Project description:Genetic manipulations to increase fetal hemoglobin (HbF, α2γ2) in postnatal red blood cells (RBCs) can alleviate β-thalassemia and sickle cell disease. We compared five strategies in CD34+ hematopoietic stem and progenitor cells, using either Cas9 nuclease, which creates uncontrolled indel mixtures, or adenine base editors (ABE), which generate more precise nucleotide changes. The most potent modification was ABE generation of γ-globin (HBG1/HBG2) −175 A>G, which creates a promoter binding motif for the transcriptional activator TAL1. In erythroid colonies with >87.5% on-target edits, those with −175 A>G expressed 81 ± 7% HbF, versus 17 ± 11% in unedited controls. In comparison, HbF levels were lower and more variable in erythroid cells modified with either of two Cas9 nuclease strategies with similar editing efficiencies, being 32 ± 19% when a BCL11A repressor binding motif in the γ-globin promoter was targeted and 52 ± 13% when the +58 BCL11A erythroid enhancer was targeted. Contrary to currently accepted models of γ-globin regulation, HbF levels varied significantly with different Cas9 indels that disrupted the γ-globin promoter BCL11A binding motif. The −175 A>G base edit also induced HbF more potently than did the Cas9 nuclease approaches in RBCs generated after transplantation of modified normal or SCD patient CD34+ cells into mice. Our data suggest a strategy for potent, uniform induction of HbF and provide insights into γ-globin gene regulation. More generally, we demonstrate that diverse indels generated by Cas9 nuclease can cause unexpected variations in biological outcomes that can be circumvented by base editing, with important implications for therapeutic gene editing efforts.
Project description:Regular blood transfusion is the cornerstone of care for patients with red blood cell (RBC) disorders such as thalassemia or sickle cell disease. With repeated transfusion, alloimmunisation often occurs due to incompatibility at the level of minor blood group antigens. We use CRISPR-mediated genome editing of an immortalised human erythroblast cell line (BEL-A) to generate multiple enucleation competent cell lines deficient in individual blood groups. Edits are combined to generate a single cell line deficient in multiple antigens responsible for the most common transfusion incompatibilities: ABO (Bombay phenotype), Rh (Rhnull), Kell (K0), Duffy (Duffynull), GPB (S- s- U-). These cells can be differentiated to generate deformable reticulocytes, illustrating the capacity for coexistence of multiple rare blood group antigen null phenotypes. This study provides the first proof-of-principle demonstration of combinatorial CRISPR-mediated blood group gene editing to generate customisable or multi-compatible RBCs for diagnostic reagents or recipients with complicated matching requirements.
Project description:Reactivation of gamma-globin is considered a promising approach for the treatment of beta-thalassaemia and sickle cell disease. Therapeutic induction of gamma-globin expression is fraught with lack of suitable therapeutic targets. In order to identify new potential targets we analysed the changes in the proteome of human primary erythroid progenitor cells by treatment with decitabine, a known, yet not clinically safe, gamma-globin inducer. Significant differentially expressed proteins were identified which were involved in various biological pathways and functional categories.
Project description:Human fetal γ-globin gene is developmentally silenced around the birth, and reactivation of γ-globin gene in adulthood sheds new light on ameliorating symptoms of hemoglobin disorders, such as sickle cell disease (SCD) and β-thalassemias. However, the precise regulation process of γ-globin remains incompletely understood. Here, we found that a new protein directly interacted with SOX6 and exerted a significant repression effect on the expression of γ-globin gene in erythroid cells. Further studies have demonstrated that it bound directly to γ-globin gene promoter via octamer binding motif, which in turn suppressed the transcriptional activity of γ-globin gene promoter. Thus, these data indicate that this new protein acts as a novel transcriptional repressor in the regulation of γ-globin gene expression through direct promoter binding, implying a potential alternative therapeutic target for the treatment of SCD and β-thalassemias.
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:Background: The thalassemias are highly diverse at both the molecular and clinical levels. Many of the HBB mutations that result in β-thalassemia are missense mutations in the coding region of the β-globin gene, but a few cause alternative splicing, and interfere with normal processing of the β-globin transcripts. Transcriptome profiling in individuals affected with β-thalassemia, especially in individuals who carry novel mutations in the HBB, may improve our understanding of the heterogeneity and molecular mechanisms of the disease. Methods: Members of a family with a daughter affected with thalassemia intermedia, although her mother was not clinically affected, were examined for physical characteristics, hematological parameters and β-globin gene sequences. We also characterized genome-wide gene expression in the family using RT-qPCR and high-throughput RNA-sequencing mRNA expression profiling of blood. Results: Clinical findings, hematological indices, DNA and RNA sequence analysis of individuals with β-thalassemia, including the description of a novel mutation in the β-globin gene, which introduces a cryptic donor splice site. More than 300 genes are differentially expressed in β-thalassemic blood with many of the DEGs involved in pathways relevant to the clinical management of β-thalassemia. β-thalassemia shows important similarities and differences with sickle cell disease at the transcriptome level. Conclusions: We described the down-regulation of the β-globin gene in β-thalassemia by RNA-sequencing analysis using a sample from an affected individual and her mother, who have a novel mutation in the HBB that creates a cryptic donor splice site. The daughter has a typical β-thalassemia allele as well, and an unexpectedly severe phenotype. The DEGs are enriched in pathways that are directly or indirectly related to β-thalassemia such as hemopoiesis, heme biosynthesis, response to oxidative stress, inflammatory responses, immune responses, control of circadian rhythm, apoptosis, and other cellular activities. We compare our findings with published results of RNA-Sequencing analysis of sickle cell disease (SCD) and erythroblasts from a KLF1-null neonate with hydrops fetalis, and recognize similarities and differences in their transcriptional expression patterns.
