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Daniel M. Knowles - One of the best experts on this subject based on the ideXlab platform.
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ebv mir bhrf1 2 targets PRDM1 blimp1 potential role in ebv lymphomagenesis
Leukemia, 2016Co-Authors: David Redmond, Olivier Elemento, Daniel M. KnowlesAbstract:PRDM1/Blimp1, a master regulator of B-cell terminal differentiation, has been identified as a tumor suppressor gene in aggressive lymphomas, including diffuse large B-cell lymphoma (DLBCL). It has been shown in DLBCL and Hodgkin lymphoma that PRDM1 is downregulated by cellular microRNAs. In this study, we identify the Epstein–Barr virus (EBV) microRNA (miRNA), EBV-miR-BHRF1-2, as a viral miRNA regulator of PRDM1. EBV-miR-BHRF1-2 repressed luciferase reporter activity by specific interaction with the seed region within the PRDM1 3’ untranslated region. EBV-miR-BHRF1-2 inhibition upregulated PRDM1 protein expression in lymphoblastoid cell lines (LCL), supporting a role of miR-BHRF1-2 in PRDM1 downregulation in vivo. Discordance of PRDM1 messenger RNA and protein expressions is associated with high EBV-miR-BHRF1-2 levels in LCLs and primary post-transplant EBV-positive DLBCL. Enforced expression of PRDM1-induced apoptosis and cell cycle arrest in LCL cells. Inhibition of EBV-miR-BHRF1-2 negatively regulates cell cycle and decreases expression of SCARNA20, a small nucleolar RNA that is also downregulated by PRDM1 overexpression. The interaction between EBV-miR-BHRF1-2 and PRDM1 may be one of the mechanisms by which EBV-miR-BHRF1-2 promotes EBV lymphomagenesis. Our results support the potential of EBV-miR-BHRF1-2 as a therapeutic target in EBV-associated lymphoma.
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EBV-miR-BHRF1-2 targets PRDM1/Blimp1 : potential role in EBV lymphomagenesis
Leukemia, 2015Co-Authors: Jiao Ma, David Redmond, Olivier Elemento, Daniel M. KnowlesAbstract:PRDM1/Blimp1, a master regulator of B-cell terminal differentiation, has been identified as a tumor suppressor gene in aggressive lymphomas, including diffuse large B-cell lymphoma (DLBCL). It has been shown in DLBCL and Hodgkin lymphoma that PRDM1 is downregulated by cellular microRNAs. In this study, we identify the Epstein–Barr virus (EBV) microRNA (miRNA), EBV-miR-BHRF1-2, as a viral miRNA regulator of PRDM1. EBV-miR-BHRF1-2 repressed luciferase reporter activity by specific interaction with the seed region within the PRDM1 3’ untranslated region. EBV-miR-BHRF1-2 inhibition upregulated PRDM1 protein expression in lymphoblastoid cell lines (LCL), supporting a role of miR-BHRF1-2 in PRDM1 downregulation in vivo. Discordance of PRDM1 messenger RNA and protein expressions is associated with high EBV-miR-BHRF1-2 levels in LCLs and primary post-transplant EBV-positive DLBCL. Enforced expression of PRDM1-induced apoptosis and cell cycle arrest in LCL cells. Inhibition of EBV-miR-BHRF1-2 negatively regulates cell cycle and decreases expression of SCARNA20, a small nucleolar RNA that is also downregulated by PRDM1 overexpression. The interaction between EBV-miR-BHRF1-2 and PRDM1 may be one of the mechanisms by which EBV-miR-BHRF1-2 promotes EBV lymphomagenesis. Our results support the potential of EBV-miR-BHRF1-2 as a therapeutic target in EBV-associated lymphoma.
