MicroRNA in Platelet Production and Activation

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. SCI-39-SCI-39
Author(s):  
Paul F. Bray
Keyword(s):  
Gene Expression ◽  
Zinc Finger Protein ◽  
Conflicts Of Interest ◽  
Platelet Reactivity ◽  
Functional Characterization ◽  
Fine Tuning ◽  
Interindividual Variation ◽  
Erythroid Progenitor ◽  
Mrna Targets ◽  
Potential Biomarker

Abstract Abstract SCI-39 Alterations in gene expression are at the heart of both megakaryocytopoiesis and interindividual variation in platelet reactivity. Over the past decade there has been an increasing awareness of the important role played by microRNAs (miRNAs) in these diverse cell biologic and physiologic processes. MiRNAs are noncoding RNAs that target complementary sequences in mRNAs, leading to mRNA degradation or inhibition of translation. More than 1000 miRNAs have been identified, which are estimated to regulate 30%-90% of all coding genes. Expression of miRNAs is cell and developmental stage specific. MiRNAs regulate hematopoietic lineage commitment, as well as B lymphopoiesis, granulopoiesis, erythropoiesis and monocytopoiesis. Recent data also demonstrate a clear role for miRNAs in megakaryocytopoiesis (Meg-poiesis). The molecular genetic basis for the transition from one stage of Meg-poiesis to another requires fine-tuning of the various control elements, and miRNAs act as “rheostats” in this process. MiRNA-150 has a strong effect on Meg-erythroid progenitor cells, inducing commitment to the Meg lineage at the expense of erythropoiesis. MiRNA-150 directly down-regulates MYB, a transcription factor important in thrombopoiesis. Over-expressed miRNA-146a knocks down CXCR4 (receptor for SDF-1), reducing Meg proliferation and maturation. MiR-146a gene expression is negatively regulated by the promyelocytic zinc finger protein, PLZF. Thus, miRNAs act as intermediaries of transcription factors that control Meg-poiesis. An increasing number of genetic diseases are being described due to mutations in miRNA genes or their mRNA targets. Deletion of miR-145 and miR-146a on 5q is sufficient to cause the 5q- phenotype; miR-125b-2 up-regulates Meg-poiesis and may be involved in megakaryoblastic leukemia. Platelets appear to be a particularly rich source of miRNAs, many of which are expressed at very high levels. Notably, platelets contain Dicer, TRBP2 and Ago2, and are capable of synthesizing miRNAs from pre-miRNAs. MiRNAs regulate Bcl-xL and Bak, raising the possibility that platelet miRNAs affect platelet lifespan. Because miRNAs are very stable, they also represent a potential biomarker, and we have found sets of miRNAs that appear to classify platelet reactivity to epinephrine. Using bioinformatic approaches, we have identified miRNA-mRNA pairs differentially expressed in platelets with differing phenotypes. This approach permits functional characterization of novel platelet mRNAs, and elucidation of a potential genetic mechanism for adjusting megakaryocyte/platelet mRNA expression. Thus, information extracted from these RNA networks continue to provide insights into systems biology of higher organisms. Disclosures: No relevant conflicts of interest to declare.

Transcriptional Regulation of Erythropoiesis.

Blood ◽  
2009 ◽  
Vol 114 (22) ◽  
pp. SCI-7-SCI-7
Author(s):  
Mitchell J. Weiss
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
Transcriptional Activation ◽  
Zinc Finger Protein ◽  
Conflicts Of Interest ◽  
Globin Gene ◽  
Globin Genes ◽  
Erythroid Development ◽  
Globin Gene Expression

