Calreticulin signaling in health and disease

CALR, JAK2 and MPL mutation status in Argentinean patients with BCR-ABL1- negative myeloproliferative neoplasms

OBJECTIVES

To establish the frequency of JAK2, MPL and CALR mutations in Argentinean patients with BCR-ABL1-negative  myeloproliferative neoplasms (MPN) and to compare their clinical and haematological features.

METHODS

Mutations of JAK2V617F, JAK2 exon 12, MPL W515L/K and CALR were analysed in 439 Argentinean patients with BCR-ABL1-negative MPN, including 176 polycythemia vera (PV), 214 essential thrombocythemia (ET) and 49 primary myelofibrosis (PMF).

RESULTS

In 94.9% of PV, 85.5% ET and 85.2% PMF, we found mutations in JAK2, MPL or CALR. 74.9% carried JAK2V617F, 12.3% CALR mutations, 2.1% MPL mutations and 10.7% were triple negative. In ET, nine types of CALR mutations were identified, four of which were novel. PMF patients were limited to types 1 and 2, type 2 being more frequent.

DISCUSSION

In ET, patients with CALR mutation were younger and had higher platelet counts than those with JAK2V617F and triple negative. In addition, JAK2V617F patients had high leucocyte and haemoglobin values compared with CALR-mutated and triple-negative patients. In PMF, patients with mutant CALR were associated with higher platelet counts.

CONCLUSION

Our study underscores the importance of JAK2, MPL and CALR genotyping for accurate diagnosis of patients with BCR-ABL1-negative MPN.

Functional Analysis and Marker Development of TaCRT-D Gene in Common Wheat (Triticum aestivum L.)

Calreticulin (CRT), an endoplasmic reticulum (ER)-localized Ca2+-binding/buffering protein, is highly conserved and extensively expressed in animal and plant cells. To understand the function of CRTs in wheat (Triticum aestivum L.), particularly their roles in stress tolerance, we cloned the full-length genomic sequence of the TaCRT-D isoform from D genome of common hexaploid wheat, and characterized its function by transgenic Arabidopsis system. TaCRT-D exhibited different expression patterns in wheat seedling under different abiotic stresses. Transgenic Arabidopsis plants overexpressing ORF of TaCRT-D displayed more tolerance to drought, cold, salt, mannitol, and other abiotic stresses at both seed germination and seedling stages, compared with the wild-type controls. Furthermore, DNA polymorphism analysis and gene mapping were employed to develop the functional markers of this gene for marker-assistant selection in wheat breeding program. One SNP, S440 (T→C) was detected at the TaCRT-D locus by genotyping a wheat recombinant inbred line (RIL) population (114 lines) developed from Opata 85 × W7984. The TaCRT-D was then fine mapped between markers Xgwm645 and Xgwm664 on chromosome 3DL, corresponding to genetic distances of 3.5 and 4.4 cM, respectively, using the RIL population and Chinese Spring nulli-tetrasomic lines. Finally, the genome-specific and allele-specific markers were developed for the TaCRT-D gene. These findings indicate that TaCRT-D function importantly in plant stress responses, providing a gene target for genetic engineering to increase plant stress tolerance and the functional markers of TaCRT-D for marker-assistant selection in wheat breeding.

JAK-STAT signaling in the therapeutic landscape of myeloproliferative neoplasms

Myeloproliferative neoplasms (MPN) are a group of disorders defined by clonal proliferation of mature myeloid cells with overlapping clinical features. The driver mutations of these disorders, namely JAK2 (Janus Kinase), MPL (Myeloproliferative Leukaemia Virus) and CALR (Calreticulin) upregulate JAK-STAT signaling with increase in downstream transcription and gene expression. Epigenetic mutations are prevalent in MPNs but their interplay with aberrant JAK-STAT signaling is not known. This understanding lead to development of first targeted treatment in MPN; ruxolitinib for primary myelofibrosis. This has shown clinical benefit in overall survival and symptoms improvement but has yet to show significant disease modifying effects. This review will focus on contemporaneous understanding of altered JAK-STAT signaling in MPN and targeted treatments in clinical practice.

Calreticulin regulates TGF-β1-induced epithelial mesenchymal transition through modulating Smad signaling and calcium signaling

As a Ca²⁺ binding protein, calreticulin (CRT) has many functions and plays an important role in a variety of tumors. The role of CRT in TGF-β1-induced EMT is unknown. In this study, we demonstrated in vitro that TGF-β1-induced EMT elevated the expression of CRT in A549 lung cancer cells. Subsequently, we confirmed that overexpression CRT had no capacity to induce A549 cells EMT alone, but successfully enhanced TGF-β1-induced-EMT. Furthermore, knockdown of CRT in A549 cells significantly suppressed changes of EMT marks expression induced by TGF-β1. On treatment with TGF-β1, overexpression of CRT could enhance the phosphorylation of both Smad2 and Smad3. Consistently, the knockdown of CRT by siRNA-CRT could inhibit Smad signaling pathway activated by TGF-β1. These results indicated that CRT regulates EMT induced by TGF-β1 through Smad signaling pathway. Finally, TGF-β1-induced-EMT enhanced store-operated Ca²⁺ influx in A549 cells. CRT knockdown was able to abolish the effect of TGF-β1 on thapsigargin (TG) -induced Ca²⁺ release, but had failed to reduce store-operated Ca²⁺ influx. The alteration of intracellular Ca²⁺ concentration by TG or BAPTA-AM was able to regulate EMT induced by TGF-β1 through Smad signaling pathway. Together, these data identify that CRT regulates TGF-β1-induced-EMT through modulating Smad signaling. Furthermore, TGF-β1-induced-EMT is highly calcium-dependent, CRT was partly involved in it.

Calcium signaling and cell cycle: Progression or death

Cytosolic Ca²⁺ concentration levels fluctuate in an ordered manner along the cell cycle, in line with the fact that Ca²⁺ is involved in the regulation of cell proliferation. Cell proliferation should be an error-free process, yet is endangered by mistakes. In fact, a complex network of proteins ensures that cell cycle does not progress until the previous phase has been successfully completed. Occasionally, errors occur during the cell cycle leading to cell cycle arrest. If the error is severe, and the cell cycle checkpoints work perfectly, this results into cellular demise by activation of apoptotic or non-apoptotic cell death programs. Cancer is characterized by deregulated proliferation and resistance against cell death. Ca²⁺ is a central key to these phenomena as it modulates signaling pathways that control oncogenesis and cancer progression. Here, we discuss how Ca²⁺ participates in the exogenous and endogenous signals controlling cell proliferation, as well as in the mechanisms by which cells die if irreparable cell cycle damage occurs. Moreover, we summarize how Ca²⁺ homeostasis remodeling observed in cancer cells contributes to deregulated cell proliferation and resistance to cell death. Finally, we discuss the possibility to target specific components of Ca²⁺ signal pathways to obtain cytostatic or cytotoxic effects.

Endoplasmic reticulum chaperones tweak the mitochondrial calcium rheostat to control metabolism and cell death

The folding of secretory proteins is a well-understood mechanism, based on decades of research on endoplasmic reticulum (ER) chaperones. These chaperones interact with newly imported polypeptides close to the ER translocon. Classic examples for these proteins include the immunoglobulin binding protein (BiP/GRP78), and the lectins calnexin and calreticulin. Although not considered chaperones per se, the ER oxidoreductases of the protein disulfide isomerase (PDI) family complete the folding job by catalyzing the formation of disulfide bonds through cysteine oxidation. Research from the past decade has demonstrated that ER chaperones are multifunctional proteins. The regulation of ER-mitochondria Ca²⁺ crosstalk is one of their additional functions, as shown for calnexin, BiP/GRP78 or the oxidoreductases Ero1α and TMX1. This function depends on interactions of this group of proteins with the ER Ca²⁺ handling machinery. This novel function makes perfect sense for two reasons: i. It allows ER chaperones to control mitochondrial apoptosis instantly without a lengthy bypass involving the upregulation of pro-apoptotic transcription factors via the unfolded protein response (UPR); and ii. It allows the ER protein folding machinery to fine-tune ATP import via controlling the speed of mitochondrial oxidative phosphorylation. Therefore, the role of ER chaperones in regulating ER-mitochondria Ca²⁺ flux identifies the progression of secretory protein folding as a central regulator of cell survival and death, at least in cell types that secrete large amount of proteins. In other cell types, ER protein folding might serve as a sentinel mechanism that monitors cellular well-being to control cell metabolism and apoptosis. The selenoprotein SEPN1 is a classic example for such a role. Through the control of ER-mitochondria Ca²⁺-flux, ER chaperones and folding assistants guide cellular apoptosis and mitochondrial metabolism.

