bluuebunny/crossref_metadata_2025_split huggingface dataset:
RON Kinase Inhibition Reduces Renal Endothelial Injury in Sickle Cell Disease Mice
Authors: Jerebtsova Marina , Khaibullina Alfia , Adjei Elena Afia , Afangbedji Nowah Kokou Apeadoufia , Ivanov Andrey , Kumari Namita , Quezado Zena , Nekhai Sergei 
Published: April 2021

Abstract
BACKGROUND: Patients with Sickle Cell Disease (SCD) have an approximately three-fold higher risk of developing chronic kidney disease (CKD) than the general population. Endothelial dysfunction and inflammation which are induced by hemolysis and lead to vasculopathy are major mechanisms in the development of CKD. Red blood cells (RBCs) hemolysis inside the renal tissue stimulates macrophages infiltration. Endocytosis of RBC hemolysis products by infiltrating macrophages activates to MT-SP1 protease which cleaves and activates non-active circulating Macrophage Stimulating Protein 1 (MSP1). MSP1 binds to and activates cell surface receptor tyrosine kinase, recepteur d'origine nantais (RON).
OBJECTIVES: To determine the role of RON in the development of renal endothelial injury.
METHODS: Human renal glomerular endothelial cells (HGEC) and a mouse model of SCD (Townes) were used. The animal protocol was approved by the Institutional Animal Care and Use Committee at the Children's National Health System. The SCD mice express human Hgb S and Hgb F. Control mice express human Hgb A1. Two-month-old mice were injected with 10 mg/kg of body weight of RONi (BSM-777607, Santa Cruz Scientific), an inhibitor of RON, subcutaneously daily for 14 consecutive days. Kidneys were collected, and paraffin-embedded sections were used for H&E and PAS staining, and immunostaining.
RESULTS: Treatment of cultured human renal glomerular endothelial cells (HGEC) with MSP1 activated RON receptor and induced downstream signaling evidenced by increased phosphorylation of ERK and AKT kinases. RONi significantly reduced ERK and AKT phosphorylation. MSP1 treatment also increased motility of HGEC, and expression of F-actin and von Willebrand Factor (vWF). Renal disease in SCD mice was characterized by glomerular hypertrophy, capillary dilation and congestion, and significant endothelial injury demonstrated by H&E and PAS staining, and ICAM, vWF and CD34 immunostaining. We observed accumulation of MSP1 in the glomerular capillaries of SCD mice. Treatment of mice with RONi significantly reduced glomerular hypertrophy, capillary dilation and congestion, and also reduced endothelial injury (Figure 1).
CONCLUSIONS: Renal glomerular accumulation of MSP1 and RON kinase activation contribute to the induction of renal endothelial injury in SCD mice. Inhibition of RON kinase activation significantly reduced endothelial injury and development of kidney disease.
ACKNOWLEDGMENTS: This work was supported by NIH Research Grants 1P50HL118006, 1R01HL125005 and 5G12MD007597. The content is solely the responsibility of the authors and does not necessarily represent the official view of NHLBI, NIMHD or NIH.

Disclosures
No relevant conflicts of interest to declare.
Valine as a Key Metabolic Regulator of Hematopoietic Stem Cell Maintenance
Authors: Nakauchi Hiromitsu 
Published: April 2021

Abstract
Hematopoietic stem cells (HSCs) are maintained by a specialized bone marrow microenvironment (niche) and are largely quiescent during the steady-state conditions1. However, upon stimulation or transplantation, HSCs can expand and differentiate into any mature hematopoietic cell type. This ability of donor HSCs to reform a recipient's hematopoietic system is key to the success of HSC transplantation (HSCT). For donor HSCs to engraft, the recipient bone marrow niche must first be emptied via myeloablative irradiation or chemotherapy. However, myeloablative conditioning can cause severe complications and even mortality. As an alternative, we have recently developed a metabolic conditioning approach for HSCT. By screening the amino acid requirements of HSCs, we identified the essential amino acid valine as indispensable for the expansion and maintenance of HSCs2. Both mouse and human HSCs failed to expand when cultured in valine-restricted conditions. In mice fed a valine-restricted diet, HSC frequency fell dramatically within one week. Dietary valine restriction thereby emptied the mouse bone marrow niche and just a two-week diet afforded long-term donor-HSC engraftment without chemoirradiative myeloablation. We conclude that valine plays a critical role in HSC maintenance and suggest dietary valine restriction as a conditioning regimen that may reduce iatrogenic complications in HSCT. These findings, and recent efforts to optimize this metabolic conditioning approach through mechanistic understanding of the HSC valine dependency, will be presented. Sudo K, Ema H, Morita Y, Nakauchi H. Age-associated characteristics of murine hematopoietic stem cells. J Exp Med. 2000;192:1273-1280.Taya Y, Ota Y, Wilkinson AC, et al. Depleting dietary valine permits nonmyeloablative mouse hematopoietic stem cell transplantation. Science. 354:1152-1155.

