bluuebunny/crossref_metadata_2025_split huggingface dataset:
Acute Megakaryoblastic Leukemia in Childhood: Comparison Between Patients with and without Down Syndrome
Authors: Felice Maria Sara , Rossi Jorge Gabriel , Gallego Marta , Alonso Cristina N. , Eandi Eberle Silvia , Guitter Myriam Ruth , Rubio Patricia L. , Alfaro Elizabeth M , Sanchez La Rosa Cristian , Zubizarreta Pedro 
Published: October 2019

Abstract
Introduction: Acute Megakaryoblastic Leukemia (AMKL) is an unusual AML subtype in childhood, being the most frequent AML in Down syndrome (DS) patients. AMKL corresponds to 19.3% of AML in our Hospital and some special characteristics have been observed.
Objective: To analyze characteristics of AMKL and to compare patients with or without DS.
Patients and Methods:From January-1990 to June-2014 AMKL was diagnosed in 77 cases: 57 in non-DS and 20 in DS children. Fivecases were secondary leukemias and 3 cases had been previouslytreated with chemotherapy due to wrong diagnosis. One patient was on induction at the time of analysis. These 9 cases were not evaluable for follow-up. Forty-eight non-DS and 20 DS caseswere evaluable. Megakayocyte lineage commitment was confirmed in all cases by fluorescence microscopy. MPO was analyzedboth by flow cytometry and cytochemistry. G-banding and RT-PCR were performed according to standard techniques. Four successive BFM-based protocols were administeredwith schedule modification for DS patients.
Results: Mean age was:2 (range: 2 mo-13 y) years of age and mean WBC count was: 27,500 (range: 1,600-250,000)/mm3. No differences were observed in age or hematological findings at diagnosis. Extramedullar compromise was detected in 10 (17.5%) of non-SD cases. Immunophenotype defined ambiguous lineage leukemia in 3 (5.0%) of the non-DS cases, with compromise of T-lineage. Interestingly, in 4 cases the megakaryoblasts also co-expressed MPO.Cytogenetic findings showed hyperdiploidy (n=7), t(1;22)(p13;q23) (n=3), t(16;21)/FUS-ERG (n=2), abnormalities in chromosome 7 (n=5) and complex karyotype (n=9). Complete remission (CR) was achieved in 51 (33 non-DS and 18 DS) (75.0%) of 68 evaluable cases;null-responses observed in7(only non-DS, 10.3%). Early deaths occurred in 10 (14.7%) during induction phase, 2 of them before treatment onset. From the 51 patients who achieved CR, 16 (14 non-DS and 2 DS) presented relapses(p: 0.04) and 9 (6 in non-DS and 3 in DS) died in CR. EFS-probability for the total population was 34 (6)%, for non-DS 21 (6)% and for DS 63 (11)%(p-value: 0.0026). LFS-probability was 45 (7)% for the total population, for non-DS 29 (8)% and for DS 70 (11)% (p-value: 0.0117). Median follow-up: 148 (range: 2-194) months.
Conclusions:
1- Extramedullar compromise and T/myeloid mixed lineage or co-expression of MPO were observed only in non-DS AMKL, in 17.5% and 12.0% respectively.
2- Null-response was observed only in non-SD patients.
3- The most frequent event of non-DS was relapse, and toxic deaths in DS.
4- The significantly better outcome of patients with DS was confirmed in our setting.

Disclosures
No relevant conflicts of interest to declare.
Regulation of Hematopoietic Stem Cells by Interferons and by DNA Methylation: Implications for Bone Marrow Failure
Authors: Goodell Margaret A. 
Published: October 2019