Assessing the thrombotic risk of patients with essential thrombocythemia in the genomic era

The molecular characterization of myeloproliferative neoplasms, including essential thrombocythemia (ET), has enabled deeper understanding of their pathogenesis. A driver lesion, namely, Janus kinase (JAK)2V617F, calreticulin (CALR) or myeloproliferative leukemia (MPL) gene mutation can be identified in the vast majority of patients. Each of these mutations is associated with distinct clinical features and may modulate the patients' clinical course, risk of complications, including vascular events, and survival. JAK2V617F appears to be a risk-modifying mutation and has been shown to increase the likelihood of thrombotic events in patients with ET across studies. As such, it has been included in prognostic models and its presence may influence treatment decisions. The association of CALR and MPL mutations with the incidence of vascular events has been less clear. Even more limited information is available on the contribution of additional non-driver lesions to the thrombotic risk. In this review we discuss the available evidence on the role of recurrent mutations in the risk of thrombotic complications in patients with ET and how these mutations weigh into modern prognostic scores.

Calreticulin Is Required for TGF-β-Induced Epithelial-to-Mesenchymal Transition during Cardiogenesis in Mouse Embryonic Stem Cells

Calreticulin, a multifunctional endoplasmic reticulum resident protein, is required for TGF-β-induced epithelial-to-mesenchymal transition (EMT) and subsequent cardiomyogenesis. Using embryoid bodies (EBs) derived from calreticulin-null and wild-type (WT) embryonic stem cells (ESCs), we show that expression of EMT and cardiac differentiation markers is induced during differentiation of WT EBs. This induction is inhibited in the absence of calreticulin and can be mimicked by inhibiting TGF-β signaling in WT cells. The presence of calreticulin in WT cells permits TGF-β-mediated signaling via AKT/GSK3β and promotes repression of E-cadherin by SNAIL2/SLUG. This is paralleled by induction of N-cadherin in a process known as the cadherin switch. We show that regulated Ca2+ signaling between calreticulin and calcineurin is critical for the unabated TGF-β signaling that is necessary for the exit from pluripotency and the cadherin switch during EMT. Calreticulin is thus a key mediator of TGF-β-induced commencement of cardiomyogenesis in mouse ESCs.

A novel signalling screen demonstrates that CALR mutations activate essential MAPK signalling and facilitate megakaryocyte differentiation

Most myeloproliferative neoplasm (MPN) patients lacking JAK2 mutations harbour somatic CALR mutations that are thought to activate cytokine signalling although the mechanism is unclear. To identify kinases important for survival of CALR-mutant cells, we developed a novel strategy (KISMET) that utilizes the full range of kinase selectivity data available from each inhibitor and thus takes advantage of off-target noise that limits conventional small-interfering RNA or inhibitor screens. KISMET successfully identified known essential kinases in haematopoietic and non-haematopoietic cell lines and identified the mitogen activated protein kinase (MAPK) pathway as required for growth of the CALR-mutated MARIMO cells. Expression of mutant CALR in murine or human haematopoietic cell lines was accompanied by myeloproliferative leukemia protein (MPL)-dependent activation of MAPK signalling, and MPN patients with CALR mutations showed increased MAPK activity in CD34 cells, platelets and megakaryocytes. Although CALR mutations resulted in protein instability and proteosomal degradation, mutant CALR was able to enhance megakaryopoiesis and pro-platelet production from human CD34+ progenitors. These data link aberrant MAPK activation to the MPN phenotype and identify it as a potential therapeutic target in CALR-mutant positive MPNs.

Association of calreticulin expression with disease activity and organ damage in systemic lupus erythematosus patients

Measurement of disease activity in patients with systemic lupus erythematosus (SLE) is important for monitoring disease progression and evaluating the therapeutic effects. The severity of organ damage correlates with clinical status and prognosis. Therefore, it is imperative to find an effective biomarker measuring disease activity and organ damage for SLE management. The present study investigated the possibility of serum calreticulin (CRT) in the assessment of disease activity and organ damage in SLE patients. Serum CRT levels from 80 patients with SLE, 55 patients with other autoimmune diseases and 60 healthy controls (HC) were measured by ELISA. Disease activity was assessed using the Systemic Lupus Erythematosus Disease Activity Index 2000 (SLEDAI-2K) scores. Organ damage was evaluated with the Systemic Lupus International Collaborating Clinics/American College of Rheumatology Damage Index. CRT levels in SLE were significantly higher than that in other autoimmune diseases and HC. CRT was correlated with SLEDAI-2K score (r=0.3345, P=0.0024), and with anti-double-stranded DNA (anti-dsDNA) (r=0.4483, P<0.0001). A significant negative correlation of CRT levels with complement 3 (r=-0.3635, P=0.0009) and complement 4 (r=-0.3507, P=0.0014) was observed in patients with SLE. Furthermore, the patients with SLE and a positive anti-Ro52 result had higher levels of CRT compared with those with a negative anti-Ro52 result (P<0.001). Elevated levels of CRT were also reported among patients with SLE who also indicated the presence of cumulative organ damage. In addition, increased expression of CRT correlated with the presence of lupus nephritis. In conclusion, the results of the current report provided that CRT may be used as a potential biomarker for clinical diagnosis and of prognosis, providing additional information regarding disease activity and organ damage alongside other traditional indices.

The nerve growth factor alters calreticulin translocation from the endoplasmic reticulum to the cell surface and its signaling pathway in epithelial ovarian cancer cells

Ovarian cancer is the seventh most common cancer among women worldwide, causing approximately 120,000 deaths every year. Immunotherapy, designed to boost the body's natural defenses against cancer, appears to be a promising option against ovarian cancer. Calreticulin (CRT) is an endoplasmic reticulum (ER) resident chaperone that, translocated to the cell membrane after ER stress, allows cancer cells to be recognized by the immune system. The nerve growth factor (NGF) is a pro-angiogenic molecule overexpressed in this cancer. In the present study, we aimed to determine weather NGF has an effect in CRT translocation induced by cytotoxic and ER stress. We treated A2780 ovarian cancer cells with NGF, thapsigargin (Tg), an ER stress inducer and mitoxantrone (Mtx), a chemotherapeutic drug; CRT subcellular localization was analyzed by immunofluorescence followed by confocal microscopy. In order to determine NGF effect on Mtx and Tg-induced CRT translocation from the ER to the cell membrane, cells were preincubated with NGF prior to Mtx or Tg treatment and CRT translocation to the cell surface was determined by flow cytometry. In addition, by western blot analyses, we evaluated proteins associated with the CRT translocation pathway, both in A2780 cells and human ovarian samples. We also measured NGF effect on cell apoptosis induced by Mtx. Our results indicate that Mtx and Tg, but not NGF, induce CRT translocation to the cell membrane. NGF, however, inhibited CRT translocation induced by Mtx, while it had no effect on Tg-induced CRT exposure. NGF also diminished cell death induced by Mtx. NGF effect on CRT translocation could have consequences in immunotherapy, potentially lessening the effectiveness of this type of treatment.

Cigarette smoke extract promotes proliferation of airway smooth muscle cells through suppressing C/EBP-α expression

Cigarette smoke has been considered a major contributor to the pathogenesis of chronic obstructive pulmonary disease (COPD). In COPD patients, the airway smooth muscle layer has been observed to be markedly thickened and the proliferation of airway smooth muscle cells (ASMCs) was therefore used by the present study as a model to assess the impact of cigarette smoke extract (CSE). ASMCs were exposed to various concentrations of CSE and the proliferation of the cells was analyzed by an MTT assay. Furthermore, the expression levels of calreticulin and CCAAT/enhancer-binding protein alpha (C/EBP-α) in CSE-stimulated ASMCs were determined by polymerase chain reaction and western blot analyses. In addition, the effects of RNA interference (RNAi) to knockdown calreticulin and/or C/EBP-α on ASMC proliferation were studied. CSE was found to promote the proliferation of ASMCs, which was associated with increased expression of calreticulin and decreased expression of C/EBP-α. Knockdown of calreticulin resulted in the upregulation of C/EBP-α and inhibition of cell proliferation, while simultaneous knockdown of C/EBP-α promoted cell proliferation. The present study revealed that CSE promoted the proliferation of ASMCs, which was mediated by inhibition of C/EBP-α. These findings shed new light on airway remodeling in COPD and may provide novel approaches for therapies.