Disclosures
Nakauchi: ReproCELL Inc: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; Megakaryon Inc: Equity Ownership, Membership on an entity's Board of Directors or advisory committees; iBUKI Corp: Equity Ownership; iCELL Inc: Equity Ownership; Advanced Immunothearpy Inc: Equity Ownership.
GATA2 in Bone Marrow Failure
Authors: Holland Steven M. 
Published: April 2021

Abstract
The syndrome now known as GATA2 haploinsufficiency had been published at least since the 1970s under different clinical guises. With the identification of the gene in 2011, GATA2 deficiency became the overarching diagnosis for a complex syndrome with acoustic, cutaneous, lymphatic, pulmonary, leukemic, hematologic and infectious manifestations. Arising in both spontaneous and autosomal dominant patterns, the genetics made it recognizable and diagnosable even before symptoms arose. Over the last several years it has become clear that GATA2 is a major contributor to: pediatric and adolescent MDS, AML in younger adults, some cases of ALL, severe genital HPV infection, disseminated mycobacterial infections, pulmonary alveolar proteinosis, pulmonary hypertension and is associated with a variety of solid tumors. Mutations with more profound effects on GATA2 expression (nonsense and deletions) appear to have a more severe phenotype than do intronic mutations that alter transcript level but not transcript integrity. These latter intronic mutations may be associated with later onset of disease and more variable penetrance. Elucidating the gene targets on which GATA2 works and which partners it engages will lead to important observations in the molecular genetics of hematopoietic control.
This variability of penetrance and expression is most apparent with the intronic mutations, in which whole generations may be relatively protected, presumably from genes in trans to GATA2 . An active search is on for these genes that appear to regulate GATA2 . One of the consequences of the variable penetrance of GATA2 deficiency is that it may be discordant within a family, allowing a false sense of security about use of a clinically well relative for bone marrow transplant donation. Hematopoietic stem cell transplantation is highly effective for cure of GATA2 deficiency. We have now done almost 40 transplants in GATA2 deficiency with high survival rates using related haploidentical donors, as well as with fully matched donors. The effects of transplantation are profound both in terms of hematopoietic and somatic results, including resolution of most HPV lesions, resolution of pulmonary alveolar proteinosis and resolution of pulmonary hypertension, when present. We have now encountered several cases of transplant from unexpectedly affected donors into a known GATA2, all of which have had poor outcomes. These cases reinforce the critical need for molecular confirmation of the GATA2 status of any related donor, regardless of lack of symptoms.
GATA2 deficiency is recently recognized but successful treatments have emerged alongside the science. Efforts to understand and allow for manipulation of GATA2 expression are underway.

Disclosures
No relevant conflicts of interest to declare.
Role of Platelets in Adaptive Changes to Anti-Angiogenesis Therapy
Authors: Sood Anil 
Published: April 2021

Abstract
While anti-angiogenesis therapies have shown remarkable activity in ovarian and other cancers, adaptive resistance can develop within weeks to months. Moreover, concerns have been raised about the potential for more aggressive tumor growth following withdrawal of anti-angiogenesis drugs. Here, we will discuss the role of platelets, specifically platelet extravasation into the tumor microenvironment in stimulating tumor growth. Among the various factors regulating this process, focal adhesion kinase (FAK) expression in platelets plays an important role in their migration into the tumor microenvironment. Mice with FAK-deficient platelets do not exhibit rebound tumor growth following exposure to anti-angiogenesis drugs. Combination therapy with a FAK inhibitor and anti-angiogenic agents reduced tumor growth and inhibited the negative effects following withdrawal of anti-angiogenic therapy. These biological findings, other emerging mechanisms and clinical implications will be discussed.