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EBV Microrna Mir-BHRF1-2 Targets PRDM1/Blimp1 : Potential Role in EBV Lymphomagenesis
Blood, 2014Co-Authors: Jiao Ma, David Redmond, Daniel M. KnowlesAbstract:PRDM1/Blimp1 , a master regulator of B-cell terminal differentiation, has been identified as a tumor suppressor gene in the pathogenesis of diffuse large B-cell lymphoma (DLBCL). In DLBCL, PRDM1 is inactivated by mutations and deletions; however, there is also evidence that PRDM1 is down-regulated by microRNAs (miRNAs) in DLBCL and Hodgkin/Reed-Sternberg cells of classical Hodgkin lymphoma (cHL). A decrease in PRDM1 activity contributes to the pathogenesis of DLBCL and cHL by inhibiting plasma cell differentiation triggered by signal transduction pathways such as the NF-kB pathway. Since malignant EBV-positive B-cell lymphoproliferations are often associated with increased NF-kB activity, it is conceivable that abnormal PRDM1 down-regulation may play a role in their pathogenesis. EBV-positive B-cell lymphomas are postulated to originate from EBV-infected B-cells with latency III growth program of EBV gene expression. Thus, EBV-immmortalized lymphoblastoid cell lines (LCLs), which are of latency III type, serve as a good model to study EBV lymphomagenesis. We observed discordance in PRDM1 mRNA and protein levels in LCLs. By quantitative real-time reverse transcriptase PCR, PRDM1 mRNA levels in LCLs varied from 14.6% to 1259.7% relative to the multiple myeloma cell line U266, which expresses high levels of PRDM1. However, PRDM1 protein was discordantly low in LCLs compared to U266 based on immunohistochemistry and Western blotting assays, consistent with post-transcriptional regulation. EBV encodes 25 viral miRNAs, and we postulate that one of more of them may function to dampen PRDM1 expression. Indeed, a miRNA binding site containing seed match to bases 2-7 of EBV miR-BHRF1-2 was identified in positions 1565 to 1589 of PRDM1 3’ untranslated region. MiR-BHRF1-2 functionally targeted this specific binding site and repressed luciferase reporter activity. Mutation in the seed region of this site relieved the repression in comparison to the wild type control. MiR-BHRF1-2 was highly expressed in LCLs, while it was barely detectable in the EBV-positive Burkitt lymphoma cell line MUTU I, which has latency type I. Importantly, immunoblotting assay demonstrated an up-regulation of PRDM1 protein level in CCL156 and CCL159 LCL cells transfected with miR-BHRF1-2 inhibitor relative to those transfected with miRNA Inhibitor negative control, supporting a role of miR-BHRF1-2 in PRDM1 down-regulation in vivo . To examine the biological consequences of increased PRDM1 expression in LCL cells, PRDM1 was over-expressed in JY25 and CCL159 LCL cell lines. Enforced expression of PRDM1 induced apoptosis in both cell lines. Furthermore, bromodeoxyuridine (Brdu) incorporation study demonstrated that overexpression of PRDM1 reduced the percentage of S phase from 43.4% to 27.6% in CCL159 cells, and 39.5% to 27.9% in JY25 cells, respectively. Whole transcriptome sequencing (RNA-seq) identified a set of potential PRDM1 direct target genes whose expressions decreased in both LCL cell lines upon PRDM1 over-expression. These genes have broad functions including cell proliferation and survival, transcription and translation, mitochondrial functions, and cytoskeleton. Although no significant changes in cell cycle and apoptosis were observed upon transfection of miR-BHRF1-2 inhibitor, RNA-seq analysis of CLL159 cells transfected with miR-BHRF1-2 inhibitor revealed a small subset of repressed genes which overlapped with those identified by PRDM1 over-expression. This finding suggests that the increase in PRDM1 expression upon miR-BHRF1-2 inhibition, albeit small, is capable of repressing a subset of PRDM1 target genes with potential biological effects. In summary, our findings demonstrate that PRDM1 is a target of EBV miR-BHRF1-2. MiR-BHRF1-2 mediated PRDM1 down-regulation may contribute to the pathogenesis of EBV-associated B-cell lymphomas by inhibiting the transcription repression program of PRDM1 and limiting PRDM1-mediated cellular changes detrimental to tumor growth, including cell cycle arrest and apoptosis. Further characterization of the target genes whose expression is up-regulated by miR-BHRF1-2-mediated PRDM1 down-regulation may provide important clues to the pathogenetic function of miR-BHRF1-2 and EBV oncogenesis in general. Disclosures No relevant conflicts of interest to declare.
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ebv microrna mir bhrf1 2 targets PRDM1 blimp1 potential role in ebv lymphomagenesis