Bone marrow failure (BMF), the inability to regenerate the differentiated cells of the blood, has a number of genetic and environmental etiologies, such as mutation of telomere-associated protein genes and immune-related aplastic anemia. Recently, mutations in DNA methyltransferase 3A (DNMT3A) have been found to be associated with approximately 15% of cases of primary myelofibrosis (MF), which can be a cause of BMF. The role of DNMT3A more broadly in hematopoiesis, and specifically in BMF, is currently poorly understood. DNMT3A is one of two de novo DNA methylation enzymes important in developmental fate choice. We showed that Dnmt3a is critical for normal murine hematopoiesis, as hematopoietic stem cells (HSCs) from Dnmt3a knockout (KO) mice displayed greatly diminished differentiation potential while their self-renewal ability was markedly increased1, in effect, leading to failure of blood regeneration or BMF. Combined with loss of Dnmt3b, HSCs exhibited a profound differentiation block, mediated in part by an increase of stabilized b-catenin. While we did not initially observe bone marrow pathology or malignancy development in mice transplanted with Dnmt3a KO HSCs, when we aged a large cohort of mice, all mice succumbed to hematologic disease within about 400 days. Roughly one-third of mice developed frank leukemia (acute lymphocytic leukemia or acute myeloid leukemia), one-third developed MDS, and the remainder developed primary myelofibrosis or chronic myelomonocytic leukemia. The pathological characteristics of the mice broadly mirror those of patients, suggesting the Dnmt3a KO mice can serve as a model for human DNMT3A-mutation associated disease. Strikingly, bone marrow of mice with different disease types exhibit distinct DNA methylation features. These will findings and the implications for disease development will be discussed. We are currently investigating the factors that drive different outcomes in the mice, including stressors such as exposure to interferons. We have hypothesized that HSC proliferation accelerates the Dnnmt3a-associated disease phenotypes. We have previously shown that interferons directly impinge on HSCs in the context of infections. Interferons activate HSCs to divide, generating differentiated progeny and cycling HSCs. Repeated interferon stimulation may permanently impair HSC function and bias stem cell output. When combined with loss of Dnmt3a, interferons may promote BMF. We will discuss broadly how external factors such as aging and infection may collaborate with specific genetic determinants to affect long-term hematopoiesis and malignancy development.
Reference: Challen GA, Sun D, Jeong M, et al. Dnmt3a is essential for hematopoietic stem cell differentiation. Nat Genet 2012; 44: 23-31
Figure 1 Figure 1.

Disclosures
No relevant conflicts of interest to declare.
Evolution and Immunogenetics of Natural Killer Cell Receptors in Health and Disease
Authors: Parham Peter 
Published: October 2019

Abstract
Natural killer (NK) cells are phenotypically diverse lymphocytes that contribute to innate immunity, adaptive immunity and placental reproduction. Unlike B and T cells, NK cells do not use rearranging genes to make diverse antigen receptors that are clonally expressed. Instead, NK cells express diverse combinations of a variety of receptors that are encoded by conventional non-rearranging genes. Several of these receptors are specific for conserved and variable determinants of major histocompatibility complex (MHC) class I molecules. In humans, the killer-cell immunoglobulin-like receptors (KIR) are a diverse and polymorphic family of NK-cell receptors that recognize determinants of human leukocyte antigen (HLA)-A, B and C, the polymorphic human MHC class I molecules. HLA-A, B and C are the most polymorphic of human genes, and they correlate with susceptibility to a wide range of diseases and clinical outcomes, including allogeneic hematopoietic cell transplantation (HCT). During NK-cell development, interactions between epitopes of HLA class I and KIR educate the NK cells to recognize the normal expression of these epitopes on healthy cells, and to respond to unhealthy cells in which that expression is perturbed. In the context of HCT, certain types of HLA class I mismatch enable donor-derived NK cells to make an alloreactive and beneficial graft-versus-leukemia response. Although it is likely that all placental mammals have NK cells, only a small minority of these species has a diverse KIR family like that in humans. These comprise the simian primates: New World monkeys, Old World monkeys and the great apes. Under pressure from diverse and rapidly evolving pathogens, both the MHC class I and KIR gene families have been driven to evolve rapidly. Consequently, much of their character is species-specific. This is especially true for the human KIR gene family, which is qualitatively different from that of our closest relatives, the chimpanzees. Whereas chimpanzee KIR haplotype diversity represents variations on a theme of genes encoding robust MHC class I receptors, humans have an even balance between group A KIR haplotypes encoding robust HLA class I receptors and group B KIR haplotypes encoding receptors that, to varying degree, have been subject to natural selection for reduced functional recognition of HLA class I. A balance of A and B is present in all human populations and thus appears essential for the long-term survival and competitiveness of human communities. Whereas the A KIR haplotypes correlate with successful defense against viral infection, maternal B KIR haplotypes correlate with reproductive success and donor B KIR haplotypes improve the outcome of allogeneic HCT as therapy for acute myeloid leukemia.

