121 research outputs found
Zebrafish mll Gene Is Essential for Hematopoiesis
No full textStudies implicate an important role for the mixed lineage leukemia (Mll) gene in hematopoiesis, mainly through maintaining Hox gene expression. However, the mechanisms underlying Mll-mediated hematopoiesis during embryogenesis remain largely unclear. Here, we investigate the role of mll during zebrafish embryogenesis, particularly hematopoiesis. Mll depletion caused severe defects in hematopoiesis as indicated by a lack of blood flow and mature blood cells as well as a significant reduction in expression of hematopoietic progenitor and mature blood cell markers. Furthermore, mll depletion prevented the differentiation of hematopoietic progenitors. In addition, we identified the N-terminal mini-peptide of Mll that acted as a dominant negative form to disrupt normal function of mll during embryogenesis. As expected, mll knockdown altered the expression of a subset of Hox genes. However, overexpression of these down-regulated Hox genes only partially rescued the blood deficiency, suggesting that mll may target additional genes to regulate hematopoiesis. In the mll morphants, microarray analysis revealed a dramatic up-regulation of gadd45 alpha a. Multiple assays indicate that mll inhibited gadd45 alpha a expression and that overexpression of gadd45 alpha a mRNA led to a phenotype similar to the one seen in the mll morphants. Taken together, these findings demonstrate that zebrafish mll plays essential roles in hematopoiesis and that gadd45 alpha a may serve as a potential downstream target for mediating the function of mll in hematopoiesis
The MLL recombinome of acute leukemias in 2017
No full text\ua9 The Author(s) 2018.Chromosomal rearrangements of the human MLL/KMT2A gene are associated with infant, pediatric, adult and therapy-induced acute leukemias. Here we present the data obtained from 2345 acute leukemia patients. Genomic breakpoints within the MLL gene and the involved translocation partner genes (TPGs) were determined and 11 novel TPGs were identified. Thus, a total of 135 different MLL rearrangements have been identified so far, of which 94 TPGs are now characterized at the molecular level. In all, 35 out of these 94 TPGs occur recurrently, but only 9 specific gene fusions account for more than 90% of all illegitimate recombinations of the MLL gene. We observed an age-dependent breakpoint shift with breakpoints localizing within MLL intron 11 associated with acute lymphoblastic leukemia and younger patients, while breakpoints in MLL intron 9 predominate in AML or older patients. The molecular characterization of MLL breakpoints suggests different etiologies in the different age groups and allows the correlation of functional domains of the MLL gene with clinical outcome. This study provides a comprehensive analysis of the MLL recombinome in acute leukemia and demonstrates that the establishment of patient-specific chromosomal fusion sites allows the design of specific PCR primers for minimal residual disease analyses for all patients
Development Refractoriness of MLL-Rearranged Human B Cell Acute Leukemias to Reprogramming into Pluripotency
No full textInduced pluripotent stem cells (iPSCs) are a powerful tool for disease modeling. They are routinely generated from healthy donors and patients from multiple cell types at different developmental stages. However, reprogramming leukemias is an extremely inefficient process. Few studies generated iPSCs from primary chronic myeloid leukemias, but iPSC generation from acute myeloid or lymphoid leukemias (ALL) has not been achieved. We attempted to generate iPSCs from different subtypes of B-ALL to address the developmental impact of leukemic fusion genes. OKSM(L)-expressing mono/polycistronic-, retroviral/lentiviral/episomal-, and Sendai virus vector-based reprogramming strategies failed to render iPSCs in vitro and in vivo. Addition of transcriptomic-epigenetic reprogramming “boosters” also failed to generate iPSCs from B cell blasts and B-ALL lines, and when iPSCs emerged they lacked leukemic fusion genes, demonstrating non-leukemic myeloid origin. Conversely, MLL-AF4-overexpressing hematopoietic stem cells/B progenitors were successfully reprogrammed, indicating that B cell origin and leukemic fusion gene were not reprogramming barriers. Global transcriptome/DNA methylome profiling suggested a developmental/differentiation refractoriness of MLL-rearranged B-ALL to reprogramming into pluripotency
Analysis of expression of MSH2 and MSH3 genes in MLL-Acute Lymphoblastic Leukemia (ALL) human cell lines