Blood, 2014Co-Authors: David Redmond, Daniel M. KnowlesAbstract:PRDM1/Blimp1 , a master regulator of B-cell terminal differentiation, has been identified as a tumor suppressor gene in the pathogenesis of diffuse large B-cell lymphoma (DLBCL). In DLBCL, PRDM1 is inactivated by mutations and deletions; however, there is also evidence that PRDM1 is down-regulated by microRNAs (miRNAs) in DLBCL and Hodgkin/Reed-Sternberg cells of classical Hodgkin lymphoma (cHL). A decrease in PRDM1 activity contributes to the pathogenesis of DLBCL and cHL by inhibiting plasma cell differentiation triggered by signal transduction pathways such as the NF-kB pathway. Since malignant EBV-positive B-cell lymphoproliferations are often associated with increased NF-kB activity, it is conceivable that abnormal PRDM1 down-regulation may play a role in their pathogenesis. EBV-positive B-cell lymphomas are postulated to originate from EBV-infected B-cells with latency III growth program of EBV gene expression. Thus, EBV-immmortalized lymphoblastoid cell lines (LCLs), which are of latency III type, serve as a good model to study EBV lymphomagenesis. We observed discordance in PRDM1 mRNA and protein levels in LCLs. By quantitative real-time reverse transcriptase PCR, PRDM1 mRNA levels in LCLs varied from 14.6% to 1259.7% relative to the multiple myeloma cell line U266, which expresses high levels of PRDM1. However, PRDM1 protein was discordantly low in LCLs compared to U266 based on immunohistochemistry and Western blotting assays, consistent with post-transcriptional regulation. EBV encodes 25 viral miRNAs, and we postulate that one of more of them may function to dampen PRDM1 expression. Indeed, a miRNA binding site containing seed match to bases 2-7 of EBV miR-BHRF1-2 was identified in positions 1565 to 1589 of PRDM1 3’ untranslated region. MiR-BHRF1-2 functionally targeted this specific binding site and repressed luciferase reporter activity. Mutation in the seed region of this site relieved the repression in comparison to the wild type control. MiR-BHRF1-2 was highly expressed in LCLs, while it was barely detectable in the EBV-positive Burkitt lymphoma cell line MUTU I, which has latency type I. Importantly, immunoblotting assay demonstrated an up-regulation of PRDM1 protein level in CCL156 and CCL159 LCL cells transfected with miR-BHRF1-2 inhibitor relative to those transfected with miRNA Inhibitor negative control, supporting a role of miR-BHRF1-2 in PRDM1 down-regulation in vivo . To examine the biological consequences of increased PRDM1 expression in LCL cells, PRDM1 was over-expressed in JY25 and CCL159 LCL cell lines. Enforced expression of PRDM1 induced apoptosis in both cell lines. Furthermore, bromodeoxyuridine (Brdu) incorporation study demonstrated that overexpression of PRDM1 reduced the percentage of S phase from 43.4% to 27.6% in CCL159 cells, and 39.5% to 27.9% in JY25 cells, respectively. Whole transcriptome sequencing (RNA-seq) identified a set of potential PRDM1 direct target genes whose expressions decreased in both LCL cell lines upon PRDM1 over-expression. These genes have broad functions including cell proliferation and survival, transcription and translation, mitochondrial functions, and cytoskeleton. Although no significant changes in cell cycle and apoptosis were observed upon transfection of miR-BHRF1-2 inhibitor, RNA-seq analysis of CLL159 cells transfected with miR-BHRF1-2 inhibitor revealed a small subset of repressed genes which overlapped with those identified by PRDM1 over-expression. This finding suggests that the increase in PRDM1 expression upon miR-BHRF1-2 inhibition, albeit small, is capable of repressing a subset of PRDM1 target genes with potential biological effects. In summary, our findings demonstrate that PRDM1 is a target of EBV miR-BHRF1-2. MiR-BHRF1-2 mediated PRDM1 down-regulation may contribute to the pathogenesis of EBV-associated B-cell lymphomas by inhibiting the transcription repression program of PRDM1 and limiting PRDM1-mediated cellular changes detrimental to tumor growth, including cell cycle arrest and apoptosis. Further characterization of the target genes whose expression is up-regulated by miR-BHRF1-2-mediated PRDM1 down-regulation may provide important clues to the pathogenetic function of miR-BHRF1-2 and EBV oncogenesis in general. Disclosures No relevant conflicts of interest to declare.
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hypermethylation of the tumor suppressor gene PRDM1 blimp 1 supports a pathogenetic role in ebv positive burkitt lymphoma
Blood Cancer Journal, 2014Co-Authors: Taotao Zhang, Carlos E Bacchi, Eduardo Queiroga, Attilio Orazi, Gabriela Gualco, Jeffery T Sample, Daniel M. KnowlesAbstract:PRDM1/Blimp-1 is a tumor suppressor gene in the activated B-cell subtype of diffuse large B-cell lymphomas. Its inactivation contributes to pathogenesis in this setting by impairing terminal B-cell differentiation induced by constitutive nuclear factor-κB activation. The role of PRDM1 in Burkitt lymphoma (BL) lymphomagenesis is not known. Here we identified hypermethylation of the promoter region and exon 1 of PRDM1 in all six Epstein–Barr virus (EBV)-positive BL cell lines and 12 of 23 (52%) primary EBV-positive BL or BL-related cases examined, but in none of the EBV-negative BL cell lines or primary tumors that we assessed, implying a tumor suppressor role for PRDM1 specifically in EBV-associated BL. A direct induction of PRDM1 hypermethylation by EBV is unlikely, as PRDM1 hypermethylation was not observed in EBV-immortalized B lymphoblastoid cell lines. Treatment of EBV-positive BL cells with 5′ azacytidine resulted in PRDM1 induction associated with PRDM1 demethylation, consistent with transcriptional silencing of PRDM1 as a result of DNA methylation. Overexpression of PRDM1 in EBV-positive BL cell lines resulted in cell cycle arrest. Our results expand the spectrum of lymphoid malignancies in which PRDM1 may have a tumor suppressor role and identify an epigenetic event that likely contributes to the pathogenesis of BL.
Elizabeth J. Robertson - One of the best experts on this subject based on the ideXlab platform.
