Project description:We hypothesized that miRNA regulation may be invloved in hydroxyurea-mediated fetal hemoglobin induction. Microarray analysis was utilized as an initial screening tool to determine differential miRNA expression in CD71+ erythroid cells comparing cells from control individuals without sickle cell anemia to patients with sickle cell anemia prior to treatment with hydroxyurea and patients receiving the maximum tolerated dose (MTD) of hydroxurea.
Project description:We hypothesized that miRNA regulation may be invloved in hydroxyurea-mediated fetal hemoglobin induction. Microarray analysis was utilized as an initial screening tool to determine differential miRNA expression in CD71+ erythroid cells comparing cells from control individuals without sickle cell anemia to patients with sickle cell anemia prior to treatment with hydroxyurea and patients receiving the maximum tolerated dose (MTD) of hydroxurea. CD71+ cells were isolated from whole blood of control individuals (n=2), pediatric patients without hydroxyurea treatment (n=3) and pediatric patients at hydroxyurea MTD (n=3). All 8 samples were analyzed for miRNA expression.
Project description:<p> <ol> <li>Implement an efficient, highly reproducible and 'scalable' system for the production of large numbers of sickle cell anemia-specific iPS cells (iPSC).</li> <li>Derive and characterize a novel, in vitro system for the production of an unlimited supply of erythroid lineage cells from the directed differentiation of 'clinical grade' transgene-free iPS cells; use this system to recapitulate erythroid-lineage ontogeny in vitro with the sequential development of primitive and definitive erythropoiesis, accompanied by the appropriate expression of stage-specific globin genes.</li> <li>Identify developmental gene expression profile differences between erythroid precursors that produce primarily HbF and those that produce primarily HbA or HbS.</li> <li>Determine the effects of the three known HbF major quantitative trait loci (QTL) on globin gene expression in disease-specific iPS cells during in vitro erythropoiesis.</li> <li>Search for novel HbF genetic modifiers associated with markedly elevated HbF levels found in sickle cell anemia patients naturally, or in response to hydroxyurea treatment, by examining gene expression profiles and mRNA sequence of their iPSC-derived erythroid cells.</li> <li>Develop and use a CRISPR-based gene editing platform to study the effect of novel HbF genetic modifiers, explore globin switching, and correct the HbS mutation in sickle iPSC lines.</li> </ol> </p>
Project description:<p>Sickle cell disease (SCD) is a severe debilitating hematological disorder associated with a high degree of morbidity and mortality. There are approximately 200,000 babies born with sickle cell disease each year, with the disease predominately affecting individuals in Africa. The overall global burden of the disease is tremendous, with more than 100,000 patients currently in the US and further millions worldwide. The governing bodies of the World Health Organization have recently adopted a resolution to strengthen the response to sickle disease in all affected countries and there is a definite need for high quality sickle cell disease research that has the potential to improve the treatment and prognosis of patients with this devastating disease. The clinical manifestations of SCD arise from a complex pathophysiology that includes hemolysis, acute vaso-occlusion, endothelial dysfunction, inflammation, and chronic organ damage. While the individual clinical course of this disease is highly variable, many of the associated complications demonstrate some degree of heritability. Intensive research into identifying genetic modifiers that can affect the pathophysiology of SCD has been limited to date and there is an urgent need to improve of our knowledge the molecular mechanisms underlying the clinical complications of SCD. The Sickle cell CIP project is investigating complication of stroke and pharmacogenomics of hydroxyurea response in patients with sickle cell anemia. The major benefit of hydroxyurea comes from its ability to induce fetal hemoglobin (HbF) and higher HbF levels are associated with reduced morbidity and mortality in SCA patients. We will perform whole exome and whole genome sequencing of SCA patients in order to identify genome variants associated with incidences of stroke and HbF response to hydroxyurea.</p>
Project description:<p>Sickle cell disease (SCD) is characterized by the presence of sickle hemoglobin (HbS) within circulating erythrocytes resulting in hemolytic anemia, vascular occlusion, and end organ damage due to alterations in the shape and deformability of the cell membrane. The disease is inherited in an autosomal recessive pattern, and is most commonly caused by a single nucleotide substitution in the hemoglobin subunit beta (HBB) gene located on chromosome 11. Participants in this study include children with SCD treated with hydroxyurea to pharmacologically increase fetal hemoglobin (HbF) levels and reduce disease severity. Therefore, the primary phenotype of interest in this study is the change in HbF levels in response to hydroxyurea treatment. Genetic factors have been shown to influence inter-individual variation in drug response, and identification of novel genes and variants associated with clinical outcomes in SCD will be achieved through collaboration between Baylor College of Medicine, Augusta University, Columbia University Medical Center, Emory University School of Medicine and Children's Healthcare of Atlanta, and St. Jude Children's Research Hospital. The NHLBI TOPMed Program is designed to generate scientific resources to enhance understanding of fundamental biological processes that underlie heart, lung, blood and sleep disorders (HLBS). It is part of a broader Precision Medicine Initiative, which aims to provide disease treatments that are tailored to an individual's unique genes and environment.</p>
Project description:Primitive erythropoiesis in the mouse yolk sac is followed by definitive erythropoiesis resulting in adult erythrocytes. In comparison to definitive erythropoiesis little is known about the genes that control the embryonic erythroid program. The purpose of this study was to generate a profile of mouse embryonic yolk sac erythroid cells and identify novel regulatory genes differentially expressed in erythroid compared to non-erythroid (epithelial cells). The identification of these genes will contribute to a greater understanding of how the primitive erythroid program is controlled. This work will have clinical implications for treating sickle cell anemia and β-thalassemia. Activating genes in adult erythroid cells that increase embryonic or fetal globin gene expression may be a therapeutic approach to treat individuals with these disorders. Keywords: Comparison between mouse embryonic day 9.5 yolk sac microdissected primitive erythroid precursors and epithelial cells
Project description:β-hemoglobin disorders, such as sickle cell disease (SCD) and β-thalassemia (BT), are the most common inherited monogenic blood disorders globally. Despite decades of research, there are only four FDA-approved medications available for the management of SCD with hydroxyurea (HU) being the most widely used drug that partially benefits patients by inducing fetal hemoglobin (HbF) production. On the other hand, there are no approved oral drugs currently available for β-thalassemia patients. To our knowledge, there are currently no well-characterized erythroid progenitor cell lines available that can accurately replicate the pathophysiology of SCD and BT while also having the same genetic background apart from the disease mutation enabling consistency and reproducibility. Our novel, physiologically relevant cellular systems provide a plethora of avenues for researchers to investigate various applications related to parasite invasion, drug validation, and genome-editing in the context of SCD and BT.