Disclosures
No relevant conflicts of interest to declare.
Genetic Disorders of Immune Tolerance: The Flip Side of Immune Deficiency Where Autoimmunity Trumps Infection
Authors: Torgerson Troy R. 
Published: April 2021

Abstract
Primary Immune Regulatory Disorders (PIRD) are group of congenital Immunodeficiencies that present primarily with autoimmunity and less frequently with infections. The paradigm for these disorders is the syndrome of Immune dysregulation, Polyendocrinopathy, Enteropathy, X-linked (IPEX), a disorder caused by a lack of functional regulatory T cells due defects in the lineage-specifying transcription factor, FOXP3. We have collected and evaluated a large cohort of patients with clinical manifestations suggestive of IPEX and have found FOXP3 mutations in more than 90 patients. This has informed our further investigation into the structure and function of the FOXP3 transcription factor. In patients that have IPEX-like clinical features but lack FOXP3 mutations, we have identified defects in several other genes now associated with an IPEX-like clinical phenotype, including germline STAT1 and STAT3 gain-of-function (GOF) mutations, CTLA4 haploinsufficiency, LRBA deficiency and others. We have shown that within this cohort, all have IPEX-like clinical features but there are some clinical and laboratory features that can help with differentiating between the different genetic syndromes. To determine the best approach to treatment of these disorders, we have also collected data on the international experience with bone marrow transplant for some of these disorders including IPEX, CTLA4 haploinsufficiency, STAT1-GOF, and STAT3-GOF disease. We have demonstrated that bone marrow transplant can be curative for each of these disorders but that patients with autosomal dominant gain-of-function mutations in STAT1 and STAT3 may pose unique challenges for transplant that will be discussed. These data will be presented along with preliminary data suggesting non-transplant approaches to management using targeted therapies.

Disclosures
Torgerson: CSL Behring: Consultancy, Research Funding; Shire Bioopharmaceuticals: Consultancy, Research Funding; UCB Biopharma: Consultancy; ADMA Biosciences: Consultancy.
Novel Glycan Dependent Platelet Clearance Mechanisms
Authors: Hoffmeister Karin M. 
Published: April 2021

Platelet numbers are intricately regulated to avoid spontaneous bleeding or arterial occlusion and organ damage. The growth factor thrombopoietin (TPO) promotes platelet biogenesis by controlling megakaryocyte maturation and differentiation. Recently, we identified a feedback mechanism by which clearance of aged, desialylated platelets stimulates TPO synthesis by hepatocytes in mice. The Ashwell-Morell receptor (AMR) of hepatocytes, originally termed the hepatic asialoglycoprotein receptor, was the first cellular receptor to be identified and isolated and the first lectin (carbohydrate-binding) to be detected in mammals. Our work showed that the AMR recognizes and removes senescent, sialic acid-depleted platelets (desialylated) under steady state conditions. Desialylated platelets and the AMR are the physiological ligand-receptor pair regulating hepatic TPO mRNA production. The AMR-mediated removal of desialylated platelets regulates hepatic TPO synthesis by recruiting JAK2 and STAT3 to increase thrombopoiesis. Recent genetics studies have revealed that AMR haplodeficiency provides protection from atherosclerosis by regulating plasma glycolipids and platelets. The potential interactions of AMR with LDL receptor may regulate the rate of LDL uptake and as a result may lower plasma non-HDL cholesterol. Taken together, the AMR appears to be a multifaceted receptor, specializing in the clearance of desialylated platelets and plasma glycolipids. Thus, platelet clearance, its biogenesis via TPO, and vascular integrity appear to be regulated by intricately interwoven mechanisms dependent on the AMR.

Disclosures
Hoffmeister: Amgen: Consultancy.
Splenic Mechanisms of Thrombocytopenia
Authors: Semple John W. 
Published: April 2021

The spleen is the largest secondary lymphoid organ in the body and contains up to 25 percent of the body's lymphocyte populations. It is not only responsible for initiating immune responses against a multitude of infectious antigens within its white pulp, it also has the exquisite ability to filter the blood and remove, for example, senescent erythrocytes and platelets. This natural process is carried out within the red pulp of the spleen which is composed monocyte-rich connective tissue cords of Billroth intertwined with sinus cavities lined by parallel-oriented endothelial cells that have interendothelial slits which allow for the mechanical sorting of "old" cells. This occurs because of the inability of the senescent cells to properly migrate through the endothelial fenestrae into the venous circulation allowing them to be identified by cells of the reticuloendothelial system (RES) and quickly destroyed by phagocytosis. This process also allows for the efficient recycling of iron from destroyed erythrocyte hemoglobin molecules. There are a wide variety of clinical conditions that can significantly alter the ability of the RES to destroy blood cells including hereditary blood cell defects, inflammation, cancer and abnormal immune responses. This lecture will focus on the central role that the spleen plays in not only generating immune responses against platelets but also in primarily causing the destruction of both senescent and antibody-opsonized platelets leading to thrombocytopenia. It will discuss the soluble and cellular mechanisms of splenic sequestration, destruction and the ability of the spleen to modulate anti-platelet immunity. Mechanisms involving complement activation, Fc Receptor-mediated phagocytosis, antibody dependent cellular cytotoxicity and platelet self-destruction will be addressed. It will compare the spleen's platelet destructive capabilities with other organs, particularly the liver and will detail how immune responses generated in the white pulp can modulate platelet destructive processes in the red pulp.

