The transition to flowering is characterized by a shift of the shoot apical meristem (SAM) from leaf production to the initiation of a floral meristem. In this study, we addressed the nature of SAM gene networks involved in the early floral initiation process in the crop legume soybean. Unique aspects (such as pod development and nitrogen fixation) of legume development make them appealing for plant development studies. Soybean, a major oilseed crop, possesses varied maturity groups; hence, understanding and unravelling initial transition control has implications in manipulating crop yield. To this end, we performed global gene expression analysis using Affymetrix soybean GeneChip with RNA isolated from micro-dissected soybean SAMs at various time points after plants were shifted from long-day to short-day growth conditions. Analysis of the resulting microarray data revealed a total of 331 transcripts that have differential expression profiles. Intriguingly, about 20% of the transcripts affected by the switch in the development program have orthologs reported to be responsive to abscisic acid (ABA), suggesting an increase in ABA levels in the SAM during this developmental change. A subsequent immunoassay verified this, thereby implicating its possible function as an endogenous signal during the floral evocation process. The striking occurrence of abiotic stress-related transcripts, including trehalose metabolism genes, in SAMs during the early transition to floral meristems points to an overlap of abiotic stress and floral signalling pathways in soybean. In addition, other hormones - auxin, jasmonic acid and brassinosteroids - and a number of candidate protein kinases may also act in the signalling process prior to or concurrently with the induction of the putative floral homeiotic transcripts. This indicates that molecular events mediated by multiple hormonal pathways are part of the mechanism employed by soybean to regulate the floral transition process.
Molecular processes underlying the floral transition in the soybean shoot apical meristem.
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View SamplesSperm cells represent the male partner that fuses with the egg cell during fertilization in all multi-cellular eukaryotic organisms, and, in flowering plants, is a founder of both embryo and nutritive endosperm. We examined the transcriptome of Oryza sativa ssp. japonica using the Affymetrix 57K rice genome GeneChip to provide an overview of genes activated in the paternal gamete.
Transcriptome-based examination of putative pollen allergens of rice (Oryza sativa ssp. japonica).
Specimen part
View SamplesThe shoot apical meristem (SAM) contains undifferentiated stem cells that are responsible for the initiation of above-ground organs, and eventually the general architecture of the plant. To gain insight into the nature of genetic programs and the regulatory networks underlying SAM function in soybean, we have used Affymetrix soybean GeneChip to investigate the transcript profiles associated with micro-dissected SAMs or axillary meristems (AMs). While the microarray data disclosed the conservation of transcriptional signature between the two types of meristems, subsequent comparison of SAM transcript profile with that of non-meristem (NM) tissue revealed a total of 1090 and 1523 transcripts that are significantly up- or down-regulated in the SAM. Further in situ hybridization analysis on selected transcripts has implicated their roles in SAM maintenance and the establishment of organ polarity. We also identified a gene that could potentially serve as a novel marker that distinguishes the differentiating cells in the meristem from the pluripotent stem cells. Along with many unknowns, transcripts with putative annotation have also been identified that has allowed us to infer SAM regulatory roles for various families of transcription factors as well as products associated with auxin-mediated responses, cell division and proliferation, epigenetic regulation, miRNA regulation and protein turnover. Computational analysis on the promoter regions of Arabidopsis orthologs of genes with high expression in the soybean SAM revealed a conserved over-representation of three cis-acting regulatory motifs. Our microarray data thus represents a rich source of target genes for further study into the meristem function and maintenance.
Genome-wide analysis of gene expression in soybean shoot apical meristem.
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View SamplesBackground: Pollen, the male partner in the reproduction of flowering plants, comprises either two or three cells at maturity. The current knowledge of the pollen transcriptome is limited to the model plant Arabidopsis thaliana, which has tri-cellular pollen grains at maturity.
Genomic expression profiling of mature soybean (Glycine max) pollen.
No sample metadata fields
View SamplesPublished molecular profiling studies in patients with lymphoma suggested the influence of hypoxia inducible factor-1 alpha (HIF1) targets in prognosis of DLBCL. Yet, the role of hypoxia in hematological malignancies remains unclear. We observed that activation of HIF1 resulted in global translation repression during hypoxic stress in DLBCL. Protein translation efficiency as measured using 35S-labeled methionine incorporation revealed a 50% reduction in translation upon activation of HIF1. Importantly, translation was not completely inhibited and expression of clinically correlated hypoxia targets such as GLUT1, HK2, and CYT-C was found to be refractory to translational repression under hypoxia in DLBCL cells. Notably, hypoxic induction of these genes was not observed in normal primary B-cells. Translational repression was coupled with a decrease in mitochondrial function. Screening of primary DLBCL patient samples revealed that expression of HK2, which encodes for the enzyme hexokinase 2, was significantly correlated with DLBCL phenotype. Genetic knockdown studies demonstrated that HK2 is required for promoting growth of DLBCL under hypoxic stress. Altogether, our findings provide strong support for the direct contribution of HK2 in B-cell lymphoma development and suggest that HK2 is a key metabolic driver of the DLBCL phenotype.ne incorporation revealed a 50% reduction in translation upon activation of HIF1. Importantly, translation was not completely blunted and expression of clinically correlated hypoxia targets such as GLUT1, HK2, and CYT-C was found to be refractory to translational repression under hypoxia in DLBCL cells. Notably, hypoxic induction of these genes was not observed in normal primary B-cells. Translational repression was coupled with decrease in mitochondrial function. Screening of DLBCL patient samples identified that expression of HK2, which encodes for the enzyme hexokinase 2, was significantly correlated with DLBCL phenotype. Genetic knockdown studies show that HK2 is required for promoting growth of DLBCL under hypoxic stress. Altogether, our findings provide more definitive proof of direct contribution of HK2 in development of B-cell lymphoma and suggest that HK2 is a key metabolic driver of DLBCL phenotype.