Mutations in MPNs: prognostic implications, window to biology, and impact on treatment decisions

The last decade has witnessed tremendous scientific advances, ushered in by the JAK2 V617F discovery, contributing to enhanced diagnostic capability and understanding of the biology of myeloproliferative neoplasms (MPNs). Discovery of the calreticulin mutations filled a diagnostic gap; more recent work sheds light on its contribution to disease pathogenesis, and prognosis. Recent studies have also identified novel JAK2 and MPL mutations in patients with essential thrombocythemia and myelofibrosis (MF). Especially in MF, the driver mutational profile has prognostic implications, with additive contributions from the acquisition of additional somatic mutations. The hope is that sophisticated molecular profiling will not only aid in prognostication, but also guide selection of therapy for patients with MPNs.

Mutations in MPNs: prognostic implications, window to biology, and impact on treatment decisions

The last decade has witnessed tremendous scientific advances, ushered in by the JAK2 V617F discovery, contributing to enhanced diagnostic capability and understanding of the biology of myeloproliferative neoplasms (MPNs). Discovery of the calreticulin mutations filled a diagnostic gap; more recent work sheds light on its contribution to disease pathogenesis, and prognosis. Recent studies have also identified novel JAK2 and MPL mutations in patients with essential thrombocythemia and myelofibrosis (MF). Especially in MF, the driver mutational profile has prognostic implications, with additive contributions from the acquisition of additional somatic mutations. The hope is that sophisticated molecular profiling will not only aid in prognostication, but also guide selection of therapy for patients with MPNs.

Detection of CALR Mutation in Clonal and Nonclonal Hematologic Diseases Using Fragment Analysis and Next-Generation Sequencing

OBJECTIVES

To describe three methods used to screen for frameshift mutations in exon 9 of the CALR gene.

METHODS

Genomic DNA from 47 patients was extracted from peripheral blood and bone marrow using the EZ1 DNA Blood Kit (Qiagen, Valencia, CA) and quantified by the Quant-iT PicoGreen dsDNA Assay Kit (Invitrogen, San Diego, CA). After clinical history, cytogenetics, and molecular tests, patients were diagnosed with either clonal or nonclonal hematologic diseases. CALR screening was primarily performed using fragment analysis polymerase chain reaction, then next-generation sequencing and Sanger sequencing.

RESULTS

Among the 18 patients diagnosed with clonal diseases, one had acute myeloid leukemia (positive for trisomy 8), and 17 had myeloproliferative neoplasms (MPNs), including chronic myeloid leukemia (CML), essential thrombocythemia (ET), primary myelofibrosis (PMF), and polycythemia vera (PV). Patients with CML were positive for the BCR-ABL1 fusion. Ten patients were positive for JAK2 (PMF, n = 1; ET, n = 2; PV, n = 7), and three were CALR positive (ET, n = 1; PMF, n = 2). Patients diagnosed with a nonclonal disease were negative for JAK2, BCR-ABL, and CALR mutations.

CONCLUSIONS

Screening for CALR mutations is essential in BCR-ABL-negative MPNs since it not only provides valuable diagnostic and prognostic information but also identifies potential treatment targets. Since this study describes the importance of screening for known and novel biomarkers, we described in detail three methods that could be easily integrated into a clinical laboratory.

CAL2 Immunohistochemical Staining Accurately Identifies CALR Mutations in Myeloproliferative Neoplasms

OBJECTIVES

Mutations in CALR (calreticulin) have been discovered in 50% to 80% of JAK2 (Janus kinase 2) and MPL (myeloproliferative leukemia protein) wild-type patients with Philadelphia-negative myeloproliferative neoplasm (MPNs). We evaluate the performance of a monoclonal antibody for immunohistochemical detection of CALR mutations.

METHODS

A computerized archival search was performed for cases of non-chronic myeloid leukemia (CML) MPNs with available CALR and JAK2 V617F mutational analysis data. Bone marrow biopsy specimens were stained with monoclonal antibody CAL2, and the percentage of stained megakaryocytes was calculated. In select cases, double immunofluorescence staining was done with CAL2 and each of the following: CD61, myeloperoxidase, CD34, and glycophorin A.

RESULTS

We studied 38 bone marrow biopsy specimens of non-CML MPNs (primary myelofibrosis, n = 21; essential thrombocythemia, n = 15; and n = 2 post-polycythemia vera myelofibrosis) from 31 patients. All eight bone marrow biopsy specimens from patients with mutant CALR showed strong cytoplasmic staining of the megakaryocytes (83.5%; range, 50%-98%; median, 87%) with the CAL2 antibody. Double immunofluorescence staining of the small mononuclear cells seen in CALR mutant cases revealed them to be myeloid blasts.

CONCLUSIONS

Immunohistochemistry in routinely processed bone marrow biopsy specimens for mutated CALR is feasible and accurately identifies mutated cases, including rare cases with additional driver mutations.

Oncogenic Drivers in Myeloproliferative Neoplasms: From JAK2 to Calreticulin Mutations

During the past 10 years, major progress has been accomplished with the discovery of activating mutations that are associated with the vast majority of BCR-ABL negative human myeloproliferative neoplasms (MPNs). The identification in 2005 of JAK2 V617F triggered great interest in the JAK2-STAT5/STAT3 pathway. Discovery in 2006 of mutants of thrombopoietin receptor (TPO-R/MPL) and later on of mutants in negative regulators of JAK-STAT pathway led to the notion that persistent JAK2 activation is a hallmark of MPNs. In 2013, mutations in the gene coding for the chaperone calreticulin were reported in 20-30% of essential thrombocythemia and primary myelofibrosis patients. Here, we will address the question: what do we know about calreticulin that could help us understand its role in MPNs? In addition to oncogenic driver mutations, certain MPNs also exhibit epigenetic mutations. Targeting of both oncogenic drivers and epigenetic defects could be required for effective therapy.

Circulating Calreticulin Is Increased in Myelofibrosis: Correlation with Interleukin-6 Plasma Levels, Bone Marrow Fibrosis, and Splenomegaly

Myelofibrosis (MF) is a clonal neoplasia of the hemopoietic stem/progenitor cells associated with genetic mutations in the Janus kinase 2 (JAK2), myeloproliferative leukemia virus oncogene (MPL), and calreticulin (CALR) genes. MF is also characterized by a state of chronic inflammation. Calreticulin (CRT), as a multifunctional protein, is involved in a spectrum of cellular processes including inflammation, autoimmunity, and cancer initiation/progression. Based on this background, we hypothesised that in MF circulating CRT might reflect the inflammatory process. In the present study we show that circulating CRT is increased in MF patients compared to healthy controls. Also, in MF, CRT levels highly correlate with bone marrow fibrosis, splenomegaly, and Interleukin-6 (IL-6) plasma levels. In turn, higher IL-6 levels also correlated with disease severity in terms of increased spleen size, bone marrow fibrosis, number of circulating CD34⁺ cells, and lower hemoglobin values. These results demonstrate that the circulating CRT takes part in the inflammatory network of MF and correlates with aggressiveness of the disease.

Identification of prohormones and pituitary neuropeptides in the African cichlid, Astatotilapia burtoni

Background

Cichlid fishes have evolved remarkably diverse reproductive, social, and feeding behaviors. Cell-to-cell signaling molecules, notably neuropeptides and peptide hormones, are known to regulate these behaviors across vertebrates. This class of signaling molecules derives from prohormone genes that have undergone multiple duplications and losses in fishes. Whether and how subfunctionalization, neofunctionalization, or losses of neuropeptides and peptide hormones have contributed to fish behavioral diversity is largely unknown. Information on fish prohormones has been limited and is complicated by the whole genome duplication of the teleost ancestor. We combined bioinformatics, mass spectrometry-enabled peptidomics, and molecular techniques to identify the suite of neuropeptide prohormones and pituitary peptide products in Astatotilapia burtoni, a well-studied member of the diverse African cichlid clade.

