Spi-1 is a putative oncogene in virally induced murine erythroleukaemias

Multi-omics joint screening of biomarkers related to M2 macrophages in gastric cancer

BACKGROUND

Due to high mortality rate and limited treatments in gastric cancer (GC), call for deeper exploration of M2 macrophages as biomarkers is needed.

METHODS

The data for this study were obtained from the Gene Expression Omnibus (GEO) and Genomic Data Commons (GDC). The Seurat package was utilized for single-cell RNA sequencing (scRNA-seq) analysis. FindAllMarkers was used to identify genes highly expressed among different cell subsets. DESeq2 package was leveraged to screen differentially expressed genes (DEGs), while limma package was utilized for identifying differentially expressed proteins (DEPs). Enrichment analyses of the genes were conducted using KOBAS-i database. MultipleROC was applied to evaluate the diagnostic potential of biomarkers, and rms package was utilized to construct diagnostic models. hTFtarget database was utilized to predict potential transcription factors (TFs). Finally, cell-based assays were performed to validate the expression and potential biological functions of the screened key markers.

RESULTS

This study found that M2 macrophages were enriched in protein, endoplasmic reticulum, and virus-related pathways. A total of 4146 DEGs and 1946 DEPs were obtained through screening, with 254 common DEGs/DEPs. The results of gene function enrichment analysis suggested that it may affect the occurrence and development of GC through DNA replication and cell cycle. This study identified three biomarkers, HSPH1, HSPD1, and IFI30, and constructed a diagnostic model based on these three genes. The AUC value greater than 0.8 proved the reliability of the model. Through screening TFs, SPI1 and KLF5 were found to be the common TFs for the three biomarkers. The expression of the three genes IFI30, HSPD1 and HSPH1 was up-regulated in GC cells, and IFI30 may play a facilitating role in the migration and invasion of GC cells.

CONCLUSION

This study identified three biomarkers and constructed a diagnostic model, providing a new perspective for the research and treatment of GC.

Decreased PU.1 expression in mature B cells induces lymphomagenesis

Diffuse large B-cell lymphoma (DLBCL) is the most common subtype of lymphoma, accounting for 30% of non-Hodgkin lymphomas. Although comprehensive analysis of genetic abnormalities has led to the classification of lymphomas, the exact mechanism of lymphomagenesis remains elusive. The Ets family transcription factor, PU.1, encoded by Spi1, is essential for the development of myeloid and lymphoid cells. Our previous research illustrated the tumor suppressor function of PU.1 in classical Hodgkin lymphoma and myeloma cells. In the current study, we found that patients with DLBCL exhibited notably reduced PU.1 expression in their lymphoma cells, particularly in the non-germinal center B-cell-like (GCB) subtype. This observation suggests that downregulation of PU.1 may be implicated in DLBCL tumor growth. To further assess PU.1's role in mature B cells in vivo, we generated conditional Spi1 knockout mice using Cγ1-Cre mice. Remarkably, 13 of the 23 knockout mice (56%) showed splenomegaly, lymphadenopathy, or masses, with some having histologically confirmed B-cell lymphomas. In contrast, no wild-type mice developed B-cell lymphoma. In addition, RNA-seq analysis of lymphoma cells from Cγ1-Cre Spi1F/F mice showed high frequency of each monoclonal CDR3 sequence, indicating that these lymphoma cells were monoclonal tumor cells. When these B lymphoma cells were transplanted into immunodeficient recipient mice, all mice died within 3 weeks. Lentiviral-transduced Spi1 rescued 60% of the recipient mice, suggesting that PU.1 has a tumor suppressor function in vivo. Collectively, PU.1 is a tumor suppressor in mature B cells, and decreased PU.1 results in mature B-cell lymphoma development.

Transcriptional Regulation of the Lineage-Determining Gene PU.1 in Normal and Malignant Hematopoiesis: Current Understanding and Therapeutic Perspective

The ETS transcription factor PU.1 plays an essential role in blood cell development. Its precise expression pattern is governed by cis-regulatory elements (CRE) acting at the chromatin level. CREs mediate the fine-tuning of graded levels of PU.1, deviations of which can cause acute myeloid leukemia. In this review, we perform an in-depth analysis of the regulation of PU.1 expression in normal and malignant hematopoiesis. We elaborate on the role of trans-acting factors and the biomolecular interplays in mediating local chromatin dynamics. Moreover, we discuss the current understanding of CRE bifunctionality exhibiting enhancer or silencer activities in different blood cell lineages and future directions toward gene-specific chromatin-targeted therapeutic development.

Spi1 R235C point mutation confers hypersensitivity to radiation-induced acute myeloid leukemia in mice

Ionizing radiation (IR) is a risk factor for acute myeloid leukemia (rAML). Murine rAMLs feature both hemizygous chromosome 2 deletions (Del2) and point mutations (R235) within the hematopoietic regulatory gene Spi1. We generated a heterozygous CBA Spi1 R235 mouse (CBASpm/+) which develops de novo AML with 100% incidence by ∼12 months old and shows a dose-dependent reduction in latency following X-irradiation. These effects are reduced on an AML-resistant C57Bl6 genetic background. CBASpm/Gfp reporter mice show increased Gfp expression, indicating compensation for Spm-induced Spi1 haploinsufficiency. Del2 is always detected in both de novo and rAMLs, indicating that biallelic Spi1 mutation is required for AML. CBASpm/+ mice show that a single Spm modification is sufficient for initiating AML development with complete penetrance, via the "two-hit" mechanism and this is accelerated by IR exposure. Similar SPI1/PU.1 polymorphisms in humans could potentially lead to enhanced susceptibility to IR following medical or environmental exposure.

FANCA deficiency promotes leukaemic progression by allowing the emergence of cells carrying oncogenic driver mutations

Leukaemia is caused by the clonal evolution of a cell that accumulates mutations/genomic rearrangements, allowing unrestrained cell growth. However, recent identification of leukaemic mutations in the blood cells of healthy individuals revealed that additional events are required to expand the mutated clones for overt leukaemia. Here, we assessed the functional consequences of deleting the Fanconi anaemia A (Fanca) gene, which encodes a DNA damage response protein, in Spi1 transgenic mice that develop preleukaemic syndrome. FANCA loss increases SPI1-associated disease penetrance and leukaemic progression without increasing the global mutation load of leukaemic clones. However, a high frequency of leukaemic FANCA-depleted cells display heterozygous activating mutations in known oncogenes, such as Kit or Nras, also identified but at low frequency in FANCA-WT mice with preleukaemic syndrome, indicating that FANCA counteracts the emergence of oncogene mutated leukaemic cells. A unique transcriptional signature is associated with the leukaemic status of FANCA-depleted cells, leading to activation of MDM4, NOTCH and Wnt/β-catenin pathways. We show that NOTCH signalling improves the proliferation capacity of FANCA-deficient leukaemic cells. Collectively, our observations indicate that loss of the FANC pathway, known to control genetic instability, fosters the expansion of leukaemic cells carrying oncogenic mutations rather than mutation formation. FANCA loss may contribute to this leukaemogenic progression by reprogramming transcriptomic landscape of the cells.