Role of hypoxia in Diffuse Large B-cell Lymphoma: Metabolic repression and selective translation of HK2 facilitates development of DLBCL.
Cell line, Treatment
View SamplesPGC1a is a transcriptional coactivator that regulates energy metabolism. PGC1a is highly expressed in a subset of melanoma tumors and cell lines. We generated gene-expression profile of control and PGC1alpha depleted A375P melanoma cells, a melanoma cell line that expresses very high levels of PGC1a to investigate the role of this gene in melanoma.
PGC1α expression defines a subset of human melanoma tumors with increased mitochondrial capacity and resistance to oxidative stress.
Specimen part
View SamplesTo determine the global transcriptome changes in mantle cell lymphoma cells following treatment with the BET bromodomain antagonist, JQ1
Synergistic activity of BET protein antagonist-based combinations in mantle cell lymphoma cells sensitive or resistant to ibrutinib.
Specimen part, Treatment
View SamplesHeat shock protein 90 (Hsp90) is an emerging therapeutic target in cancer. We report that Hsp90 inhibitors selectively kill DLBCLs that are biologically dependent on the BCL6 transcriptional repressor. We examined the pharmacokinetics, toxicity and efficacy of PUH71, a recently developed purine scaffold Hsp90 inhibitor. PUH71 preferentially accumulated in tumors vs. normal tissues, and unlike the widely used benzoquinone Hsp90 inhibitors, displayed no signs of organ toxicity. PUH71 selectively and potently induced the regression of BCL6-dependent DLBCLs in vivo, through reactivation of key BCL6 target genes and apoptosis.
A purine scaffold Hsp90 inhibitor destabilizes BCL-6 and has specific antitumor activity in BCL-6-dependent B cell lymphomas.
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View SamplesThe BET (bromodomain and extra terminal) protein family members including BRD4 bind to acetylated lysines on histones and regulate the expression of important oncogenes, e.g., MYC and BCL2. Here we demonstrate the sensitizing effects of the histone hyperacetylation inducing pan-histone deacetylase inhibitor (HDI) panobinostat (PS) on human AML blast progenitor cells (BPCs) to the BET protein inhibitor JQ1. Treatment with JQ1 but not its inactive enantiomer (R-JQ1) was highly lethal against AML BPCs expressing mutant NPM1c+ with or without co-expression of FLT3-ITD, or AML expressing MLL fusion oncoprotein. JQ1 treatment reduced binding of BRD4 and RNA polymerase II to the DNA of MYC and BCL2, and reduced their levels in the AML cells. Co-treatment with JQ1 and the HDAC inhibitor panobinostat (PS) synergistically induced apoptosis of the AML BPCs, but not of normal CD34+ hematopoietic progenitor cells. This was associated with greater attenuation of MYC and BCL2, while increasing p21, BIM and cleaved PARP levels in the AML BPCs. Co-treatment with JQ1 and PS significantly improved the survival of the NOD/SCID mice engrafted with OCI-AML3 or MOLM13 cells (p < 0.01). These findings highlight co-treatment with a BRD4 antagonist and an HDI as a potentially efficacious therapy of AML.
Highly active combination of BRD4 antagonist and histone deacetylase inhibitor against human acute myelogenous leukemia cells.
Specimen part
View SamplesBromodomain extraterminal protein (BETP) inhibitors transcriptionally repress oncoproteins and NFkB target genes, which undermines the growth and survival of MCL cells. However, BETi treatment causes accumulation of BETPs, associated with reversible binding and incomplete inhibition of BRD4, which potentially compromises the activity of BETi in MCL cells. Unlike BETi, BET-PROTACs (proteolysis-targeting chimera) ARV-825 and ARV-771 (Arvinas, Inc.) recruit and utilize an E3-ubiquitin ligase to effectively degrade BETPs in MCL cells. BET-PROTACs induce more apoptosis than BETi of MCL cells, including those resistant to ibrutinib. BET-PROTAC treatment induced more perturbations in the mRNA and protein expressions than BETi, with depletion of c-Myc, CDK4, cyclin D1, and the NFkB transcriptional targets Bcl-xL, XIAP and BTK, while inducing the level of HEXIM1, NOXA and CDKN1A/p21. Treatment with ARV-771, which possesses superior pharmacological properties compared to ARV-825, inhibited the in vivo growth and induced greater survival improvement than the BETi OTX015 of immune-depleted mice engrafted with MCL cells. Co-treatment of ARV-771 with ibrutinib or the BCL2-antagonist venetoclax or CDK4/6 inhibitor palbociclib synergistically induced apoptosis of MCL cells. These studies highlight promising and superior pre-clinical activity of BET-PROTAC than BETi, requiring further in vivo evaluation of BET-PROTAC as a therapy for ibrutinib-sensitive or resistant MCL. Overall design: Twelve samples in biologic triplicates
BET protein proteolysis targeting chimera (PROTAC) exerts potent lethal activity against mantle cell lymphoma cells.
Subject
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