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blimp1 PRDM1 governs terminal differentiation of endovascular trophoblast giant cells and defines multipotent progenitors in the developing placenta
Genes & Development, 2012Co-Authors: Arne W Mould, Marc A. Morgan, Elizabeth K Bikoff, Li Li, Elizabeth J. RobertsonAbstract:Developmental arrest of Blimp1/PRDM1 mutant embryos at around embryonic day 10.5 (E10.5) has been attributed to placental disturbances. Here we investigate Blimp1/PRDM1 requirements in the trophoblast cell lineage. Loss of function disrupts specification of the invasive spiral artery-associated trophoblast giant cells (SpA-TGCs) surrounding maternal blood vessels and severely compromises the ability of the spongiotrophoblast layer to expand appropriately, secondarily causing collapse of the underlying labyrinth layer. Additionally, we identify a population of proliferating Blimp1(+) diploid cells present within the spongiotrophoblast layer. Lineage tracing experiments exploiting a novel PRDM1.Cre-LacZ allele demonstrate that these Blimp1(+) cells give rise to the mature SpA-TGCs, canal TGCs, and glycogen trophoblasts. In sum, the transcriptional repressor Blimp1/PRDM1 is required for terminal differentiation of SpA-TGCs and defines a lineage-restricted progenitor cell population contributing to placental growth and morphogenesis.
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Blimp1/PRDM1 governs terminal differentiation of endovascular trophoblast giant cells and defines multipotent progenitors in the developing placenta
Genes & Development, 2012Co-Authors: Arne W Mould, Marc A. Morgan, Elizabeth K Bikoff, Li Li, Elizabeth J. RobertsonAbstract:Developmental arrest of Blimp1/PRDM1 mutant embryos at around embryonic day 10.5 (E10.5) has been attributed to placental disturbances. Here we investigate Blimp1/PRDM1 requirements in the trophoblast cell lineage. Loss of function disrupts specification of the invasive spiral artery-associated trophoblast giant cells (SpA-TGCs) surrounding maternal blood vessels and severely compromises the ability of the spongiotrophoblast layer to expand appropriately, secondarily causing collapse of the underlying labyrinth layer. Additionally, we identify a population of proliferating Blimp1(+) diploid cells present within the spongiotrophoblast layer. Lineage tracing experiments exploiting a novel PRDM1.Cre-LacZ allele demonstrate that these Blimp1(+) cells give rise to the mature SpA-TGCs, canal TGCs, and glycogen trophoblasts. In sum, the transcriptional repressor Blimp1/PRDM1 is required for terminal differentiation of SpA-TGCs and defines a lineage-restricted progenitor cell population contributing to placental growth and morphogenesis.
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blimp 1 PRDM1 alternative promoter usage during mouse development and plasma cell differentiation
Molecular and Cellular Biology, 2009Co-Authors: Marc A. Morgan, Kathryn Calame, Erna Magnusdottir, C. Tunyaplin, S. J. Arnold, Elizabeth J. Robertson, J Harper, Elizabeth K BikoffAbstract:The PR/SET domain zinc-finger transcriptional repressor Blimp-1/PRDM1 was initially cloned as a negative regulator of IFNB1 (beta interferon) expression (30) and later identified as a factor both necessary and sufficient for B-cell terminal differentiation and antibody secretion (74, 79). Blimp-1, the protein encoded by PRDM1, silences expression of key transcription factors, such as c-Myc, required for cell cycle progression (43), as well as Pax5, Id3, and Spi-B, which maintain mature B-cell identity (41, 71). PRDM1 inactivation in the T-cell lineage results in fatal inflammatory bowel disease associated with reduced interleukin 10 and upregulated expression of interleukin 2 and gamma interferon (28, 49). In the skin, PRDM1 is required for sebaceous gland homeostasis (22) and epidermal terminal differentiation (48). PRDM1 has a dynamic pattern of expression in the developing mouse embryo (10, 60, 67, 81). Loss-of-function mutant embryos fail to specify primordial germ cells, display pharyngeal arch defects, and die around embryonic day 10.5 (E10.5) due to placental insufficiency (60, 81). Conditional rescue experiments have revealed additional roles in multipotent progenitor cell populations in the forelimb, secondary heart field, and sensory vibrissae (67). Thus, PRDM1 regulates cell fate decisions in diverse contexts in the embryo and governs tissue homeostasis in multiple cell types in the adult organism. The cis-acting regulatory elements that direct tissue-specific PRDM1 expression in these specialized cell types are largely unknown. A Venus fluorescent reporter transgene embedded within a 230-kb bacterial artificial chromosome (kb −140 to +90 relative to the transcription start site) faithfully drives temporally and spatially restricted expression at numerous sites in the embryo, including primordial germ cells, anterior definitive endoderm, somites, pharyngeal arches, limb buds, and dermal papillae (60, 61). In contrast, an enhanced green fluorescent protein reporter construct containing 4.4 kb upstream of the PRDM1 transcription start site is sufficient for expression in adult hematopoietic tissues and mediates lipopolysaccharide (LPS) responsiveness of splenic B cells (83). However, this construct also leads to ectopic expression at numerous