SPI1 involvement in malignant melanoma pathogenesis by regulation of HK2 through the AKT1/mTOR pathway

Spi-1 proto-oncogene (SPI1) plays a vital role in carcinogenesis. Our work aimed to investigate the potential regulatory mechanism of SPI1 in melanoma. The mRNA and protein levels were measured via qRT-PCR and Western blotting. Cell viability was assessed by CCK-8 assay. The target relationship between SPI1 and hexokinase 2 (HK2) was determined using dual-luciferase reporter detection. ChIP was conducted to confirm the targeted relationship between SPI1 and the HK2 promoter. Immunohistochemistry analysis was conducted to measure the positive cell number of SPI1 and HK2 in melanoma tissues. The cell migration abilities were determined using a wound healing assay. Glucose consumption, pyruvate dehydrogenase activity, lactate production and ATP levels were measured to assess glycolysis. SPI1 transcription in melanoma cells and tissues was dramatically higher than that in adjacent normal tissues and epidermal melanocyte HEMa-LP, respectively. Knockdown of SPI1 restrained cell viability, metastasis and glycolysis in melanoma cells. SPI1 directly targeted HK2, and knockdown of SPI1 repressed HK2 expression. Overexpression of HK2 weakened the inhibitory effects of SPI1 knockdown on the viability, metastasis and glycolysis of melanoma cells. The serine-threonine kinase 1 (AKT1)/mammalian target of rapamycin (mTOR) axis is involved in melanoma progression. SPI1 knockdown restrained melanoma cell proliferation, metastasis and glycolysis by regulating the AKT1/mTOR pathway.

Vagal-mAChR4 signaling promotes Friend virus complex (FV)-induced acute erythroleukemia

Erythroleukemia belongs to acute myeloid leukemia (AML) type 6 (M6), and treatment remains difficult due to the poor prognosis of the disease. Friend virus (FV) is a complex of two viruses: Friend murine leukemia virus (F-MuLV) strain along with a defective spleen focus forming virus (SFFV), which can induce acute erythroleukemia in mice. We have previously reported that activation of vagal α7 nicotinic acetylcholine receptor (nAChR) signaling promotes HIV-1 transcription. Whether vagal muscarinic signaling mediates FV-induced erythroleukemia and the underlying mechanisms remain unclear. In this study, sham and vagotomized mice were intraperitoneally injected with FV. FV infection caused anemia in sham mice, and vagotomy reversed this change. FV infection increased erythroblasts ProE, EryA, and EryB cells in the spleen, and these changes were blocked by vagotomy. In bone marrow, FV infection reduced EryC cells in sham mice, an effect that was counteracted by vagotomy. FV infection increased choline acetyltransferase (ChAT) expression in splenic CD4⁺ and CD8⁺ T cells, and this change was reversed by vagotomy. Furthermore, the increase of EryA and EryB cells in spleen of FV-infected wild-type mice was reversed after deletion of ChAT in CD4⁺ T cells. In bone marrow, FV infection reduced EryB and EryC cells in sham mice, whereas lack of ChAT in CD4⁺ T cells did not affect this change. Activation of muscarinic acetylcholine receptor 4 (mAChR4) by clozapine N-oxide (CNO) significantly increased EryB in the spleen but decreased the EryC cell population in the bone marrow of FV-infected mice. Thus, vagal-mAChR4 signaling in the spleen and bone marrow synergistically promotes the pathogenesis of acute erythroleukemia. We uncover an unrecognized mechanism of neuromodulation in erythroleukemia.

Dissecting cell identity via network inference and in silico gene perturbation

Cell identity is governed by the complex regulation of gene expression, represented as gene-regulatory networks1. Here we use gene-regulatory networks inferred from single-cell multi-omics data to perform in silico transcription factor perturbations, simulating the consequent changes in cell identity using only unperturbed wild-type data. We apply this machine-learning-based approach, CellOracle, to well-established paradigms-mouse and human haematopoiesis, and zebrafish embryogenesis-and we correctly model reported changes in phenotype that occur as a result of transcription factor perturbation. Through systematic in silico transcription factor perturbation in the developing zebrafish, we simulate and experimentally validate a previously unreported phenotype that results from the loss of noto, an established notochord regulator. Furthermore, we identify an axial mesoderm regulator, lhx1a. Together, these results show that CellOracle can be used to analyse the regulation of cell identity by transcription factors, and can provide mechanistic insights into development and differentiation.

PU.1 interacts with KLF7 to suppress differentiation and promote proliferation in chicken preadipocytes

<p indent="0mm">Krüppel-like factor 7 (KLF7) is a negative regulator of preadipocyte differentiation. Our previous KLF7 ChIP-seq analysis showed that the binding motif of PU.1 was found among the KLF7 binding peaks, indicating that an interaction between KLF7 and PU.1 at preadipocyte gene promoters and other regulatory elements might be common. Here, Co-IP and FRET assays are used to confirm that PU.1 can directly bind to KLF7 and enhance the transcription activity of cyclin-dependent kinase inhibitor 3 ( <italic>CDKN3</italic>), which is a downstream target gene of KLF7. We show that the PU.1 expression level is decreased during preadipocyte differentiation. Furthermore, PU.1 overexpression and knockdown experiments reveal that PU.1 negatively regulates chicken preadipocyte differentiation, as evidenced by appropriate changes in lipid droplet accumulation and altered expressions of PPARγ, FAS, and PLIN. In addition, PU.1 overexpression promotes preadipocyte proliferation, while knockdown of <italic>PU</italic>. <italic>1</italic> inhibits preadipocyte proliferation. We further demonstrate that PU.1 inhibits differentiation and promotes proliferation in preadipocytes, in part by directly interacting with KLF7. </p>.

The Myeloid-Specific Transcription Factor PU.1 Upregulates Mannose Receptor Expression but Represses Basal Activity of the HIV-LTR Promoter

Human mannose receptor 1 (MRC1) is a cell surface receptor expressed in macrophages and other myeloid cells that inhibits human immunodeficiency virus type 1 (HIV-1) particle release by tethering virions to producer cell membranes. HIV-1 counteracts MRC1 expression by inhibiting mrc1 transcription. Here, we investigated the mechanism of MRC1 downregulation in HIV-1-infected macrophages. We identified the myeloid cell-specific transcription factor PU.1 as critical for regulating MRC1 expression. In the course of our study, we recognized a complex interplay between HIV-1 Tat and PU.1 transcription factors: Tat upregulated HIV-1 gene expression but inhibited mrc1 transcription, whereas PU.1 inhibited HIV-1 transcription but activated MRC1 expression. Disturbing this equilibrium by silencing PU.1 resulted in increased HIV-1 gene expression and reduced MRC1 promoter activity. Our study identified PU.1 as a central player in transcriptional control, regulating a complex interplay between viral and host gene expression in HIV-infected macrophages. IMPORTANCE HIV-1 replication in primary human cells depends on the activity of virus-encoded proteins but also involves cellular factors that can either promote (viral dependency factors) or inhibit (host restriction factors) virus replication. In previous work, we identified human MRC1 as a macrophage-specific host restriction factor that inhibits the detachment of viral particles from infected cells. Here, we report that HIV-1 counteracts this effect of MRC1 by imposing a transcriptional block on cellular MRC1 gene expression. The transcriptional inhibition of the MRC1 gene is accomplished by Tat, an HIV-1 factor whose best-described function actually is the enhancement of HIV-1 gene expression. Thus, HIV-1 has evolved to use the same protein for (i) activation of its own gene expression while (ii) inhibiting expression of MRC1 and other host factors.