Project description:As high fetal hemoglobin (HbF) levels ameliorate the underlying pathophysiologic defects in sickle cell anemia and β-thalassemia, understanding the mechanisms that enforce silencing of HbF postnatally offers the promise of effective molecular therapy. Depletion of Methyl cytosine Binding Domain protein 2 (MBD2) causes a 10-20 fold increase in γ-globin gene expression in adult β-YAC transgenic mice. To determine the effect of MBD2 depletion in human erythroid cells, CRISPR-Cas9 mediated knockout (KO) was carried out in Human Umbilical cord Derived Erythroid Progenitor-2 (HUDEP-2) erythroid cells resulting in γ/γ+β mRNA levels of ~50% and ~40% HbF by HPLC. In contrast, MBD3 KO had no appreciable effect on γ-globin mRNA. Knockdown (Kd) of MBD2 in primary adult erythroid cells consistently increased γ/γ+β mRNA ratios by ~10-fold resulting in ~30-40% γ/γ+β mRNA levels and a corresponding increase in γ-globin protein. MBD2 exerts its repressive effects through recruitment of the CHD4 chromatin remodeling component of NuRD through a coiled-coil (CC) domain, and the histone deacetylase (HDCC) component via an intrinsically disordered region (IDR). Enforced expression of wild-type MBD2 in MBD2KO HUDEP-2 cells caused a 5-fold decrease in γ-globin mRNA while neither the CC mutant nor the IDR mutant MBD2 proteins had an inhibitory effect. Consistently, co-immunoprecipitation assays showed that the CC and IDR domain mutations disrupt NuRD complex formation by dissociating the CHD4 and HDCC domains respectively. These results establish MBD2-NuRD as a major silencer of HbF in human erythroid cells and point to the CC and IDR domains of MBD2-NuRD as potential therapeutic targets.
Project description:Sickle cell disease and Beta-thalassemia represent hemoglobinopathies arising from dysfunctional or under produced beta-globin chains, respectively. In both diseases, red blood cell injury and anemia are the impetus for end organ injury. Because persistent erythrophagocytosis is a hallmark of these genetic maladies it is critical to understand how macrophage phenotype polarizations in tissue compartments can inform on disease progression. Murine models of sickle cell disease and Beta-thalassemia allow for a basic understanding of mechanisms and provide for translation to human disease. A multi-omics approach to understanding macrophage metabolism and protein changes in two murine models of beta-globinopathy was performed on peripheral blood mononuclear cells as well as spleen and liver macrophages isolated from Berkley sickle cell disease (Berk-ss) and heterozygous B1/B2 globin gene deletion (Hbbth3/+) mice. Results from these experiments revealed the metabolome and proteome of macrophages are polarized to a distinct phenotype in Berk-ss and Hbbth3/+ compared each other and their common background mice (C57BL6/J). Further, spleen and liver macrophages revealed distinct disease specific phenotypes, suggesting macrophages become differentially polarized and reprogrammed within tissue compartments. We conclude that tissue recruitment, polarization, metabolic and proteomic reprogramming of macrophages in Berk-ss and Hbb mice may be relevant to disease to progression in other tissue.
Project description:Delta-Beta thalassemia is an unusual variant of thalassemia caused by large deletions in the β globin gene cluster involving δ- and β-globin genes. The mutations are characterized by high fetal hemoglobin with significant phenotypic diversity. Routinely used diagnostic tests targeting point mutations and small insertions, deletions of the β-globin gene are not suitable for detection of large deletion mutations. This is overcome by either direct globin chain synthesis analysis or beta-cluster gene analysis using different methods. In the current study, we use direct globin chain analysis to diagnose a family with δβ-thalassemia using high resolution mass spectrometry.
Project description:BCL11A represses gamma globin expression by binding to the gamma globin gene (HBG1 and HBG2) promoters. Genome editing of the BCL11A erythroid enhancer in the intron 2 of BCL11A gene or the BCL11A binding site at the HBG1/2 promoters disrupts this pathway and leads to gamma globin induction. Transcriptomic profiling of erythroid cells derived from human CD34+ cells edited at either target site using CRISPR-Cas9 revealed broader transcriptome perturbation when edited at the BCL11A erythroid enhancer.