Myeloproliferative neoplasm-driving Calr frameshift promotes the development of pulmonary hypertension in mice

Abstract

Frameshifts in the Calreticulin (CALR) exon 9 provide a recurrent driver mutation of essential thrombocythemia (ET) and primary myelofibrosis among myeloproliferative neoplasms (MPNs). Here, we generated knock-in mice with murine Calr exon 9 mimicking the human CALR mutations, using the CRISPR-Cas9 method. Knock-in mice with del10 [Calrdel10/WT (wild−type) mice] exhibited an ET phenotype with increases of peripheral blood (PB) platelets and leukocytes, and accumulation of megakaryocytes in bone marrow (BM), while those with ins2 (Calrins2/WT mice) showed a slight splenic enlargement. Phosphorylated STAT3 (pSTAT3) was upregulated in BM cells of both knock-in mice. In BM transplantation (BMT) recipients from Calrdel10/WT mice, although PB cell counts were not different from those in BMT recipients from CalrWT/WT mice, Calrdel10/WT BM-derived macrophages exhibited elevations of pSTAT3 and Endothelin-1 levels. Strikingly, BMT recipients from Calrdel10/WT mice developed more severe pulmonary hypertension (PH)—which often arises as a comorbidity in patients with MPNs—than BMT recipients from CalrWT/WT mice, with pulmonary arterial remodeling accompanied by an accumulation of donor-derived macrophages in response to chronic hypoxia. In conclusion, our murine model with the frameshifted murine Calr presented an ET phenotype analogous to human MPNs in molecular mechanisms and cardiovascular complications such as PH.

Impaired Repopulating Ability of Uhrf2−/− Hematopoietic Progenitor Cells in Mice

“…Mouse hematopoietic cells were prepared, as described previously [ 12 , 13 ]. Briefly, peripheral blood cells of mice were drawn from the tail vein and counted by XT-1800i (Sysmex, Kobe, Japan).…”

Cellular carcinogenesis in preleukemic conditions:drivers and defenses

“…Functional analysis of the CALR mutant, which is the second most frequent driver mutation in MPNs, has been insufficient, especially regarding its collaboration with other mutations. Recently, we generated Calr -del10 mice that lack 10 base pairs in exon 9 of Calr , mimicking type2-like CALR mutation in MPN patients; these mice presented mild phenotypes of MPN 98) . Our preliminary data have shown that addition of Hmga2 -Tg to Calr -del10 evokes progression of MPN phenotypes but not myelofibrosis or leukemic transformation, while deletion of Ezh2 can provoke myelofibrosis or leukemic transformation after a long latency.…”

Novel insights and new therapeutic potentials for macrophages in pulmonary hypertension

“…Specific pathological features, such as fibrosis alterations, can be detected via histopathological assessment at the early stage of PH progression [ 3 ]. Both external and internal stimuli, such as genetic mutations, hypoxia, cold exposure, air pollution, and respiratory infection, can initiate immune responses and therefore lead to the proliferation of vascular cells, autoantibody formation, and dysregulated immunity [ 16 – 20 ]. Histopathological evidence has suggested that perivascular infiltration of inflammatory cells is common in PH and precedes structural remodelling in vessels [ 5 , 6 , 17 , 21 , 22 ].…”