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Updated: Jul 13, 2026
Transduction-Transplantation Mouse Model of Myeloproliferative Neoplasm
Published on: December 22, 2016
Evidence for MPL W515L/K mutations in hematopoietic stem cells in primitive myelofibrosis
Ronan Chaligné1, Chloé James, Carole Tonetti
1Institut National de la Santé et de la Recherche Médicale (INSERM), U790, Université Paris XI, Institut Gustave Roussy, Villejuif, France.
Abstract:
The MPL (W515L and W515K) mutations have been detected in granulocytes of patients suffering from certain types of primitive myelofibrosis (PMF). It is still unknown whether this molecular event is also present in lymphoid cells and therefore potentially at the hematopoietic stem cell (HSC) level. Toward this goal, we conducted MPL genotyping of mature myeloid and lymphoid cells and of lymphoid/myeloid progenitors isolated from PMF patients carrying the W515 mutations. We detected both MPL mutations in granulocytes, monocytes, and platelets as well as natural killer (NK) cells but not in T cells. B/NK/myeloid and/or NK/myeloid CD34(+)CD38(-)-derived clones were found to carry the mutations. Long-term reconstitution of MPL W515 CD34(+) cells in nonobese diabetic/severe combined immunodeficient (NOD/SCID) mice was successful for as long as 12 weeks after transplantation, indicating that MPL W515 mutations were present in HSCs. Moreover, the 2 MPL mutations induced a spontaneous megakaryocytic growth in culture with an overall normal response to thrombopoietin (TPO). In contrast, erythroid progenitors remained EPO dependent. These results demonstrate that in PMF, the MPL W515L or K mutation induces a spontaneous megakaryocyte (MK) differentiation and occurs in a multipotent HSCs.
Insights
The MPL W515 mutations in primitive myelofibrosis (PMF) are present in hematopoietic stem cells (HSCs), driving spontaneous megakaryocyte differentiation.
Area of Science:
- Hematology
- Molecular Biology
- Stem Cell Research
Background:
- Mutations in the MPL gene, specifically W515L and W515K, are found in granulocytes of patients with primitive myelofibrosis (PMF).
- The presence of these MPL mutations at the hematopoietic stem cell (HSC) level and in lymphoid cells remains uncharacterized.
Purpose of the Study:
- To investigate the presence of MPL W515 mutations in various cell types, including lymphoid cells and HSCs, from PMF patients.
- To determine the functional consequences of MPL W515 mutations on hematopoietic stem and progenitor cells in vitro and in vivo.
Main Methods:
- MPL genotyping of mature myeloid and lymphoid cells, as well as lymphoid/myeloid progenitors, isolated from PMF patients with W515 mutations.
- Analysis of CD34(+)CD38(-) progenitor clones for MPL mutation carriage.
- Long-term transplantation of MPL W515-mutated CD34(+) cells into NOD/SCID mice.
- In vitro culture of mutated cells to assess megakaryocytic and erythroid progenitor responses.
Main Results:
- MPL W515 mutations were detected in granulocytes, monocytes, platelets, and natural killer (NK) cells, but not in T cells.
- Mutations were found in B/NK/myeloid and NK/myeloid CD34(+)CD38(-) progenitor clones, indicating HSC involvement.
- MPL W515-mutated HSCs successfully reconstituted mice for up to 12 weeks post-transplantation.
- MPL W515 mutations induced spontaneous megakaryocytic growth in culture, with normal thrombopoietin (TPO) response, while erythroid progenitors remained EPO dependent.
Conclusions:
- The MPL W515L or K mutation in PMF originates in multipotent HSCs.
- These mutations drive spontaneous megakaryocyte differentiation and contribute to the pathogenesis of PMF.
