Recent trends in the gene therapy of β-thalassemia

Upregulation of miR‑6747‑3p affects red blood cell lineage development and induces fetal hemoglobin expression by targeting BCL11A in β‑thalassemia

In β‑thalassemia, excessive α‑globin chain impedes the normal development of red blood cells resulting in anemia. Numerous miRNAs, including miR‑6747‑3p, are aberrantly expressed in β‑thalassemia major (β‑TM), but there are no reports on the mechanism of miR‑6747‑3p in regulating red blood cell lineage development and fetal hemoglobin (HbF) expression. In the present study, RT‑qPCR was utilized to confirm miR‑6747‑3p expression in patients with β‑TM and the healthy controls. Electrotransfection was employed to introduce the miR‑6747‑3p mimic and inhibitor in both HUDEP‑2 and K562 cells, and red blood cell lineage development was evaluated by CCK‑8 assay, flow cytometry, Wright‑Giemsa staining and Benzidine blue staining. B‑cell lymphoma/leukemia 11A (BCL11A) was selected as a candidate target gene of miR‑6747‑3p for further validation through FISH assay, dual luciferase assay and Western blotting. The results indicated that miR‑6747‑3p expression was notably higher in patients with β‑TM compared with healthy controls and was positively related to HbF levels. Functionally, miR‑6747‑3p overexpression resulted in the hindrance of cell proliferation, promotion of cell apoptosis, facilitation of cellular erythroid differentiation and γ‑globin expression in HUDEP‑2 and K562 cells. Mechanistically, miR‑6747‑3p could specifically bind to the 546‑552 loci of BCL11A 3'‑UTR and induce γ‑globin expression. These data indicate that upregulation of miR‑6747‑3p affects red blood cell lineage development and induces HbF expression by targeting BCL11A in β‑thalassemia, highlighting miR‑6747‑3p as a potential molecular target for β‑thalassemia therapy.

First clinical and pedigree study of rare HBB: c.316-90 A > G variant in β-globin gene in Chinese population using third-generation sequencing

INTRODUCTION

β-thalassemia is a common genetic disease mainly caused by point mutations in the β-globin gene, eliciting a high prevalence in South China. The aim of the present study is to identify a rare HBB: c.316-90 A > G variant and provide the clinical and hematological features in two unrelated Chinese families.

METHODS

In this study, we collected eight subjects from two unrelated Chinese families. Conventional thalassemia gene testing was performed to investigate common α and β-thalassemia variants based on the PCR reverse dot hybridization technique. Third-generation sequencing (TGS) was utilized to examine the rare or novel HBA1, HBA2 and HBB gene variants, which will be further verified using Sanger sequencing.

RESULTS

A rare HBB: c.316-90 A > G variant was identified in the proband of Family 1 using TGS, and exhibited remarkably low levels of hemoglobin (Hb), Hb A2, MCV and MCH. The other members in Family 1 did not have the HBB: c.316-90 A > G variant and elicited normal hematological screening results. In Family 2, the proband also carried the HBB: c.316-90 A > G variant and exhibited low levels of MCV, MCH and Hb A2, but with normal Hb value. However, pedigree analysis results revealed that the proband's mother and nephew also carried the HBB: c.316-90 A > G variant, but with normal hematological screening results.

CONCLUSION

This study first conducts clinical and hematological analysis of the HBB: c.316-90 A > G variant in two unrelated Chinese families, which provides valuable data for genetic counseling of the corresponding individuals.

Mass spectrometry for metabolomics analysis: Applications in neonatal and cancer screening

Chemical analysis by analytical instrumentation has played a major role in disease diagnosis, which is a necessary step for disease treatment. While the treatment process often targets specific organs or compounds, the diagnostic step can occur through various means, including physical or chemical examination. Chemically, the genome may be evaluated to give information about potential genetic outcomes, the transcriptome to provide information about expression actively occurring, the proteome to offer insight on functions causing metabolite expression, or the metabolome to provide a picture of both past and ongoing physiological function in the body. Mass spectrometry (MS) has been elevated among other analytical instrumentation because it can be used to evaluate all four biological machineries of the body. In addition, MS provides enhanced sensitivity, selectivity, versatility, and speed for rapid turnaround time, qualities that are important for instance in clinical procedures involving the diagnosis of a pediatric patient in intensive care or a cancer patient undergoing surgery. In this review, we provide a summary of the use of MS to evaluate biomarkers for newborn screening and cancer diagnosis. As many reviews have recently appeared focusing on MS methods and instrumentation for metabolite analysis, we sought to describe the biological basis for many metabolomic and additional omics biomarkers used in newborn screening and how tandem MS methods have recently been applied, in comparison to traditional methods. Similar comparison is done for cancer screening, with emphasis on emerging MS approaches that allow biological fluids, tissues, and breath to be analyzed for the presence of diagnostic metabolites yielding insight for treatment options based on the understanding of prior and current physiological functions of the body.