MicroRNA-223-3p promotes pyroptosis of cardiomyocyte and release of inflammasome factors via downregulating the expression level of SPI1 (PU.1)

Diabetic cardiomyopathy (DCM) is a common heart disease in patients with diabetes mellitus (DM), and is sometimes its main cause of death. Among all the causes of DCM, myocardial cell death is considered to be the most basic pathological change. Furthermore, studies have shown that pyroptosis, the pro-inflammatory programmed cell death, contributes to the progress of DCM. MicroRNAs (miRNAs) also have been proved to take part in the formation of DCM. However, it is not clear whether and how miRNAs regulate myocardial cell pyroptosis in DCM development. In our study, the results showed that the expression of miR-223-3p was significantly increased in cardiomyocytes induced by high glucose, whereas the down-regulation of miR-223-3p weakened it. To understand the the signal transduction mechanism of miR-223-3p leading to pyroptosis, we found inhibition of miR-223-3p expression down-reguulated caspase-1, pro-inflammatory cytokines IL-1β and other pyroptosis-associated poteins. Moreover, miR-223-3p repressed SPI1 expression. Furthermore, we silenced SPI1 with siRNA to mimick the effect of miR-223-3p, up-regulating the expression of caspase-1 and resulting to pyroptosis. The above findings inspired us to propose a new signaling pathway to regulate scoria of cardiomyocytes under hyperglycemia: miR-223-3p↑→ SPI1↓→ caspase-1↑ → IL-1β and other pyroptosis-associated poteins↑→ pyroptosis↑. In summary, miR-223-3p could be a potential therapeutic target for DCM.

Comprehensive Analysis of Immune Implications and Prognostic Value of SPI1 in Gastric Cancer

Background

The transcription factor Spi-1 proto-oncogene (SPI1, also known as PU.1) is a key regulator of signal communication in the immune system and is essential for the development of myeloid cells and lymphocytes. However, the potential role of SPI1 in gastric cancer (GC) and the correlations between SPI1 and immune infiltration remain unclear.

Methods

In the present study, multiple databases including ONCOMINE, TIMER, Kaplan–Meier Plotter, and The Cancer Genome Atlas were used to explore the expression levels and prognostic value of SPI1 in GC. cBioPortal was used to explore the possible reasons for the increased expression of SPI1 in GC. The correlations between SPI1 expression and tumor-infiltrating immune cells (TICs) were analyzed using CIBERSORT and TIMER. Gene set enrichment analysis was used to determine the biological function of SPI1 in the development of GC. In addition, a risk signature based on SPI1-related immunomodulators was constructed to accurately evaluate the prognosis of patients with GC. The upregulation of SPI1 expression in GC was further confirmed through immunohistochemistry, western blotting, and real-time quantitative PCR (RT-qPCR) assay.

Results

The expression of SPI1 was increased significantly in GC according to multiple databases, and high expression of SPI1 was related to poor prognosis and progression of GC. The main factor influencing the high expression of SPI1 mRNA in GC may be diploidy, not DNA methylation. Moreover, immunohistochemistry, western blotting, and RT-qPCR assays also confirmed the upregulated expression of SPI1 in GC. CIBERSORT analysis revealed that SPI1 expression was correlated with seven types of TICs (naive B cells, resting memory CD4 T cells, activated memory CD4 T cells, activated natural killer cells, resting natural killer cells, M2 macrophages, and resting dendritic cells). Gene set enrichment analysis indicated that SPI1 might be related to immune activation in GC and participate in cell cycle regulation. In addition, based on SPI1-related immunomodulators, we developed multiple-gene risk prediction signatures and constructed a nomogram that can independently predict the clinical outcome of GC.

Conclusion

The results of the present study suggest that SPI1 has a critical role in determining the prognosis of GC patients and may be a potential immunotherapeutic target.

RNA-binding proteins as drivers of AML and novel therapeutic targets

Acute myeloid leukemia (AML) is a group of genetically complex and heterogeneous invasive hematological malignancies with a low 5-year overall survival rate of 30%, which highlights the urgent need for improved treatment measures. RNA-binding proteins (RBPs) regulate the abundance of isoforms of related proteins by regulating RNA splicing, translation, stability, and localization, thereby affecting cell differentiation and self-renewal. It is increasingly believed that RBPs are essential for normal hematopoiesis, and RBPs play a key role in hematological tumors, especially AML, by acting as oncogenes or tumor suppressors. In addition, targeting an RBP that is significantly related to AML can trigger the apoptosis of leukemic stem cells or promote the proliferation of stem and progenitor cells by modulating the expression of important pathway regulatory factors such as HOXA9, MYC, and CDKN1A. Accordingly, RBPs involved in normal myeloid differentiation and the occurrence of AML may represent promising therapeutic targets.

ETS factors in prostate cancer

The ETS family of proteins consists of 28 transcription factors, many of which play critical roles in both normal tissue development and homeostasis and have been implicated in development and progression of a variety of cancers. In prostate cancer, gene fusion and overexpression of ETS factors ERG, FLI1, ETV1, ETV4 and ETV5 have been found in half of prostate cancer patients in Caucasian men and define the largest genetic subtype of prostate cancer. This review summarizes the data on the discovery, modeling, molecular taxonomy, lineage plasticity and therapeutic targeting of ETS family members in prostate cancer.

An erythroid-to-myeloid cell fate conversion is elicited by LSD1 inactivation

Histone H3 lysine 4 methylation (H3K4Me) is most often associated with chromatin activation, and removing H3K4 methyl groups has been shown to be coincident with gene repression. H3K4Me demethylase KDM1a/LSD1 is a therapeutic target for multiple diseases, including for the potential treatment of β-globinopathies (sickle cell disease and β-thalassemia), because it is a component of γ-globin repressor complexes, and LSD1 inactivation leads to robust induction of the fetal globin genes. The effects of LSD1 inhibition in definitive erythropoiesis are not well characterized, so we examined the consequences of conditional inactivation of Lsd1 in adult red blood cells using a new Gata1creERT2 bacterial artificial chromosome transgene. Erythroid-specific loss of Lsd1 activity in mice led to a block in erythroid progenitor differentiation and to the expansion of granulocyte-monocyte progenitor-like cells, converting hematopoietic differentiation potential from an erythroid fate to a myeloid fate. The analogous phenotype was also observed in human hematopoietic stem and progenitor cells, coincident with the induction of myeloid transcription factors (eg, PU.1 and CEBPα). Finally, blocking the activity of the transcription factor PU.1 or RUNX1 at the same time as LSD1 inhibition rescued myeloid lineage conversion to an erythroid phenotype. These data show that LSD1 promotes erythropoiesis by repressing myeloid cell fate in adult erythroid progenitors and that inhibition of the myeloid-differentiation pathway reverses the lineage switch induced by LSD1 inactivation.

