P&F Projects 2022-2023

Antony Abstract Type B P&F 2023

Hematopoietic Stem and Progenitor Cells (HSPCs) are regulated by the combinatorial action of group of master transcriptional regulators. Their coordinated activity dictates the fate of HSCs and multipotent progenitors towards self-renewal vs differentiation. This precise control by transcription factors (TFs) needs optimal TF concentration in each cell. To date, our understanding of TFs is obtained from studies of RNAi, knockout, or overexpression. However, there is a knowledge gap in understanding how dosages of critical transcription factors modulate HSPCs. Targeted protein degradation is an attractive approach to study the role of TF dosages in regulating HSPC cell states, however this approach has largely been deployed thus far in cell lines, which cannot capture all aspects of primary cell biology. The goal of this proposal is to A) Integrate FKBPV degrons into endogenous loci of TFs SPI1, MYB, and GATA2 in human CD34+ cells, and 2) Perform dose-dependent degradation of SPI1, MYB, and GATA2 and study their effect on proliferation and lineage commitment of human CD34+ cells. I am thus proposing to engineer a degron-based model system in human CD34+ cells, which will allow me to study the dosages of endogenous TFs, and establish a valuable kit that can be extended towards broader studies in human hematopoiesis.

My mentor’s research focused on understanding the role of cell-type specific TFs in the rRNA transcription and ribosome biogenesis in hematopoiesis. For this project, my PI received an NIGMS grant and I received an ASH Scholar Award. However, my future independent research will focus on engineering bi-allelic degron systems in human primary hematopoietic cells to study the dosage-dependent roles of key hematopoietic regulators. This necessitates proficiency in HSC culturing and maintenance. I take this award as an opportunity to learn 1) Long-term ex vivo culturing of CD34+ cells and assays related to HSC differentiation and 2) Hands-on training to prepare non-integrating AAV virus. This training will provide key tools to begin my independent research lab.

Also, research data derived from this pilot study will provide preliminary data to lay a strong foundation for my future R01 grant application on developing primary human ex vivo and mouse in vivo HSC degron models to study bone marrow failures.

Lab link: https://paralkarlab.med.upenn.edu/



Mulcrone Abstract Type A P&F 2023

Abstract: Cellular niches present in bone are involved in tissue maintenance and responsible for key processes like angiogenesis, hematopoietic cell maintenance, and osteogenesis. Indeed, interactions between cells comprising the bone hematopoietic and bone vascular niches are known to be essential for bone homeostasis and are a focus for researchers studying various aspects of bone biology and bone diseases. Therefore, more investigation is warranted regarding how different treatments and stimuli may be altering the relationship between these niches at a cellular as well as a comprehensive, whole-organ level. Thrombopoietin (TPO) is a megakaryocyte growth factor known to enhance vessel formation, promote new bone development, and alter hematopoietic stem cell biology. Therefore, TPO may be changing the interactions between the hematopoietic and vascular niches in the bone at both a micro and macro scale. Excitingly, the CODEX PhenoCycler technology provides a method by which spatial, whole-organ proteomic analysis, as well as cellular neighborhood analysis, of the bone hematopoietic and vascular niches and their interactions can be performed. Given that many of the current CODEX-applicable antibodies identify immune cells, we have comprised a panel of 16 antibodies to expand the focus of this technology to encompass the bone vascular and hematopoietic niches. Our 16-antibody panel includes 7 validated cell surface proteins, and 9 proteins present in the bone that will be identified by novel CODEX-applicable antibodies. This panel will mark cells of the hematopoietic niche, such as bone marrow stromal cells, hematopoietic stem cells, and megakaryocytes, and those of the vascular niche, namely endothelial cells, osteoblasts, and pericytes with the goal to test what alterations can be detected by CODEX in the bone hematopoietic and vascular niches after TPO treatment. Results from our study will broaden the application of the CODEX PhenoCycler technology for non-malignant hematology research that focuses on bone and vascular biology.

