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 4

MplW514L mutation enhanced megakaryocyte lineage commitment in hematopoietic stem cells.

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MplW514L mutation enhanced megakaryocyte lineage commitment in hematopoi...
(A) The UMAP visualization of all cells from the scRNA-seq datasets from young (2 months) and old (10 months) MplW514L mice and their WT littermates (n = 19,190 cells). (B) The stacked bar chart showed the proportions of each cluster in A excluding EryP1 and EryP2. Red arrows highlight the increased populations of young MplW514L mice compared with young WT control. (C) UMAP-based feature plots illustrated the expression levels of selected genes at single-cell resolution. (D) Gene pairwise Spearman correlation within the CD201_HSC. The heatmaps show increased expression of MkP-associated gene modules. (E) Enriched pathways of upregulated genes in CD201_HSCs compared with canonical HSC subpopulation. (F) Developmental trajectories of HSC, CD201_HSC, MEP, and MkP cells by Monocle (v2&v3). UMAP-based trajectory plot showing the differentiation progression of indicated cell populations, in which darker colors represent early differentiation stages and lighter colors indicate later stages (Left). Pseudotime-based dimension reduction plot, where arrows denote the inferred direction of cellular differentiation (Right).