Expression profile of PU.1 in CD4+T cells from patients with systemic lupus erythematosus

Systemic lupus erythematosus (SLE) is a multisystem autoimmune disease with complex genetic predisposing factors involved. PU.1 is an important member of the ETS transcription factors family which has diverse functions such as regulating the proliferation, differentiation of immune cells and multiple inflammatory cytokines. Previous studies preliminary explored the relation between PU.1 and SLE. To further explain the potential role of PU.1 in the pathogenesis of SLE, 40 SLE patients and 20 age-sex matched healthy controls (HC) were recruited in this study. Flow cytometry was used to test the percentages of CD4+PU.1+T cells in peripheral blood mononuclear cells (PBMCs) from patients with SLE and HC. Expression levels of PU.1 mRNA in CD4+T cells from SLE patients and HC were analyzed by real-time transcription-polymerase chain reaction. Expression levels of plasma IL-1β, IL-9, IL-18, IL-6, IFN-α, TNF-α, IL-10 and TGF-β1 were measured by enzyme-linked immunosorbent assay. The percentage of CD4+PU.1+T cells in PBMCs from patients with SLE was significantly higher than that from HC (P < 0.001). In addition, the PU.1 mRNA expression in CD4+T cells from SLE patients was increased than that from HC (P = 0.002). In SLE patients, no significant correlation was found between the percentage of CD4+PU.1+T cells and the expression of PU.1 mRNA in CD4+T cells (P > 0.05). Associations of PU.1 mRNA expression in CD4+T cells with major clinical and laboratory parameters of SLE patients were also analyzed, but no significant correlations were found. Consistent with previous studies, SLE patients had increased IL-1β, IL-18, IL-6, IFN-α, TNF-α and IL-10 plasma concentrations than HC (P < 0.01). The expression level of plasma TGF-β1 was significantly decreased in SLE patients than in HC (P < 0.001). In SLE patients, the expression level of IL-1β was positive correlated with PU.1 mRNA expression in CD4+T cells (P = 0.001). Our study first time evaluated the expression profile of PU.1 in CD4+T cells from SLE patients confirming that PU.1 may participate in the pathogenesis of SLE.

Oncogenic cooperation between TCF7-SPI1 and NRAS(G12D) requires β-catenin activity to drive T-cell acute lymphoblastic leukemia

Spi-1 Proto-Oncogene (SPI1) fusion genes are recurrently found in T-cell acute lymphoblastic leukemia (T-ALL) cases but are insufficient to drive leukemogenesis. Here we show that SPI1 fusions in combination with activating NRAS mutations drive an immature T-ALL in vivo using a conditional bone marrow transplant mouse model. Addition of the oncogenic fusion to the NRAS mutation also results in a higher leukemic stem cell frequency. Mechanistically, genetic deletion of the β-catenin binding domain within Transcription factor 7 (TCF7)-SPI1 or use of a TCF/β-catenin interaction antagonist abolishes the oncogenic activity of the fusion. Targeting the TCF7-SPI1 fusion in vivo with a doxycycline-inducible knockdown results in increased differentiation. Moreover, both pharmacological and genetic inhibition lead to down-regulation of SPI1 targets. Together, our results reveal an example where TCF7-SPI1 leukemia is vulnerable to pharmacological targeting of the TCF/β-catenin interaction.

To bi or not to bi: Acute erythroid leukemias and hematopoietic lineage choice

Acute erythroid leukemia (AEL) is an acute leukemia characterized by erythroid lineage transformation. The World Health Organization (WHO) 2008 classification recognized two subtypes of AEL: bilineage erythroleukemia (erythroid/myeloid leukemia) and pure erythroid leukemia. The erythroleukemia subtype was removed in the updated 2016 WHO classification, with about half of cases reclassified as myelodysplastic syndrome (MDS) and half as acute myeloid leukemia (AML). Diagnosis and classification are currently based on morphology using standard blast cutoffs, without integration of underlying genomic and other molecular features. Key outstanding questions are therefore whether AEL can be accurately diagnosed based solely on morphology or whether genetic or other molecular criteria should be included in its classification, and whether considering AEL as an entity distinct from AML and MDS is clinically relevant. We discuss recent work on the molecular basis of AEL, including the identification of mutations causative of AEL and of transcriptional and epigenetic features that can be used to distinguish AEL from MDS and nonerythroid AML, and the prognostic value of these molecular features.

Molecular Landscapes and Models of Acute Erythroleukemia

Malignancies of the erythroid lineage are rare but aggressive diseases. Notably, the first insights into their biology emerged over half a century ago from avian and murine tumor viruses-induced erythroleukemia models providing the rationale for several transgenic mouse models that unraveled the transforming potential of signaling effectors and transcription factors in the erythroid lineage. More recently, genetic roadmaps have fueled efforts to establish models that are based on the epigenomic lesions observed in patients with erythroid malignancies. These models, together with often unexpected erythroid phenotypes in genetically modified mice, provided further insights into the molecular mechanisms of disease initiation and maintenance. Here, we review how the increasing knowledge of human erythroleukemia genetics combined with those from various mouse models indicate that the pathogenesis of the disease is based on the interplay between signaling mutations, impaired TP53 function, and altered chromatin organization. These alterations lead to aberrant activity of erythroid transcriptional master regulators like GATA1, indicating that erythroleukemia will most likely require combinatorial targeting for efficient therapeutic interventions.

Modeling and targeting of erythroleukemia by hematopoietic genome editing

Acute erythroid leukemia (AEL) is characterized by a distinct morphology, mutational spectrum, lack of preclinical models, and poor prognosis. Here, using multiplexed genome editing of mouse hematopoietic stem and progenitor cells and transplant assays, we developed preclinical models of AEL and non-erythroid acute leukemia and describe the central role of mutational cooperativity in determining leukemia lineage. Different combination of mutations in Trp53, Bcor, Dnmt3a, Rb1, and Nfix resulted in the development of leukemia with an erythroid phenotype, accompanied by the acquisition of alterations in signaling and transcription factor genes that recapitulate human AEL by cross-species genomic analysis. Clonal expansion during tumor evolution was driven by mutational cooccurrence, with clones harboring a higher number of founder and secondary lesions (eg, mutations in signaling genes) showing greater evolutionary fitness. Mouse and human AEL exhibited deregulation of genes regulating erythroid development, notably Gata1, Klf1, and Nfe2, driven by the interaction of mutations of the epigenetic modifiers Dnmt3a and Tet2 that perturbed methylation and thus expression of lineage-specific transcription factors. The established mouse leukemias were used as a platform for drug screening. Drug sensitivity was associated with the leukemia genotype, with the poly (ADP-ribose) polymerase inhibitor talazoparib and the demethylating agent decitabine efficacious in Trp53/Bcor-mutant AEL, CDK7/9 inhibitors in Trp53/Bcor/Dnmt3a-mutant AEL, and gemcitabine and bromodomain inhibitors in NUP98-KDM5A leukemia. In conclusion, combinatorial genome editing has shown the interplay of founding and secondary genetic alterations in phenotype and clonal evolution, epigenetic regulation of lineage-specific transcription factors, and therapeutic tractability in erythroid leukemogenesis.