Results

Utilizing the A. burtoni genome, we identified 148 prohormone genes, with 21 identified as a single copy and 39 with at least 2 duplicated copies. Retention of prohormone duplicates was therefore 41 %, which is markedly above previous reports for the genome-wide average in teleosts. Beyond the expected whole genome duplication, differences between cichlids and mammals can be attributed to gene loss in tetrapods and additional duplication after divergence. Mass spectrometric analysis of the pituitary identified 620 unique peptide sequences that were matched to 120 unique proteins. Finally, we used in situ hybridization to localize the expression of galanin, a prohormone with exceptional sequence divergence in cichlids, as well as the expression of a proopiomelanocortin, prohormone that has undergone an additional duplication in some bony fish lineages.

Conclusion

We characterized the A. burtoni prohormone complement. Two thirds of prohormone families contain duplications either from the teleost whole genome duplication or a more recent duplication. Our bioinformatic and mass spectrometric findings provide information on a major vertebrate clade that will further our understanding of the functional ramifications of these prohormone losses, duplications, and sequence changes across vertebrate evolution. In the context of the cichlid radiation, these findings will also facilitate the exploration of neuropeptide and peptide hormone function in behavioral diversity both within A. burtoni and across cichlid and other fish species.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-016-2914-9) contains supplementary material, which is available to authorized users.

Mutant calreticulin: when a chaperone becomes intrusive

In this issue of Blood, Marty et al, Chachoua et al, and Araki et al report results of studies unraveling the molecular pathogenesis of CALR-mutant myeloproliferative neoplasms (MPNs). Together, these 3 reports define a novel disease paradigm, whereby a mutant chaperone constitutively activates receptor signaling through an abnormal interaction with the thrombopoietin (TPO) receptor (MPL).

Involvement of calreticulin in cell proliferation, invasion and differentiation in diallyl disulfide-treated HL-60 cells

Diallyl disulfide (DADS) has shown potential as a therapeutic agent in various cancers. Previously, calreticulin (CRT) was found to be downregulated in differentiated HL-60 cells treated with DADS. The present study investigated the role of CRT proteins in DADS-induced proliferation, invasion and differentiation in HL-60 cells. The present study demonstrated that DADS treatment significantly changed the morphology of HL-60 cells and caused the significant time-dependent downregulation of CRT. Small interfering RNA (siRNA)-mediated knockdown of CRT expression significantly inhibited proliferation, decreased invasion ability, increased the expression of cluster of differentiation (CD)11b and reduced the expression of CD33 in DADS-treated HL-60 cells. DADS also significantly affected cell proliferation, invasion and differentiation in CRT-overexpressed HL-60 cells. Nitroblue tetrazolium (NBT) reduction assays showed decreased NBT reduction activity in the CRT overexpression group and increased NBT reduction in the CRT siRNA group. Following treatment with DADS, the NBT reduction abilities in all groups were increased. In conclusion, the present study clearly demonstrates the downregulation of CRT during DADS-induced differentiation in HL-60 cells and indicates that CRT is involved in cell proliferation, invasion and differentiation in DADS-treated HL-60 cells.

Calreticulin expression: Interaction with the immune infiltrate and impact on survival in patients with ovarian and non-small cell lung cancer

Loss of expression of calreticulin (CALR) has been detected by immunohistochemistry in a fraction of non-small cell lung cancers (NSCLC) and has been demonstrated to have a major negative prognostic impact on overall patient survival. Here, we analyzed the impact of CALR expression levels detected by microarray finding a positive correlation between CALR and the expression of a metagene indicating the presence of cytotoxic T lymphocytes (CTL) in NSCLC and ovarian cancer. In addition, we detected a positive correlation with a metagene suggestive of activated dendritic cell (aDC) infiltration in ovarian cancer. Combination of two parameters (CALR + DC (dendritic cell) in NSCL and CALR + aDC in ovarian cancer) or three parameters (CALR + CTL + DC in NSCL and CALR + CTL + aDC in ovarian cancer) had a significant impact on overall patient survival in NSCL (Adenoconsortium) and ovarian cancer (TCGA collection), allowing the stratification of patients in high-risk and low-risk groups. In addition, CALR and aDC alone have a significant impact on overall survival in ovarian cancer. In contrast, in mammary, colorectal and prostate cancer, CALR had no impact on patient survival if analyzed alone or in combination with the immune infiltrate. In addition, CALR correlates with CTL infiltrate in three cancer types (colorectal, breast, ovarian). Altogether, these results support the contention that, at least in some cancers, loss of CALR expression may negatively affect immunosurveillance, thereby reducing patient survival.

A molluscan calreticulin ortholog from Haliotis discus discus: Molecular characterization and transcriptional evidence for its role in host immunity

Calreticulin (CALR), a Ca(2+) binding chaperone of the endoplasmic reticulum (ER) and mainly involved in Ca(2+) storage and signaling. In this study, we report the molecular characterization and immune responses of CALR homolog from disk abalone (AbCALR). The full length AbCALR cDNA (1837 bp) had an ORF of 1224 bp. According to the multiple alignments analysis, N- and P-domains were highly conserved in all the selected members of CALRs. In contrast, the C-domain which terminated with the characteristic ER retrieval signal (HDEL) was relatively less conserved. The phylogenetic analysis showed that all the selected molluscan homologs clustered together. Genomic sequence of AbCALR revealed that cDNA sequence was dispersed into ten exons interconnected with nine introns. AbCALR mRNA expression shows the significant (P < 0.05) up-regulation of AbCALR transcripts in hemocytes upon bacterial (Listeria monocytogenes and Vibrio parahaemolyticus), viral (Viral haemorrhagic septicaemia virus; VHSV) and immune stimulants (LPS and poly I:C) challenges at middle and/or late phases. These results collectively implied that AbCALR is able to be stimulated by pathogenic signals and might play a potential role in host immunity.

Mapping the Ca(2+) induced structural change in calreticulin

Calreticulin is a highly conserved multifunctional protein implicated in many different biological systems and has therefore been the subject of intensive research. It is primarily present in the endoplasmatic reticulum where its main functions are to regulate Ca(2+) homeostasis, act as a chaperone and stabilize the MHC class I peptide-loading complex. Although several high-resolution structures of calreticulin exist, these only cover three-quarters of the entire protein leaving the extended structures unsolved. Additionally, the structure of calreticulin is influenced by the presence of Ca(2+). The conformational changes induced by Ca(2+) have not been determined yet as they are hard to study with traditional approaches. Here, we investigated the Ca(2+)-induced conformational changes with a combination of chemical cross-linking, mass spectrometry, bioinformatics analysis and modelling in Rosetta. Using a bifunctional linker, we found a large Ca(2+)-induced change to the cross-linking pattern in calreticulin. Our results are consistent with a high flexibility in the P-loop, a stabilization of the acidic C-terminal and a relatively close interaction of the P-loop and the acidic C-terminal.

BIOLOGICAL SIGNIFICANCE

The function of calreticulin, an endoplasmatic reticulin chaperone, is affected by fluctuations in Ca(2+)concentration, but the structural mechanism is unknown. The present work suggests that Ca(2+)-dependent regulation is caused by different conformations of a long proline-rich loop that changes the accessibility to the peptide/lectin-binding site. Our results indicate that the binding of Ca(2+) to calreticulin may thus not only just be a question of Ca(2+) storage but is likely to have an impact on the chaperone activity.

Amblyomma americanum tick calreticulin binds C1q but does not inhibit activation of the classical complement cascade

In this study we characterized Amblyomma americanum (Aam) tick calreticulin (CRT) homolog in tick feeding physiology. In nature, different tick species can be found feeding on the same animal host. This suggests that different tick species found feeding on the same host can modulate the same host anti-tick defense pathways to successfully feed. From this perspective it's plausible that different tick species can utilize universally conserved proteins such as CRT to regulate and facilitate feeding. CRT is a multi-functional protein found in most taxa that is injected into the vertebrate host during tick feeding. Apart from it's current use as a biomarker for human tick bites, role(s) of this protein in tick feeding physiology have not been elucidated. Here we show that annotated functional CRT amino acid motifs are well conserved in tick CRT. However our data show that despite high amino acid identity levels to functionally characterized CRT homologs in other organisms, AamCRT is apparently functionally different. Pichia pastoris expressed recombinant (r) AamCRT bound C1q, the first component of the classical complement system, but it did not inhibit activation of this pathway. This contrast with reports of other parasite CRT that inhibited activation of the classical complement pathway through sequestration of C1q. Furthermore rAamCRT did not bind factor Xa in contrast to reports of parasite CRT binding factor Xa, an important protease in the blood clotting system. Consistent with this observation, rAamCRT did not affect plasma clotting or platelet aggregation. We discuss our findings in the context of tick feeding physiology.

