |
| Databáze: | OpenAIRE |
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