Effect of purine-rich box1 on proliferation of fibroblasts

Fibroblasts are pleomorphic cells that have a multi-directional effect on organ morphogenesis, tissue homeostasis, and immune response. In fibrotic diseases, fibroblasts synthesize large amounts of extracellular matrix (ECM), leading to scarring and organ failure. Purine-rich box1 (PU.1) is a specific transcription factor of hematopoietic cell and belongs to the E26 transformation specificity (ETS) family. Recently, it was found that the transcription factor PU.1 is an important regulatory factor of the profibrotic gene expression program. TGF-β had been proved to play an important role in many ocular tissue fibrosis diseases, and up-regulated the expression of PU.1 in fibroblasts producing ECM in a Smad-3 dependent manner. We explore the effect of PU.1 on fibrosis of different ocular tissues from this perspective. This article reviews the role of PU.1 and its effects on fibrosis of ocular tissue and other tissues.

C/EBPα and GATA-2 Mutations Induce Bilineage Acute Erythroid Leukemia through Transformation of a Neomorphic Neutrophil-Erythroid Progenitor

Acute erythroid leukemia (AEL) commonly involves both myeloid and erythroid lineage transformation. However, the mutations that cause AEL and the cell(s) that sustain the bilineage leukemia phenotype remain unknown. We here show that combined biallelic Cebpa and Gata2 zinc finger-1 (ZnF1) mutations cooperatively induce bilineage AEL, and that the major leukemia-initiating cell (LIC) population has a neutrophil-monocyte progenitor (NMP) phenotype. In pre-leukemic NMPs Cebpa and Gata2 mutations synergize by increasing erythroid transcription factor (TF) expression and erythroid TF chromatin access, respectively, thereby installing ectopic erythroid potential. This erythroid-permissive chromatin conformation is retained in bilineage LICs. These results demonstrate that synergistic transcriptional and epigenetic reprogramming by leukemia-initiating mutations can generate neomorphic pre-leukemic progenitors, defining the lineage identity of the resulting leukemia.

NONO and tumorigenesis: More than splicing

The non-POU domain-containing octamer-binding protein NONO/p54^nrb , which belongs to the Drosophila behaviour/human splicing (DBHS) family, is a multifunctional nuclear protein rarely functioning alone. Emerging solid evidences showed that NONO engages in almost every step of gene regulation, including but not limited to mRNA splicing, DNA unwinding, transcriptional regulation, nuclear retention of defective RNA and DNA repair. NONO is involved in many biological processes including cell proliferation, apoptosis, migration and DNA damage repair. Dysregulation of NONO has been found in many types of cancer. In this review, we summarize the current and fast-growing knowledge about the regulation of NONO, its biological function and implications in tumorigenesis and cancer progression. Overall, significant findings about the roles of NONO have been made, which might make NONO to be a new biomarker or/and a possible therapeutic target for cancers.

Candidate Cancer Driver Mutations in Distal Regulatory Elements and Long-Range Chromatin Interaction Networks

A comprehensive catalog of cancer driver mutations is essential for understanding tumorigenesis and developing therapies. Exome-sequencing studies have mapped many protein-coding drivers, yet few non-coding drivers are known because genome-wide discovery is challenging. We developed a driver discovery method, ActiveDriverWGS, and analyzed 120,788 cis-regulatory modules (CRMs) across 1,844 whole tumor genomes from the ICGC-TCGA PCAWG project. We found 30 CRMs with enriched SNVs and indels (FDR < 0.05). These frequently mutated regulatory elements (FMREs) were ubiquitously active in human tissues, showed long-range chromatin interactions and mRNA abundance associations with target genes, and were enriched in motif-rewiring mutations and structural variants. Genomic deletion of one FMRE in human cells caused proliferative deficiencies and transcriptional deregulation of cancer genes CCNB1IP1, CDH1, and CDKN2B, validating observations in FMRE-mutated tumors. Pathway analysis revealed further sub-significant FMREs at cancer genes and processes, indicating an unexplored landscape of infrequent driver mutations in the non-coding genome.

Friend retrovirus studies reveal complex interactions between intrinsic, innate and adaptive immunity

Approximately 4.4% of the human genome is comprised of endogenous retroviral sequences, a record of an evolutionary battle between man and retroviruses. Much of what we know about viral immunity comes from studies using mouse models. Experiments using the Friend virus (FV) model have been particularly informative in defining highly complex anti-retroviral mechanisms of the intrinsic, innate and adaptive arms of immunity. FV studies have unraveled fundamental principles about how the immune system controls both acute and chronic viral infections. They led to a more complete understanding of retroviral immunity that begins with cellular sensing, production of type I interferons, and the induction of intrinsic restriction factors. Novel mechanisms have been revealed, which demonstrate that these earliest responses affect not only virus replication, but also subsequent innate and adaptive immunity. This review on FV immunity not only surveys the complex host responses to a retroviral infection from acute infection to chronicity, but also highlights the many feedback mechanisms that regulate and counter-regulate the various arms of the immune system. In addition, the discovery of molecular mechanisms of immunity in this model have led to therapeutic interventions with implications for HIV cure and vaccine development.

Bioinformatic identification of candidate biomarkers and related transcription factors in nasopharyngeal carcinoma

Background

The incidence of nasopharyngeal carcinoma (NPC) is rare, but a certain amount of mortality remains in NPC patients. Our study aimed to identify candidate genes as biomarkers for NPC screening, diagnosis, and therapy.

Methods

We investigated two microarray profile datasets GSE64634 and GSE12452 to screen the potential differentially expressed genes (DEGs) in NPC. Gene ontology and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis of the DEGs were also performed. A protein-protein interaction (PPI) network of DEGs was constructed by STRING and visualized by Cytoscape software. The associated transcriptional factor regulatory network of the DEGs was also constructed.

Results

A total of 152 DEGs were identified from the GSE64634 and GSE12452 datasets, including 10 upregulated and 142 downregulated genes. Gene functional enrichment analysis indicated that these DEGs were enriched in the cilium movement, antimicrobial humoral response, O-glycan processing, mucosal immune response, carbohydrate transmembrane transporter activity, hormone biosynthetic process, neurotransmitter biosynthetic process, and drug metabolism-cytochrome P450 pathway. Five hub genes (DNALI1, RSPH4A, RSPH9, DNAI2, and ALDH3A1) and one significant module (score = 5.6) were obtained from the PPI network. Key transcriptional factors, such as SPI1, SIN3B, and GATA2, were identified with close interactions with these five hub DEGs from the gene-transcriptional factor network.

Conclusions

With the integrated bioinformatic analysis, numerous DEGs related to NPC were screened, and the hub DEGs we identified may be potential biomarkers for NPC.

Friend virus limits adaptive cellular immune responses by imprinting a maturation-resistant and T helper type 2-biased immunophenotype in dendritic cells

The murine Friend virus (FV) retrovirus model has been widely used to study anti-viral immune responses, and virus-induced cancer. Here we analyzed FV immune evasion mechanisms on the level of dendritic cells (DC) essential for the induction of primary adaptive immune responses. Comparative quantitative proteome analysis of FV-infected DC (FV-DC) of different genotypes (BALB/c, C57BL/6) and non-infected DC revealed numerous genotype-independently regulated proteins rergulating metabolic activity, cytoskeletal rearrangements, and antigen processing/presentation. These alterations may promote virion production in FV-DC. Stimulation of FV-DC with LPS resulted in strongly enhanced IL-10 production which was partially responsible for their attenuated T cell (CD4⁺, CD8⁺) stimulatory capacity. Stimulated FV-DC induced less IFN-γ production in T cells required for cellular anti-viral responses, but more T helper cell type 2 (Th2)-associated cytokines (IL-4, IL-5, IL-13). We conclude that FV reprograms DC to promote viral spreading and immune deviation by imprinting a largely maturation-resistant, Th2-biased immunophenotype.