Abstract Abstract SCI-7 Efforts to define the mechanisms of globin gene expression and transcriptional control of erythrocyte formation have provided key insights into our understanding of developmental hematopoiesis. Our group has focused on GATA-1, a zinc finger protein that was initially identified through its ability to bind a conserved cis element that regulates globin gene expression. GATA-1 is essential for erythroid development and mutations in the GATA1 gene are associated with human cytopenias and leukemia. Several general principles have emerged through studies to define the mechanisms of GATA-1 action. First, GATA-1 activates not only globin genes, but also virtually every gene that defines the erythroid phenotype. This observation sparked successful gene discovery efforts to identify new components of erythroid development and physiology. Second, GATA-1 also represses transcription through multiple mechanisms. This property may help to explain how GATA-1 regulates hematopoietic lineage commitment and also how GATA1 mutations contribute to cancer, since several directly repressed targets are proto-oncogenes. Third, GATA-1 regulates not only protein coding genes, but also microRNAs, which in turn, modulate erythropoiesis through post-transcriptional mechanisms. Fourth, GATA-1 interacts with other essential erythroid-specific and ubiquitous transcription factors. These protein interactions regulate gene expression by influencing chromatin modifications and controlling three-dimensional proximity between widely spaced DNA elements. Recently, we have combined transcriptome analysis with ChIP-chip and ChIP-seq studies to correlate in vivo occupancy of DNA by GATA-1 and other transcription factors with mRNA expression genome-wide in erythroid cells. These studies better elucidate how GATA-1 recognizes DNA, discriminates between transcriptional activation versus repression and interacts functionally with other nuclear proteins. I will review published and new aspects of our work in these areas. Disclosures No relevant conflicts of interest to declare.

Recurrent 11q24.3 Gain Contributes to the Pathogenesis of Diffuse Large B Cell Lymphoma (DLBCL) by Deregulating ETS1 and FLI1

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1386-1386
Author(s):  
Paola Bonetti ◽  
Monica Testoni ◽  
Marta Scandurra ◽  
Maurilio Ponzoni ◽  
Roberto Piva ◽  
...  
Keyword(s):  
Gene Expression ◽  
Transcription Factors ◽  
B Cell ◽  
Germinal Center ◽  
Conflicts Of Interest ◽  
Cell Lymphoma ◽  
Functional Characterization ◽  
B Cell Lymphoma ◽  
Transcriptional Program ◽  
Down Regulation

Abstract Abstract 1386 DLBCL represents the most common form of B-cell non-Hodgkin lymphoma (B-NHL). It is an aggressive and heterogeneous disease, comprising at least three distinct subtypes based on gene expression profile analysis: germinal center B cell-like DLBCL (GCB), activated B cell-like DLBCL (ABC) and primary mediastinal B-cell lymphoma (PMBL). These subtypes are supposed to derive from B cells at different stages of differentiation. Normal germinal center (GC) B-cell differentiation requires a complex transcriptional program and alterations of genes involved in this process are relevant for DLBCL pathogenesis. Identification and functional characterization of new genetic lesions would provide critical information to better understand the pathogenesis of DLBCL. With this aim, we studied the genomic profiles of 166 DLBCL patients, identified and characterized a recurrent gain mapping to chromosome 11q24.3. Methods. Genomic profiles were obtained from 166 Affymetrix 250K SNP arrays and integrated with gene expression data (GeneChip U133 plus 2.0) in 54 cases. Data were validated by PCR and immunohistochemistry. Gene silencing experiments were done with shRNA. Results. A minimal common region 11q24.3 gain was present in 26% of DLBCL samples and it encompassed six genes (ETS1, FLI1, KCNJ1, KCNJ5, P53AIP1, RICS). Samples with the 11q24.3 gain were significantly associated with high expression of the transcription factors ETS1 and FLI1. Data were confirmed by real-time PCR and by immunohistochemical analysis. Gene expression analysis showed 228 transcripts with a significantly different expression between cases with or without the lesion (p<0.01, >2-fold change): 215 genes were up-regulated in the patients with the gain and 13 were down-regulated, suggesting that this lesion has an impact on the transcriptional program of the tumor cells. To study the biological meaning of the lesion, ETS1 and FLI1 expression was down-regulated in a DLBCL cell line bearing the same lesion observed in clinical specimens (OCI-Ly7). Results showed that ETS1 and FLI1 down-regulation caused a reduced proliferation rate and activation of apoptosis leading to cell death. Concomitant ETS1 and FLI1 down-regulation resulted in a more severe phenotype. Only FLI1 was confirmed to be essential for cell viability in other DLBCL cell lines (SUDHL4, VAL, U2932), whereas ETS1 did not, suggesting a distinct role of the two transcription factors in different DLBCL samples. Preliminary results showed that down-regulation of ETS1 affected the transcriptional program of GC B-cell terminal differentiation causing an up-regulation of BLIMP1, the master regulator of plasma cells differentiation. Conclusions. In DLBCL, a recurrent gain at 11q24.3 determines the over-expression of the transcription factors ETS1 and FLI1. Functional experiments showed that the lesion might sustain DLBCL proliferation and viability, and contribute to a differentiation blockade of the GC B-cell towards a plasma cell lineage by negatively regulating BLIMP1. Disclosures: No relevant conflicts of interest to declare.