Lab link: https://medicine.iu.edu/faculty/38833/mulcrone-patrick


Hewitt Abstract Type B P&F 2023

Coordinated checks and balances maintain steady rates of red blood cell production and allow for the rate of production to accelerate in contexts of acute anemia. The mechanisms driving this accelerated rate and phenotypic diversity of anemia responses in human populations are poorly understood. The aims of this proposal will develop new tools and methods to interrogate DNA elements controlling acceleration of stem cell activities in anemia model systems. We previously implemented a multifactor prioritization strategy to identify and functionally interrogate cis-regulatory elements involved in recovery from acute anemia. This analysis revealed important transcriptional control of newly identified anemia induced genes, including the Ssx-2 interacting protein (Ssx2ip). Over a week-long time course of acute anemia recovery, we observed erythroid gene activation mediated by GATA factor occupied cis-elements occurs during a phase coincident with low hematocrit and high progenitor activities. However, this analysis also revealed distinct transcriptional programs activated at earlier and later time points. Specifically, our analysis identified AP-1 transcription factor activity is transiently increased at 24 hours post-anemia, but then rapidly turned off. Despite established roles for AP-1 in inflammatory responses, the role of this crucial transcription factor in anemia response mechanisms has not been studied. We hypothesize that AP-1 transcription factors are required to initiate transcriptional programs in HSPCs and erythroid precursors to mediate effective anemia recovery. This pilot project will explore and develop preliminary data to test mechanistic models for dynamic transcriptional control in anemia recovery. We will use multiple facilities sponsored by the Cooperative Centers of Excellence in Hematology (CCEH) to acquire quality controlled human hematopoietic stem/progenitor cells (HSPCs) and for next-generation sequencing of ATACseq samples. We will also initiate a new collaboration with Dr. Kellie Machlus to investigate erythroid precursor function in bone marrow-like organoid systems. These aims will test mechanisms of AP-1 mediated transcriptional activation in anemia and develop better tools for studying dynamic changes throughout the anemia recovery timeline. This research direction represents a new avenue for our lab to study AP-1 activity. By testing the role of enhancer mediated mechanisms required for anemia recovery, these findings will have important implications for understanding the genetic requirements for erythropoietic progenitors’ activities in red blood cell disorders. The proposed experiments are expected to reveal unique enhancer-responsive mechanisms with broad biomedical implications in hematologic disease, including myelodysplasia, bone marrow transplantation, and chronic anemias.

Lab link: https://www.unmc.edu/genetics/faculty/bios/hewitt.html


Termini Abstract Type B P&F 2023

Maintaining and restoring hematopoietic homeostasis is necessary to respond to hematopoietic stressorsthroughout our lifetime; the inability to do so can lead individuals to succumb to deadly hematopoietic threats like infection, hemorrhage, or anemia. Anemia is the most common blood disorder and is caused by deficient or dysfunctional red blood cells (RBCs). Previous work demonstrated that lipids, such as cholesterol, and their synthesis and/or metabolism contribute to erythropoiesis. However, the cholesterol synthesis pathway (CSP)

has yet to be investigated as a targetable pathway to correct red blood cell disorders. Thus, there is an unmet medical need to mechanistically interrogate the role of lipids and their metabolism in regulating erythropoiesis, which this proposal seeks to fill. The cholesterol synthesis pathway (CSP) is an enzyme-driven process that generates cholesterol and isoprenoids. Mutations to the CSP give rise to anemia, but how the CSP regulates

erythropoiesis remains to be defined. Our preliminary identified a role for the CSP in regulating RBC production and functions, but whether this occurs intrinsically or extrinsically is unclear. The objective of this proposal is to elucidate the function of distinct enzymes in the CSP in RBC production. The rationale underlying this proposal is that understanding the fundamental role of the CSP in RBC homeostasis is likely to identify novel targets that could be leveraged to treat patients with red blood cell disorders. We will test our central hypothesis that the

CSP regulates erythropoiesis via alterations in hematopoietic cell proliferation and death. In Specific Aim 1, we will determine how the CSP controls erythropoiesis through erythroid progenitor cells. In Specific Aim 2, we will examine the function of hematopoietic stem cell CSP in regulating hematopoietic cell fate and self-renewal. This work is of strong clinical and translational significance for patients with erythroid disorders like anemia and

polycythemia vera. Further, cancer patients who receive radiation and chemotherapy exhibit RBC depletion. Therefore, understanding how RBC homeostasis is regulated is likely to identify novel targets that could be usedto accelerate hematologic recovery from stress.

Lab link: https://research.fredhutch.org/termini/en.html


Termini Abstract Type A P&F 2023

While myeloablative treatments are commonly used to rid the body of cancerous cells, these regimens deplete normal hematopoietic cells. Further, myeloablation significantly remodels the physical and molecular features of the bone marrow microenvironment, putting patients at risk for developing life-threatening complications such as hemorrhage or infection. To accelerate hematopoietic recovery from these toxic therapies, it is imperative to identify the molecular regulators of hematopoietic regeneration. Prior approaches to visualize the regenerating bone marrow niche primarily used reporter mice or limited antibody panels for immunofluorescence imaging. In this proposal, we seek to use CODEX imaging to define the regenerating bone marrow niche with spatial and molecular precision.