No full textAround 820 new cases of Acute Lymphoblastic Leukemia (ALL) are diagnosed in the United Kingdom every year. Cytarabine (Ara-C) is a chemotherapeutic drug used to treat leukemic patients, however, chemotherapy resistance occurs frequently. Mechanisms of chemotherapy resistance to Ara-C are poorly understood. DNA mismatch repair (MMR) pathway is one of the pathways responsible to repair errors caused during DNA replication. MMR can also repair the damage due to Ara-C and therefore a proficient MMR can confer resistance to Ara-C. Our project aims to investigate the expression of MMR genes MSH2 and MSH3 in ALL carrying MLL (Mixed Lineage Leukemia, also known as KMT2A) chromosomal translocations. The purpose of this study was to examine a potential correlation between the expression of these genes in MLL-ALL and Ara-C resistance. RNA was isolated from cultured cell lines: Kasumi-1 and K562 (positive non MLL controls) and HB-1119 and SEM-1 (experimental MLL-cell lines), retro-transcribed into cDNA. Endpoint and Semi-quantitative PCR were employed to amplify the cDNA and analyze the expression of MSH2 and MSH3 in the experimental cell lines. The results indicate that MSH2 and MSH3 are expressed in both Ara-C resistant MLL-ALL cell lines HB-1119 and SEM-1 and that the expression levels in HB-1119 were lower than SEM1. Further research is needed to understand the contribution of MMR to Ara-C response in ALL. This research should be focused on testing the functionality of MMR in Ara-C resistant and sensitive leukemic cell lines. Furthermore, the contribution of each MMR genes to Ara-C resistance should be addressed by knock-down and over-expression studies.© 2020 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. See http://creativecommons.org/licenses/by/4.0
Analysis of expression of MSH2 and MSH3 genes in MLL-Acute Lymphoblastic Leukemia (ALL) human cell lines
No full textAround 820 new cases of Acute Lymphoblastic Leukemia (ALL) are diagnosed in the United Kingdom every year. Cytarabine (Ara-C) is a chemotherapeutic drug used to treat leukemic patients, however, chemotherapy resistance occurs frequently. Mechanisms of chemotherapy resistance to Ara-C are poorly understood. DNA mismatch repair (MMR) pathway is one of the pathways responsible to repair errors caused during DNA replication. MMR can also repair the damage due to Ara-C and therefore a proficient MMR can confer resistance to Ara-C. Our project aims to investigate the expression of MMR genes MSH2 and MSH3 in ALL carrying MLL (Mixed Lineage Leukemia, also known as KMT2A) chromosomal translocations. The purpose of this study was to examine a potential correlation between the expression of these genes in MLL-ALL and Ara-C resistance. RNA was isolated from cultured cell lines: Kasumi-1 and K562 (positive non MLL controls) and HB-1119 and SEM-1 (experimental MLL-cell lines), retro-transcribed into cDNA. Endpoint and Semi-quantitative PCR were employed to amplify the cDNA and analyze the expression of MSH2 and MSH3 in the experimental cell lines. The results indicate that MSH2 and MSH3 are expressed in both Ara-C resistant MLL-ALL cell lines HB-1119 and SEM-1 and that the expression levels in HB-1119 were lower than SEM1. Further research is needed to understand the contribution of MMR to Ara-C response in ALL. This research should be focused on testing the functionality of MMR in Ara-C resistant and sensitive leukemic cell lines. Furthermore, the contribution of each MMR genes to Ara-C resistance should be addressed by knock-down and over-expression studies.© 2020 The Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution 4.0 International License (CC-BY 4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. See http://creativecommons.org/licenses/by/4.0
MLL-AF4 Spreading Identifies Binding Sites that Are Distinct from Super-Enhancers and that Govern Sensitivity to DOT1L Inhibition in Leukemia
No full text\ua9 2017 The Author(s) Understanding the underlying molecular mechanisms of defined cancers is crucial for effective personalized therapies. Translocations of the mixed-lineage leukemia (MLL) gene produce fusion proteins such as MLL-AF4 that disrupt epigenetic pathways and cause poor-prognosis leukemias. Here, we find that at a subset of gene targets, MLL-AF4 binding spreads into the gene body and is associated with the spreading of Menin binding, increased transcription, increased H3K79 methylation (H3K79me2/3), a disruption of normal H3K36me3 patterns, and unmethylated CpG regions in the gene body. Compared to other H3K79me2/3 marked genes, MLL-AF4 spreading gene expression is downregulated by inhibitors of the H3K79 methyltransferase DOT1L. This sensitivity mediates synergistic interactions with additional targeted drug treatments. Therefore, epigenetic spreading and enhanced susceptibility to epidrugs provides a potential marker for better understanding combination therapies in humans
Regulation of DNA replication and chromosomal polyploidy by the MLL-WDR5-RBBP5 methyltransferases