Disclosures
No relevant conflicts of interest to declare.
Neutrophil Extracellular Traps and von Willebrand Factor in Thrombosis
Authors: Wagner Denisa D. 
Published: October 2019

For many years, my lab has been studying the interplay between inflammation and thrombosis. These processes occur together, stimulate each other and share cellular and molecular components. The latest example of a common functional component is neutrophil extracellular traps (NETs). NETs are chromatin released together with toxic granular components from highly stimulated neutrophils. Originally found to trap/sequester invading pathogens, they were soon also seen to be part of sterile inflammatory and thrombotic processes. They interact with von Willebrand factor (VWF), which is also involved in platelet and leukocyte recruitment and is crucial for venous thrombus development after inferior vena cava stenosis. It is possible that NETs and VWF work together and cleavage of either by DNase 1 or ADAMTS13 is beneficial in ischemia/reperfusion injury. This will be discussed together with the role of NETs and the enzyme that generates them (PAD4) in animal models of deep vein thrombosis, myocardial infarction and in physiological wound healing. Interestingly, we observed that various cancers in mice prime neutrophils for NETosis. This causes cancer-associated thrombosis, and the production of NETs may affect tumor biology.

Disclosures
No relevant conflicts of interest to declare.
Shared Mechanisms of RNA Biology
Authors: Dreyfuss Gideon 
Published: October 2019

Abstract
Our recent observation that most primary RNA polymerase II (polII) nascent transcripts (pre-mRNAs and long non-coding RNAs, lncRNAs) in animal cells fail to produce full gene-length transcripts when U1 snRNP (U1) is inhibited, revealed a new dimension in gene expression regulation. This essential U1 protective activity, which allows transcription to go farther (telescripting), suppresses premature cleavage and polyadenylation from cryptic signals (PASs) in introns. It is separate from U1’s splicing function; both depend on U1’s base pairing through its 5’ sequence, but 5’ modified U1 variants that cannot function in splicing are still effective in telescripting. Our studies have further shown that partial U1 inhibition with an antisense oligonucleotide to its 5’-end dose-dependently shortens mRNAs. Widespread mRNA shortening of 3’ untranslated regions (3’UTRs) occurs in cancer, proliferating cells, and activated immune cells and neurons. 3’UTRs have many mRNA regulatory elements, including miRNA targets that generally repress translation, and their removal contributes to oncogenicity. We have investigated the potential role of U1 telescripting in these phenomena. We found that moderate U1 decrease shortened 3’UTRs of hundreds of genes in HeLa cancer cells while its over-expression lengthened 3’UTRs of >2,000 genes that are already shortened in these cells. Concomitantly, U1 increase dose-dependently attenuated protein synthesis, cell migration and invasiveness, while its decrease drastically enhanced these cancer cell characteristics. U1-dependent 3’UTR length changes recapitulated cancer-causing miRNA target deregulation in numerous oncogenes. The strong correlation between U1’s bi-directional effects on nascent transcripts’ length and cell phenotype suggests that mRNA shortening in cancer can be explained by a deficit in U1 telescripting. Our findings establish telescripting’s major role in gene regulation. Notably, the ability of U1 modulation alone to profoundly modify cancer aggressiveness suggests telescripting as a potential target for moderating tumorigenesis.

Disclosures
No relevant conflicts of interest to declare.
Stem Cell Rejuvenation
Authors: Wagers Amy J. 
Published: October 2019

Effective functioning of the body’s tissues and organs depends upon innate regenerative processes that maintain proper cell numbers during homeostasis and replace damaged cells after injury. In many tissues, regenerative potential is determined by the presence and functionality of dedicated populations of stem and progenitor cells, which respond to exogenous cues to produce replacement cells when needed. Understanding how these unspecialized precursors are maintained and regulated is essential for understanding the fundamental biology of tissues. In addition, this knowledge has practical implications, as stem cell regenerative potential can be exploited therapeutically by transplantation to replenish the stem cell pool or by pharmacological manipulation to boost the repair activity of cells already present in the tissue. Ongoing work in my laboratory focuses on defining how changes in stem cell activity impact tissue regeneration throughout life, and identifying physiological and pathological signals that modulate regenerative function in an age-dependent manner. Our recent data using parabiosis and transplantation models suggests that the circulatory system serves as a major source of such signals. In particular, exposure of aged tissues, including skeletal muscle, cardiac muscle and neural cells, to a “youthful” systemic environment appears to reverse many indicators of age-related pathology and restores robust regeneration following injury. While prior studies have identified a handful of systemic “aging” factors, discovery of the humoral “rejuvenating” factors that act on tissue stem cells to restore regenerative function has been relatively more elusive. In recent work, we identified that the circulating hormone Growth Differentiation Factor 11 (GDF11) is a rejuvenating factor for skeletal muscle and other tissues. Supplementation of systemic GDF11 levels, which normally decline with age in mice and humans, was sufficient to restore stem cell function in the skeletal muscle and other tissues, and improved physical function in aged mice. Taken together, these data reveal critical mechanisms in the regulation of aging by blood-borne factors and identify a promising therapeutic target candidate for the reversal of age-related tissue and stem cell dysfunction.

