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CALR mutation-induced transcriptional changes in cord blood-derived hematopoietic stem and progenitor cells

ABSTRACT: Recurrent mutations in calreticulin (CALR) are present in 70-80% of JAK2 unmutated myeloproliferative neoplasms (MPN). Current models of CALR mutant MPNs are mainly based on cancer cell lines with ectopic overexpression or transgenic mouse models with a lack of data for primary human hematopoietic stem and progenitor cells (HSPCs) with endogenous CALR expression. Thus, we developed a CRISPR/Cas9 and AAV6-mediated knock-in approach to introduce the two most common CALR mutations (52 bp deletion, DEL; 5 bp insertion, INS) at the endogenous gene locus in human cord blood-derived HSPCs. We used these cells to investigate transcriptional changes induced upon CALR mutation acquisition in HSPCs in a prospective manner by performing RNA-sequencing 4 days after CRISPR-mediated knock-in.

ORGANISM(S): Homo sapiens

PROVIDER: GSE195705 | GEO | 2023/01/09

REPOSITORIES: GEO

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Calreticulin Ins5 and Del52 mutations impair unfolded protein and oxidative stress responses in K562 cells expressing CALR mutants.

Project description:Somatic mutations of calreticulin (CALR) have been described in approximately 30-40% of JAK2 and MPL unmutated Essential Thrombocythemia and Primary Myelofibrosis patients. CALR is an endoplasmic reticulum (ER) chaperone responsible for proper protein folding and calcium retention. Recent data demonstrated that the TPO receptor (MPL) is essential for the development of CALR mutant-driven Myeloproliferative Neoplasms (MPNs). However, the precise mechanism of action of CALR mutants haven't been fully unraveled. In this study, we showed that CALR mutants impair the ability to respond to the ER stress and reduce the activation of the pro-apoptotic pathway of the unfolded protein response (UPR). Moreover, our data demonstrated that CALR mutations induce increased sensitivity to oxidative stress, leading to increase oxidative DNA damage. We finally demonstrated that the downmodulation of OXR1 in CALR-mutated cells could be one of the molecular mechanisms responsible for the increased sensitivity to oxidative stress mediated by mutant CALR. Altogether, our data identify novel mechanisms collaborating with MPL activation in CALR-mediated cellular transformation. CALR mutants negatively impact on the capability of cells to respond to oxidative stress leading to genomic instability and on the ability to react to ER stress, causing resistance to UPR-induced apoptosis.

2019-08-04 | GSE127250 | GEO

Targeting the CALR Interactome in Myeloproliferative Neoplasms

Project description:Mutations in the endoplasmic reticulum (ER) chaperone calreticulin (CALR) are common in myeloproliferative neoplasm (MPN) patients, activate the thrombopoietin receptor (MPL), and mediate constitutive JAK/STAT signaling. The mechanisms by which CALR mutations cause myeloid transformation are incompletely defined. We employed mass spectrometry proteomics to identify novel CALR-mutant interacting proteins. Mutant CALR caused mislocalization of binding partners and increased recruitment of FLI1, ERP57 and CALR to the MPL promoter to enhance transcription. CALR 52 mutant was also found to increase genome-wide recruitment of Fli1 to the chromatin. Overall, these results show that type 1 CALR mutant modulates Fli1 cellular localization and recruitment.

2018-09-19 | GSE120134 | GEO

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

Project description:In this dataset, we compare the gene expression data of induced pluripotent stem (iPS) cell-derived CD61+ megakaryocytes carrying heterozygous or homozygous Calreticulin (CALR) ins5 mutations or the CALR wildtype gene.

2021-10-21 | GSE182479 | GEO

Whole-genome CRISPR screening identifies N-glycosylation as an essential pathway and a potential novel therapeutic target in CALR-mutant MPN (Pooled CRISPR Screen).

Project description:Calreticulin (CALR) mutations are frequent, disease-initiating events in myeloproliferative neoplasms (MPN). Although the biological mechanism by which CALR mutations cause MPN has been elucidated, there currently are no clonally selective therapies for CALR-mutant MPN. To identify unique genetic dependencies in CALR-mutant MPN, we performed a whole-genome CRISPR knockout depletion screen in mutant CALR-transformed hematopoietic cells. We found that genes in the N-glycosylation pathway (amongst others) were differentially depleted in mutant CALR-transformed cells as compared with control cells. Using a focused pharmacological screen targeting unique vulnerabilities uncovered in the CRISPR screen, we found that chemical inhibition of N-glycosylation impaired the growth of mutant CALR-transformed cells in vitro. We treated Calr-mutant knockin mice with the N-glycosylation inhibitor, 2-deoxy-glucose (2-DG), and found a preferential sensitivity of Calr-mutant cells to 2-DG as compared to wild-type cells, and a normalization of key MPN disease features. These findings advance the development of clonally selective treatments for CALR-mutant MPN.

2022-09-21 | GSE203455 | GEO

Whole-genome CRISPR screening identifies N-glycosylation as an essential pathway and a potential novel therapeutic target in CALR-mutant MPN (Whole Genome CRISPR Screen).

