The Hippo pathway regulates human megakaryocytic differentiation

Inhibition of LATS kinases reduces tumorigenicity and increases the sensitivity of human chronic myelogenous leukemia cells to imatinib

Chronic myelogenous leukemia (CML) is a clonal hematologic malignancy of the myeloid lineage caused by the oncogenic BCR/ABL fusion protein that promotes CML cell proliferation and protects them against drug-induced apoptosis. In this study, we determine LATS1 and LATS2 expression in CML cells derived from patients who are resistant to imatinib (IM) treatment. Significant upregulation of LATS1 and LATS2 was found in these CML patients compared to healthy donors. To further explore whether the expression of LATS1/2 contributes to the IM-resistant phenotype, IM-resistant CML cell lines generated by culturing CML-derived erythroblastic K562 cells in increasing concentrations of IM were used as in vitro models. Up-regulation of LATS1 and LATS2 was observed in IM-resistant K562 cells. Reduction of LATS using either Lats-IN-1 (TRULI), a specific LATS inhibitor, or shRNA targeting LATS1/2 significantly reduced clonogenicity, increased apoptosis and induced differentiation of K562 cells to late-stage erythroid cells. Furthermore, depletion of LATS1 and LATS2 also increased the sensitivity of K562 cells to IM. Taken together, our results suggest that LATS could be one of the key factors contributing to the rapid proliferation, reduced apoptosis, and IM resistance of CML cells. Targeting LATS could be a promising treatment to enhance the therapeutic effect of a conventional BCR/ABL tyrosine kinase inhibitor such as IM.

Role of YAP in hematopoietic differentiation and erythroid lineage specification of human-induced pluripotent stem cells

BACKGROUND

In vitro production of hematopoietic stem/progenitor cells (HSPCs) from human-induced pluripotent stem cells (hiPSCs) provides opportunities for fundamental research, disease modeling, and large-scale production of HLA-matched HSPCs for therapeutic applications. However, a comprehensive understanding of the signaling mechanisms that regulate human hematopoiesis is needed to develop a more effective procedure for deriving HSPCs from hiPSCs.

METHODS

In this study, we investigate the role of YAP during the hematopoietic differentiation of hiPSCs to HSPCs and erythrocytes using the isogenic YAP-overexpressing (YAP-S5A) and YAP-depleting (YAP-KD) hiPSCs to eliminate the effects of a genetic background variation.

RESULTS

Although YAP is dispensable for maintaining the self-renewal and pluripotency of these hiPSCs, it affects the early cell-fate determination and hematopoietic differentiation of hiPSCs. Depleting YAP enhances the derivation efficiency of HSPCs from hiPSCs by inducing the mesodermal lineage commitment, promoting hematopoietic differentiation, and preventing the differentiation toward endothelial lineage. On the contrary, the overexpression of YAP reduced HSPCs yield by inducing the endodermal lineage commitment, suppressing hematopoietic differentiation, and promoting the differentiation toward endothelial lineage.

CONCLUSIONS

Expression of YAP is crucial for the differentiation of hiPSC-derived HSPCs toward mature erythrocytes. We believe that by manipulating YAP activity using small molecules, the efficiency of the large-scale in vitro production system for generating hematopoietic stem/progenitor cells for future therapeutic use could be improved.

Emerging role of Hippo pathway in the regulation of hematopoiesis

In various organisms, the Hippo signaling pathway has been identified as a master regulator of organ size determination and tissue homeostasis. The Hippo signaling coordinates embryonic development, tissue regeneration and differentiation, through regulating cell proliferation and survival. The YAP and TAZ (YAP/TAZ) act as core transducers of the Hippo pathway, and they are tightly and exquisitely regulated in response to various intrinsic and extrinsic stimuli. Abnormal regulation or genetic variation of the Hippo pathway causes a wide range of human diseases, including cancer. Recent studies have revealed that Hippo signaling plays a pivotal role in the immune system and cancer immunity. Due to pathophysiological importance, the emerging role of Hippo signaling in blood cell differentiation, known as hematopoiesis, is receiving much attention. A number of elegant studies using a genetically engineered mouse (GEM) model have shed light on the mechanistic and physiological insights into the Hippo pathway in the regulation of hematopoiesis. Here, we briefly review the function of Hippo signaling in the regulation of hematopoiesis and immune cell differentiation. [BMB Reports 2023; 56(8): 417-425].