Lab link: https://research.fredhutch.org/termini/en.html

Shahbazi Abstract Type A P&F 2023

Cells are in continuous communication and signaling with each other to prime the environment for their survival and growth. Hormones, growth factors, and cytokines are known signaling molecules that play a key role in this communication however, there is a fairly unknown communication mechanism that happens through the release of nanovesicles called exosomes. These tiny particles carry important protein or RNA signaling molecules that change the cellular behavior in the target cell, tissue, or organ. In this regard, bone marrow (BM) space is one of the complex and rich environments that homes various cell types with different roles in the human body. The focus of this study is to understand the exosomal communication with the hematopoietic stem and progenitor cells (HSPCs) in the bone marrow space that are responsible for the repopulation of the human blood including all myeloid and lymphoid progenies. Moreover, we will study the exosomal communication with a special population of HSPCs called long-term hematopoietic stem cells (LT-HSCs) that stand on top of the hematopoietic hierarchy and have this great capability of self-renewing and differentiation to different lineages. In this project, we will look at the interaction of exosomes released from bone marrow stromal cells with HSPCs and try to understand their effect on the self-renewal, expansion, and differentiation of HSPCs. We will approach this by delineating the role of exosomal communication using the ImageStream single-cell imaging platform, flow cytometry analysis, and colony-forming unit assay.


Lab link: https://medicine.iu.edu/faculty/59877/shahbazi-reza

Thompson Abstract Type A P&F 2023

The purpose of this Pilot & Feasibility Grant is to elucidate the role of High Mobility Group A1 (HMGA1) chromatin regulators in clonal hematopoiesis (CH) and associated cardiovascular disease (CVD). CH results from expansion of hematopoietic stem cells (HSCs) harboring a mutation that provides a fitness advantage. In addition to myeloid malignancies, CH mutations are associated with increased risk of diverse cardiovascular diseases (CVD), including venous thromboembolism (VTE), atherosclerosis (AS), coronary artery disease (CAD), myocardial infarction (MI), and stroke, all independent of typical CVD risk factors such as hyperlipidemia, obesity, and diabetes. Importantly, incidence of CH is rising as our population ages and there is an unmet need for treatments to prevent CVD associated with CH. Indeed, individuals harboring CH mutations in TET2, DNMT3A, ASXL1, or JAK2 have an almost 2-fold higher risk for CVD; however, the underlying mechanisms are only beginning to emerge and further studies to identify therapeutic targets are needed. Here, we take a novel approach by focusing on the HMGA1 chromatin regulators in CVD associated with CH. Our

premise that HMGA1 plays a critical role in CVD associated with CH is based on the following preliminary data: 1) HMGA1 overexpression induces clonal expansion in adult stem cells by amplifying genes involved in inflammation and proliferation1. 2) In JAK2V617F transgenic mouse models of CH and myeloproliferative neoplasms (MPN), loss of just a single Hmga1 allele in hematopoietic stem cells (HSCs) dampens thrombocytosis, erythrocytosis, and neutrophilia, all of which are linked to CVD. 3) Moreover, HMGA1 deficiency prevents splenomegaly, megakaryocyte hyperplasia, and progression to myelofibrosis (MF). 4) Importantly, MF is characterized by excessive inflammatory signals from megakaryocytes and other progenitors, all of which could fuel CVD1. 5) HMGA1 also expands HSC with a monocyte-bias and increases IL6 expression, which are also linked to atherosclerosis (AS) and CVD. Together, these exciting results led us to the following hypotheses: 1) HMGA1 is required for the development of AS and other manifestations of CVD in CH through specific transcriptional networks, and, 2) HMGA1 networks expand specific stem and progenitor populations that increase pro-inflammatory signals. To begin to test this, we propose a strategic collaboration with Dr. Krause at YCCEH to elucidate aberrant inflammatory cytokine/chemokine networks induced by HMGA1

in well-established Tet2 mutant mouse models of atherosclerosis (AS) with the following Aims:

A) To identify HMGA1 transcriptional networks and the cell(s) of origin for Hmga1-driven, aberrant inflammatory signaling in Tet2 mutant CH using single cell RNA sequencing (scRNAseq) and,

B) To define HMGA1-dependent cytokines and chemokine pathways in Tet2 mutant mice with AS. Our focus will be on cytokines and networks that could be targeted in therapy. Thus, our collaborative studies with Dr. Diane Krause (Director of the Yale CCEH and expert in hematopoiesis), will not only reveal mechanistic insight into disease-related cytokine pathways in CH, but we also expect to discover new actionable mechanisms to prevent progression.