Project description:Adult hematopoietic stem cells (HSCs) react to various stress conditions by rapidly proliferating and preferentially differentiating towards desired cell types. However, it is unclear whether and how HSCs respond to severe anemic conditions. Here we demonstrate that HSCs rapidly proliferate and enhance their erythroid potential upon induction of acute anemia. Under severe anemic conditions, the concentration of erythropoietin (EPO) does not increase in the bone marrow. Instead, lipoprotein profiles largely changed, and the concentration of apolipoprotein E (ApoE) increased. In HSCs, transcription levels of lipid metabolism-related genes such as very low-density lipoprotein receptor (Vldlr) were significantly up-regulated. Stimulation of HSCs with recombinant ApoE enhanced the erythroid potential, while HSCs of ApoE knockout mice did not respond to the hemolysis induction. We also found that VLDLRhighHSCs have higher erythroid differentiation potential, particularly after acute anemia induction. VLDLRhighHSCs were epigenetically distinct from VLDLRlowHSCs, as their chromatin accessibility was lower and more chromatin regions were closed upon acute anemia induction. Finally, we identified that the chromatin regions closed upon the acute anemia induction were mainly binding sites of a transcription factor Erg. Treatment of HSC with Erg inhibitor enhanced erythroid differentiation potential, as seen in the ApoE treatment. Our findings indicate that lipoprotein metabolism, particularly ApoE, plays a crucial role in HSC regulation under severe anemia conditions in a non-canonical fashion, unlike a conventional factor such as EPO.
Project description:Primitive erythropoiesis in the mouse yolk sac is followed by definitive erythropoiesis resulting in adult erythrocytes. In comparison to definitive erythropoiesis little is known about the genes that control the embryonic erythroid program. The purpose of this study was to generate a profile of mouse embryonic yolk sac erythroid cells and identify novel regulatory genes differentially expressed in erythroid compared to non-erythroid (epithelial cells). The identification of these genes will contribute to a greater understanding of how the primitive erythroid program is controlled. This work will have clinical implications for treating sickle cell anemia and β-thalassemia. Activating genes in adult erythroid cells that increase embryonic or fetal globin gene expression may be a therapeutic approach to treat individuals with these disorders. Experiment Overall Design: Embryonic day 9.5 (E9.5) yolk sacs were dissected from the embryos of timed-pregnant FVB/N mice. These tissues were frozen in OCT media and 8-micron frozen sections were obtained. Laser capture microdissection (LCM) was used to isolate primitive erythroid precursors and epithelial cells from these E9.5 yolk sac frozen sections using 2 to 4 yolk sacs from 2 different litters per biological replicate. Paired erythroid and epithelial samples were collected from the same microscope slides. Total RNA was isolated from 4 different pairs of erythroid and epithelial samples and hybridized to Affymetrix 430 A 2.0 microarrays.
Project description:Increasing fetal hemoglobin (HbF) provides clinical benefit in patients with sickle cell disease (SCD). We recently identified heme-regulated inhibitor (HRI, EIF2AK1) as a novel HbF regulator. Since HRI is an erythroid-specific protein kinase it presents a potential target for pharmacologic intervention. We find that maximal HbF induction requires >80-85% HRI depletion. As it remains unclear whether this degree of HRI inhibition can be achieved pharmacologically, we explored whether HRI knockdown can be combined with pharmacologic HbF inducers to achieve greater HbF production and minimize potential adverse effects associated with treatments. Strongly cooperative HbF induction was observed when HRI depletion was combined with exposure to pomalidomide or the EHMT1/2 inhibitor UNC0638, but not hydroxyurea. Mechanistically, reduction in the levels of the HbF repressor BCL11A reflected the cooperativity of HRI loss and pomalidomide treatment, whereas UNC0638 did not modulate BCL11A levels. In conjunction with HRI loss, pomalidomide maintained its HbF inducing activity at 10-fold lower concentrations, at which condition there were minimal observed detrimental effects on erythroid cell maturation and viability as well as fewer alterations in the erythroid transcriptome. In sum, this study provides a foundation for the exploration of combining future small molecule HRI inhibitors with additional pharmacologic HbF inducers to maximize HbF production and preserve erythroid cell functionality for the treatment of SCD and other hemoglobinopathies.