CALR frameshift mutations in MPN patient-derived iPSCs accelerate maturation of megakaryocytes

ABSTRACT: Summary Calreticulin (CALR) mutations are driver mutations in myeloproliferative neoplasms (MPNs), leading to activation of the thrombopoietin receptor and causing abnormal megakaryopoiesis. Here, we generated patient-derived CALRins5- or CALRdel52-positive induced pluripotent stem cells (iPSCs) to establish an MPN disease model for molecular and mechanistic studies. We demonstrated myeloperoxidase deficiency in granulocytic cells derived from homozygous CALR mutant iPSCs, rescued by repairing the mutation using CRISPR/Cas9. iPSC-derived megakaryocytes showed characteristics of primary megakaryocytes such as formation of demarcation membrane system and cytoplasmic pro-platelet protrusions. Importantly, CALR mutations led to enhanced megakaryopoiesis and accelerated megakaryocytic development in a thrombopoietin-independent manner. Mechanistically, our study identified differentially regulated pathways in mutated versus unmutated megakaryocytes, such as hypoxia signaling, which represents a potential target for therapeutic intervention. Altogether, we demonstrate key aspects of mutated CALR-driven pathogenesis dependent on its zygosity, and found novel therapeutic targets, making our model a valuable tool for clinical drug screening in MPNs. Graphical abstract Highlights • CALR-mutated iPSCs allow efficient modeling of human MPN disease• CRISPR-mediated repair of CALR mutations rescues normal iPSC function• Megakaryopoiesis in CALR-mutated iPSCs is hyperplastic and accelerated• Transcriptome screen of mutated megakaryocytes identifies novel therapeutic options In this article, Koschmieder and colleagues establish a novel MPN patient-specific iPSC model to investigate the impact of calreticulin (CALR) frameshift mutations in hematopoiesis. They report hyperplastic and accelerated megakaryopoiesis caused by CALR mutations. RNA sequencing of iPSC-derived megakaryocytes highlights transcriptomic differences between mutated and unmutated megakaryocytes, such as upregulation of hypoxia-related pathways.

SUBMITTER: Olschok K 

PROVIDER: S-EPMC8581168 | biostudies-literature |

REPOSITORIES: biostudies-literature