Lab link: https://www.linkedin.com/in/zanshe-thompson

Zheng Abstract Type B P&F 2023

ANKRD26 in Megakaryopoiesis (Ankyrin repeat domain-containing protein-26) is a highly conserved protein that is involved in platelet production. Mutations in the 5’ untranslated region (5’UTR) of ANKRD26 gene lead to ANKRD26 overexpression during megakaryocyte differentiation, resulting in impaired proplatelet formation. Point mutations and small size deletions in the 5’UTR of ANKRD26 have been identified in patients with inherited thrombocytopenia 2 (THC2), a life-long thrombocytopenia with a predisposition to developing hematological malignancies. However, little is known about the underlying mechanism of ANKRD26 mutation-associated thrombocytopenia. To explore the function of ANKRD26 and its role in megakaryopoiesis, we established and characterized the first animal model of THC2. Our preliminary results demonstrated that zebrafish ankrd26 mutants with mutations in the 5’UTR of ankrd26 resulted in overexpression of Ankrd26 and reduction of thrombocyte count, similar to the clinical presentation of THC2 patients. Moreover, we found that the level of ANKRD26 was positively corelated with the level of PRMT1 in the megakaryoblastic leukemia cells and in the platelets of immune thrombotic thrombocytopenic purpura patients. PRMT1 is an arginine methyltransferase for RUNX1 (runt-related transcription factor 1), which is a negative regulator for ANKRD26 expression. We hypothesize that dysregulation of the PRMT1-RUNX1-ANKRD26 pathway may affect both hereditary and acquired thrombocytopenia. Our study will further evaluate the role of this novel pathway in platelet development and production, providing a potential avenue for developing novel therapeutic strategies for patients with thrombocytopenia.

Omelianczyk Abstract Type B P&F 2023

Red blood cell (RBC)-mediated transport of oxygen throughout the body is a tightly controlled process. During hypoxia, the body increases blood adenosine levels to signal RBCs to release more oxygen. Adenosine is sensed in the RBC by the ADORA2B receptor, which initiates a signaling cascade that ultimately elevates levels of 2,3-bisphosphoglyceric acid (2,3-BPG) that binds hemoglobin to reduce its oxygen affinity. Acute hypoxia also reduces RBC fatty acid levels short-term, although these levels increase during prolonged hypoxia beyond steady-state levels. The mechanisms and biological implications of these changes are unclear. Sickle cell disease, which is caused by a single point mutation in the b-subunit of hemoglobin, phenocopies hypoxia, including elevated blood adenosine levels, active ADORA2B signaling, and increased levels of 2,3-BPG within the RBC. The release of oxygen from mutant hemoglobin, however, causes a conformational change, resulting in the characteristic sickling of the RBC. Sickle cell disease is widespread in sub-Saharan Africa, as it confers near complete protection from malaria, which is also endemic to this region. Recent work, however, indicates that this protection dwindles during infection by Plasmodium falciparum malaria parasites that harbor specific mutations that counter-act the protective effects of sickle trait and enable parasites to thrive in these patients. Intriguingly, two of the nonsynonymous parasite mutations that counteract sickle protection are in genes coding for proteins exported to the infected RBC. We posit that parasites actively interfere with RBC lipid signaling pathways to overcome the protective properties of sickle cell disease. We propose i) to unravel the lipid changes that underpin altered signaling in normoxic versus hypoxic conditions in RBCs from healthy and sickle-cell patients and ii) to understand how malaria parasites interfere with lipid signaling in RBCs and counteract sickle protection via specific adaptations. We expect to gain insights into red blood cell lipid metabolism beyond the current knowledge. This project will characterize the impact of ADORA2B signaling on lipid metabolism in healthy and sickling RBCs during hypoxia.

This might open avenues for future studies ultimately novel treatment possibilities of patients suffering from acute and chronic hypoxia. Furthermore, the adaptation of Plasmodium falciparum to sickle cell blood puts large populations in sub-Saharan Africa at risk of severe malaria. This will further complicate the already slowing efforts to eradicate malaria. This work will help understand the underlying mechanism behind this newly discovered condition.

Shinha Abstract Type A P&F 2023

Myelodysplastic syndromes (MDS) are a heterogeneous group of blood disorders characterized by the ineffective production of mature blood cells from the bone marrow. Somatic mutations in genes encoding RNA splicing factors (SF) such as SRSF2 and U2AF1 are found in ~20% of MDS patients. These patients are generally associated with poor prognoses and are at an increased risk of leukemic transformation. The precise cellular and molecular mechanisms by which spliceosome gene mutations endow HSPCs with a competitive advantage in disease initiation and progression are still poorly understood. Several murine models have been developed to model the effects of somatic mutations in SRSF2 and U2AF1; however, the degree of splicing overlap between mouse and human was low due to low intronic sequence conservation across species. Moreover, cells are unable to tolerate lentiviral-based expression of splicing factors, which severely limits our ability to perform functional assays. To overcome this challenge, we are proposing to develop an AAV-based gene editing strategy to introduce the SRSF2P95H somatic mutation directly into the endogenous SRSF2 locus in primary human hematopoietic progenitors. Successful development of this technique will allow us to perform a wide range of molecular and functional assays to better understand how aberrant RNA splicing drives clonal blood diseases such as MDS.