Transcriptomic and proteomic analysis of mouse radiation-induced acute myeloid leukaemia (AML)

A combined transcriptome and proteome analysis of mouse radiation-induced AMLs using two primary AMLs, cell lines from these primaries, another cell line and its in vivo passage is reported. Compared to haematopoietic progenitor and stem cells (HPSC), over 5000 transcriptome alterations were identified, 2600 present in all materials. 55 and 3 alterations were detected in the proteomes of the cell lines and primary/in vivo passage material respectively, with one common to all materials. In cell lines, approximately 50% of the transcriptome changes are related to adaptation to cell culture, and in the proteome this proportion was higher. An AML 'signature' of 17 genes/proteins commonly deregulated in primary AMLs and cell lines compared to HPSCs was identified and validated using human AML transcriptome data. This also distinguishes primary AMLs from cell lines and includes proteins such as Coronin 1, pontin/RUVBL1 and Myeloperoxidase commonly implicated in human AML. C-Myc was identified as having a key role in radiation leukaemogenesis. These data identify novel candidates relevant to mouse radiation AML pathogenesis, and confirm that pathways of leukaemogenesis in the mouse and human share substantial commonality.

Senescence is a Spi1-induced anti-proliferative mechanism in primary hematopoietic cells

Transcriptional deregulation caused by epigenetic or genetic alterations is a major cause of leukemic transformation. The Spi1/PU.1 transcription factor is a key regulator of many steps of hematopoiesis, and limits self-renewal of hematopoietic stem cells. The deregulation of its expression or activity contributes to leukemia, in which Spi1 can be either an oncogene or a tumor suppressor. Herein we explored whether cellular senescence, an anti-tumoral pathway that restrains cell proliferation, is a mechanism by which Spi1 limits hematopoietic cell expansion, and thus prevents the development of leukemia. We show that Spi1 overexpression triggers cellular senescence both in primary fibroblasts and hematopoietic cells. Erythroid and myeloid lineages are both prone to Spi1-induced senescence. In hematopoietic cells, Spi1-induced senescence requires its DNA-binding activity and a functional p38MAPK14 pathway but is independent of a DNA-damage response. In contrast, in fibroblasts, Spi1-induced senescence is triggered by a DNA-damage response. Importantly, using our well-established Spi1 transgenic leukemia mouse model, we demonstrate that Spi1 overexpression also induces senescence in erythroid progenitors of the bone marrow in vivo before the onset of the pre-leukemic phase of erythroleukemia. Remarkably, the senescence response is lost during the progression of the disease and erythroid blasts do not display a higher expression of Dec1 and CDKN1A, two of the induced senescence markers in young animals. These results bring indirect evidence that leukemia develops from cells which have bypassed Spi1-induced senescence. Overall, our results reveal senescence as a Spi1-induced anti-proliferative mechanism that may be a safeguard against the development of acute myeloid leukemia.

[Immortalization of erythroid progenitors for in vitro large-scale red cell production]

Population ageing and increase in cancer incidence may lead to a decreased availability of red blood cell units. Thus, finding an alternative source of red blood cells is a highly relevant challenge. The possibility to reproduce in vitro the human erythropoiesis opens a new era, particularly since the improvement in the culture systems allows to produce erythrocytes from induced-Pluripotent Stem Cells (iPSCs), or CD34⁺ Hematopoietic Stem Cells (HSCs). iPSCs have the advantage of in vitro self-renewal, but lead to poor amplification and maturation defects (high persistence of nucleated erythroid precursors). Erythroid differentiation from HSC allows a far better amplification and adult-like hemoglobin synthesis. But the inability of these progenitors to self-renew in vitro remains a limit in their use as a source of stem cells. A major improvement would consist in immortalizing these erythroid progenitors so that they could expand indefinitively. Inducible transgenesis is the first way to achieve this goal. To date, the best immortalized-cell models involve strong oncogenes induction, such as c-Myc, Bcl-xL, and mostly E6/E7 HPV16 viral oncoproteins. However, the quality of terminal differentiation of erythroid progenitors generated by these oncogenes is not optimal yet and the long-term stability of such systems is unknown. Moreover, viral transgenesis and inducible expression of oncogenes raise important problems in term of safety, since the enucleation rate is not 100% and no nucleated cells having replicative capacities should be present in the final product.

Recurrent SPI1 (PU.1) fusions in high-risk pediatric T cell acute lymphoblastic leukemia

The outcome of treatment-refractory and/or relapsed pediatric T cell acute lymphoblastic leukemia (T-ALL) is extremely poor, and the genetic basis for this is not well understood. Here we report comprehensive profiling of 121 cases of pediatric T-ALL using transcriptome and/or targeted capture sequencing, through which we identified new recurrent gene fusions involving SPI1 (STMN1-SPI1 and TCF7-SPI1). Cases positive for fusions involving SPI1 (encoding PU.1), accounting for 3.9% (7/181) of the examined pediatric T-ALL cases, showed a double-negative (DN; CD4^-CD8^-) or CD8⁺ single-positive (SP) phenotype and had uniformly poor overall survival. These cases represent a subset of pediatric T-ALL distinguishable from the known T-ALL subsets in terms of expression of genes involved in T cell precommitment, establishment of T cell identity, and post-β-selection maturation and with respect to mutational profile. PU.1 fusion proteins retained transcriptional activity and, when constitutively expressed in mouse stem/progenitor cells, induced cell proliferation and resulted in a maturation block. Our findings highlight a unique role of SPI1 fusions in high-risk pediatric T-ALL.

Fli-1 overexpression in erythroleukemic cells promotes erythroid de-differentiation while Spi-1/PU.1 exerts the opposite effect

The ETS transcription factors play a critical role during hematopoiesis. In F-MuLV-induced erythroleukemia, Fli-1 insertional activation producing high expression of this transcription factor required to promote proliferation. How deregulated Fli-1 expression alters the balance between erythroid differentiation and proliferation is unknown. To address this issue, we exogenously overexpressed Fli-1 in an erythroleukemic cell harboring activation of spi-1/PU.1, another ETS gene involved in erythroleukemogenesis. While the proliferation in culture remains unaffected, Fli-1 overexpression imparts morphological and immunohistochemical characteristics of immature erythroid progenitors. Fli-1 overexpression in erythroleukemic cells increased the numbers of erythroid colonies on methylcellulose and reduced tumorigenicity as evidenced by increase latency of erythroleukemogenesis in mice inoculated with these cells. Although all transplanted mice developed enlargement of the spleen and liver due to leukemic infiltration, Fli-1 overexpression altered the hematopoietic phenotype, significantly increasing the expression of regulatory hematopoietic genes cKIT, SCA-1, CD41 and CD71. In contrast, expression of Spi-1/PU.1 in a Fli-1 producing erythroleukemia cell line in which fli-1 is activated, resulted in increased proliferation through activation of growth promoting proteins MAPK, AKT, cMYC and JAK2. Importantly, these progenitors express high levels of markers such as CD71 and TER119 associated with more mature erythroid cells. Thus, Fli-1 overexpression induces a de-differentiation program by reverting CFU-E to BFU-E erythroid progenitor activity, while Spi-1/PU.1 promoting maturation from BFU-E to CFU-E.