Disclosures
No relevant conflicts of interest to declare.
Macrophages and Infection Control
Authors: Ramakrishnan Lalita 
Published: October 2019

Abstract
We have developed a zebrafish model for the study of infection focusing on mycobacteria, which are intracellular pathogens of macrophages, inducing their aggregation into hallmark structures called granulomas. Exploiting the optical transparency and genetic tractability of the developing zebrafish, we can visualize macrophage-pathogen interactions in great detail in live animals and study the consequences of genetic perturbations. We have identified pathways through which macrophages restrict infection and also those that alter macrophage migration, microbicidal capacity, susceptibility to apoptosis and necrosis so as to render them as tools for bacterial expansion. The complex interactions we have uncovered provide new insights into macrophage biology that are relevant not only for tuberculosis and other infectious diseases but also for the pathogenesis of noninfectious inflammatory diseases in which macrophages are increasingly recognized to play an integral role.

Disclosures
No relevant conflicts of interest to declare.
Comparing the Desmopressin (DDAVP) Challenge Test to DDAVP Clinical Response in Pediatric Patients with Von Willebrand's Disease: A Single Center Experience
Authors: Nadella Divya , Al-Ghafry Maha , Imran Hamayun , Siddiqui Abdul H. 
Published: October 2019

Abstract
Introduction
Von Willebrand's disease (VWD) is the most common inherited bleeding disorder. It is characterized by both quantitative and qualitative defects of the von Willebrand Factor (VWF) and generally manifests as menorrhagia, epistaxis and easy bruising. Initial treatment involves the use of desmopressin (DDAVP) that induces the release of VWF from the endothelium. Patients undergo a DDAVP challenge test that involves intravenous DDAVP (IV-DDAVP) infusion with multiple blood draws to determine an increase in the VWD panel. Due to the DDAVP challenge test being a costly and lengthy process, we sought to evaluate the prognostic utility of the challenge test in patients who responded favorably.
Methods
A retrospective cohort study was conducted in pediatric patients aged 18 years or younger with a laboratory diagnosis of VWD who underwent the DDAVP challenge test between 2005 and 2015 at our institution. VWD panel results pre and post DDAVP challenge test were obtained from clinical records. A complete response was defined as a 2-fold increase at 1-3 hours or at least 1.5-fold increase at 4-6 hours post-infusion. Patients' clinical records were reviewed for initial presentation and response to DDAVP. SPSS version 23.0.0 was used to analyze demographic and laboratory data, with frequencies and paired t-tests performed for comparison where appropriate.
Results
Seventy two pediatric patients were identified with a diagnosis of VWD: 34 (47%) were VW type 1, 51 (72%) were females and 50 (69%) were Caucasian. Challenge results were available for 48 patients (66%): Post-DDAVP levels were significantly higher than baseline (p = <0.001) in the VWD panel for either times (1-3 or 4-6 hours). Thirty-seven patients (51%) had both challenge results and clinical symptoms reported with 78% (29/37) considered responders and 22% (8/37) considered non-responders to IV-DDAVP. 86% (25/29) of responders were initially placed on intranasal DDAVP (IN-DDAVP) alone while the others received combined therapy with addition of a plasma derived product (PDP). All non-responders initially received DDAVP therapy with some improvement in their clinical symptoms. Eleven (38% of responders) and four (50% of non-responders) were switched to a PDP, mostly for better symptom control. Six responders (16%) had side-effects with DDAVP.
Conclusion
A high proportion of our patients with VWD responded to the DDAVP challenge test, but subsequently required therapy with a PDP; and half of non-responders were able to use DDAVP. In our pediatric patient population, an initial IV-DDAVP challenge test did not identify those that would respond clinically to IN-DDAVP therapy long-term. Thus, more studies addressing the utility of the challenge test in VWD would be needed before drawing further conclusions on its prognostic value.