Collins Abstract Type B P&F 2023

Hematopoiesis is a highly regulated process during which hematopoietic stem cells (HSCs) expand and differentiate, dynamically supplying a diversity of blood cells for the entire life of an organism. In vivo mouse models are essential for fundamental studies of hematopoiesis, providing numerous tools and methods for flexible in vivo experimentation that is restricted in in vivo studies of human hematopoiesis. Here, I propose to provide these critical tools by developing a protocol C-FiSHH; i.e., CRISPR-based Functional in vivo Screen of Human Hematopoiesis. I will build on state-of-the art technologies developed or adopted by my lab, following two Specific Aims. First, I will optimize a protocol to deliver a protein-barcoded gRNA/Cas9 complex in the humanized hematopoietic system of ‚ÄėMISTRG‚Äô mice that I helped develop. Second, I will assess the feasibility of an in vivo singlecell CRISPR screen of human hematopoiesis. As a proof-of-principle, I will design a gRNA library that targets genes essential for the development of specific hematopoietic lineages. Once optimized, my technology will be highly versatile and will enable functional screens to identify mechanisms underlying fundamental characteristics of human hematopoiesis, such as the long-term maintenance of self-renewing HSCs, lineage commitment, and the role of cytokines in these processes. I expect to provide a necessary complement to the high-dimensional mapping of human hematopoiesis transcriptomes, adding a functional perspective to descriptive studies.

Guo Abstract Type A P&F 2023

Proliferation followed by differentiation of the granulocyte and macrophage progenitors (GMPs) sustains the rapid cellular turnover of the myeloid lineages. Their essentiality is highlighted by the side effects of many chemotherapy drugs designed to target the proliferating cancer cells. This highly proliferative state, however, is transient for a given GMP cell, which exits from the proliferative state upon differentiation. My lab previously found that GMPs divide every 6-8 hours at their peak proliferative state, and this state lasts for ~1-2 days, at least in vitro, when cell cycle slows upon differentiation. These proliferative progenitors possess enormous regenerative potential; agents that can tap into this regenerative power without transformation would provide ample therapeutic opportunities. In our search for such agents, we discovered a small molecule to yield orders of magnitude more expansion without impairing subsequent differentiation. While experiments are being planned to test its effect in vivo, we propose to identify the molecular target(s) for this small molecule compound. We have teamed up with renowned Yale experts in medicinal chemistry and target identification, Dr. Craig Crews, and have obtained critical evidence to support that this compound may act by metabolic reprogramming. Therefore, we seek the CCEH Type A support from the University of Utah Metabolomics Core to test our hypothesis. Overall, the experiments in this proposal could unveil a novel class of chemical agents with pharmacologic potential for hematopoietic regeneration.

Abkowitz Abstract Type A P&F 2023

FLVCR1 has a critical role in maintaining intracellular heme levels during the CFU E/proerythroblast stages of erythropoiesis. Mice lacking FLVCR1 die around E12 with a severe anemia. Adult mice with an induced deletion of FLVCR1 develop severe anemia from ineffective erythropoiesis. The developing erythroblasts in Flvcr1-deleted mice have high heme content and heme-dependent pathologies. Choline is an essential metabolite involved in three key pathways. First, choline is utilized in the production of phosphatidylcholine and other cell

membrane components. Second, choline is utilized as a methyl group donor for amino acid production and DNA methylation. Third, choline is essential for production of the neurotransmitter acetylcholine. While acetylcholine is not needed for erythropoiesis, the other two pathways are utilized during erythropoiesis. One study demonstrated that phosphatidyl choline synthesis was important during early erythropoiesis corresponding to the stages that we demonstrated heme export via FLVCR1 is also critical. This is of particular interest as several

recent studies demonstrated FLVCR1 is a choline importer. FLVCR1 is a member of the major facilitator superfamily (MFS) of transmembrane transporters. When we originally cloned FLVCR1, it appeared to be a member of the antiporter subgroup of MFS proteins. This new finding suggests that heme and choline are antiporter substrates and raises the question of whether their transport is obligately linked or if one substrate plays a regulatory role in the transport of the other substrate. The purpose of this project is to address this question. We will first utilize the NRK cell line which lacks endogenous FLVCR1 as demonstrated via the lack of

infectability with FeLV-C, and the lack of heme export. This provides a clean model system to test if and how heme export will affect choline import and metabolism and also if and how choline import effects heme export. We will also evaluate the role of FLVCR1 on choline metabolism in vivo in our Flvcr1-deleted mice and if expression of the high affinity choline importer SLC5A7 or the FLVCR1 paralog FLVCR2 (also identified as a choline importer) in Flvcr1-deleted mice can rescue anemia and whether they alter choline metabolism during


Lab link: https://iscrm.uw.edu/faculty/janis-abkowitz/

Marinkovic Abstract Type A P&F 2023

The bone marrow (BM) microenvironment directs the self-renewal, differentiation, and homeostasis of hematopoietic stem cells and progenitors. Aging-associated perturbations in the BM niche, attributed in large part to alterations in regulatory cues within the local extracellular matrix (ECM), contribute to declining hematopoietic function. However, interactions between hematopoietic cells and the local ECM remain largely uncharacterized, and the contribution of changes in the spatial organization of cell-matrix crosstalk to diminished hematopoiesis is not understood. Our recent studies have indicated that the ECM produced by elderly BM stromal cells negatively affects the function of the BM niche and entails significant alterations in the matrix proteome relative to that in young BM. The study intends to identify aging-related changes in the spatial organization of key matrix proteins and their relationship with BM cell types. This will be achieved through high resolution mapping of cell-matrix interactions in BM of young and elderly mice using PhenoCycler multiplex imaging (CODEX). Ultimately, this research seeks to unravel the fundamental mechanisms by which aging related alterations in matrix architecture impair the function of the BM niche, with potential implications for addressing aging-associated hematological disorders and repairing the damaged or dysregulated BM niche.