Isolation and Functional Characterization of Human Erythroid Progenitors: BFU-E and CFU-E

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1028-1028
Author(s):  
Pooja Bhagia ◽  
Narla Mohandas ◽  
Xiuli An
Keyword(s):  
Bone Marrow ◽  
Conflicts Of Interest ◽  
Bone Marrow Failure ◽  
Functional Characterization ◽  
Human Bone ◽  
Human Bone Marrow ◽  
Erythroid Progenitor ◽  
Expression Levels ◽  
Cd34 Cells

Abstract Abstract 1028 The two committed erythroid progenitor populations that have been functionally defined by colony assays are burst-forming unit-erythroid (BFU-E) and colony-forming unit-erythroid (CFU-E). While significant progress has been made in defining these two progenitor populations in the murine system, their characterization in the human system is incomplete. To address this issue, we have characterized the dynamic changes in surface expression levels of number of proteins including CD34, c-kit, IL-3R, CD36, CD71, GPA and CD45 during proliferation of purified human CD34+ cells from cord blood during the first phase of the two-phase in vitro erythroid culture system. In the presence of stem cell factor, IL-3 and erythropoietin during this phase, CD34+ cells differentiate first into BFU-E and then into CFU-E during 7 days of culture with peak levels of BFU-E at day 4 and of CFU-E at day 6. During this period of time, the expression levels of CD34 and IL-3R decreased, while that that of CD36 and CD71 increased. CD45 was expressed during the entire 7 day culture period while there was no expression of GPA. Based on these findings, we sorted pure populations of CD34+CD36−IL3-R+ and CD34− CD36+IL-3R− cells and characterized their behavior in colony forming assays. The sorted CD34+CD36−IL3-R+ population gave rise to BFU-E colonies while CD34− CD36+IL-3R− population gave rise CFU-E colonies, both at a purity of over 80%. The identity of the sorted BFU-E and CFU-E cells was further supported by their differential responsiveness to dexamethasone and lenalidomide (Narla A et al Blood 2011), with increased proliferation BFU-E population by dexamethasone and increased proliferation of CFU-E by lenalidomide. These findings were further validated by isolation of pure populations of BFU-E and CFU-E from primary human bone marrow based on the identified markers. The ability to isolate pure populations of human BFU-E and CFU-E progenitors should enable detailed molecular and cellular characterization of these distinct erythroid progenitor populations. Furthermore, enumeration of the number of these progenitor populations in human bone marrow may help in delineating mechanisms of disordered erythropoiesis in various disorders such as bone marrow failure syndromes. Disclosures: No relevant conflicts of interest to declare.

LSD1 Influences Both Histone and DNA Methylation During Terminal Erythroid Maturation

Blood ◽  
2013 ◽  
Vol 122 (21) ◽  
pp. 3671-3671
Author(s):  
Michael Getman ◽  
Jeffrey Malik ◽  
James Palis ◽  
Laurie A Steiner
Keyword(s):  
Gene Expression ◽  
Dna Methylation ◽  
Differentially Expressed Genes ◽  
Molecular Mechanisms ◽  
Conflicts Of Interest ◽  
Histone Demethylase ◽  
Differentially Expressed ◽  
Enzyme Linked Immunosorbent Assay ◽  
Erythroid Progenitor ◽  
Erythroid Maturation