Combined approaches for increasing fetal hemoglobin (HbF) and de novo production of adult hemoglobin (HbA) in erythroid cells from β-thalassemia patients: treatment with HbF inducers and CRISPR-Cas9 based genome editing

Genome editing (GE) is one of the most efficient and useful molecular approaches to correct the effects of gene mutations in hereditary monogenetic diseases, including β-thalassemia. CRISPR-Cas9 gene editing has been proposed for effective correction of the β-thalassemia mutation, obtaining high-level "de novo" production of adult hemoglobin (HbA). In addition to the correction of the primary gene mutations causing β-thalassemia, several reports demonstrate that gene editing can be employed to increase fetal hemoglobin (HbF), obtaining important clinical benefits in treated β-thalassemia patients. This important objective can be achieved through CRISPR-Cas9 disruption of genes encoding transcriptional repressors of γ-globin gene expression (such as BCL11A, SOX6, KLF-1) or their binding sites in the HBG promoter, mimicking non-deletional and deletional HPFH mutations. These two approaches (β-globin gene correction and genome editing of the genes encoding repressors of γ-globin gene transcription) can be, at least in theory, combined. However, since multiplex CRISPR-Cas9 gene editing is associated with documented evidence concerning possible genotoxicity, this review is focused on the possibility to combine pharmacologically-mediated HbF induction protocols with the "de novo" production of HbA using CRISPR-Cas9 gene editing.

Health-related quality of life among thalassemia patients in Bangladesh using the SF-36 questionnaire

Thalassemia is one of the most common autosomal recessive hereditary blood disorders worldwide, especially in developing countries, including Bangladesh. Thus, this study aimed to determine HRQoL and its determinants of thalassemia patients (TP) in Bangladesh. A cross-sectional survey was performed on 356 randomly selected thalassemia patients. Participants were invited to face-to-face interviews. Descriptive statistics (frequencies and percentages), independent t-test, ANOVA, and multivariate (linear and logistic regression) analysis was performed to analyze the data. Our demographic data showed that among 356 patients, 54% and 46% were male and female, respectively, with an average age of 19.75 (SD = 8.02) years. Most were transfusion-dependent (91%), 26% had comorbidities, and 52% were from low-income families. In the case of HRQoL, male patients showed significantly higher scores of bodily pains and physical health summaries than female patients. Lower income, high blood transfusion status, disease severity, comorbidities, and medical expenses (p < 0.05; CI 95%) are significantly associated with lower SF-36 scores. This study found an association between lower income, blood transfusion, disease severity, comorbidities, as well as medical expenses, and the deterioration of HRQoL among TP. Male patients experienced poorer HRQoL than females. National action plans are required to guarantee the holistic welfare of thalassemia patients.

The Roles of Mitophagy and Autophagy in Ineffective Erythropoiesis in β-Thalassemia

β-Thalassemia is one of the most common genetically inherited disorders worldwide, and it is characterized by defective β-globin chain synthesis leading to reduced or absent β-globin chains. The excess α-globin chains are the key factor leading to the death of differentiating erythroblasts in a process termed ineffective erythropoiesis, leading to anemia and associated complications in patients. The mechanism of ineffective erythropoiesis in β-thalassemia is complex and not fully understood. Autophagy is primarily known as a cell recycling mechanism in which old or dysfunctional proteins and organelles are digested to allow recycling of constituent elements. In late stage, erythropoiesis autophagy is involved in the removal of mitochondria as part of terminal differentiation. Several studies have shown that autophagy is increased in earlier erythropoiesis in β-thalassemia erythroblasts, as compared to normal erythroblasts. This review summarizes what is known about the role of autophagy in β-thalassemia erythropoiesis and shows that modulation of autophagy and its interplay with apoptosis may provide a new therapeutic route in the treatment of β-thalassemia. Literature was searched and relevant articles were collected from databases, including PubMed, Scopus, Prospero, Clinicaltrials.gov, Google Scholar, and the Google search engine. Search terms included: β-thalassemia, ineffective erythropoiesis, autophagy, novel treatment, and drugs during the initial search. Relevant titles and abstracts were screened to choose relevant articles. Further, selected full-text articles were retrieved, and then, relevant cross-references were scanned to collect further information for the present review.