The ETS family of oncogenic transcription factors in solid tumours

Findings over the past decade have identified aberrant activation of the ETS transcription factor family throughout all stages of tumorigenesis. Specifically in solid tumours, gene rearrangement and amplification, feed-forward growth factor signalling loops, formation of gain-of-function co-regulatory complexes and novel cis-acting mutations in ETS target gene promoters can result in increased ETS activity. In turn, pro-oncogenic ETS signalling enhances tumorigenesis through a broad mechanistic toolbox that includes lineage specification and self-renewal, DNA damage and genome instability, epigenetics and metabolism. This Review discusses these different mechanisms of ETS activation and subsequent oncogenic implications, as well as the clinical utility of ETS factors.

Mouse models for radiation-induced cancers

Potential ionising radiation exposure scenarios are varied, but all bring risks beyond the simple issues of short-term survival. Whether accidentally exposed to a single, whole-body dose in an act of terrorism or purposefully exposed to fractionated doses as part of a therapeutic regimen, radiation exposure carries the consequence of elevated cancer risk. The long-term impact of both intentional and unintentional exposure could potentially be mitigated by treatments specifically developed to limit the mutations and precancerous replication that ensue in the wake of irradiation The development of such agents would undoubtedly require a substantial degree of in vitro testing, but in order to accurately recapitulate the complex process of radiation-induced carcinogenesis, well-understood animal models are necessary. Inbred strains of the laboratory mouse, Mus musculus, present the most logical choice due to the high number of molecular and physiological similarities they share with humans. Their small size, high rate of breeding and fully sequenced genome further increase its value for use in cancer research. This chapter will review relevant m. musculus inbred and F1 hybrid animals of radiation-induced myeloid leukemia, thymic lymphoma, breast and lung cancers. Method of cancer induction and associated molecular pathologies will also be described for each model.

PU.1 is involved in the immune response to Aspergillus fumigatus through upregulating Dectin-1 expression

Background

Invasive aspergillosis is a life-threatening disease, and its incidence has increased in the recent past. Dectin-1 recognizes β-glucans and mediates innate immune responses to Aspergillus fumigatus. Transcription factor PU.1 has been the focus of recent research due to its role in inflammation and infection. However, its role in Dectin-1 regulation during A. fumigatus infection remains to be elucidated.

Methods

THP-1 cells were stimulated with A. fumigatus conidia. We then used real-time RT-PCR, Western blot, and immunofluorescence assays to analyze the mRNA and protein levels and cellular distribution, respectively, of Dectin-1 and PU.1 in stimulated THP-1 cells. Additionally, we used the luciferase reporter assays, chromatin immunoprecipitation (ChIP) assays, electrophoretic mobility shift assays (EMSA), and RNA interference experiments to investigate the role of PU.1 in Dectin-1 regulation.

Results

Our results revealed that Dectin-1 mRNA and protein levels as well as the PU.1 protein level were increased in THP-1 cells stimulated with A. fumigatus conidia, while the mRNA expression level did not significantly change between the stimulated and control groups. We also observed that PU.1 translocated into the nucleus in stimulated THP-1 cells. The results of the luciferase reporter assay showed that PU.1 promoted human Dectin-1 (hDectin-1) gene activity. ChIP and EMSA indicated that PU.1 could bind with hDectin-1 gene promoter at three potential transcription factor-binding sites (TFBSs). In addition, knockdown of PU.1 significantly decreased Dectin-1 expression.

Conclusions

This study demonstrated the novel role of PU.1 in the immune response to A. fumigatus through upregulation of Dectin-1 expression and its translocation to the nucleus in A. fumigatus-stimulated THP-1 cells.

GATA-1 Inhibits PU.1 Gene via DNA and Histone H3K9 Methylation of Its Distal Enhancer in Erythroleukemia

GATA-1 and PU.1 are two important hematopoietic transcription factors that mutually inhibit each other in progenitor cells to guide entrance into the erythroid or myeloid lineage, respectively. PU.1 controls its own expression during myelopoiesis by binding to the distal URE enhancer, whose deletion leads to acute myeloid leukemia (AML). We herein present evidence that GATA-1 binds to the PU.1 gene and inhibits its expression in human AML-erythroleukemias (EL). Furthermore, GATA-1 together with DNA methyl Transferase I (DNMT1) mediate repression of the PU.1 gene through the URE. Repression of the PU.1 gene involves both DNA methylation at the URE and its histone H3 lysine-K9 methylation and deacetylation as well as the H3K27 methylation at additional DNA elements and the promoter. The GATA-1-mediated inhibition of PU.1 gene transcription in human AML-EL mediated through the URE represents important mechanism that contributes to PU.1 downregulation and leukemogenesis that is sensitive to DNA demethylation therapy.

A semi-supervised approach uncovers thousands of intragenic enhancers differentially activated in human cells

Background

Transcriptional enhancers are generally known to regulate gene transcription from afar. Their activation involves a series of changes in chromatin marks and recruitment of protein factors. These enhancers may also occur inside genes, but how many may be active in human cells and their effects on the regulation of the host gene remains unclear.

Results

We describe a novel semi-supervised method based on the relative enrichment of chromatin signals between 2 conditions to predict active enhancers. We applied this method to the tumoral K562 and the normal GM12878 cell lines to predict enhancers that are differentially active in one cell type. These predictions show enhancer-like properties according to positional distribution, correlation with gene expression and production of enhancer RNAs. Using this model, we predict 10,365 and 9777 intragenic active enhancers in K562 and GM12878, respectively, and relate the differential activation of these enhancers to expression and splicing differences of the host genes.

Conclusions

We propose that the activation or silencing of intragenic transcriptional enhancers modulate the regulation of the host gene by means of a local change of the chromatin and the recruitment of enhancer-related factors that may interact with the RNA directly or through the interaction with RNA binding proteins. Predicted enhancers are available at http://regulatorygenomics.upf.edu/Projects/enhancers.html.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-015-1704-0) contains supplementary material, which is available to authorized users.

PU.1 downregulation in murine radiation-induced acute myeloid leukaemia (AML): from molecular mechanism to human AML

The transcription factor PU.1, encoded by the murine Sfpi1 gene (SPI1 in humans), is a member of the Ets transcription factor family and plays a vital role in commitment and maturation of the myeloid and lymphoid lineages. Murine studies directly link primary acute myeloid leukaemia (AML) and decreased PU.1 expression in specifically modified strains. Similarly, a radiation-induced chromosome 2 deletion and subsequent Sfpi1 point mutation in the remaining allele lead to murine radiation-induced AML. Consistent with murine data, heterozygous deletion of the SPI1 locus and mutation of the −14kb SPI1 upstream regulatory element were described previously in human primary AML, although they are rare events. Other mechanisms linked to PU.1 downregulation in human AML include TP53 deletion, FLT3-ITD mutation and the recurrent AML1-ETO [t(8;21)] and PML-RARA [t(15;17)] translocations. This review provides an up-to-date overview on our current understanding of the involvement of PU.1 in the initiation and development of radiation-induced AML, together with recommendations for future murine and human studies.