Abstract The molecular mechanisms that drive the maturation of a committed erythroid progenitor to a functional red blood cell are incompletely understood. LSD1 (Lysine-Specific Histone Demethylase 1) is a widely expressed histone demethylase that plays an important role in erythroid maturation (Kereyni, elife, 2013). Although LSD1 is important for a number of biologic processes ranging from embryonic development to leukemogenesis, the molecular mechanisms underlying the influence of LSD1 on gene expression are incompletely understood. The goal of our study is to elucidate the molecular mechanisms by which LSD1 regulates erythroid gene expression and influences erythroid maturation. We hypothesize that LSD1 promotes specific patterns of histone and DNA methylation that facilitate gene expression changes necessary for normal erythroid maturation to occur. To address this hypothesis, the functional and molecular consequences of LSD1 knockdown were assessed in Extensively Self Renewing Erythroblasts (ESREs), a non-transformed, karyotypically normal model of terminal erythroid maturation (England, Blood, 2011). Primary fetal liver was cultured in the presence of EPO, SCF, IGF1 and dexamethasone to derive ESREs. The ESREs were capable of extensive ex-vivo expansion, doubling daily at the proerythroblast phase, however when matured, >90% of cells became benzidine positive and >65% enucleated within 3 days. Lentiviral-mediated shRNA was used to knock down LSD1 in expanding ESREs. Imaging flow cytometry done on maturation day 3 demonstrated that the knockdown cells had impairments in multiple facets of maturation, with larger cell and nuclear areas, higher kit expression, and lower rates of enucleation than the scramble control. LSD1 knockdown was also associated with impaired hemoglobin accumulation (78% vs. 95% benzidine positive; p<0.005). Treatment of ESREs with an inhibitor to LSD1 (Tranylcypromine; TCP) resulted in similar abnormalities in cell and nuclear size, kit expression, hemoglobin accumulation, and enucleation (40% vehicle vs.1% TCP). The functional deficits in maturation, including abnormal kit expression and low rates of enucleation, persisted on maturation day 4. To delineate the molecular mechanisms underlying this maturation impairment, RNA-seq was done in LSD1 knockdown and scramble control samples, and 230 differentially expressed genes (FDR<0.01) were identified using cuffdiff (Trapnell, Nat Biotech, 2013). Consistent with LSD1’s role in erythroid maturation, Ingenuity Pathway Analysis identified multiple networks involving hemoglobin synthesis, and GATA1, EPO, and KLF1 were all predicted as upstream regulators (p-values of 8.24e10-11, 7.25 e10-6, and 3.86e10-4, respectively). To better understand how LSD1 influences gene expression, chromatin immunoprecipitation coupled with high throughput sequencing was used to identify sites of H3K4me2 binding in the differentially expressed genes. 214/230 differentially expressed genes were associated with sites of H3K4me2 occupancy. Quantitative ChIP demonstrated that LSD1 inhibition was associated with increases in H3K4me2 levels at a subset of these sites, however consistent with previous studies, global levels of H3K4me2, determined by Enzyme Linked Immunosorbent Assay (ELIZA), did not change significantly. Although it is known that LSD1 demethylates and stabilizes the maintenance DNA methyltransferase DNMT1 (Wang, Nat Genet 2009), the consequences of LSD1 loss on DNA methylation (5-methyl cytosine; 5-mC) have yet to be investigated. To gain a comprehensive understanding of how LSD1 regulates erythroid gene expression, changes in the level of 5-mC were assessed after knockdown or inhibition of LSD1. Global 5-mC levels, determined by ELIZA assay, were ∼30% lower in TCP treated samples than vehicle treated control (p<0.02) and western blot demonstrated a 3-fold decrease in DNMT1 protein in the TCP treated samples. Both methyl binding domain pull-down coupled with quantitative PCR and genome-wide bisulfite sequencing were utilized to assess changes in 5-mC levels in the differentially expressed genes. Loss of LSD1 was associated with significantly lower levels of 5-mC at several differentially expressed, erythroid-specific genes, such as bh1. Taken together, these data support the hypothesis that LSD1 influences both histone and DNA methylation at genes important for erythroid maturation. Disclosures: No relevant conflicts of interest to declare.

The Mir-17~92 Cluster Family Determines the Responsiveness of CLL Cells with Unmutated IGHV Genes to Toll-Like Receptor 9 Triggering

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2407-2407
Author(s):  
Riccardo Bomben ◽  
Stefano Volinia ◽  
Stefania Gobessi ◽  
Daniela Marconi ◽  
Michele Dal Bo ◽  
...  
Keyword(s):  
Gene Expression ◽  
Cell Cycle ◽  
B Cell ◽  
Conflicts Of Interest ◽  
Cell Lymphoma ◽  
B Cell Lymphoma ◽  
Differentially Expressed ◽  
Toll Like Receptor ◽  
Mrna Targets ◽  
Mutational Status

