Physiological MplW514L expression in hematopoietic stem cell causes an essential thrombocythemia and progressive myelofibrosis
Shujing Zhang, Jingjing Liu, Yuan Li, Yi Wang, Lingling Wang, Miaomiao Xu, Yanxia Li, Ge Dong, Shanshan Wang, Yanmei Li, Zhigang Cai, Baobing Zhao
Shujing Zhang, Jingjing Liu, Yuan Li, Yi Wang, Lingling Wang, Miaomiao Xu, Yanxia Li, Ge Dong, Shanshan Wang, Yanmei Li, Zhigang Cai, Baobing Zhao
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Research Article Hematology Oncology

Physiological MplW514L expression in hematopoietic stem cell causes an essential thrombocythemia and progressive myelofibrosis

Abstract

Typ515 (W515) mutations in the protein MPL are one of the key driver mutations promoting BCR-ABL-negative myeloproliferative neoplasms (MPNs), but, to our knowledge, their effects on hematopoietic stem cells (HSCs) and MPN-related hematological abnormalities have not been studied in physiological contexts. Here, we established a MplW514L knock-in mouse model, which largely mimics human MPLW515L mutation during hematopoiesis. The mutant mice developed an essential thrombocythemia–like (ET-like) MPN phenotype, displaying excess megakaryopoiesis and thrombocytosis and progressive myelofibrosis. Mechanistically, we observed that the MplW514L-conditioned HSC compartment had a unique disease-initiating capacity; however, it did not exhibit a obvious advantage of competitive repopulation over the WT control. Notably, single-cell analysis and flow cytometry profiles support that MplW514L expression led to a significant expansion of megakaryocyte-biased stem cell fate within the HSC pool. Finally, JAK2 inhibitor treatment phenotypically alleviated the ET signs but failed to eliminate the disease-initiating HSCs. These findings underscore the etiology of physiological expression of the MPLW515L mutation in HSCs and also provide a valuable in vivo model to evaluate potential therapeutic options for patients with MPLW515L-positive MPN.

Authors

Shujing Zhang, Jingjing Liu, Yuan Li, Yi Wang, Lingling Wang, Miaomiao Xu, Yanxia Li, Ge Dong, Shanshan Wang, Yanmei Li, Zhigang Cai, Baobing Zhao

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Figure 5

MplW514L mutation drove the expansion of CD201+ HSCs to initiate MPN.

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MplW514L mutation drove the expansion of CD201+ HSCs to initiate MPN. (A...
(A) Representative flow cytometric analysis of CD201+ SLAM-LSK and CD41+ SLAM-LSK cells in the bone marrow of the indicated mice at 2 months of age. (B and C) Quantification of the frequency and absolute cell number of CD201+ SLAM-LSK and CD41+ SLAM-LSK cells in A. (D) Schematic study of the biological functions of CD201+ HSCs. CD201+ HSCs were sorted from the bone marrow of MplW514L mice and their WT littermates and subjected to in vitro liquid culture and in vivo bone marrow transplantation. (E) Indicated CD201+ HSCs were cultured in TPO-containing medium for 7 days, and CD41+ cells count was detected by flow cytometry. Data were obtained from 3 different experiments. (F) Platelet parameters in peripheral blood of mice in D. A total of 2 × 103 CD201+ HSCs were sorted from the bone marrow of MplW514L mice and their WT littermates and injected into lethally irradiated CD45.1 mice, together with 5 × 105 bone marrow cells as supporting cells. The notation “donor cell population > recipient genotype” denotes the origin of donor cells and the recipient background. (G and H) Statistical analysis of CD41+ and LSK cells in the bone marrow of mice in D. (I) Representative H&E staining of bone marrow from the mice in D. Arrows indicated the megakaryocytic hyperplasia. Scale bar: 50 μm. All data are presented as mean ± SD. For dot plots, each dot represents one mouse. All P values were determined by 2-tailed unpaired Student’s t test.