A novel zinc finger gene, ZNF465, is inappropriately expressed in acute myeloid leukaemia cells

To increase our knowledge of leukaemia-associated antigens, especially in acute myeloid leukaemia (AML) M4, we prepared a phage display cDNA library using mRNA from the bone marrow cells of a patient with AML M4 at diagnosis. We immunoscreened 10(6) pfu with autologous sera and identified an antigen which we named GKT-AML8. The cDNA showed more than 99% similarity to a sequence on 2q21.2 and 95% sequence similarity to a sequence on 19q13.3. These genes were named ZNF465 and ZNF466, respectively, following HUGO Gene Nomenclature Committee (HGNC) guidelines. Expressed sequence tag data suggests that both genes are transcriptionally active. ZNF465 and ZNF466 encode a 5' krüppel associated box domain typical of negative regulators of gene transcription. We have confirmed the translational start site in the +1 frame in a near-Kozak sequence that produces a 102 amino acid polypeptide from ZNF465. The high level of sequence similarity between ZNF465 and ZNF466 makes their transcripts almost indistinguishable by real-time polymerase chain reaction (RT-PCR). However, GKT-AML8 showed most sequence similarity to ZNF465 and no transcript matching the 3' ZNF466 sequence could be detected in patient samples or healthy volunteers. ZNF465/466 expression was detectable in 12/13 AML and 10/14 chronic myeloid leukaemia patients' samples but not in normal donor peripheral blood (0/8) or 0/3 bone marrow samples which had been separated into CD34(+) and CD34(-) samples. The altered expression of ZNF465/466 in patients' samples and its absence in healthy donor haematopoietic samples indicate that ZNF465 is overexpressed in early myeloid disease and as such may represent a promising target for immunotherapy.

Transcriptional Factor PU.1 Regulates Decidual C1q Expression in Early Pregnancy in Human

C1q is the first recognition subcomponent of the complement classical pathway, which in addition to being synthesized in the liver, is also expressed by macrophages and dendritic cells (DCs). Trophoblast invasion during early placentation results in accumulation of debris that triggers the complement system. Hence, both early and late components of the classical pathway are widely distributed in the placenta and decidua. In addition, C1q has recently been shown to significantly contribute to feto-maternal tolerance, trophoblast migration, and spiral artery remodeling, although the exact mechanism remains unknown. Pregnancy in mice, genetically deficient in C1q, mirrors symptoms similar to that of human preeclampsia. Thus, regulated complement activation has been proposed as an essential requirement for normal successful pregnancy. Little is known about the molecular pathways that regulate C1q expression in pregnancy. PU.1, an Ets-family transcription factor, is required for the development of hematopoietic myeloid lineage immune cells, and its expression is tissue-specific. Recently, PU.1 has been shown to regulate C1q gene expression in DCs and macrophages. Here, we have examined if PU.1 transcription factor regulates decidual C1q expression. We used immune-histochemical analysis, PCR, and immunostaining to localize and study the gene expression of PU.1 transcription factor in early human decidua. PU.1 was highly expressed at gene and protein level in early human decidual cells including trophoblast and stromal cells. Surprisingly, nuclear as well as cytoplasmic PU.1 expression was observed. Decidual cells with predominantly nuclear PU.1 expression had higher C1q expression. It is likely that nuclear and cytoplasmic PU.1 localization has a role to play in early pregnancy via regulating C1q expression in the decidua during implantation.

Single-cell technologies sharpen up mammalian stem cell research

Analysis of the mechanisms underlying cell fates requires the molecular quantification of cellular features. Classical techniques use population average readouts at single time points. However, these approaches mask cellular heterogeneity and dynamics and are limited for studying rare and heterogeneous cell populations like stem cells. Techniques for single-cell analyses, ideally allowing non-invasive quantification of molecular dynamics and cellular behaviour over time, are required for studying stem cells. Here, we review the development and application of these techniques to stem cell research.

Radiation-induced myeloid leukemia in murine models

The use of radiation therapy is a cornerstone of modern cancer treatment. The number of patients that undergo radiation as a part of their therapy regimen is only increasing every year, but this does not come without cost. As this number increases, so too does the incidence of secondary, radiation-induced neoplasias, creating a need for therapeutic agents targeted specifically towards incidence reduction and treatment of these cancers. Development and efficacy testing of these agents requires not only extensive in vitro testing but also a set of reliable animal models to accurately recreate the complex situations of radiation-induced carcinogenesis. As radiation-induced leukemic progression often involves genomic changes such as rearrangements, deletions, and changes in methylation, the laboratory mouse Mus musculus, with its fully sequenced genome, is a powerful tool in cancer research. This fact, combined with the molecular and physiological similarities it shares with man and its small size and high rate of breeding in captivity, makes it the most relevant model to use in radiation-induced leukemia research. In this work, we review relevant M. musculus inbred and F₁ hybrid animal models, as well as methods of induction of radiation-induced myeloid leukemia. Associated molecular pathologies are also included.

Concise review: erythroid versus myeloid lineage commitment: regulating the master regulators

Developmental processes, like blood formation, are orchestrated by transcriptional networks. Those transcriptional networks are highly responsive to various environmental stimuli and affect common precursors resulting in increased production of cells of the erythroid lineage or myeloid lineage (granulocytes, neutrophils, and macrophages). A significant body of knowledge has accumulated describing transcription factors that drive differentiation of these two major cellular pathways, in particular the antagonistic master regulators such as GATA-1 and PU.1. However, little is known about factors that work upstream of master regulators to enhance differentiation toward one lineage. These functions become especially important under various stress conditions like sudden loss of red blood cells or pathogen infection. This review describes recent studies that begin to provide evidence for such factors. An increased understanding of factors regulating cellular commitment will advance our understanding of the etiology of diseases like anemia, cancer, and possibly other blood related disorders.

Dual regulation of SPI1/PU.1 transcription factor by heat shock factor 1 (HSF1) during macrophage differentiation of monocytes

In addition to their cytoprotective role in stressful conditions, heat shock proteins (HSPs) are involved in specific differentiation pathways, for example, we have identified a role for HSP90 in macrophage differentiation of human peripheral blood monocytes that are exposed to macrophage colony-stimulating factor (M-CSF). Here, we show that deletion of the main transcription factor involved in heat shock gene regulation, heat shock factor 1 (HSF1), affects M-CSF-driven differentiation of mouse bone marrow cells. HSF1 transiently accumulates in the nucleus of human monocytes undergoing macrophage differentiation, including M-CSF-treated peripheral blood monocytes and phorbol ester-treated THP1 cells. We demonstrate that HSF1 has a dual effect on SPI1/PU.1, a transcription factor essential for macrophage differentiation and whose deregulation can lead to the development of leukemias and lymphomas. Firstly, HSF1 regulates SPI1/PU.1 gene expression through its binding to a heat shock element within the intron 2 of this gene. Furthermore, downregulation or inhibition of HSF1 impaired both SPI1/PU.1-targeted gene transcription and macrophage differentiation. Secondly, HSF1 induces the expression of HSP70 that interacts with SPI1/PU.1 to protect the transcription factor from proteasomal degradation. Taken together, HSF1 appears as a fine-tuning regulator of SPI1/PU.1 expression at the transcriptional and post-translational levels during macrophage differentiation of monocytes.