Abstract Abstract 2407 Introduction: The clinical course of chronic lymphocytic leukemia (CLL) is highly variable and prognosis is strongly associated with the mutational status of the IGHV genes. Recently, it has been observed that CLL cells expressing unmutated (UM) IGHV genes can be more efficiently induced to proliferate by stimulation of Toll-like Receptor 9 (TLR9) with unmethylated CpG oligonucleotides (CpG) than CLL cells expressing mutated (M) IGHV genes. MicroRNA (miRNAs) are 18- to 22-nucleotide-long RNA molecules that regulate gene expression and play a key role in several biological process including oncogenesis. Although the recognized pathogenetic relevance of miRNAs in CLL, their involvement in regulating activation/proliferation processes of CLL cells has still to be elucidated. Patients and Methods: Freshly-isolated negatively-selected CLL cells from 19 patients (9 UM and 10 M CLL) were stimulated with CpG or left unstimulated for 18 hours. MiRNA profiling and Gene expression profiling (GEP) were performed according to Agilent Technologies protocols. Bioinformatics analyses were performed integrating three different methods for supervised analysis (LIMMA algorithm, Agilent and Partek softwares). Results: The miRNA profile of CLL cells treated or not with CpG was separately evaluated in M and UM CLL. Consistent with the notion that M CLL cells are usually non-responsive to CpG stimulation, no miRNA was found to be differentially expressed between CpG-stimulated and unstimulated CLL cells belonging to this subgroup. In contrast, in UM CLL, as many as 28 miRNAs resulted differentially expressed, 24 up-regulated (miR-1260, miR-1274a, miR-1274b, miR-1280, miR-155, miR-155*, miR-17, miR-17*, miR-18a, miR-196a, miR-19b-1*, miR-20a, miR-20b, miR-221, miR-221*, miR-222, miR-29b-1*, miR-30b*, miR-30d*, miR-374b*, miR-720, miR-886-3p, miR-92a-1*, miR-939) and 4 down-regulated (miR-1226*, miR-125a-3p, miR-135a*, miR-150*) upon CpG stimulation. Data were confirmed by quantitative real time PCR. In order to identify the miRNAs actually involved in regulating activation/proliferation processes induced by TLR9 triggering, a concomitant GEP was performed comparing the same UM CLL cells exposed or not to CpG. Data analysis was carried out by taking advantage of the T-REX software that, by integrating four algorithms and six different target prediction programs, allows the identification of the regulated miRNAs on the basis of their repression activity on target mRNA. T-REX application selected four miRNAs whose mRNA targets resulted significantly down-regulated upon TLR9 triggering, namely miR-17, miR-20a, miR-20b and miR-93a. All these miRNAs belong to the miR-17~92 cluster family, known to be over-expressed in a variety of B-cell lymphomas, including diffuse large B-cell lymphoma, Burkitt lymphoma, follicular lymphoma and mantle cell lymphoma. Notably, three of these miRNAs and four additional miRNAs also belonging to the miR-17~92 cluster family (e.g. miR-17*, miR-18a, mir-19b-1* and mir-92a-1*) turned out to be among the 24 up-regulated miRNAs in CpG-stimulated UM CLL cells. In-silico analyses performed with the “Onto-Express” software, found that several differentially expressed genes were included in Gene Ontology (GO) categories related to regulation of cell proliferation, G1/S transition, apoptosis and NFkB signalling, in keeping with the typical proliferative response induced by CpG stimulation in UM CLL cells. The down-regulated genes included in these categories comprised CDKN1B/P27, CCNG2, NCOA3, E2F5, MAPK4, TRIM8, ZBTB4 and TP53INP1, all known target of miR-17~92 cluster family. Notably, the gene for the negative cell cycle regulator CDKN1B/P27 is also targeted by miR-221 and miR-222, two miRNAs both up-regulated in UM CLL cells upon CpG stimulation. Finally, transcripts for the proto-oncogene MYC also resulted over-expressed upon CpG stimulation. This observation may be relevant given the capacity of MYC to directly and positively regulate expression of miRNAs belonging to the miR-17~92 cluster family. Conclusion: Induction of the miR-17~92 family is a specific feature of UM CLL cells triggered through TLR9 and is associated with down-regulation of genes involved in cell cycle control and apoptosis regulation. MiRNAs belonging to the miR-17~92 family may represent promising novel targets for biological therapies of high risk CLL. Disclosures: No relevant conflicts of interest to declare.

scholarly journals GATA-1 Deacetylation and Interaction with HDAC1 Is Critical for GATA-1 Mediated Gene Transcription

Blood ◽  
2017 ◽  
Vol 130 (Suppl_1) ◽  
pp. 945-945
Author(s):  
Bowen Yan ◽  
Suming Huang ◽  
Yi Qiu
Keyword(s):  
Gene Expression ◽  
Gene Transcription ◽  
Conflicts Of Interest ◽  
Expression Profiles ◽  
Globin Gene ◽  
Gene Expression Pattern ◽  
Direct Interaction ◽  
Erythroid Differentiation ◽  
Wild Type ◽  
Erythroid Progenitor