tissue sites. The cis-acting regulatory elements controlling dynamic patterns of PRDM1 expression in vivo thus potentially span a large genomic region. Dose-dependent BMP-Smad signals activate PRDM1 expression in committed primordial germ cells when they initially appear at the base of the allantois (60). However, it remains unknown whether PRDM1 is a direct Smad target. A recent study identified a Gli3 binding site ∼27 kb downstream of the PRDM1 coding region that drives expression in the developing limb (82). Similarly, studies of zebra fish have shown that Sonic Hedgehog controls PRDM1 expression during pectoral fin and muscle development (5, 40). However, multipotent progenitor cell populations allocated at numerous tissue sites express PRDM1 only transiently (67). Multiple, as yet uncharacterized enhancer and repressor elements are almost certainly required to regulate graded PRDM1 activities throughout development. Alternative promoter usage offers an attractive mechanism for regulating PRDM1 gene expression. Two alternative promoters control spatially and temporally distinct blimp1/krox expression patterns during sea urchin development (44, 45). These alternative transcripts encode nearly identical proteins except that the 1b isoform contains 50 additional residues at its amino terminus. Specific morpholino knockdown of the 1a and 1b transcripts results in tissue-specific disturbances in the gut endoderm and vegetal plate, respectively (44). The activity of an alternative promoter region located 5′ of PRDM1 exon 4 that generates a protein lacking the PR/SET domain with reduced repressive activity on multiple target genes is elevated in human myeloma lines relative to levels in primary B cells (21). The PRDM1 basal promoter and multiple transcriptional start sites were previously mapped immediately upstream of exon 1 (78). To learn more about developmentally regulated expression, we characterized the 5′ ends of PRDM1 transcripts in the developing embryo. We identified two novel alternative first exons that both splice directly to exon 3, containing the translational start site. Exon 1B, located 70 kb upstream of exon 1A, is strongly expressed in the yolk sac. An additional first exon (exon 1C) is located in the intron downstream of exon 1A. To evaluate the possibly distinct functional activities contributed by alternative promoters, we generated targeted alleles that selectively eliminate either exon 1A (Δex1A) or exon 1B (Δex1B) transcripts. The exon 1B deletion slightly decreases expression in the yolk sac but otherwise has no noticeable effect in the embryo or adult tissues. Surprisingly, the exon 1A deletion encompassing NF-κB sites upstream of the promoter eliminates PRDM1 expression in LPS-stimulated B cells and blocks plasma cell differentiation but fails to disrupt embryonic development. Consistent with this, we observe only modestly reduced PRDM1 expression levels in the embryo. However, compound heterozygotes also carrying the null allele display partially penetrant developmental defects. The novel alternative promoters described in this report are likely to play important roles in generating regulatory diversity and controlling gene dosage effects.
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an expanding job description for blimp 1 PRDM1
Current Opinion in Genetics & Development, 2009Co-Authors: Elizabeth K Bikoff, Marc A. Morgan, Elizabeth J. RobertsonAbstract:The master transcriptional regulator Blimp-1/PRDM1 contains an N-terminal PR/SET domain and five C2H2 zinc fingers located near its C-terminus that mediate DNA binding, nuclear import and recruitment of histone modifying enzymes. These activities account for its ability to control cell-fate decisions in the embryo and govern tissue homeostasis in multiple cell types in the adult organism. New experiments demonstrate an increasing degree of complexity associated with Blimp-1/PRDM1 target site selection and its associations with epigenetic modifiers. Our current understanding of how this single unique species within the family of structurally similar PRDM proteins regulates gene expression patterns and governs developmental programmes in different cell lineages is discussed.
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An expanding job description for Blimp-1/PRDM1
Current Opinion in Genetics and Development, 2009Co-Authors: Elizabeth K Bikoff, Marc A. Morgan, Elizabeth J. RobertsonAbstract:The master transcriptional regulator Blimp-1/PRDM1 contains an N-terminal PR/SET domain and five C2H2 zinc fingers located near its C-terminus that mediate DNA binding, nuclear import and recruitment of histone modifying enzymes. These activities account for its ability to control cell-fate decisions in the embryo and govern tissue homeostasis in multiple cell types in the adult organism. New experiments demonstrate an increasing degree of complexity associated with Blimp-1/PRDM1 target site selection and its associations with epigenetic modifiers. Our current understanding of how this single unique species within the family of structurally similar PRDM proteins regulates gene expression patterns and governs developmental programmes in different cell lineages is discussed. © 2009 Elsevier Ltd. All rights reserved.
Philip W Ingham - One of the best experts on this subject based on the ideXlab platform.