Disclosures
Semple: Amgen: Consultancy, Honoraria, Speakers Bureau; Rigel: Consultancy, Honoraria; UCB: Consultancy, Honoraria.
Understanding the Transferrin Receptor and Cellular Iron Deficiency Outside the Erythron
Authors: Andrews Nancy C. 
Published: April 2021

Our laboratory showed that mouse embryos lacking the classical transferrin receptor, Tfrc, experienced anemia, pericardial effusion and a kinking of the neural tube, but otherwise appeared to be developing normally, suggesting that Tfrc was not needed by most tissues (Levy et al. 1999). Subsequently, we reported that Tfrc was essential for hematopoiesis but seemed to be dispensable in other tissues (Ned et al., 2003). A recent paper showing that a missense mutation in the TFRC internalization motif resulted in immunodeficiency without other clinical manifestations was consistent with this idea (Jabara et al., 2016). Nonetheless, we were not entirely convinced. More than thirty years ago, Larrick and Hyman described a patient with an anti-TFRC autoantibody who suffered from a broader range of clinical problems, suggesting that TFRC might have other roles (Larrick and Hyman, 1984). To help resolve the issue, we developed mice carrying an allele of Tfrc that can be conditionally inactivated, and used Cre/lox-mediated recombination to disrupt that allele in vivo, in several key cell types. We asked two questions: (1) is Tfrc important in those cell types and, if so, (2) what are the cellular consequences of Tfrc loss? We found that some cell types do not need Tfrc but others are highly dependent upon it. Those cell types that depend upon Tfrc generally need it for iron uptake, as expected, with one exception. Tfrc is critically important for normal development of the intestinal epithelium, but our data indicate that its essential role does not involve iron uptake. While surprising in view of our earlier results, the roles of Tfrc that we have unmasked through conditional knockout experiments would not have been apparent prior to the death of global Tfrc knockout embryos in mid-gestation. Nonetheless those roles are important, and our results give insight into why iron deficiency exacerbates heart failure, how muscle iron deficiency leads to disruption of systemic carbon metabolism, and how iron deficiency, rather than iron excess, may play a role in the pathogenesis of neurodegenerative disorders.
Levy JE, Jin O, Fujiwara Y, Kuo F, Andrews NC. Transferrin receptor is necessary for development of erythrocytes and the nervous system. Nat Genet. 1999;21:396-9.
Ned RM, Swat W, Andrews NC. Transferrin receptor 1 is differentially required in lymphocyte development. Blood. 2003;102:3711-8.
Jabara HH, Boyden SE, Chou J et al. A missense mutation in TFRC, encoding transferrin receptor 1, causes combined immunodeficiency. Nat Genet. 2016;48:74-8.
Larrick JW, Hyman ES. Acquired iron-deficiency anemia caused by an antibody against the transferrin receptor. N Engl J Med. 1984;311:214-8.

Disclosures
Andrews: Novartis: Membership on an entity's Board of Directors or advisory committees.
Enforcing Post-Transcriptional Circuitries to Achieve Human Hematopoietic Stem Cell Expansion
Authors: Hope Kristin 
Published: April 2021