Application and investigation of thrombopoiesis-stimulating agents in the treatment of thrombocytopenia

Platelets, derived from a certain subpopulation of megakaryocytes, are closely related to hemostasis, coagulation, metastasis, inflammation, and cancer progression. Thrombopoiesis is a dynamic process regulated by various signaling pathways in which thrombopoietin (THPO)-MPL is dominant. Thrombopoiesis-stimulating agents could promote platelet production, showing therapeutic effects in different kinds of thrombocytopenia. Some thrombopoiesis-stimulating agents are currently used in clinical practices to treat thrombocytopenia. The others are not in clinical investigations to deal with thrombocytopenia but have potential in thrombopoiesis. Their potential values in thrombocytopenia treatment should be highly regarded. Novel drug screening models and drug repurposing research have found many new agents and yielded promising outcomes in preclinical or clinical studies. This review will briefly introduce thrombopoiesis-stimulating agents currently or potentially valuable in thrombocytopenia treatment and summarize the possible mechanisms and therapeutic effects, which may enrich the pharmacological armamentarium for the medical treatment of thrombocytopenia.

Role of YAP as a Mechanosensing Molecule in Stem Cells and Stem Cell-Derived Hematopoietic Cells

Yes-associated protein (YAP) and WW domain-containing transcription regulator protein 1 (WWTR1, also known as TAZ) are transcriptional coactivators in the Hippo signaling pathway. Both are well-known regulators of cell proliferation and organ size control, and they have significant roles in promoting cell proliferation and differentiation. The roles of YAP and TAZ in stem cell pluripotency and differentiation have been extensively studied. However, the upstream mediators of YAP and TAZ are not well understood. Recently, a novel role of YAP in mechanosensing and mechanotransduction has been reported. The present review updates information on the regulation of YAP by mechanical cues such as extracellular matrix stiffness, fluid shear stress, and actin cytoskeleton tension in stem cell behaviors and differentiation. The review explores mesenchymal stem cell fate decisions, pluripotent stem cells (PSCs), self-renewal, pluripotency, and differentiation to blood products. Understanding how cells sense their microenvironment or niche and mimic those microenvironments in vitro could improve the efficiency of producing stem cell products and the efficacy of the products.

Carbohydrates and ginsenosides in shenmai injection jointly improve hematopoietic function during chemotherapy-induced myelosuppression in mice

Background

Shenmai injection (SMI), a traditional Chinese medicine (TCM) injection prepared from Red ginseng and Ophiopogon japonicus, is widely used in clinics to treat chemotherapy-induced myelosuppression. Similar to other TCM injections, SMI contains a high amount of carbohydrates (fructose, sucrose, and maltose) in addition to the bioactive substances, specifically ginsenosides (Rg1, Re, and Rb1). To date, the role of these carbohydrates in the hematopoietic function of SMI remains unclear.

Purpose

We aimed to investigate the hematopoietic effects and potential mechanisms of SMI and its components, focusing on the carbohydrates present in SMI.

Experimental design/methods

First, we evaluated the hematopoietic effect of SMI on 5-fluorouracil (5-FU)-induced myelotoxicity in a tumor-bearing mouse model. Then we prepared mixtures of ginsenosides and carbohydrates according to their proportions in SMI and evaluated their hematopoietic function in mice with 5-FU-induced myelosuppression. Finally, hematopoiesis-related molecular networks were built based on RNA sequencing (RNA-seq) of the bone marrow stromal cells (BMSCs), and the potential mechanisms of carbohydrates and ginsenosides were evaluated.

Results

SMI attenuated 5-FU-induced myelotoxicity in tumor-bearing mice. Both ginsenosides and carbohydrates increased the bone marrow nucleated cell (BMNC) count and improved the bone marrow morphology in myelosuppressive mice; they promoted the proliferation of BMSCs derived from those myelosuppressive mice. Bioinformatics analyses revealed ECM-receptor interaction, Hippo signaling, and Wnt signaling are common pathways regulated by both ginsenosides and carbohydrates; Gstt1, Gstp2, Gsta4 and Oplah in Glutathione metabolism pathway and Cd19, Cd79a, and Cd79b in B cell receptor pathway are uniquely regulated genes related to carbohydrates but not ginsenosides.

Conclusions

Carbohydrates may collaborate with ginsenosides and contribute to the hematopoietic function of SMI. Carbohydrates could be considered as a bioactive component in this TCM injection.

Graphical Abstract

YAP and TAZ play a crucial role in human erythrocyte maturation and enucleation

BACKGROUND

Yes-associated protein (YAP) and WW domain-containing transcription regulator protein 1 (WWTR1, also known as TAZ) are two key transcription co-activators of the Hippo pathway. Both were originally characterized as organ size and cell proliferation regulators. Later studies demonstrated that the Hippo pathway may play a role in Drosophila and mammal hematopoiesis. However, the role of the Hippo pathway in human erythropoiesis has not yet been fully elucidated.

