Downregulation of STAT5 in CD34⁺ Cells Promotes Megakaryocytic Development while Activation of STAT5 Drives Erythropoiesis

¹ Department of Hematology, University of Groningen, University Medical Center Groningen, Groningen, Department of Research and Education, Sanquin Blood Bank, North East Region, Groningen, The Netherlands
² Department of Hematology, University of Groningen, University Medical Center Groningen, Groningen, The Netherlands
³ Department of Research and Education, Sanquin Blood Bank, North East Region, Groningen, The Netherlands

^* To whom correspondence should be addressed. E-mail: j.schuringa{at}int.umcg.nl.

Correspondence may also be addressed to Edo Vellenga at e.vellenga@int.umcg.nl

	Abstract

While it has been proposed that the common myeloid progenitor (CMP) gives rise to granulocyte/monocyte progenitors (GMP) and megakaryocyte/erythrocyte progenitors (MEP), little is know about molecular switches that determine whether MEPs develop into either erythrocytes or megakayocytes. We have utilized the thrombopoietin receptor c-Mpl as well as the megakaryocytic marker CD41 to optimize progenitor sorting procedures to further subfractionate the MEP (CD34⁺CD110⁺CD45RA^-) into erythroid (Ery: CD34⁺CD110⁺CD45RA^-CD41^-) and megakaryocytic (Mk: CD34⁺CD110⁺CD45RA^-CD41⁺) progenitors from peripheral blood (PB). We have identified STAT5 as a critical denominator that determined lineage commitment between erythroid and megakaryocytic cell fates. Depletion of STAT5 from CD34⁺ cells by a lentiviral RNAi approach in the presence of TPO and SCF resulted in an increase in megakaryocytic progenitors (CFU-Mk) while erythroid progenitors (BFU-E) were decreased. Furthermore, an increase in cells expressing megakaryocytic markers CD41 and CD42b was observed in STAT5 RNAi cells, as well as an increase in the percentage of polyploid cells. Reversely, overexpression of activated STAT5A(1*6) mutants severely impaired megakaryocyte development and induced a robust erythroid differentiation. Microarray and Q-PCR analysis revealed a number of gene expression changes, including GATA1, which was downmodulated by STAT5 RNAi and upregulated by activated STAT5.