The Gata1^low murine megakaryocyte-erythroid progenitor cells expand robustly and alter differentiation potential

GATA1 is a master transcription factor of megakaryopoiesis and erythropoiesis, and loss-of-function mutation can induce accumulation of megakaryocyte-erythroid progenitors (MEPs) in mice and humans. Accordingly, the murine MEP cell line (termed G1ME2 cells) encoding doxycycline (dox)-inducible anti-Gata1 shRNA on Hprt locus has been developed. The cells were CD41⁺CD71⁺KIT⁺, expand under dox, stem cell factor, and thrombopoietin (TPO), and terminally differentiate into erythroid cells or megakaryocytes upon removal of dox. Surprisingly, in this study, these Gata1^low murine MEPs displayed accelerated growth from around 90-100 days after cell culture, impeded megakaryocytic potential, and maintained erythropoiesis. We specified them as late G1ME2 cells and discovered that increased CD41^-KIT⁺ population during long-term culture was the main reason for the delayed megakaryopoiesis. The CD41 expression level was partially de-repressed by PI3K/AKT inhibitors, suggesting that TPO-mediated cell survival signaling pathway might have impacted on CD41 in the late G1ME2 cells. Nevertheless, among the late cells, the CD41⁺KIT⁺ cells could still generate megakaryocytes on dox withdrawal. Taken together, G1ME2 cells could provide a good model to study molecular mechanism of hematopoiesis because of their ability to expand excessively without artificial immortalization.