Dysregulation of the intrinsic apoptotic pathway mediates megakaryocytic hyperplasia in myeloproliferative neoplasms

AIMS

Megakaryocyte expansion in myeloproliferative neoplasms (MPNs) is due to uncontrolled proliferation accompanied by dysregulation of proapoptotic and antiapoptotic mechanisms. Here we have investigated the intrinsic and extrinsic apoptotic pathways of megakaryocytes in human MPNs to further define the mechanisms involved.

METHODS

The megakaryocytic expression of proapoptotic caspase-8, caspase-9, Diablo, p53 and antiapoptotic survivin proteins was investigated in bone marrow specimens of the MPNs (n=145) and controls (n=15) using immunohistochemistry. The megakaryocyte percentage positivity was assessed by light microscopy and correlated with the MPN entity, JAK2V617F/CALR mutation status and platelet count.

RESULTS

The proportion of megakaryocytes in the MPNs expressing caspase-8, caspase-9, Diablo, survivin and p53 was significantly greater than controls. A greater proportion of myeloproliferative megakaryocytes expressed survivin relative to its reciprocal inhibitor, Diablo. Differences were seen between myelofibrosis, polycythaemia vera and essential thrombocythaemia for caspase-9 and p53. CALR-mutated cases had greater megakaryocyte p53 positivity compared to those with the JAK2V617F mutation. Proapoptotic caspase-9 expression showed a positive correlation with platelet count, which was most marked in myelofibrosis and CALR-mutated cases.

CONCLUSIONS

Disruptions targeting the intrinsic apoptotic cascade promote megakaryocyte hyperplasia and thrombocytosis in the MPNs. There is progressive dysfunction of apoptosis as evidenced by the marked reduction in proapoptotic caspase-9 and accumulation of p53 in myelofibrosis. The dysfunction of caspase-9, which is necessary for proplatelet formation, may be the mechanism for the excess thrombocytosis associated with CALR mutations. Survivin seems to be the key protein mediating the megakaryocyte survival signature in the MPNs and is a potential therapeutic target.

PAX4 preserves endoplasmic reticulum integrity preventing beta cell degeneration in a mouse model of type 1 diabetes mellitus

AIMS/HYPOTHESIS

A strategy to enhance pancreatic islet functional beta cell mass (BCM) while restraining inflammation, through the manipulation of molecular and cellular targets, would provide a means to counteract the deteriorating glycaemic control associated with diabetes mellitus. The aims of the current study were to investigate the therapeutic potential of such a target, the islet-enriched and diabetes-linked transcription factor paired box 4 (PAX4), to restrain experimental autoimmune diabetes (EAD) in the RIP-B7.1 mouse model background and to characterise putative cellular mechanisms associated with preserved BCM.

METHODS

Two groups of RIP-B7.1 mice were genetically engineered to: (1) conditionally express either PAX4 (BPTL) or its diabetes-linked mutant variant R129W (mutBPTL) using doxycycline (DOX); and (2) constitutively express luciferase in beta cells through the use of RIP. Mice were treated or not with DOX, and EAD was induced by immunisation with a murine preproinsulin II cDNA expression plasmid. The development of hyperglycaemia was monitored for up to 4 weeks following immunisation and alterations in the BCM were assessed weekly by non-invasive in vivo bioluminescence intensity (BLI). In parallel, BCM, islet cell proliferation and apoptosis were evaluated by immunocytochemistry. Alterations in PAX4- and PAX4R129W-mediated islet gene expression were investigated by microarray profiling. PAX4 preservation of endoplasmic reticulum (ER) homeostasis was assessed using thapsigargin, electron microscopy and intracellular calcium measurements.

RESULTS

PAX4 overexpression blunted EAD, whereas the diabetes-linked mutant variant PAX4R129W did not convey protection. PAX4-expressing islets exhibited reduced insulitis and decreased beta cell apoptosis, correlating with diminished DNA damage and increased islet cell proliferation. Microarray profiling revealed that PAX4 but not PAX4R129W targeted expression of genes implicated in cell cycle and ER homeostasis. Consistent with the latter, islets overexpressing PAX4 were protected against thapsigargin-mediated ER-stress-related apoptosis. Luminal swelling associated with ER stress induced by thapsigargin was rescued in PAX4-overexpressing beta cells, correlating with preserved cytosolic calcium oscillations in response to glucose. In contrast, RNA interference mediated repression of PAX4-sensitised MIN6 cells to thapsigargin cell death.

CONCLUSIONS/INTERPRETATION

The coordinated regulation of distinct cellular pathways particularly related to ER homeostasis by PAX4 not achieved by the mutant variant PAX4R129W alleviates beta cell degeneration and protects against diabetes mellitus. The raw data for the RNA microarray described herein are accessible in the Gene Expression Omnibus database under accession number GSE62846.

The C-Terminal Acidic Region of Calreticulin Mediates Phosphatidylserine Binding and Apoptotic Cell Phagocytosis

Calreticulin is a calcium-binding chaperone that is normally localized in the endoplasmic reticulum. Calreticulin is detectable on the surface of apoptotic cells under some apoptosis-inducing conditions, where it promotes the phagocytosis and immunogenicity of dying cells. However, the precise mechanism by which calreticulin, a soluble protein, localizes to the outer surface of the plasma membrane of dying cells is unknown, as are the molecular mechanisms that are relevant to calreticulin-induced cellular phagocytosis. Calreticulin comprises three distinct structural domains: a globular domain, an extended arm-like P-domain, and a C-terminal acidic region containing multiple low-affinity calcium binding sites. We show that calreticulin, via its C-terminal acidic region, preferentially interacts with phosphatidylserine (PS) compared with other phospholipids and that this interaction is calcium dependent. Additionally, exogenous calreticulin binds apoptotic cells via a higher-affinity calcium-dependent mode that is acidic region dependent. Exogenous calreticulin also binds live cells, including macrophages, via a second, lower-affinity P-domain and globular domain-dependent, but calcium-independent binding mode that likely involves its generic polypeptide binding site. Truncation constructs lacking the acidic region or arm-like P-domain of calreticulin are impaired in their abilities to induce apoptotic cell phagocytosis by murine peritoneal macrophages. Taken together, the results of this investigation provide the first molecular insights into the phospholipid binding site of calreticulin as a key anchor point for the cell surface expression of calreticulin on apoptotic cells. These findings also support a role for calreticulin as a PS-bridging molecule that cooperates with other PS-binding factors to promote the phagocytosis of apoptotic cells.

Comparative proteomics analysis of apoptotic Spodoptera frugiperda cells during p35 knockout Autographa californica multiple nucleopolyhedrovirus infection

Infection with Autographa californica multiple nucleopolyhedrovirus (AcMNPV) mutants lacking a functional p35 gene can induce host cell apoptosis, which provides the possibility to use the potential of these viruses in the biological control of pest insects. Nonetheless, the proteomics or the protein changes of Spodoptera frugiperda (Sf9) cells infected with p35 knockout AcMNPV have not yet been studied. To further improve the use of AcMNPV, we set out to analyze the protein composition and protein changes of Sf9 cells of different infection stages by isobaric tag for relative and absolute quantification (iTRAQ) techniques. A total of 4004 sf9 proteins were identified by iTRAQ. After comparation of the significantly expressed 483 proteins from p35koAcMNPV-infected Sf9 cells and the significantly expressed 413 proteins from wtAcMNPV-infected Sf9 cells, we found that 226 proteins were specific to p35koAcMNPV-infected Sf9 cells. The 226 proteins were categorized according to GO classification for insects and were categorized into: biological processes, molecular functions and cellular components. Of interest, the most up-regulated proteins related to Epstein-Barr virus infection, RNA transport, Calcium signaling pathway, cGMP-PKG signaling pathway, oxidative phosphorylation and N-Glycan biosynthesis. Determination of the protein changes in p35 knockout AcMNPV-infected Sf9 cells would facilitate the better use of this virus-host cell interaction in pest insect control and other related fields.