Abstract The transcription factor GATA-1 is an essential factor for globin gene transcrption and is required for erythroid and megakaryocytic cell differentiation and maturation. GATA-1 can be acetylated by p300/CBP, and the acetylation modulates GATA-1 chromatin binding activity. However, it is not clear whether GATA-1 acetylation can be reversed by a deacetylase. It is showed that GATA-1 can indirectly interact with histone deacetylase 1 (HDAC1) associated NURD corepressor complexes through binding to FOG-1. However, we found that the NURD complex does not deacetylate GATA-1. We discovered that GATA-1 can directly interact with HDAC1 in a FOG-1 independent manner. The interaction results in deacetylation of GATA-1. We have identified two arginine sites within GATA-1 that are important for the interaction with HDAC1. The arginine to alanine mutation on these sites (2RA) blocks the interaction of HDAC1, but doesn't affect its DNA binding in vitro. Importantly, the mutation does not affect the interaction with FOG-1, indicating that GATA-1 direct interaction and indirect association via FOG-1 with HDAC1 are separate events. To further understand the role of the HDAC1-GATA-1 direct interaction in gene transcription and erythropoiesis, we introduced the 2RA mutant of GATA-1 fused with estrogen receptor ligand binding domains into G1E cells, a GATA-1-null erythroid progenitor cell line. Interestingly, upon estradiol induction, GATA-1 2RA does not promote b-globin gene transcription and erythroid differentiation of G1E cells, although GATA-1 2RA is highly acetylated. Chromatin immunoprecipitation assay (ChIP) shows that GATA-1 2RA binds poorly to HS3 and β-globin promoter. Similar binding defect is also detected on GATA-1 promoter, indicating defective GATA-1 recruitment on chromatin. Interestingly, HDAC1 binding to these regions are also significantly reduced, suggesting HDAC1-GATA-1 interaction may be important for GATA-1 deacetylation, as well as stabilizing GATA-1 binding. In order to investigate the effect of GATA-1 2RA in vivo, we generated a GATA-1 2RA knock in mice. The knock in mice are viable but suffered from anemia and thrombocytopenia. β-globin expression reduced at least 50% in knock in mice compare to wild type litter mate. To further identify and compare gene expression profiles regulated by HDAC1 direct or indirect associated GATA-1 during erythroid differentiation, we performed RNA sequencing assays to study the effects of GATA-1 2RA in gene expression in comparison with wild type GATA-1 or GATA-1-V205M (a mutation abolished binding with FOG-1). Expression of GATA-1 2RA largely affects gene expression profile in both GATA-1 activated and repressed genes compared to cells expressing wild type GATA-1. The gene expression pattern in 2RA cells also is largely different from cells expressing GATA-1 V205M, indicating the direct and indirect interaction with HDAC1 may mediate differential functions. Our results indicate that HDAC1 is required for GATA-1 recruitment and GATA-1 mediated transcription regulation. Thus, this study unveils a novel regulation of GATA-1 by its direct interaction with HDAC1. Disclosures No relevant conflicts of interest to declare.

scholarly journals Human genetic variation and its effect on miRNA biogenesis, activity and function

2014 ◽  
Vol 42 (4) ◽  
pp. 1184-1189 ◽  
Author(s):  
Daniel R. Hogg ◽  
Lorna W. Harries
Keyword(s):  
Gene Expression ◽  
Genetic Variation ◽  
Secondary Structure ◽  
Target Genes ◽  
Tertiary Structure ◽  
Copy Number Variants ◽  
Fine Tuning ◽  
Mirna Biogenesis ◽  
Nucleotide Polymorphisms ◽  
Mrna Targets

miRNAs are small non-coding regulators of gene expression that are estimated to regulate over 60% of all human genes. Each miRNA can target multiple mRNA targets and as such, miRNAs are responsible for some of the ‘fine tuning’ of gene expression and are implicated in regulation of all cellular processes. miRNAs bind to target genes by sequence complementarity, resulting in target degradation or translational blocking and usually a reduction in target gene expression. Like mRNA, miRNAs are transcribed from genomic DNA and are processed in several steps that are heavily reliant on correct secondary and tertiary structure. Secondary structure is determined by RNA sequence, which is in turn determined by the sequence of the genome. The human genome, however, like most eukaryotes is variable. Large numbers of SNPs (single nucleotide polymorphisms), small insertions and deletions (indels) and CNVs (copy number variants) have been described in our genome. Should this genetic variation occur in regions critical for the correct secondary structure or target binding, it may interfere with normal gene regulation and cause disease. In this review, we outline the consequences of genetic variation involving different aspects of miRNA biosynthesis, processing and regulation, with selected examples of incidences when this has potential to affect human disease.