Efficient CRISPR-Cas9-based genome editing of β-globin gene on erythroid cells from homozygous β039-thalassemia patients

Gene editing by the CRISPR-Cas9 nuclease system technology can be considered among the most promising strategies to correct hereditary mutations in a variety of monogenic diseases. In this paper, we present for the first time the correction, by CRISPR-Cas9 gene editing, of the β039-thalassemia mutation, one of the most frequent in the Mediterranean area. The results obtained demonstrated the presence of normal β-globin genes after CRISPR-Cas9 correction of the β039-thalassemia mutation performed on erythroid precursor cells from homozygous β039-thalassemia patients. This was demonstrated by allele-specific PCR and sequencing. Accumulation of corrected β-globin mRNA and relevant "de novo" production of β-globin and adult hemoglobin (HbA) were found with high efficiency. The CRISPR-Cas9-forced HbA production levels were associated with a significant reduction of the excess of free α-globin chains. Genomic toxicity of the editing procedure (low indels and no off-targeting) was analyzed. The protocol might be the starting point for the development of an efficient editing of CD34+ cells derived from β039 patients and for the design of combined treatments using, together with the CRISPR-Cas9 editing of the β-globin gene, other therapeutic approaches, such as, for instance, induction of HbA and/or fetal hemoglobin (HbF) using chemical inducers.

Universal Gene Correction Approaches for β-hemoglobinopathies Using CRISPR-Cas9 and Adeno-Associated Virus Serotype 6 Donor Templates

Mutations in the human β-globin gene are the cause of β-hemoglobinopathies, one of the most common inherited single-gene blood disorders in the world. Novel therapeutic approaches are based on lentiviral vectors (LVs) or CRISPR-Cas9-mediated gene disruption to express adult hemoglobin (HbA), or to reactivate the completely functional fetal hemoglobin, respectively. Nonetheless, LVs present a risk of insertional mutagenesis, while gene-disrupting transcription factors (BCL11A, KLF1) involved in the fetal-to-adult hemoglobin switch might generate dysregulation of other cellular processes. Therefore, universal gene addition/correction approaches combining CRISPR-Cas9 and homology directed repair (HDR) by delivering a DNA repair template through adeno-associated virus could mitigate the limitations of both lentiviral gene transfer and gene disruption strategies, ensuring targeted integration and controlled transgene expression. In this study, we attained high rates of gene addition (up to 12%) and gene correction (up to 38%) in hematopoietic stem and progenitor cells from healthy donors without any cell sorting/enrichment or the application of HDR enhancers. Furthermore, these approaches were tested in heterozygous (β⁰/β⁺) and homozygous (β⁰/β⁰, β⁺/β⁺) β-thalassemia patients, achieving a significant increase in HbA and demonstrating the universal therapeutic potential of this study for the treatment of β-hemoglobinopathies.

Comparative targeting analysis of KLF1, BCL11A, and HBG1/2 in CD34+ HSPCs by CRISPR/Cas9 for the induction of fetal hemoglobin

β-hemoglobinopathies are caused by abnormal or absent production of hemoglobin in the blood due to mutations in the β-globin gene (HBB). Imbalanced expression of adult hemoglobin (HbA) induces strong anemia in patients suffering from the disease. However, individuals with natural-occurring mutations in the HBB cluster or related genes, compensate this disparity through γ-globin expression and subsequent fetal hemoglobin (HbF) production. Several preclinical and clinical studies have been performed in order to induce HbF by knocking-down genes involved in HbF repression (KLF1 and BCL11A) or disrupting the binding sites of several transcription factors in the γ-globin gene (HBG1/2). In this study, we thoroughly compared the different CRISPR/Cas9 gene-disruption strategies by gene editing analysis and assessed their safety profile by RNA-seq and GUIDE-seq. All approaches reached therapeutic levels of HbF after gene editing and showed similar gene expression to the control sample, while no significant off-targets were detected by GUIDE-seq. Likewise, all three gene editing platforms were established in the GMP-grade CliniMACS Prodigy, achieving similar outcome to preclinical devices. Based on this gene editing comparative analysis, we concluded that BCL11A is the most clinically relevant approach while HBG1/2 could represent a promising alternative for the treatment of β-hemoglobinopathies.