The miR-27a-calreticulin axis affects drug-induced immunogenic cell death in human colorectal cancer cells

Immunogenic cell death (ICD) evoked by chemotherapeutic agents implies emission of selected damage-associated molecular patterns (DAMP) such as cell surface exposure of calreticulin, secretion of ATP and HMGB1. We sought to verify whether miR-27a is implicated in ICD, having demonstrated that it directly targets calreticulin. To this goal, we exposed colorectal cancer cell lines, genetically modified to express high or low miR-27a levels, to two bona fide ICD inducers (mitoxantrone and oxaliplatin). Low miR-27a-expressing cells displayed more ecto-calreticulin on the cell surface and increased ATP and HMGB1 secretion than high miR-27a-expressing ones in time-course experiments upon drug exposure. A calreticulin target protector counteracted the miR-27a effects while specific siRNAs mimicked them, confirming the results reported. In addition, miR-27a negatively influenced the PERK-mediated route and the late PI3K-dependent secretory step of the unfolded protein response to endoplasmic reticulum stress, suggesting that miR-27a modulates the entire ICD program. Interestingly, upon chemotherapeutic exposure, low miR-27a levels associated with an earlier and stronger induction of apoptosis and with morphological and molecular features of autophagy. Remarkably, in ex vivo setting, under the same chemotherapeutic induction, the conditioned media from high miR-27a-expressing cells impeded dendritic cell maturation while increased the secretion of specific cytokines (interleukin (IL)-4, IL-6, IL-8) and negatively influenced CD4⁺ T-cell interferon γ production and proliferation, all markers of a tumor immunoevasion strategy. In conclusion, we provide the first evidence that miR-27a impairs the cell response to drug-induced ICD through the regulatory axis with calreticulin.

A link between the driver mutations and dysregulated apoptosis in BCR-ABL1 negative myeloproliferative neoplasms

The current understanding of BCR-ABL1 negative myeloproliferative neoplasms pathogenesis is centred on the phenotypic driver mutations in JAK2, MPL, or CALR genes, and the constitutive activation of JAK-STAT pathway. Nonetheless, there is still a need to better characterize the cellular processes that are triggered by these genetic alterations, such as apoptosis that might play a role in the pathological expansion of the myeloid lineages and, especially, in the morphological anomalies of the bone marrow megakaryocytes. In this article we will explore the connection between the driver mutations in MPN and the abnormal apoptosis that might be translated in new therapeutic strategies.

Presence of atypical thrombopoietin receptor (MPL) mutations in triple-negative essential thrombocythemia patients

Enrichment of atypical MPL mutations in essential thrombocythemia. MPLS204P and MPLY591N mutants are weak gain-of-function mutants.

[CALR gene mutation detection and clinical observation of 150 essential thrombocythemia patients]

目的

研究原发性血小板增多症（ET)患者CALR基因突变情况，比较其与JAK2 V617F、MPL W515K突变及三种突变阴性患者部分临床参数的差异。

方法

采用基因组DNA-PCR扩增产物直接测序法检测150例ET患者CALR基因9号外显子及MPL W515K突变；采用等位基因特异性PCR检测JAK2 V617F突变检出情况。

结果

①150例ET患者中共检出CALR突变38例（25.3%)，Ⅰ型（c.1092_1143del52bp) 17例，Ⅱ型（c.1154_1155insTTGTC) 16例，Ⅲ型（c.1094_1139del46bp) 4例，Ⅳ型（c.1103_1136del34bp) 1例。②JAK2 V617F和MPL W515K的突变检出率分别为61.3% (92/150)和2.7% (4/150)；54例JAK2 V617F及MPL W515K突变阴性患者中CALR突变检出率为70.4% (38/54)，未检测到任何两种基因突变共存。③CALR突变组的外周血白细胞和血红蛋白水平低于JAK2 V617F突变组(P<0.05)，中位年龄为59 (29~89)岁，高于三种突变阴性组的29.5 (16~67)岁(P<0.01)；147例患者有染色体核型分析结果，其中4例存在核型异常，异常核型与正常核型患者中CALR基因突变检出率分别为75.0% (3/4)、24.5% (35/143)，差异有统计学意义(P=0.019)。

结论

CALR突变在JAK2 V617F及MPL W515K突变阴性的ET患者中有较高的检出率，并与异常核型相关；CALR突变组外周血白细胞和血红蛋白水平低于JAK2 V617F突变组。

N-Glycan-based ER Molecular Chaperone and Protein Quality Control System: The Calnexin Binding Cycle

Helenius and colleagues proposed over 20-years ago a paradigm-shifting model for how chaperone binding in the endoplasmic reticulum was mediated and controlled for a new type of molecular chaperone- the carbohydrate-binding chaperones, calnexin and calreticulin. While the originally established basics for this lectin chaperone binding cycle holds true today, there has been a number of important advances that have expanded our understanding of its mechanisms of action, role in protein homeostasis, and its connection to disease states that are highlighted in this review.

Shared weapons of blood- and plant-feeding insects: Surprising commonalities for manipulating hosts

Insects that reprogram host plants during colonization remind us that the insect side of plant-insect story is just as interesting as the plant side. Insect effectors secreted by the salivary glands play an important role in plant reprogramming. Recent discoveries point to large numbers of salivary effectors being produced by a single herbivore species. Since genetic and functional characterization of effectors is an arduous task, narrowing the field of candidates is useful. We present ideas about types and functions of effectors from research on blood-feeding parasites and their mammalian hosts. Because of their importance for human health, blood-feeding parasites have more tools from genomics and other - omics than plant-feeding parasites. Four themes have emerged: (1) mechanical damage resulting from attack by blood-feeding parasites triggers "early danger signals" in mammalian hosts, which are mediated by eATP, calcium, and hydrogen peroxide, (2) mammalian hosts need to modulate their immune responses to the three "early danger signals" and use apyrases, calreticulins, and peroxiredoxins, respectively, to achieve this, (3) blood-feeding parasites, like their mammalian hosts, rely on some of the same "early danger signals" and modulate their immune responses using the same proteins, and (4) blood-feeding parasites deploy apyrases, calreticulins, and peroxiredoxins in their saliva to manipulate the "danger signals" of their mammalian hosts. We review emerging evidence that plant-feeding insects also interfere with "early danger signals" of their hosts by deploying apyrases, calreticulins and peroxiredoxins in saliva. Given emerging links between these molecules, and plant growth and defense, we propose that these effectors interfere with phytohormone signaling, and therefore have a special importance for gall-inducing and leaf-mining insects, which manipulate host-plants to create better food and shelter.

Late progamic phase and fertilization affect calreticulin expression in the Hyacinthus orientalis female gametophyte

Calreticulin expression is upregulated during sexual reproduction of Hyacinthus orientalis, and the protein is localized both in the cytoplasm and a highly specialized cell wall within the female gametophyte. Several evidences indicate calreticulin (CRT) as an important calcium (Ca(2+))-binding protein that is involved in the generative reproduction of higher plants, including both pre-fertilization and post-fertilization events. Because CRT is able to bind and sequester exchangeable Ca(2+), it can serve as a mobile intracellular store of easily releasable Ca(2+) and control its local cytosolic concentrations in the embryo sac. This phenomenon seems to be essential during the late progamic phase, gamete fusion, and early embryogenesis. In this report, we demonstrate the differential expression of CRT within Hyacinthus female gametophyte cells before and during anthesis, during the late progamic phase when the pollen tube enters the embryo sac, and at the moment of fertilization and zygote/early endosperm activation. CRT mRNA and the protein localize mainly to the endoplasmic reticulum (ER) and Golgi compartments of the cells, which are involved in sexual reproduction events, such as those in sister synergids, the egg cell, the central cell, zygote and the developing endosperm. Additionally, immunogold research demonstrates selective CRT distribution in the filiform apparatus (FA), a highly specific component of the synergid cell wall. In the light of our previous data showing the total transcriptional activity of the Hyacinthus female gametophyte and the results presented here, we discuss the possible functions of CRT with respect to the critical role of Ca(2+) homeostasis during key events of sexual plant reproduction. Moreover, we propose that the elevated expression of CRT within the female gametophyte is a universal phenomenon in the cells involved in double fertilization in higher plants.