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PRDM1 and sox6 mediated transcriptional repression specifies muscle fibre type in the zebrafish embryo
EMBO Reports, 2008Co-Authors: Jonas Von Hofsten, Stone Elworthy, Michael J Gilchrist, J C Smith, Fiona C Wardle, Philip W InghamAbstract:The zebrafish u-boot (ubo) gene encodes the transcription factor PRDM1, which is essential for the specification of the primary slow-twitch muscle fibres that derive from adaxial cells. Here, we show that PRDM1 functions by acting as a transcriptional repressor and that slow-twitch-specific muscle gene expression is activated by PRDM1-mediated repression of the transcriptional repressor Sox6. Genes encoding fast-specific isoforms of sarcomeric proteins are ectopically expressed in the adaxial cells of ubotp39 mutant embryos. By using chromatin immunoprecipitation, we show that these are direct targets of PRDM1. Thus, PRDM1 promotes slow-twitch fibre differentiation by acting as a global repressor of fast-fibre-specific genes, as well as by abrogating the repression of slow-fibre-specific genes.
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expression of multiple slow myosin heavy chain genes reveals a diversity of zebrafish slow twitch muscle fibres with differing requirements for hedgehog and PRDM1 activity
Development, 2008Co-Authors: Stone Elworthy, Murray Hargrave, Rob Knight, Katharina Mebus, Philip W InghamAbstract:The zebrafish embryo develops a series of anatomically distinct slow twitch muscle fibres that characteristically express genes encoding lineage-specific isoforms of sarcomeric proteins such as MyHC and troponin. We show here that different subsets of these slow fibres express distinct members of a tandem array of slow MyHC genes. The first slow twitch muscle fibres to differentiate, which are specified by the activity of the transcription factor PRDM1 (also called Ubo or Blimp1) in response to Hedgehog (Hh) signalling, express the smyhc1 gene. Subsequently, secondary slow twitch fibres differentiate in most cases independently of Hh activity. We find that although some of these later-forming fibres also express smyhc1 , others express smyhc2 or smyhc3 . We show that the smyhc1 -positive fibres express the ubo ( PRDM1 ) gene and adopt fast twitch fibre characteristics in the absence of PRDM1 activity, whereas those that do not express smyhc1 can differentiate independently of PRDM1 function. Conversely, some smyhc2 -expressing fibres, although independent of PRDM1 function, require Hh activity to form. The adult trunk slow fibres express smyhc2 and smyhc3 , but lack smyhc1 expression. The different slow fibres in the craniofacial muscles variously express smyhc1, smyhc2 and smyhc3 , and all differentiate independently of PRDM1.
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PRDM1‐ and Sox6‐mediated transcriptional repression specifies muscle fibre type in the zebrafish embryo
EMBO Reports, 2008Co-Authors: Jonas Von Hofsten, Stone Elworthy, Michael J Gilchrist, J C Smith, Fiona C Wardle, Philip W InghamAbstract:The zebrafish u-boot (ubo) gene encodes the transcription factor PRDM1, which is essential for the specification of the primary slow-twitch muscle fibres that derive from adaxial cells. Here, we show that PRDM1 functions by acting as a transcriptional repressor and that slow-twitch-specific muscle gene expression is activated by PRDM1-mediated repression of the transcriptional repressor Sox6. Genes encoding fast-specific isoforms of sarcomeric proteins are ectopically expressed in the adaxial cells of ubotp39 mutant embryos. By using chromatin immunoprecipitation, we show that these are direct targets of PRDM1. Thus, PRDM1 promotes slow-twitch fibre differentiation by acting as a global repressor of fast-fibre-specific genes, as well as by abrogating the repression of slow-fibre-specific genes.
Elizabeth K Bikoff - One of the best experts on this subject based on the ideXlab platform.
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blimp1 PRDM1 governs terminal differentiation of endovascular trophoblast giant cells and defines multipotent progenitors in the developing placenta
Genes & Development, 2012Co-Authors: Arne W Mould, Marc A. Morgan, Elizabeth K Bikoff, Li Li, Elizabeth J. RobertsonAbstract:Developmental arrest of Blimp1/PRDM1 mutant embryos at around embryonic day 10.5 (E10.5) has been attributed to placental disturbances. Here we investigate Blimp1/PRDM1 requirements in the trophoblast cell lineage. Loss of function disrupts specification of the invasive spiral artery-associated trophoblast giant cells (SpA-TGCs) surrounding maternal blood vessels and severely compromises the ability of the spongiotrophoblast layer to expand appropriately, secondarily causing collapse of the underlying labyrinth layer. Additionally, we identify a population of proliferating Blimp1(+) diploid cells present within the spongiotrophoblast layer. Lineage tracing experiments exploiting a novel PRDM1.Cre-LacZ allele demonstrate that these Blimp1(+) cells give rise to the mature SpA-TGCs, canal TGCs, and glycogen trophoblasts. In sum, the transcriptional repressor Blimp1/PRDM1 is required for terminal differentiation of SpA-TGCs and defines a lineage-restricted progenitor cell population contributing to placental growth and morphogenesis.