Mesenchymal stem cells as carrier of the therapeutic agent in the gene therapy of blood disorders

Nonhematopoietic stem cells as a delivery platform of therapeutic useful genes have attracted widespread attention in recent years, owing to gained a long lifespan, easy separation, high proliferation, and high transfection capacity. Mesenchymal stem/stromal cells (MSCs) are the choice of the cells for gene and cell therapy due to high self-renewal capacity, high migration rate to the site of the tumor, and with immune suppressive and anti-inflammatory properties. Hence, it has a high potential of safety genetic modification of MSCs for antitumor gene expression and has paved the way for the clinical application of these cells to target the therapy of cancers and other diseases. The aim of gene therapy is targeted treatment of cancers and diseases through recovery, change, or enhancement cell performance to the sustained secretion of useful therapeutic proteins and induction expression of the functional gene in intended tissue. Recent developments in the vectors designing leading to the increase and durability of expression and improvement of the safety of the vectors that overcome a lot of problems, such as durability of expression and the host immune response. Nowadays, gene therapy approach is used by MSCs as a delivery vehicle in the preclinical and the clinical trials for the secretion of erythropoietin, recombinant antibodies, coagulation factors, cytokines, as well as angiogenic inhibitors in many blood disorders like anemia, hemophilia, and malignancies. In this study, we critically discuss the status of gene therapy by MSCs as a delivery vehicle for the treatment of blood disorders. Finally, the results of clinical trial studies are assessed, highlighting promising advantages of this emerging technology in the clinical setting.

Inhibition of γ/β Globin Gene Switching in CD 34+ Derived Erythroid Cells by BCL11A RNA Silencing

The induction of fetal haemoglobin (Hb F), due to the sustained clinical effects, is one of the most promising methods for the treatment of β hemoglobinopathies, such as thalassemia major and sickle cell disease (SCD). Inhibition of γ-globin gene silencing, possibly is a suitable strategy to induce HbF expression in these patients. In this study, the possibility of increasing HbF in the CD34+ derived erythroid cells was investigated by BCL11A inhibition using specific small-interfering RNAs (siRNAs). Human peripheral blood-derived hematopoietic stem cells were isolated and differentiated to erythroid cells. Erythroid maturation was investigated using cell morphology parameters and flow cytometry analysis of CD235a expression On day 20, siRNA complementary to BCL11A was transfected to differentiating cells via electroporation. BCL11A expression was evaluated through real-time quantitative reverse transcription polymerase chain reaction (qRT-PCR) and enzyme linked immunosorbant assay (ELISA). β actin was used as the reference gene to confirm the relative expression level of BCL11A gene mRNA. 48 hours after transfection, BCL11A siRNA significantly reduced BCL11A mRNA levels and consequently led to 2.0 fold decrease in corresponding protein. On the 28th day, haemoglobin electrophoresis results showed that Hb F levels in transfected erythroid cells increased 3.3-fold when compared with non transfected cells. In this study we showed that BCL11A inhibition in erythroid cells could increase fetal hemoglobin, and this strategy can be the basis for designing a γ globin expressing cellular system to increase Hb F in patients with thalassemia and SCD.

In Utero Gene Therapy (IUGT) Using GLOBE Lentiviral Vector Phenotypically Corrects the Heterozygous Humanised Mouse Model and Its Progress Can Be Monitored Using MRI Techniques

In utero gene therapy (IUGT) to the fetal hematopoietic compartment could be used to treat congenital blood disorders such as β-thalassemia. A humanised mouse model of β-thalassemia was used, in which heterozygous animals are anaemic with splenomegaly and extramedullary hematopoiesis. Intrahepatic in utero injections of a β globin-expressing lentiviral vector (GLOBE), were performed in fetuses at E13.5 of gestation. We analysed animals at 12 and 32 weeks of age, for vector copy number in bone marrow, peripheral blood liver and spleen and we performed integration site analysis. Compared to noninjected heterozygous animals IUGT normalised blood haemoglobin levels and spleen weight. Integration site analysis showed polyclonality. The left ventricular ejection fraction measured using magnetic resonance imaging (MRI) in treated heterozygous animals was similar to that of normal non-β-thalassemic mice but significantly higher than untreated heterozygous thalassemia mice suggesting that IUGT ameliorated poor cardiac function. GLOBE LV-mediated IUGT normalised the haematological and anatomical phenotype in a heterozygous humanised model of β-thalassemia.

Omics Studies in Hemoglobinopathies

Hemoglobinopathies include all genetic diseases of hemoglobin and are grouped into thalassemia syndromes and structural hemoglobin variants. The β-thalassemias constitute a group of severe anemias with monogenic inheritance, caused by β-globin gene mutations. This review is focused on omics studies in hemoglobinopathies and mainly β-thalassemia, and discusses genomic, epigenomic, transcriptomic, proteomic and metabolomic findings. Omics analyses have identified various disease modifiers with an impact on disease severity and efficacy of treatments. These modifiers have contributed to the understanding of globin genes regulation/hemoglobin switching and the development of novel therapies. How omics data and their integration can contribute to efficient patient stratification, therapeutic management, improvements in existing treatments and application of novel personalized therapies is discussed.

