Congenital amegakaryocytic thrombocytopenia iPS cells exhibit defective MPL-mediated signaling

Abstract

Congenital amegakaryocytic thrombocytopenia (CAMT) is caused by the loss of thrombopoietin receptormediated (MPL-mediated) signaling, which causes severe pancytopenia leading to bone marrow failure with onset of thrombocytopenia and anemia prior to leukopenia. Because Mpl -/-mice do not exhibit the human disease phenotype, we used an in vitro disease tracing system with induced pluripotent stem cells (iPSCs) derived from a CAMT patient (CAMT iPSCs) and normal iPSCs to investigate the role of MPL signaling in hematopoiesis. We found that MPL signaling is essential for maintenance of the CD34 + multipotent hematopoietic progenitor (MPP) population and development of the CD41 + GPA + megakaryocyte-erythrocyte progenitor (MEP) population, and its role in the fate decision leading differentiation toward megakaryopoiesis or erythropoiesis differs considerably between normal and CAMT cells. Surprisingly, complimentary transduction of MPL into normal or CAMT iPSCs using a retroviral vector showed that MPL overexpression promoted erythropoiesis in normal CD34 + hematopoietic progenitor cells (HPCs), but impaired erythropoiesis and increased aberrant megakaryocyte production in CAMT iPSC-derived CD34 + HPCs, reflecting a difference in the expression of the transcription factor FLI1. These results demonstrate that impaired transcriptional regulation of the MPL signaling that normally governs megakaryopoiesis and erythropoiesis underlies CAMT.

Mouse prenatal platelet-forming lineages share a core transcriptional program but divergent dependence on MPL

“…[6][7][8][9][10][11][12][13][14] These mouse-based observations are consistent with the megakaryocytic and thrombocytic components of the human CAMT disorder, 30 where disease severity correlates with degree of failure of THPO/MPL signaling. 5,31,32 However, an outstanding inconsistency was that, although CAMT patients can present with TP as neonates, 5,31 the disease could also progress within the first year of life.…”

Multicolor Staining of Globin Subtypes Reveals Impaired Globin Switching During Erythropoiesis in Human Pluripotent Stem Cells

“…We have developed a coculture system with which human ESCs or iPSCs can be differentiated into multipotent hematopoietic progenitors capable of yielding megakaryocytes, erythroblasts, or lymphocytes [21][22][23]27]. Using this culture system, we first sought to generate erythroblasts from the H1 and KhES-3 hESC lines using the protocol diagrammed in Figure 1A and from human CB-CD34 + cells using the protocol diagrammed in Figure 1B.…”

Thrombocytopenia and Anemia with Anti-c-Mpl antibodies Effectively Treated with Cyclosporine in a Patient with Rheumatoid Arthritis and Chronic Renal Failure

“…In addition, we considered the diagnosis of AATP and PRCA based on the results of a bone marrow examination, which revealed the complete absence of megakaryocytes and erythro- Recently, Hirata et al analyzed induced pluripotent stem cells derived from a patient with CAMT and demonstrated that MPL signaling is indispensable for the maintenance of MPPs and for the transition from MPPs to MEPs during early hematopoiesis. The absence of functional MPL leads to deficiencies in both erythropoiesis and megakaryopoiesis, although some development of myeloid cells is retained (4). These reports suggested the possibility that, in our case, the inhibitory effect of anti-c-Mpl antibodies on MEP proliferation occurred due to the total absence of both megakaryocytes and erythroblasts.…”

“…TPO receptor c-Mpl is expressed on hematopoietic stem cells (HSCs) and progenitor cells (HPCs) (3). TPO/MPL signaling plays an important role in the maintenance and regulation of HSCs and is indispensable for the maintenance of multipotent progenitors (MPPs) and their transition to common megakaryocyte-erythrocyte progenitors (MEPs) (4). To the best of our knowledge, this is the first report of a patient with (probable) pure red cell aplasia (PRCA) with acquired amegakaryocytic thrombocytopenic purpura (AATP), a rare disorder that is characterized by thrombocytopenia causing the total absence or a marked reduction of megakaryocytes in the bone marrow (5), and which is associated with anti-cMpl antibodies.…”