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Blimp1/PRDM1 governs terminal differentiation of endovascular trophoblast giant cells and defines multipotent progenitors in the developing placenta
Genes & Development, 2012Co-Authors: Arne W Mould, Marc A. Morgan, Elizabeth K Bikoff, Li Li, Elizabeth J. RobertsonAbstract:Developmental arrest of Blimp1/PRDM1 mutant embryos at around embryonic day 10.5 (E10.5) has been attributed to placental disturbances. Here we investigate Blimp1/PRDM1 requirements in the trophoblast cell lineage. Loss of function disrupts specification of the invasive spiral artery-associated trophoblast giant cells (SpA-TGCs) surrounding maternal blood vessels and severely compromises the ability of the spongiotrophoblast layer to expand appropriately, secondarily causing collapse of the underlying labyrinth layer. Additionally, we identify a population of proliferating Blimp1(+) diploid cells present within the spongiotrophoblast layer. Lineage tracing experiments exploiting a novel PRDM1.Cre-LacZ allele demonstrate that these Blimp1(+) cells give rise to the mature SpA-TGCs, canal TGCs, and glycogen trophoblasts. In sum, the transcriptional repressor Blimp1/PRDM1 is required for terminal differentiation of SpA-TGCs and defines a lineage-restricted progenitor cell population contributing to placental growth and morphogenesis.
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blimp 1 PRDM1 alternative promoter usage during mouse development and plasma cell differentiation
Molecular and Cellular Biology, 2009Co-Authors: Marc A. Morgan, Kathryn Calame, Erna Magnusdottir, C. Tunyaplin, S. J. Arnold, Elizabeth J. Robertson, J Harper, Elizabeth K BikoffAbstract:The PR/SET domain zinc-finger transcriptional repressor Blimp-1/PRDM1 was initially cloned as a negative regulator of IFNB1 (beta interferon) expression (30) and later identified as a factor both necessary and sufficient for B-cell terminal differentiation and antibody secretion (74, 79). Blimp-1, the protein encoded by PRDM1, silences expression of key transcription factors, such as c-Myc, required for cell cycle progression (43), as well as Pax5, Id3, and Spi-B, which maintain mature B-cell identity (41, 71). PRDM1 inactivation in the T-cell lineage results in fatal inflammatory bowel disease associated with reduced interleukin 10 and upregulated expression of interleukin 2 and gamma interferon (28, 49). In the skin, PRDM1 is required for sebaceous gland homeostasis (22) and epidermal terminal differentiation (48). PRDM1 has a dynamic pattern of expression in the developing mouse embryo (10, 60, 67, 81). Loss-of-function mutant embryos fail to specify primordial germ cells, display pharyngeal arch defects, and die around embryonic day 10.5 (E10.5) due to placental insufficiency (60, 81). Conditional rescue experiments have revealed additional roles in multipotent progenitor cell populations in the forelimb, secondary heart field, and sensory vibrissae (67). Thus, PRDM1 regulates cell fate decisions in diverse contexts in the embryo and governs tissue homeostasis in multiple cell types in the adult organism. The cis-acting regulatory elements that direct tissue-specific PRDM1 expression in these specialized cell types are largely unknown. A Venus fluorescent reporter transgene embedded within a 230-kb bacterial artificial chromosome (kb −140 to +90 relative to the transcription start site) faithfully drives temporally and spatially restricted expression at numerous sites in the embryo, including primordial germ cells, anterior definitive endoderm, somites, pharyngeal arches, limb buds, and dermal papillae (60, 61). In contrast, an enhanced green fluorescent protein reporter construct containing 4.4 kb upstream of the PRDM1 transcription start site is sufficient for expression in adult hematopoietic tissues and mediates lipopolysaccharide (LPS) responsiveness of splenic B cells (83). However, this construct also leads to ectopic expression at numerous tissue sites. The cis-acting regulatory elements controlling dynamic patterns of PRDM1 expression in vivo thus potentially span a large genomic region. Dose-dependent BMP-Smad signals activate PRDM1 expression in committed primordial germ cells when they initially appear at the base of the allantois (60). However, it remains unknown whether PRDM1 is a direct Smad target. A recent study identified a Gli3 binding site ∼27 kb downstream of the PRDM1 coding region that drives expression in the developing limb (82). Similarly, studies of zebra fish have shown that Sonic Hedgehog controls PRDM1 expression during pectoral fin and muscle development (5, 40). However, multipotent progenitor cell populations allocated at numerous tissue sites express PRDM1 only transiently (67). Multiple, as yet uncharacterized enhancer and repressor elements are almost certainly required to regulate graded PRDM1 activities throughout development. Alternative promoter usage offers an attractive mechanism for regulating PRDM1 gene expression. Two alternative promoters control spatially and temporally distinct blimp1/krox expression patterns during sea urchin development (44, 45). These alternative transcripts encode nearly identical proteins except that the 1b isoform contains 50 additional residues at its amino terminus. Specific morpholino knockdown of the 1a and 1b transcripts results in tissue-specific