Disclosures
No relevant conflicts of interest to declare.
Amino Acid Transporter X Is Required for Hematopoietic Stem Cell Maintenance through Regulating Specific Amino Acids Level
Authors: Li Zhenrui , Takubo Keiyo , Qian Pengxu , Suda Toshio , Li Linheng 
Published: October 2019

Abstract
Hematopoietic stem cells (HSCs) maintenance is required to preserve stem cell pool and compensate the dynamic loss of blood cells. Previous studies of HSCs maintenance mainly focus on the quiescent versus active state of HSCs and accumulated evidence indicates that metabolism plays a critical role in coordinating divergent stem cell states. While recent reports largely emphasized the role of catabolic glycolysis on long-term (LT) HSC maintenance, we found that free amino acids are enriched in primitive stem cell by ~1.5 fold. Given that amino acid metabolism in HSCs is largely unknown, we first cultured bone marrow (BM) cells with individual amino acid deprived medium to study the function of individual amino acids on HSCs in vitro. Surprisingly, we found that specific amino acids, including valine, methionine and threonine (VMT), are essential for maintaining primitive HSCs, as removing them (VMT) individually from media dramatically reduced primitive HSC number by over 95%. Thus, we hypothesize that specific amino acids are critical for preserving the stem cell pool and maintaining their function. To test it, we transplanted equal number of cells cultured with complete or individual VMT deprived media into lethally irradiated recipient mice and found VMT deprivation in vitro impaired stem cell repopulation ability. We also identified the amino acid transporter X (AATX) that is specifically expressed in HSCs and maintain VMT levels within the cell. Furthermore, inhibition of AATX reduced LT-HSC (LSK CD34- Flk2-) number in vivo. BM transplantation indicated that AATX inhibition impaired stem cell long-term reconstitution ability by over 2 fold. Our studies uncovered a role of amino acid metabolism in HSC maintenance and discovered the underlying molecular mechanism related to the amino acid transport. This finding may impact clinical treatment of blood disorders including leukemia.

Disclosures
No relevant conflicts of interest to declare.
Prmt5 Negatively Regulates Erythropoiesis By Multiple Mechanisms, Including Controlling DNA Methyltransferase 3A Protein Levels
Authors: Hamard Pierre-Jacques , Luciani Luisa , Liu Fan , Cheng Guoyan , Hatlen Megan A. , Guryanova Olga A , Zhao Xinyang , Levine Ross L. , Nimer Stephen D. 
Published: October 2019

Abstract
The shift in sites of hematopoiesis during embryonic development leads to primitive hematopoiesis within the fetal liver at E12.5, which generates primarily erythrocytes. Definitive hematopoiesis, which occurs within the bone marrow, follows at birth. During the erythroid differentiation of fetal hematopoiesis, progenitor cell maturation is accompanied by global DNA demethylation, a process necessary for fetal liver erythrocyte formation and accompanied by diminishing expression of the de novo DNA methyltransferases, Dnmt3a and Dnmt3b.
In our current study of hematopoietic cell specific Prmt5 knockout mice, we have identified Prmt5 as a master regulator of erythropoiesis; the cell-specific deletion of Prmt5 in fetal liver cells is embryonic lethal as Prmt5-null embryos have severe anemia and increased expression of Dnmt3a and Dnmt3b proteins. RNA-seq and pathway analysis studies revealed profound defects in several critical pathways that regulate normal hematopoiesis, including the tumor suppressor p53 pathway. Methyl-seq studies are currently being conducted to determine the effects of the enforced expression of key DNA methyltransferases on global DNA methylation and gene expression in erythroid progenitors and how it leads to a block in erythrocyte maturation. To decipher the extent of Dnmt3a or p53's involvement in the observed phenotypes, we have generated double knockout mouse models that are being analyzed. Mechanistically, p53 has been shown to be directly methylated by Prmt5, a modification that affects its tumor suppressor activity. Here we have found that Dnmt3a is also a substrate of Prmt5 and the effects of the di methylation of Dnmt3a on its function are currently under investigation. Thus, we have uncovered a potential functional interaction between DNA methylation and protein arginine methylation triggered by Prmt5 that regulates primitive erythropoiesis.

Disclosures
Levine: Foundation Medicine: Consultancy; CTI BioPharma: Membership on an entity's Board of Directors or advisory committees; Loxo Oncology: Membership on an entity's Board of Directors or advisory committees.