scholarly journals Essential Role of Endogenous MOZ in Aberrant HoxA9 and Meis1 Expressions Induced By MOZ Fusion Gene

Blood ◽  
2014 ◽  
Vol 124 (21) ◽  
pp. 2191-2191
Author(s):  
Takuo Katsumoto ◽  
Kazutsune Yamagata ◽  
Yoko Ogawara ◽  
Takuro Nakamura ◽  
Issay Kitabayashi
Keyword(s):  
Gene Expression ◽  
Stem Cells ◽  
Hematopoietic Stem Cells ◽  
Molecular Mechanisms ◽  
Zinc Finger Protein ◽  
Conflicts Of Interest ◽  
Expression Profiles ◽  
Leukemia Cells ◽  
Hematopoietic Stem

Abstract Monocytic leukemia Zinc finger protein (MOZ), a histone acetyltransferase, is involved in chromosome translocations associated with FAB M4/M5 types of acute myeloid leukemia (AML). In normal hematopoiesis, MOZ is essential for self-renewal of hematopoietic stem cells (HSCs) and for expression of HoxA9/Meis1 in hematopoietic stem/progenitor cells (HSPCs). Previously we found that endogenous MOZ is critical for MOZ-TIF2-induced AML. Although MOZ-/- cells expressing the MOZ-fusion serially generated colonies in vitro, they did not induce AML after transplantation into recipient mice. In these cells, up-regulation of Meis1 was impaired, while HoxA9 expression was induced. However, roles of endogenous MOZ in MOZ fusion induced leukemia remained unclear. To elucidate molecular mechanisms, we performed experiments described below. First, to reveal mechanisms in defect of Meis1 expression in MOZ-/- MOZ-fusion leukemia cells, we performed chromatin immune-precipitation assays on Meis1 locus. Coincident with gene expression, active histone marks (H3K9ac, H3K27ac etc.) were disrupted. In contrast, repressive histone modifications (H3K9me2, H3K27me3) were elevated. Next we analyzed requirement of HoxA9 and Meis1 in MOZ fusion induced AML development. When mice were transplanted with MOZ-/- HSPCs simultaneously introduced with MOZ-fusion and Meis1 genes, AML development were induced. On the other hand, when Meis1 was conditionally deleted in MOZ-fusion leukemia cells, AML development was significantly delayed. Mice transplanted with MOZ-/- HSPCs, which were introduced with both HoxA9 and Meis1 genes elicited AML development. Furthermore, we analyzed gene expression profiles of MOZ-/- MOZ fusion leukemia cells. In these cells, expressions of monocyte/macrophage lineage characteristic genes (C/EBPa, Irf8, CD68 etc.) and MLL fusion target genes (Meis1, Mef2c) were decreased. In contract, other hematopoietic lineage characteristic genes (GATA1-3, FOG-1, CD41, Aiolos, Helios, Eag, Epx etc.) were increased. In addition, expression of CDK inhibitor INK4A was also up-regulated. Finally, we tested requirement of endogenous MOZ in various cellular conditions. Previous report showed that AML development was induced by introduction of MOZ-TIF2 not only in hematopoietic stem cells but also in more differentiated Common myeloid progenitors (CMPs) and Granulocyte/Monocyte progenitors (GMPs) (Huntly et al, Cancer Cell 2004). So we introduced MOZ fusion genes in HSCs and CMPs collected from E14.5 MOZ-/- fetal liver. MOZ-/- HSCs, not CMPs, expressing MOZ-TIF2 continuously formed colonies in vitro. In the CMPs expressing MOZ-TIF2, expression of both Meis1 and HoxA9, were abolished. These results suggest that high levels of HoxA9 and Meis1 expressions were respectively required for MOZ-TIF2-induced AML development, and that endogenous MOZ is critical for MOZ-TIF2-induced AML development. Disclosures No relevant conflicts of interest to declare.

Sign in / Sign up

Export Citation Format

Share Document