disturbances in the gut endoderm and vegetal plate, respectively (44). The activity of an alternative promoter region located 5′ of PRDM1 exon 4 that generates a protein lacking the PR/SET domain with reduced repressive activity on multiple target genes is elevated in human myeloma lines relative to levels in primary B cells (21). The PRDM1 basal promoter and multiple transcriptional start sites were previously mapped immediately upstream of exon 1 (78). To learn more about developmentally regulated expression, we characterized the 5′ ends of PRDM1 transcripts in the developing embryo. We identified two novel alternative first exons that both splice directly to exon 3, containing the translational start site. Exon 1B, located 70 kb upstream of exon 1A, is strongly expressed in the yolk sac. An additional first exon (exon 1C) is located in the intron downstream of exon 1A. To evaluate the possibly distinct functional activities contributed by alternative promoters, we generated targeted alleles that selectively eliminate either exon 1A (Δex1A) or exon 1B (Δex1B) transcripts. The exon 1B deletion slightly decreases expression in the yolk sac but otherwise has no noticeable effect in the embryo or adult tissues. Surprisingly, the exon 1A deletion encompassing NF-κB sites upstream of the promoter eliminates PRDM1 expression in LPS-stimulated B cells and blocks plasma cell differentiation but fails to disrupt embryonic development. Consistent with this, we observe only modestly reduced PRDM1 expression levels in the embryo. However, compound heterozygotes also carrying the null allele display partially penetrant developmental defects. The novel alternative promoters described in this report are likely to play important roles in generating regulatory diversity and controlling gene dosage effects.
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an expanding job description for blimp 1 PRDM1
Current Opinion in Genetics & Development, 2009Co-Authors: Elizabeth K Bikoff, Marc A. Morgan, Elizabeth J. RobertsonAbstract:The master transcriptional regulator Blimp-1/PRDM1 contains an N-terminal PR/SET domain and five C2H2 zinc fingers located near its C-terminus that mediate DNA binding, nuclear import and recruitment of histone modifying enzymes. These activities account for its ability to control cell-fate decisions in the embryo and govern tissue homeostasis in multiple cell types in the adult organism. New experiments demonstrate an increasing degree of complexity associated with Blimp-1/PRDM1 target site selection and its associations with epigenetic modifiers. Our current understanding of how this single unique species within the family of structurally similar PRDM proteins regulates gene expression patterns and governs developmental programmes in different cell lineages is discussed.
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An expanding job description for Blimp-1/PRDM1
Current Opinion in Genetics and Development, 2009Co-Authors: Elizabeth K Bikoff, Marc A. Morgan, Elizabeth J. RobertsonAbstract:The master transcriptional regulator Blimp-1/PRDM1 contains an N-terminal PR/SET domain and five C2H2 zinc fingers located near its C-terminus that mediate DNA binding, nuclear import and recruitment of histone modifying enzymes. These activities account for its ability to control cell-fate decisions in the embryo and govern tissue homeostasis in multiple cell types in the adult organism. New experiments demonstrate an increasing degree of complexity associated with Blimp-1/PRDM1 target site selection and its associations with epigenetic modifiers. Our current understanding of how this single unique species within the family of structurally similar PRDM proteins regulates gene expression patterns and governs developmental programmes in different cell lineages is discussed. © 2009 Elsevier Ltd. All rights reserved.
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transcription of PRDM1 the master regulator for plasma cell differentiation depends on an sp1 sp3 egr 1 gc box
European Journal of Immunology, 2008Co-Authors: Francisco Moralopez, Nuria Pedrenohorrillo, Luis Delgadoperez, Jose A Brieva, Antonio CamposcaroAbstract:The positive regulatory domain containing 1, encoded by the PRDM1 gene, is a transcriptional repressor considered as a master regulator that is required and sufficient for plasma cell differentiation. In the present study we have performed sequence analysis of the upstream region of the human PRDM1 gene to detect the minimal promoter region necessary for PRDM1 gene transcription. This region comprises the region upstream of the initiation site, as well as the first exon. Collectively, deletion and mutation analysis in conjunction with luciferase reporter assays, EMSA and supershift assays identified a phylogenetically conserved GC-box as an essential element for PRDM1 expression. This GC-box element matches to a binding site for multiple transcription factors such as SP1 and SP3 isoforms as well as early growth response 1. Chromatin immunoprecipitation assays confirmed the in vivo binding capability of these factors to the human PRDM1 promoter. These studies together characterize for the first time the basal activity of the human PRDM1 promoter, through which several factors, including SP1, SP3 and early growth response 1, modulate its expression through a conserved GC-box.