Myeloproliferative neoplasms: Current molecular biology and genetics

Myeloproliferative neoplasms (MPNs) are clonal disorders characterized by increased production of mature blood cells. Philadelphia chromosome-negative MPNs (Ph-MPNs) consist of polycythemia vera (PV), essential thrombocythemia (ET), and primary myelofibrosis (PMF). A number of stem cell derived mutations have been identified in the past 10 years. These findings showed that JAK2V617F, as a diagnostic marker involving JAK2 exon 14 with a high frequency, is the best molecular characterization of Ph-MPNs. Somatic mutations in an endoplasmic reticulum chaperone, named calreticulin (CALR), is the second most common mutation in patients with ET and PMF after JAK2 V617F mutation. Discovery of CALR mutations led to the increased molecular diagnostic of ET and PMF up to 90%. It has been shown that JAK2V617F is not the unique event in disease pathogenesis. Some other genes' location such as TET oncogene family member 2 (TET2), additional sex combs-like 1 (ASXL1), casitas B-lineage lymphoma proto-oncogene (CBL), isocitrate dehydrogenase 1/2 (IDH1/IDH2), IKAROS family zinc finger 1 (IKZF1), DNA methyltransferase 3A (DNMT3A), suppressor of cytokine signaling (SOCS), enhancer of zeste homolog 2 (EZH2), tumor protein p53 (TP53), runt-related transcription factor 1 (RUNX1) and high mobility group AT-hook 2 (HMGA2) have also identified to be involved in MPNs phenotypes. Here, current molecular biology and genetic mechanisms involved in MNPs with a focus on the aforementioned factors is presented.

Overexpression of a Triticum aestivum Calreticulin gene (TaCRT1) Improves Salinity Tolerance in Tobacco

Calreticulin (CRT) is a highly conserved and abundant multifunctional protein that is encoded by a small gene family and is often associated with abiotic/biotic stress responses in plants. However, the roles played by this protein in salt stress responses in wheat (Triticum aestivum) remain obscure. In this study, three TaCRT genes were identified in wheat and named TaCRT1, TaCRT2 and TaCRT3-1 based on their sequence characteristics and their high homology to other known CRT genes. Quantitative real-time PCR expression data revealed that these three genes exhibit different expression patterns in different tissues and are strongly induced under salt stress in wheat. The calcium-binding properties of the purified recombinant TaCRT1 protein were determined using a PIPES/Arsenazo III analysis. TaCRT1 gene overexpression in Nicotiana tabacum decreased salt stress damage in transgenic tobacco plants. Physiological measurements indicated that transgenic tobacco plants showed higher activities of superoxide dismutase (SOD), peroxidase (POD) and catalase (CAT) than non-transgenic tobacco under normal growth conditions. Interestingly, overexpression of the entire TaCRT1 gene or of partial TaCRT1 segments resulted in significantly higher tolerance to salt stress in transgenic plants compared with their WT counterparts, thus revealing the essential role of the C-domain of TaCRT1 in countering salt stress in plants.

Megakaryocytic hyperplasia in myeloproliferative neoplasms is driven by disordered proliferative, apoptotic and epigenetic mechanisms

AIMS

Myeloproliferative neoplasms (MPN) are a heterogeneous group of clonal proliferative bone marrow diseases characterised by extensive megakaryocytic hyperplasia and morphological atypia. Despite knowledge of genomic defects, the pathobiological processes driving these megakaryocytic abnormalities in MPN remain poorly explained. We have explored the proliferative, apoptotic and epigenetic profiles of megakaryocytes in human MPN.

METHODS

Immunohistochemical staining was performed on bone marrow trephine biopsies of 81 MPN (with and without JAK2(V617F) and CALR mutations) and 15 normal controls to assess the megakaryocytic expression of biomarkers associated with proliferation (Ki67), apoptosis (Bcl-XL, BNIP-3) and epigenetic regulation (EZH2, SUZ12).

RESULTS

Myeloproliferative megakaryocytes showed significantly greater expression of proliferative Ki67 and anti-apoptotic Bcl-XL, reduced pro-apoptotic BNIP-3 and increased SUZ12 compared with controls. In essential thrombocythaemia, large-giant megakaryocytes with hyperlobated nuclei showed a trend towards a proliferative signature. In contrast, myelofibrotic megakaryocytes with condensed nuclear chromatin, and cases with CALR mutations, had significant reductions in pro-apoptotic BNIP-3.

CONCLUSIONS

Uncontrolled megakaryocytic expansion in MPN results from a combination of increased proliferation, attenuated apoptosis and defective epigenetic regulation with CALR mutations favouring apoptotic failure. The higher platelet counts reported to be seen in MPN with CALR mutations may be due to greater dysregulation of megakaryocyte apoptosis.

The Mutation Profile of Calreticulin in Patients with Myeloproliferative Neoplasms and Acute Leukemia

OBJECTIVE

Calreticulin (CALR) plays important roles in cell proliferation, apoptosis, and immune responses. CALR mutations were described recently in Janus kinase 2 gene (JAK2)-negative or MPL-negative primary myelofibrosis (PMF) and essential thrombocythemia (ET) patients. CALR trails JAK2 as the second most mutated gene in myeloproliferative neoplasms (MPNs). However, little is known about CALR mutation in Chinese patients with leukemia. In the present study, a cohort of 305 Chinese patients with hematopoietic neoplasms was screened for CALR mutations, with the aim of uncovering the frequency of CALR mutations in leukemia and MPNs.

MATERIALS AND METHODS

Polymerase chain reaction and direct sequencing were performed to analyze mutations of CALR in 305 patients with hematopoietic malignancies, including 135 acute myeloid leukemia patients, 57 acute lymphoblastic leukemia patients, and 113 MPN patients.

RESULTS

CALR mutations were found in 10.6% (12 of 113) of samples from patients with MPNs. CALR mutations were determined in 11.3% (6 of 53), 21.7% (5 of 23), and 9.1% (1/11) of patients with ET, PMF, and unclassifiable MPN, respectively.

CONCLUSION

We showed that MPN patients carrying CALR mutations presented with higher platelet counts and lower hemoglobin levels compared to those with mutated JAK2. However, all of the leukemia patients had negative results for CALR mutations.

Comparative proteomics analysis of Spodoptera frugiperda cells during Autographa californica multiple nucleopolyhedrovirus infection

Background

Increasing evidence sugggest that in addition of balculovirus controling insect host, host cells also responds to balculovirus infection. However, compared to existing knowledge on virus gene, host cell responses are relatively poorly understood.

Methods

In this study, Spodoptera frugiperda (Sf9) cells were infected with Autographa californica multiple nucleopolyhedrovirus (AcMNPV). The protein composition and protein changes of Spodoptera frugiperda (Sf9) cells of different infection stages were analysed by isobaric tag for relative and absolute quantification (iTRAQ) techniques.

Results

A total of 4004 Sf9 proteins were identified by iTRAQ and 413 proteins were found as more than 1.5-fold changes in abundance. The 413 proteins were categorised according to GO classification for insects and were categorised into: biological process, molecular function and cellular component.

Conclusions

The determination of the protein changes in infected Sf9 cells would help to better understanding of host cell responses and facilitate better design of this virus-host cell interaction in pest insect control and other related fields.

Electronic supplementary material

The online version of this article (doi:10.1186/s12985-015-0346-9) contains supplementary material, which is available to authorized users.

Systems biology surveillance decrypts pathological transcriptome remodeling

BACKGROUND

Pathological cardiac development is precipitated by dysregulation of calreticulin, an endoplasmic reticulum (ER)-resident calcium binding chaperone and critical contributor to cardiogenesis and embryonic viability. However, pleiotropic phenotype derangements induced by calreticulin deficiency challenge the identification of specific downstream transcriptome elements that direct proper cardiac formation. Here, differential transcriptome navigation was used to diagnose high priority calreticulin domain-specific gene expression changes and decrypt complex cardiac-specific molecular responses elicited by discrete functional regions of calreticulin.

METHODS

Wild type (WT), calreticulin-deficient (CALR(-/-)), and calreticulin truncation variant (CALR(-/-)-NP and CALR(-/-)-PC) pluripotent stem cells were used to investigate molecular remodeling underlying a model of cardiopathology. Bioinformatic deconvolution of isolated transcriptomes was performed to identify predominant expression trends, gene ontology prioritizations, and molecular network features characteristic of discrete cell types.

