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Mechanisms of platelet production and release by mammalian megakaryocytes are poorly understood. We used thrombocytopenic knockout mice to better understand these processes. Proplatelets are filamentous extensions of terminally differentiated megakaryocytes that are thought to represent one mechanism of platelet release; however, these structures have largely been recognized in cultured cells and there has been no correlation between thrombocytopoiesis in vivo and proplatelet formation. Mice lacking transcription factor NF-E2 have a late arrest in megakaryocyte maturation, resulting in profound thrombocytopenia. In contrast to normal megakaryocytes, which generate abundant proplatelets, cells from these mice never produce proplatelets, even after prolonged stimulation with c-Mpl ligand. Similarly, megakaryocytes from thrombocytopenic mice with lineage-selective loss of transcription factor GATA-1 produce proplatelets very rarely. These findings establish a significant correlation between thrombocytopoiesis and proplatelet formation and suggest that the latter represents a physiologic mechanism of platelet release. We further show that proplatelet formation by normal megakaryocytes and its absence in cells lacking NF-E2 are independent of interactions with adherent (stromal) cells. Similarly, thrombocytopenia in NF-E2(-/-) mice reflects intrinsic defects in the megakaryocyte lineage. These observations improve our understanding of platelet production and validate the study of proplatelets in probing the underlying mechanisms.

Type

Journal article

Journal

Blood

Publication Date

01/09/1998

Volume

92

Pages

1608 - 1616

Keywords

Animals, Blood Platelets, DNA-Binding Proteins, Erythroid-Specific DNA-Binding Factors, Fetal Tissue Transplantation, GATA1 Transcription Factor, Hematopoiesis, Hematopoietic Stem Cells, Liver, Liver Transplantation, Megakaryocytes, Mice, Mice, Inbred Strains, Mice, Knockout, Microscopy, Electron, Scanning, NF-E2 Transcription Factor, NF-E2 Transcription Factor, p45 Subunit, Thrombocytopenia, Transcription Factors