Lab link: https://directory.uthscsa.edu/academics/profile/marinkovic

Scalf Abstract Type B P&F 2022

Proliferation followed by differentiation of the granulocyte and macrophage progenitors (GMPs) sustains the rapid cellular turnover of the myeloid lineages. Their essentiality is highlighted by the side effects of many chemotherapy drugs designed to target the proliferating cancer cells. This highly proliferative state, however, is transient for a given GMP cell, which exits from the proliferative state upon differentiation. My lab previously found that GMPs divide every 6-8 hours at their peak proliferative state, and this state lasts for ~1-2 days, at least in vitro, when cell cycle slows upon differentiation. These proliferative progenitors possess enormous regenerative potential; agents that can tap into this regenerative power without transformation would provide ample therapeutic opportunities. In our search for such agents, I discovered a small molecule to display such activity, yielding orders of magnitude more expansion without impairing subsequent differentiation. My proposal is to identify the molecular target(s) for the small molecule and to test whether it can promote hematopoietic recovery following injury in vivo. We have teamed up with renowned Yale experts in medicinal chemistry and target identification, Dr. Craig Crews, and have obtained critical evidence to support feasibility using a targeted proteomic approach to unveil the molecular target(s)/mechanism for the small molecule. In a second aim as supported by encouraging preliminary results, I will administer the small molecule to mice post irradiation and 5’ fluorouracil to test whether it promotes hematopoietic/myeloid recovery post injury. Overall, the experiments in this proposal could unveil a novel class of chemical agents with pharmacologic potential for hematopoietic regeneration.

Klein Abstract Type B P&F 2022

This collaborative proposal targets fatty acid oxidation (FAO) to expand human hematopoietic stem cells (HSCs) in chemically defined culture conditions. Independent research paths in the Tong and Klein labs have converged on the unexpected finding that FAO activation enhances HSC function during ex vivo expansion. The Tong lab has found that genetic disruption of the adaptor protein LNK, which expands long-term HSCs >10-fold, activates a metabolic program that increases FAO and reduces oxidative stress. Independently, a high throughput screen in the Klein lab identified drugs that induce FAO through activation of PPARa as potent enhancers of ex vivo HSC expansion. Here we propose to test the hypothesis that FAO activation is required for HSC expansion and that PPARa agonists can be used for therapeutic HSC expansion ex vivo. Investigation of metabolic regulators of hematopoiesis is a new area of research for both the Tong and Klein labs that could have substantial therapeutic impact. The significance of this proposal includes: 1. The ability to expand human HSCs in umbilical cord blood units will substantially increase the number of available HLA matches for patients needing HSC transplant, notably patients with myelodysplastia, advanced myeloproliferative disorders, and bone marrow failure. 2. Gene editing techniques for the treatment of inherited blood disorders are limited by the loss of long term (LT)-HSCs during ex vivo manipulations; our low cytokine culture conditions maintain LT-HSCs ex vivo without loss of reconstituting activity, providing an ideal platform for therapeutic gene editing. At a basic science level, our preliminary data and published work from others identify a role for FAO in the maintenance of LT-HSCs. However, the mechanisms by which FAO enhances HSC function have not been explored. Furthermore, while PPARa agonists are widely used clinically to treat hyperlipidemia (e.g. gemfibrozil/lopid), these drugs have not previously been applied to therapeutic HSC expansion. Our data are too preliminary for an R01 submission; these high risk/high gain experiments will require transplantation studies in mice and additional metabolic analyses to support a collaborative R01 submission to the NIDDK in the future.

Karnik Abstract Type A P&F 2022

Bone marrow (BM) is the primary site of hematopoiesis in mammals and where hematopoietic stem cells (HSCs) reside. As the age advances, the BM architecture changes and the hematopoietic potential of HSCs declines. The pathways involved with this decline in HSC regenerative potential are not fully understood. However, we know that from previous studies by our group and others on dissociated bone marrow, the cells of the hematopoietic niche (HN) such as osteomacs (OMs), megakaryocytes (MKs), and osteoblasts (OBs) are involved in maintaining the HSC function. These studies use established techniques such as flow cytometry and immunofluorescence which use dissociated BM either to quantify the cells of the HN or the tissue to visualize up to three cell markers at a time. However, it is important to understand the spatial relationships of the cells of the HN with each other in an unperturbed BM to better comprehend the interactions of these cells in the BM niche and how they change as the age advances. A multiplex high-resolution imaging technology, CODEX, that can visualize up to 60 markers simultaneously can overcome the limitations of traditional techniques to visualize the entire niche. We propose to use the CODEX to image the HN to study the spatial relationships between the cells of HN in young and old mice to better understand the HN architectural landscape and to develop the methodology for CODEX use so it can become a research and investigative tool for other hematology investigators. Plotting the architectural landscape of the BM of both young and old mice will enhance our understanding of the relationship between these cells in the BM niche and to help us develop the methodology and protocols of the CODEX so it can become a research and investigative tool for non-malignant hematology investigators.