RESULTS

Stem cell lines with wild type (WT), calreticulin-deficient (CALR(-/-)) genomes, as well as calreticulin truncation variants exclusively expressing either the chaperoning (CALR(-/-)-NP) or the calcium binding (CALR(-/-)-PC) domain exhibited characteristic molecular signatures determined by unsupervised agglomerative clustering. Kohonen mapping of RNA expression changes identified transcriptome dynamics that segregated into 12 discrete gene expression meta-profiles which were enriched for regulation of Eukaryotic Initiation Factor 2 (EIF2) signaling. Focused examination of domain-specific gene ontology remodeling revealed a general enrichment of Cardiovascular Development in the truncation variants, with unique prioritization of "Cardiovascular Disease" exclusive to the cohort of down regulated genes of the PC truncation variant. Molecular cartography of genes that comprised this cardiopathological category revealed uncharacterized and novel gene relationships, with identification of Pitx2 as a critical hub within the topology of a CALR(-/-) compromised network.

CONCLUSIONS

Diagnostic surveillance, through an algorithm that integrates pluripotent stem cell transcriptomes with advanced high throughput assays and computational bioinformatics, revealed collective gene expression network changes that underlie differential phenotype development. Stem cell transcriptomes provide a deep collective molecular index that reflects ad hoc robustness of the pluripotent gene network. Remodeling events such as monogenic lesions provide a background by which high priority candidate disease effectors and regulators can be identified, demonstrated here by a molecular profiling algorithm that decrypts pluripotent wild type versus disrupted genomes.

Cytosolic calreticulin inhibits microwave radiation-induced microvascular endothelial cell injury through the integrin-focal adhesion kinase pathway

OBJECTIVE

To determine the effects of cytosolic CRT on MR-induced MMEC injury, and the underlying mechanism.

METHODS

MMECs were randomized into eight groups: control, AdCRT (infected with pAdCMV/V5-DEST-CRT adenovirus), stCRT (transfected with rCRT-siRNAs), Mock (transfected with scrambled siRNAs), MR (exposed to MR for six minutes), AdCRT + MR, stCRT + MR, and Mock + MR. The magnitude of cell injury were assessed by Annexin V-PI staining, LDH activity in culture medium, MMEC migration ability, ultrastructure and cytoskeletal stability. Subcellular colocalization of CRT and ConA or integrin were evaluated by immunocytochemistry. The mRNA and protein expression levels of target genes were examined by qRT-PCR and western blotting, respectively.

RESULTS

MR-induced cytotoxicity was dose-dependent. Overexpression of cytosolic CRT suppressed MR injury, shown as decreased cell apoptosis, reduced LDH activity, enhanced cell migration capability, and maintenance of ultrastructure and cytoskeleton integrity. Conversely, CRT deficiency aggravated MR-induced injury. Exposure of AdCRT MMECs to MR promoted membrane translocation of CRT and the interaction of CRT-integrin-α. Correlation analysis revealed that integrin-α expression or FAK phosphorylation was positively associated with cytosolic CRT expression.

CONCLUSIONS

Cytosolic CRT inhibits MR-induced MMEC injury through activation of the integrin-FAK pathway.

The Prevalence of JAK2, MPL, and CALR Mutations in Chinese Patients With BCR-ABL1-Negative Myeloproliferative Neoplasms

OBJECTIVES

To evaluate the mutation frequency of JAK2 V617F, JAK2 exon 12, MPL exon 10, and CALR exon 9 and the value of the combined tests in the diagnosis of BCR-ABL1-negative myeloproliferative neoplasms (MPNs).

METHODS

In the current study, mutations of JAK2 V617F, JAK2 exon 12, MPL exon 10, and CALR exon 9 were analyzed in 929 Chinese patients with BCR-ABL1-negative MPN, including 234 cases of polycythemia vera (PV), 428 ETs, 187 PMFs, and 80 unclassifiable MPNs (MPN-Us).

RESULTS

Our result showed that the positive rate of any of four mutations in patients with PV, ET, PMF, and MPN-U was 89.3%, 83.4%, 87.2%, and 77.5%, respectively, which significantly improved the diagnostic rate, especially in ET and PMF. Meanwhile, we also found that the patients without any of four mutations were younger than those with one or more mutations. Unexpectedly, the coexistence of JAK2 V617F and CALR exon 9 was identified in six (0.6%) patients, and JAK2 V617F and MPL exon 10 were present simultaneously in two (0.2%) patients. In addition, we also identified several novel mutation types in CALR exon 9.

CONCLUSIONS

The combined genetic tests of JAK2 V617F, JAK2 exon 12, MPL exon 10, and CALR exon 9 help improve the diagnostic rate for BCR-ABL1-negative MPN.

Calreticulin and Arginylated Calreticulin Have Different Susceptibilities to Proteasomal Degradation

Post-translational arginylation has been suggested to target proteins for proteasomal degradation. The degradation mechanism for arginylated calreticulin (R-CRT) localized in the cytoplasm is unknown. To evaluate the effect of arginylation on CRT stability, we examined the metabolic fates and degradation mechanisms of cytoplasmic CRT and R-CRT in NIH 3T3 and CHO cells. Both CRT isoforms were found to be proteasomal substrates, but the half-life of R-CRT (2 h) was longer than that of cytoplasmic CRT (0.7 h). Arginylation was not required for proteasomal degradation of CRT, although R-CRT displays ubiquitin modification. A CRT mutant incapable of dimerization showed reduced metabolic stability of R-CRT, indicating that R-CRT dimerization may protect it from proteasomal degradation. Our findings, taken together, demonstrate a novel function of arginylation: increasing the half-life of CRT in cytoplasm.

Anthracyclines/trastuzumab: new aspects of cardiotoxicity and molecular mechanisms

Anticancer drugs continue to cause significant reductions in left ventricular ejection fraction resulting in congestive heart failure. The best-known cardiotoxic agents are anthracyclines (ANTHs) such as doxorubicin (DOX). For several decades cardiotoxicity was almost exclusively associated with ANTHs, for which cumulative dose-related cardiac damage was the use-limiting step. Human epidermal growth factor (EGF) receptor 2 (HER2; ErbB2) has been identified as an important target for breast cancer. Trastuzumab (TRZ), a humanized anti-HER2 monoclonal antibody, is currently recommended as first-line treatment for patients with metastatic HER2(+) tumors. The use of TRZ may be limited by the development of drug intolerance, such as cardiac dysfunction. Cardiotoxicity has been attributed to free-iron-based, radical-induced oxidative stress. Many approaches have been promoted to minimize these serious side effects, but they are still clinically problematic. A new approach to personalized medicine for cancer that involves molecular screening for clinically relevant genomic alterations and genotype-targeted treatments is emerging.

CSF3R and CALR mutations in paediatric myeloid disorders and the association of CSF3R mutations with translocations, including t(8; 21)

Mutations in the colony-stimulating factor 3 receptor (CSF3R) and calreticulin (CALR) genes have been reported in a proportion of adults with myeloproliferative disease. However, little is known about CSF3R or CALR mutations in paediatric myeloid disorders. We analysed CSF3R exons 14 and 17, and CALR exon 9, using direct sequencing in samples of paediatric acute myeloid leukaemia (AML; n = 521), juvenile myelomonocytic leukaemia (JMML; n = 40), myelodysplastic syndrome (MDS; n = 20) and essential thrombocythaemia (ET; n = 21). CSF3R mutations were found in 10 (1.2%) of 521 patients with AML; two in exon 14 (both missense mutations resulting in p.T618I) and eight in exon 17 (three frameshift mutations: p.S715X, p.Q774R, and p.S783Q; and five novel missense mutations: p.Q754K, p.R769H, p.L777F, p.T781I, and S795R). All of the patients with mutations in CSF3R exon 17 had chromosomal translocations, including four with t(8;21). At the time of reporting, seven of these ten patients are alive; three have died, due to side effects of chemotherapy. No CSF3R mutations were found in cases of MDS, JMML or ET. The only mutation found in the CALR gene was a frameshift (p.L367 fs) in one ET patient. We discuss the potential impact of these findings for the leukaemogenesis and clinical features of paediatric myeloid disorders.