Abstract
The balance between hematopoietic stem cell (HSC) differentiation and self-renewal is central to clinical regenerative paradigms. Unravelling the precise molecular mechanisms that govern HSC fate choices will thus have far reaching consequences for the development of effective therapies for hematopoietic and immunological disorders. There is an emerging recognition that beyond transcription, HSC homeostasis is subject to post-transcriptional control by RNA-binding proteins (RBPs) that ensure precise control of gene expression by modulating mRNA splicing, polyadenylation, localization, degradation or translation. RBPs can synchronously regulate the fates of operationally similar RNAs, in what have been termed RNA regulons. We have used a variety of functional approaches, in combination with unbiased genome- and proteome-scale, methods to define the tenets that govern this regulation and to determine key downstream circuitries of stem cell-regulating RBPs whose targeting could provide the basis for novel regenerative treatments. Through loss-of-function efforts, we have identified the RBP, MSI2, as a required factor for human HSC maintenance. By contrast, at supraphysiological levels, MSI2 has a profound positive effect on human HSC self-renewal decisions. Using a combination of global profiling, including mapping MSI2's targets through cross-linking immunoprecipitation (CLIP)-seq, we show that MSI2 achieves its ex vivo self-renewal-promoting effects by directing a co-ordinated post-transcriptional repression of key targets within the aryl hydrocarbon receptor (AHR) pathway. We are currently exploring the "rules" by which MSI2 influences its downstream effects on target RNAs and how it functions, in combination with other protein interactors, to instill a putative RBP regulatory code in HSCs. HSCs exhibit highly unique epigenomes, transcriptomes and proteomes and it is this distinctive molecular landscape that provides the canvas upon which MSI2, and indeed any other HSC-specific RBP exert their post-transcriptional influence over stem cell function. As such, to decipher the bona fide RNA networks that RBPs function upon in HSCs and to understand how they influence this network to enforce self-renewal, we are working towards performing systematic studies of RBP regulons in these cells specifically. In turn these approaches are elucidating a host of RBPs and post-transcriptional control mechanisms previously unappreciated for their role in HSC control. When modulated appropriately, we can successfully tailor these post-transcriptional regulons to enforce desired HSC outputs ex vivo. In summary, approaches to elucidate key HSC-regulatory RBPs and their protein and RNA interactomes provide valuable insights into a layer of HSC control previously not well understood, and one that can be capitalized on to achieve successful HSC expansion.

Disclosures
No relevant conflicts of interest to declare.
IL-17-Driven Immune Signaling in Autoimmunity and Fungal Infections
Authors: Gaffen Sarah 
Published: April 2021

Abstract
Interleukin (IL)-17 is a pro-inflammatory cytokine that is the founding member of a distinct subclass of cytokines (reviewed in Amatya et al., 2017). IL0-17 is produced by conventional Th17 cells as well as a variety of innate immune subtypes (gd-T cells, ILC3 and NKT cells, for example). IL-17 promotes immunity to extracellular microbes, particularly fungi. On the flip side, dysregulation of IL-17 expression or signaling promotes pathology in a variety of autoimmune settings, particularly plaque psoriasis. Consequently, biologic therapies targeting the IL-17/Th17 pathway have been used successfully in the clinic. Understanding how the balance between host defense and autoimmune inflammation is maintained remains a vital issue. Candida albicans is a commensal fungus responsible for opportunistic oropharyngeal candidiasis (OPC, thrush) in settings of immunodeficiency such as HIV/AIDS and chemotherapy. C. albicans also causes systemic and dermal infections. In recent years it has become evident that IL-17 is essential for protective immunity to C. albicans (Conti and Gaffen, 2015). In both mice and humans, T cell deficiencies and more specifically impairments in IL-17 receptor (IL-17R) signaling components (for example, IL-17RA, IL-17RC, Act1) are associated with chronic mucosal candidiasis. However, to date we lack a detailed understanding of the signaling components and effector activities of IL-17 that promote antifungal immunity. The IL-17R complex is ubiquitously expressed, and antifungal signaling by IL-17 has been documented in cells of mesenchymal and epithelial origin but also in hematopoietic cells. This talk will focus on multiple mechanisms by which IL-17 drives immunity to C. albicans, including (i) tissue-specific effects of IL-17 signaling, (ii) sources of IL-17 that drive immunity to mucosal candidiasis, and (iii) fungal-derived factors that drive IL-17 production in vivo in the context of infection.
Amatya N, Garg AV, Gaffen SL. IL-17 signaling: The Yin and the Yang. Trends Immunol. 2017; 38:310-322.
Conti HR, Gaffen SL. IL-17 and Candida albicans infections. J Immunol, 2015; 195:780-788.

Disclosures
Gaffen: Lycera: Membership on an entity's Board of Directors or advisory committees; Janssen: Research Funding; Abbvie: Consultancy; UCB Celltech: Consultancy; Genentech: Speakers Bureau; Novartis: Consultancy.