Leibold Abstract Type A P&F 2022

Due to its presence in proteins involved in hemoglobin synthesis, DNA synthesis and mitochondrial respiration, eukaryotic cells require iron for growth and proliferation.  Regulation of cellular iron content is crucial: excess cellular iron catalyzes the generation of reactive oxygen species  that damage DNA and proteins, while cellular iron deficiency causes cell cycle arrest and cell death. Dysregulation of iron homeostasis caused by iron deficiency or iron excess leads to hematological, neurodegenerative and metabolic disorders. Vertebrate iron metabolism is controlled post-transcriptionally by iron-regulatory protein 2 (Irp2). Irp2 binds to iron-responsive elements (IREs) in the mRNAs of proteins involved in iron uptake (transferrin receptor 1), sequestration (ferritin) and export (ferroportin), and regulates the translation or stability of these mRNAs. Our previous work show that Irp2 is regulated by iron-dependent proteolysis by the FBXL5 SCF-ubiquitin ligase. We also discovered a novel iron-independent mechanism for regulating Irp2 RNA-binding activity during the cell cycle. Irp2 is phosphorylated at S157 by Cdk1/cyclin B during G2/M and dephosphorylated by Cdc14A during mitotic exit. Irp2-S157 phosphorylation blocks its interaction with RNA to increase ferritin synthesis and decrease TfR1 mRNA stability during mitosis. The significance of  S157 phosphorylation was investigated in mice where Ser157 was mutated to Ala157 (Irp2A/A)). Irp2A/A mice display anemia, defective erythroid terminal differentiation and dysregulated systemic iron metabolism. Our overall objective is to determine the role of Irp2-S157 phosphorylation in hematopoiesis. Our goal here is characterize the anemia in WT and Irp2A/A mice. For these studies, we propose to utilize the University of Utah Center for Iron & Heme Disorders Core for quantification of iron and heme content in tissue samples from WT and Irp2A/A mice.

Mayday Abstract Type B P&F 2022

RNA binding motif protein 15 (RBM15) is a key regulator of N6-methyladenosine (m6A) epitranscriptome modification and is essential for recruitment of the m6A writer protein complex to target RNAs. It has been shown that RBM15 is important for hematopoietic stem cell (HSC) maintenance and quiescence, but its role in the fate specification of hematopoietic progenitor cells (HPCs) remains poorly understood. RBM15 is part of the recurrent t(1;22) translocation associated with infantile acute megakaryoblastic leukemia; therefore, investigation into its role in megakaryocyte differentiation and maturation is warranted. Understanding the mechanistic role of RBM15 in the process of megakaryocyte maturation will not only provide potential avenues of investigation for treatment of AMKL but will also shed light on the role of this protein and the m6A epitranscriptome in megakaryopoiesis. This proposal aims to understand the transcriptomic targets of RBM15 (Aim 1) and the m6A epitranscriptomic modifications regulated by RBM15 (Aim 2) in a model of megakaryopoiesis. Using enhanced crosslinking and immunoprecipitation sequencing techniques, we will characterize these targets at single nucleotide resolution. Comparison to RNA-seq will provide insight into the consequences of RBM15 binding and modification on target transcripts. By determining the exact nucleotide bound by RBM15 and the exact adenosine modified nearby, we will gain detailed insight into the epitranscriptome dynamics involved in hematopoietic differentiation. Completion of this project will illuminate the transcriptome and epitranscriptome interactions of RBM15 and will provide candidate genes that may be critical for downstream mechanistic effects driving megakaryopoiesis. By filling gaps in the field, this work will lay the foundation for further investigation of the epitranscriptome in hematopoietic fate decision.