METHODS

The role of YAP and TAZ was studied in human erythropoiesis and hematopoietic stem cell (HSC) lineage determination by using mobilized peripheral blood (PB) and cord blood (CB)-derived HSC as a model. HSCs were isolated and cultured in an erythroid differentiation medium for erythroid differentiation and culture in methylcellulose assay for HSC lineage determination study.

RESULTS

YAP and TAZ were barely detectable in human HSCs, but became highly expressed in pro-erythroblasts and erythroblasts. Depletion or knockdown of YAP and/or TAZ did not affect the ability of HSC lineage specification to erythroid lineage in either methylcellulose assay or liquid culture. However, depletion of YAP and TAZ did impair erythroblast terminal differentiation to erythrocytes and their enucleation. Moreover, ectopic expression of YAP and TAZ in pro-erythroblasts did not exert an apparent effect on erythroid differentiation, expansion, or morphology.

CONCLUSIONS

This study demonstrated that YAP/TAZ plays important role in erythroid maturation and enucleation but is dispensable for lineage determination of human HSCs.

Genomic methylation variations predict the susceptibility of six chemotherapy related adverse effects and cancer development for Chinese colorectal cancer patients

Colorectal cancer (CRC) remains a major concern with high morbidity and mortality worldwide. Despite the positive influence of chemotherapy on the decline in CRC mortality, the negative influence of chemotherapy-related adverse effects (CRAEs) caused by capecitabine (Cap) remains a challenging problem. DNA methylation alteration plays a pivotal role in gene expression regulation. Here, we aimed to screen reliable and novel biomarkers for CRC diagnosis and CRAE prediction using the advanced Illumina Infinium MethylationEPIC (850 K) BeadChip. Paired tumor and normal tissues from 21 Chinese CRC patients who received Cap-based adjuvant chemotherapy were analyzed. CRC-related methylation was characterized by hypermethylated promoter islands and hypomethylated intragenic openseas; CRAE-related methylation was characterized by hyper- (or hypo-) methylated intragenic (or intergenic) regions. Based on three types of methylation profiles (differentially methylated probes, differentially methylated regions, and gene-function-differentially methylated regions), pathway enrichment analyses revealed that CRC-related genes were significantly enriched in the neuronal system, metabolism of RNA, and extracellular matrix organization; CRAE-related genes were abundantly enriched in pathways controlling regeneration functions and immune response. Finally, based on genes within the mostly related pathways and LASSO logistic regression selection, the integrated-methylation-marker systems developed here demonstrated high discriminative accuracy in both CRC diagnosis (AUROC = 1) and CRAE prediction (AUROC = 0.817-1). In conclusion, we conducted a comprehensive DNA methylation analysis of CRC patients with chemotherapy, which provided new insights into the formation of CRC and CRAEs. Most importantly, our findings identified potentially CRAE-related metabolic pathways and markers, providing a valuable reference for personalized medicine promising better safety. Trail registration:ClinicalTrials.gov,NCT03030508, Registered 25 January 2017,https://www.clinicaltrials.gov/ct2/show/NCT03030508?term=NCT03030508&draw=2&rank=1.

A novel BLOC1S5-related HPS-11 patient and zebrafish with bloc1s5 disruption

Hermansky-Pudlak Syndrome (HPS) cases present with a variable degree of OCA and bleeding tendency. HPS is categorized into eleven types based on eleven causative genes, and disease severity varies among different types. By whole-exome sequencing performed on a family trio and Sanger sequencing of candidate variants, we identified a novel homozygous variant (NM_201280.3: c.181delC, p.Val61*) in BLOC1S5 in the patient who presents OCA and mild bleeding diathesis, and his healthy parents are heterozygous carriers. The variant can be considered pathogenic based on the guideline American College of Medical Genetics and Genomics, and the patient is proposed to be affected with HPS-11. In this study, we also explored bloc1s5 in zebrafish. bloc1s5 mRNA can be detected during early development of zebrafish. bloc1s5 knockdown zebrafish present with retinal hypopigmentation, thrombocytes loss and pericardial edema, and dll4/notch1 signaling and vascular integrity signaling are down-regulated at mRNA level in bloc1s5 morphants. The data from the first HPS-11 patient in Chinese population expand phenotypic and genotypic spectrum of HPS-11. Disruption of bloc1s5 in zebrafish recapitulates HPS-11-like phenotypes, and the potential signaling pathways associated with bloc1s5 are proposed. Altogether, this study may facilitate genetic counseling of HPS and investigation about BLOC1S5.