No full textDNA replication licensing occurs on chromatin, but how the chromatin template is regulated for replication remains mostly unclear. Here, we have analyzed the requirement of histone methyltransferases for a specific type of replication: the DNA re-replication induced by the downregulation of either Geminin, an inhibitor of replication licensing protein CDT1, or the CRL4CDT2 ubiquitin E3 ligase. We found that siRNA-mediated reduction of essential components of the MLL-WDR5-RBBP5 methyltransferase complexes including WDR5 or RBBP5, which transfer methyl groups to histone H3 at K4 (H3K4), suppressed DNA re-replication and chromosomal polyploidy. Reduction of WDR5/RBBP5 also prevented the activation of H2AX checkpoint caused by re-replication, but not by ultraviolet or X-ray irradiation; and the components of MLL complexes co-localized with the origin recognition complex (ORC) and MCM2-7 replicative helicase complexes at replication origins to control the levels of methylated H3K4. Downregulation of WDR5 or RBBP5 reduced the methylated H3K4 and suppressed the recruitment of MCM2-7 complexes onto replication origins. Our studies indicate that the MLL complexes and H3K4 methylation are required for DNA replication but not for DNA damage repair
Long-term Miniaturized Stabilization of Ultrafast Laser based on Rubidium Coherent Population Trapping Atomic Resonator
No full textMany locking approaches have been exploited to stabilize the mode-locked laser (MLL), helping to generate high-stable microwave sources. We present a novel miniaturized stabilization scheme for MLL, based on a rubidium coherent population trapping (CPT) atomic resonator. By directly frequency-locking the repetition rate of the MLL to a Rb-85 CPT resonance, we demonstrate a very small stabilization system (length of 5 cm, width of 5 cm and height of 2.2 cm) for MLL with a long-term instability of similar to 3x10(-12).Automation & Control SystemsComputer Science, Information SystemsEngineering, Electrical & ElectronicEICPCI-S(ISTP)
Monitoring Mixed Lineage Leukemia Expression May Help Identify Patients with Mixed Lineage Leukemia–Rearranged Acute Leukemia Who Are at High Risk of Relapse after Allogeneic Hematopoietic Stem Cell Transplantation
No full textAbstractTo evaluate the prognostic value of the expression of the mixed lineage leukemia (MLL) gene for predicting the relapse of patients with MLL-rearranged acute leukemia (AL) after allogeneic hematopoietic stem cell transplantation (allo-HSCT), the levels of MLL transcripts in bone marrow (BM) specimens were monitored serially by real-time quantitative polymerase chain reaction (RQ-PCR) at predetermined time points in 40 patients with MLL-rearranged AL who were treated with allo-HSCT. These patients were followed for a median of 24.5 months (range, 8 to 60 months). A total of 236 BM samples were collected and analyzed. Of these, 230 were monitored concurrently for minimal residual disease (MRD) by flow cytometry (FCM) for leukemia-associated aberrant immune phenotypes and by RQ-PCR for the expression of the Wilms tumor (WT1) gene. The 3-year cumulative incidence of relapse in patients who experienced MLL-positive patients (MLL > .0000%) (n = 9) after HSCT was 93.5% (95% confidence interval [CI], 87% to 100%) compared with 12.5% (95% CI, 5.6% to 19.4%) for MLL-negative patients (n = 31) (P < .001). For these 2 patient groups, the 3-year overall survival (OS) was 12.5% (95% CI, .8% to 24.2%) and 77.8% (95% CI, 68.4% to 87.2%) (P < .001), respectively, and the 3-year leukemia-free survival (LFS) was 0% and 72.2% (95% CI, 61.1% to 83.3%), respectively (P < .001). MLL positivity was associated with a higher rate of relapse (hazard ratio [HR], 18.643; 95% CI, 3.449 to 57.025; P = .001), lower LFS (HR, 7.267; 95% CI, 2.038 to 25.916; P = .002), and lower OS (HR, 8.259; 95% CI, 2.109 to 32.336; P = .002), as determined by Cox multivariate analysis. The expression of the MLL gene had a higher specificity and sensitivity than WT1 or MRD monitored by FCM for predicting the relapse of the patients with MLL + AL. Our results suggest that monitoring the expression of the MLL gene may help to identify patients with MLL + AL who are at high risk of relapse after allo-HSCT and may provide a guide for suitable intervention
Optical sampling ADC based on dual optical frequency combs with rubidium frequency reference
No full textThis paper reports an optical sampling analog-todigital converter (ADC) system based on dual optical frequency combs with a rubidium (Rb) coherent population trapping (CPT) atomic resonator. The repetition frequency of one mode-locked laser (MLL) is locked to an Rb-85 3.035 GHz CPT atomic resonance. The repetition frequency of the other MLL is locked to the Rb frequency reference with a little difference. The optical pulses trains of these two lasers are coupled to implement highspeed optical sampling ADC system. This scheme provides a portable and long-term stable approach for optical sampling ADC system based on dual optical combs.CPCI-S(ISTP)[email protected]
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