Prasada Rao Jarajapu Abstract Type B P&F 2022

Diabetes increases risk for cardiovascular diseases. Chronic inflammation and oxidative stress appear to be underlying mechanisms of diabetic dysfunction in cardiovascular tissues. Systemic inflammation is due to myelopoietic bias in the stem/progenitor cells and the resulting increased generation of pro-inflammatory monocyte-macrophages. TERT is a subunit of telomerase that is responsible for telomere maintenance and chromosomal stability. Independent of telomerase, TERT regulates hematopoiesis and mitochondrial functions. Our preliminary studies discovered that diabetic CD34+ hematopoietic stem/progenitor cells (HSPCs) express one or more deletion variants of TERT, őĪ-, ő≤- or őĪő≤-variants, while nondiabetic cells do not. Deletion variants of TERT are known to oppose full-length TERT function. The presence of variants correlated with decreased telomerase activity and elevated mitochondrial reactive oxygen species (mitoROS) in diabetic CD34+ cells compared to the nondiabetic. Furthermore, we found that silencing of TGFÔĀĘ1 blocked TERT-splicing that accompanied decreased mitoROS and reversed myelopoiesis. This pilot proposal tests the hypothesis that splice variants of TERT mediate increased myelopoiesis and mitochondrial oxidative stress in diabetic CD34+ HSPCs. Splice variants will be silenced by using morpholino-oligonucleotide sequences complementary to specific intron-exon or exon-intron boundaries of the TERT pre-mRNA sequence of TERT, which block the alternate splice sites őĪ- (intron 5/exon 6) and ő≤- (intron 6/exon 7). We will test the impact of this molecular modification on myelopoietic potential in ex vivo and in vivo. A novel mouse model NSGS mouse that support myelopoietic differentiation of human CD34+ cells will be used. Beneficial effects of the TERT variants‚Äô knockdown on mitochondrial functions including oxidative stress, metabolism - glycolysis and oxidative phosphorylation, and mitoDNA damage will be evaluated. This pilot study will enhance our understanding of TERT physiology in diabetic HSPC

Xiao Abstract Type B P&F 2022

Iron is an essential micronutrient required for many biological processes, including erythropoiesis, but excess iron is toxic due to its ability to generate reactive oxygen species. Aberrant regulation of the master iron hormone hepcidin is a major underlying cause of most iron disorders including anemia of chronic disease, iron refractory iron deficiency anemia, beta-thalassemia, and hemochromatosis. Hepcidin functions by binding and inducing degradation of the sole iron exporter ferroportin to reduce iron influx into the circulation from dietary sources and body stores. Liver hepcidin expression is regulated by several different signals that indicate whether the body needs more or less iron, including serum and tissue iron levels, erythropoietic drive, and inflammation. Previous studies have discovered that the bone morphogenetic protein (BMP)-SMAD signaling pathway is a central regulator of hepcidin transcription in response to most of its known signals. However, there are many facets of hepcidin regulation that are still not understood, including how hepcidin is regulated by homeostatic iron regulator HFE. Mutations in HFE are the most common cause of hereditary hemochromatosis, an autosomal recessive iron overload disorder with a prevalence of 1 in 300 individuals in the United States. Although HFE mutations were linked to hereditary hemochromatosis over 20 years ago, the precise mechanisms of action of HFE in hepcidin regulation are still unclear. The current working model is that HFE deficiency leads to impaired SMAD signaling responses to BMP ligands. In the current proposal, preliminary data will be presented using a novel mouse model demonstrating that HFE also regulates hepcidin through a SMAD-independent pathway. Herein, I propose to perform bulk RNA sequencing (Seq) and single cell RNA-seq in this mouse model as a discovery approach to identify the unknown SMAD-independent signaling pathway(s) governing hepcidin regulation by HFE. This work holds the promise to shift the paradigm in understanding the mechanism of action of HFE and to discover a novel signaling pathway governing hepcidin and iron homeostasis regulation that may ultimately identify new therapeutic targets for treating iron disorders.

Belot Abstract Type B P&F 2022

Heme, an iron-containing organic ring, is a vital cofactor responsible for diverse biological functions and is the major source of bioavailable iron in the human diet. The current dogma states that mammalian heme levels within cells are controlled by balance between heme biosynthesis and heme catabolism. In the past few years, the Hamza lab has led the field by contributing to the discovery of eukaryotic heme transporters and heme trafficking pathways. Our overarching, paradigm-shifting hypothesis is that cellular heme levels are not only maintained by internal heme synthesis (cell-autonomous), but also by distally located proteins which signal systemic heme requirements to a heme trafficking network (cell-nonautonomous). Although emerging evidence supports the existence of a cell-nonautonomous heme communication system in mammals, this concept has remained unexplored. Our recent preliminary studies have revealed an unexpected and novel finding that adult mice under heme depletion and acute need for red blood cells production upregulate erythroid HRG1 expression. This strongly suggests that heme homeostasis during erythropoiesis involves previously unappreciated mechanism(s). Thus, the overall goal of the proposed studies is to use stress erythropoiesis condition (chronic phlebotomies) in different mouse model (WT, HRG1 KO, HRG1EpoR/EpoR mice) to elucidate whether HRG1 heme importer could participate in hemoglobinization of red blood cells.  We plan to (a) elucidate the role of HRG1 in erythroid progenitors, and (b) identify the heme-responsive cell-nonautonomous pathway using RNA-seq in WT and HRG1-KO mice.