Metabolic sensor O-GlcNAcylation regulates megakaryopoiesis and thrombopoiesis through c-Myc stabilization and integrin perturbation

Metabolic state of hematopoietic stem cells (HSCs) is an important regulator of self‐renewal and lineage‐specific differentiation. Posttranslational modification of proteins via O‐GlcNAcylation is an ideal metabolic sensor, but how it contributes to megakaryopoiesis and thrombopoiesis remains unknown. Here, we reveal for the first time that cellular O‐GlcNAcylation levels decline along the course of megakaryocyte (MK) differentiation from human‐derived hematopoietic stem and progenitor cells (HSPCs). Inhibition of O‐GlcNAc transferase (OGT) that catalyzes O‐GlcNAcylation prolongedly decreases O‐GlcNAcylation and induces the acquisition of CD34⁺CD41a⁺ MK‐like progenitors and its progeny CD34⁻CD41a⁺/CD42b⁺ megakaryoblasts (MBs)/MKs from HSPCs, consequently resulting in increased CD41a⁺ and CD42b⁺ platelets. Using correlation and co‐immunoprecipitation analyses, we further identify c‐Myc as a direct downstream target of O‐GlcNAcylation in MBs/MKs and provide compelling evidence on the regulation of platelets by novel O‐GlcNAc/c‐Myc axis. Our data indicate that O‐GlcNAcylation posttranslationally regulates c‐Myc stability by interfering with its ubiquitin‐mediated proteasomal degradation. Depletion of c‐Myc upon inhibition of OGT promotes platelet formation in part through the perturbation of cell adhesion molecules, that is, integrin‐α4 and integrin‐β7, as advised by gene ontology and enrichment analysis for RNA sequencing and validated herein. Together, our findings provide a novel basic knowledge on the regulatory role of O‐GlcNAcylation in megakaryopoiesis and thrombopoiesis that could be important in understanding hematologic disorders whose etiology are related to impaired platelet production and may have clinical applications toward an ex vivo platelet production for transfusion.

Effect of YAP/TAZ on megakaryocyte differentiation and platelet production

Platelet transfusion is required for life-threatening thrombocytopenic bleeding, and single donor platelet concentrate is the ideal transfusion product. However, due to the inadequate number of donors that can donate a large volume of platelets, in vitro platelets production could be an alternative. We developed an in vitro production system designed to increase the platelet production yield from cultured cells. Previously, we reported that depletion of a Hippo pathway core kinase (LATS1/2) inhibited platelet production from cultured megakaryocytes. In the present study, we further investigated the role of the Hippo pathway in megakaryocyte proliferation and platelet production by focusing on the role of its effector proteins (YAP and TAZ), which are down-stream targets of LATS1/2 kinase. We found that YAP plays an essential role in megakaryoblastic cell proliferation, maturation, and platelet production, while TAZ showed minor effect. Knockdown of YAP, either by genetic manipulation or pharmaceutical molecule, significantly increased caspase-3-mediated apoptosis in cultured megakaryocytes, and increased platelet production as opposed to overexpressing YAP. We, therefore, demonstrate a paradigm for the regulation of megakaryocyte development and platelet production via the Hippo signaling pathway, and suggest the potential use of an FDA-approved drug to induce higher platelet production in cultured cells.

Association of recurrent venous thromboembolism and circulating microRNAs

BACKGROUND

Patients with unprovoked first venous thromboembolism (VTE) are at a high risk of recurrence. Although circulating microRNAs (miRNAs) have been found to be associated with VTE and are markers of hypercoagulability, this study is the first to examine whether circulating miRNAs are associated with the risk of VTE recurrence.

RESULTS

A nested case-control study design was used where plasma samples were obtained from 78 patients with unprovoked VTE from the Malmö Thrombophilia Study (MATS). A total of 39 VTE patients with recurrent VTE (cases) were matched with 39 VTE patients without recurrent VTE (controls) defined by age and sex (MATS population). Plasma levels of 179 different miRNAs were evaluated in the 78 samples (after anticoagulant treatment was stopped) using qPCR. A total of 110 miRNAs were detected in all samples. Among those, 12 miRNAs (miR-15b-5p, miR-106a-5p, miR-197-3p, miR-652-3p, miR-361-5p, miR-222-3p, miR-26b-5p, miR-532-5p, miR-27b-3p, miR-21-5p, miR-103a-3p, and miR-30c-5p) were found to be associated with recurrent VTE after multiple correction test and conditional logistic regression analysis. A further analysis showed that miR-15b-5p, miR-197-3p, miR-27b-3p, and miR-30c-5p exhibited a trend over time, with a larger difference in miRNA levels between cases and controls for earlier recurrence. Of these 12 miRNAs, 8 miRNAs significantly correlated with circulating transforming growth factor β1/2 (TGFβ1/2). Three of them correlated with platelet count.

CONCLUSION

We have identified 12 plasma miRNAs that may have the potential to serve as novel, non-invasive predictive biomarkers for VTE recurrence.