2022-09-21 | GSE203456 | GEO

Calreticulin Ins5 and Del52 mutations impair unfolded protein and oxidative stress responses in hematopoietic cells

Project description:Somatic mutations of calreticulin (CALR) have been described in approximately 30-40% of JAK2 and MPL unmutated essential trombocytemia and primary myelofibrosis patients. CALR is a chaperone that localizes primarily in the endoplasmic reticulum (ER) where it is responsible for the control of proper protein folding and for the calcium retention. Recent data have demonstrated that the TPO receptor (MPL) is essential for the development of CALR mutant-driven myeloproliferative neoplasms (MPNs). However, the precise mechanism of action of CALR mutants haven't been fully unraveled. In this study, we attempted to clarify whether CALR mutations may affect the functions of CALR in the ER under homeostatic conditions. Our results showed that CALR mutants impair the ability to respond to the ER stress and reduce the activation of the pro-apoptotic pathway of the unfolded protein response, therefore allowing the accumulation of unfolded proteins and conferring resistance to ER-stress induced apoptosis. Moreover, our data demonstrated that CALR mutations induce increased sensitivity to oxidative stress, reducing the ability to counteract ROS intracellular accumulation and thus leading to increase oxidative DNA damage. We finally demonstrated that the downmodulation of OXR1 in CALR-mutated cells could be one of the molecular mechanisms responsible for the increased sensitivity to oxidative stress mediated by CALR mutations. Altogether, our data identify a novel MPL-independent mechanism involved in the development of MPNs mediated by CALR mutants: CALR mutations negatively impact on the capability of cells to respond to oxidative stress, and this in turn leads to increase DNA damage and genomic instability. We used microarrays to detail the change of gene expression caused by calreticulin mutations in K562 cells

2020-08-20 | GSE102900 | GEO

Gene and miRNA expression profiles in Polycythemia Vera and Essential Thrombocythemia according to CALR and JAK2 mutations [miEP]

Project description:Polycythemia vera (PV) and essential thrombocythemia (ET) are Philadelphia-negative myeloproliferative neoplasms (MPNs) characterized by erythrocytosis and thrombocytosis, respectively. Approximately 95% of PV and 50–70% of ET patients harbour the V617F mutation in the exon 14 of JAK2 gene, while about 20-30% of ET patients carry CALRins5 or CALRdel52 mutations. These ET CARL-mutated subjects show higher platelet count and lower thrombotic risk compared to JAK2-mutated patients. Here we showed that CALR-mutated and JAK2V617F-positive CD34+ cells have different gene and miRNA expression profiles. Indeed, we highlighted several pathways differentially activated between JAK2V617F- and CALR-mutated progenitors, i.e. mTOR, MAPK/PI3K and MYC pathways. Furthermore, we unveiled that the expression of several genes involved in DNA repair, chromatin remodelling, splicing and chromatid cohesion are decreased in CALR-mutated cells. According to the low risk of thrombosis in CALR-mutated patients, we also found the down-regulation of several genes involved in thrombin signalling and platelet activation. As a whole, these data support the model in which CALR-mutated ET could be considered as a distinct disease entity from JAK2V617F-positive MPNs and may provide the molecular basis supporting the different clinical features of these patients.

2018-03-01 | GSE103238 | GEO

Gene and miRNA expression profiles in Polycythemia Vera and Essential Thrombocythemia according to CALR and JAK2 mutations [GEP]

2018-03-01 | GSE103237 | GEO

Expression data from C. elegans harboring type 1-like and type 2-like calreticulin mutations of MPN patients

Project description:There is growing evidence that Ph-negative myeloproliferative neoplasms (MPNs) are blood cancers in which multiple molecular mechanisms are significantly disturbed. Since their discovery in 2016, CALR (calreticulin) type 1 and type 2 driver mutations have been demonstrated to trigger pathogenic mechanisms apart from the well-documented activation of JAK2/MPL-related pathways affecting these diseases. C. elegans seems to be a suitable model for the study of these mechanisms since they have a CALR ortholog (crt-1) but have no JAK or MPL ortholog. We used microarrays in C. elegans strains harboring patient-like calreticulin mutations to identify JAK/MPL-independent molecular mechanisms derived from mutant calreticulin and identified a significant disruption of some of the typically altered biological processes in cancer and Ph-negative MPN patients. Finally, we compared the expression of the genes participating in these processes with a calreticulin knockout strain in order to examine if the alteration of these processes is a consequence of a gain or a loss of function of the mutant protein.

2023-01-09 | GSE201599 | GEO

CALR-mutated cells are vulnerable to combined inhibition of the proteasome and the endoplasmic reticulum stress response

Project description:Cancer is driven by somatic mutations that provide a fitness advantage. While targeted therapies often focus on the mutated gene or its direct downstream effectors, imbalances brought on by cell-state alterations may also confer unique vulnerabilities. In myeloproliferative neoplasms (MPN), somatic mutations in the calreticulin (CALR) gene are disease-initiating through aberrant binding of mutant CALR to the thrombopoietin receptor MPL and ligand-independent activation of JAK-STAT signaling. Despite these mechanistic insights into the pathogenesis of CALR-mutant MPN, there are currently no mutant CALR-selective therapies available. Here, we identified differential upregulation of unfolded and ubiquitinylated proteins, the proteasome and the ER stress response in CALR-mutant hematopoietic stem cells and megakaryocyte progenitors. We further found that combined pharmacological inhibition of the proteasome and IRE1-XBP1 axis of the ER stress response preferentially targets Calr-mutated stem and progenitors over wild-type cells in vivo, resulting in an amelioration in the MPN phenotype. Together, these findings leverage loss of proteostasis in Calr-mutant MPN to identify combinatorial dependencies that may be targeted for therapeutic benefit.

2023-10-12 | GSE207684 | GEO

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