Iron Toxicity and Hemopoietic Cell Transplantation: Time to Change the Paradigm

The issue of iron overload in hemopoietic cell transplantation has been first discussed in the field of transplantation for thalassemia. Thalassemia major is characterized by ineffective erythropoiesis and hemolysis leading to severe anemia. Patients require regular blood transfusion therefore they develop iron overload causing organ damage and hematopoietic cell transplantation (HCT) is a consolidated reliably curative option.

In this category of patients an important issue for transplant outcome is the iron burden before transplant and in the long-life post-transplant. Nevertheless today the concept of the impact of iron overload / toxicity on the outcome of HCT has been extended to other diseases characterized by periods of variable duration of transfusion dependence.

Recent preclinical data has shown how increased production of reactive oxygen species (ROS) resulting under iron overload condition, could impair the stem cells clonality capacity, proliferation and maturation. Also, microenvironment cells could be affected through this mechanism. For this reason, iron overload is becoming an important issue also in the engraftment period post-transplant.

The aim of this review is to update consolidated knowledge about the role of iron overload/iron toxicity in the HCT setting in non-malignant and in malignant diseases introducing the concept of exposition of free toxic iron forms and related cellular damage in the different stage of transplant.

MicroRNAs and Long Non-coding RNAs in Genetic Diseases

Since the discovery and classification of non-coding RNAs, their roles have gained great attention. In this respect, microRNAs and long non-coding RNAs have been firmly demonstrated to be linked to regulation of gene expression and onset of human diseases, including rare genetic diseases; therefore they are suitable targets for therapeutic intervention. This issue, in the context of rare genetic diseases, is being considered by an increasing number of research groups and is of key interest to the health community. In the case of rare genetic diseases, the possibility of developing personalized therapy in precision medicine has attracted the attention of researchers and clinicians involved in developing "orphan medicinal products" and proposing these to the European Medicines Agency (EMA) and to the Food and Drug Administration (FDA) Office of Orphan Products Development (OOPD) in the United States. The major focuses of these activities are the evaluation and development of products (drugs, biologics, devices, or medical foods) considered to be promising for diagnosis and/or treatment of rare diseases or conditions, including rare genetic diseases. In an increasing number of rare genetic diseases, analysis of microRNAs and long non-coding RNAs has been proven a promising strategy. These diseases include, but are not limited to, Duchenne muscular dystrophy, cystic fibrosis, Rett syndrome, and β-thalassemia. In conclusion, a large number of approaches based on targeting microRNAs and long non-coding RNAs are expected in the field of molecular diagnosis and therapy, with a facilitated technological transfer in the case of rare genetic diseases, in virtue of the existing regulation concerning these diseases.

Production and Transduction of a Human Recombinant β-Globin Chain into Proerythroid K-562 Cells To Replace Missing Endogenous β-Globin

Protein replacement therapy (PRT) has been applied to treat severe monogenetic/metabolic disorders characterized by a protein deficiency. In disorders where an intracellular protein is missing, PRT is not easily feasible due to the inability of proteins to cross the cell membrane. Instead, gene therapy has been applied, although still with limited success. β-Thalassemias are severe congenital hemoglobinopathies, characterized by deficiency or reduced production of the adult β-globin chain. The resulting imbalance of α-/β-globin chains of adult hemoglobin (α₂β₂) leads to precipitation of unpaired α-globin chains and, eventually, to defective erythropoiesis. Since protein transduction domain (PTD) technology has emerged as a promising therapeutic approach, we produced a human recombinant β-globin chain in fusion with the TAT peptide and successfully transduced it into human proerythroid K-562 cells, deficient in mature β-globin chain. Notably, the produced human recombinant β-globin chain without the TAT peptide, used as internal negative control, failed to be transduced into K-562 cells under similar conditions. In silico studies complemented by SDS-PAGE, Western blotting, co-immunoprecipitation and LC-MS/MS analysis indicated that the transduced recombinant fusion TAT-β-globin protein interacts with the endogenous native α-like globins to form hemoglobin α₂β₂-like tetramers to a limited extent. Our findings provide evidence that recombinant TAT-β-globin is transmissible into proerythroid K-562 cells and can be potentially considered as an alternative protein therapeutic approach for β-thalassemias.

Rapid and Sensitive Assessment of Globin Chains for Gene and Cell Therapy of Hemoglobinopathies

The β-hemoglobinopathies sickle cell anemia and β-thalassemia are the focus of many gene-therapy studies. A key disease parameter is the abundance of globin chains because it indicates the level of anemia, likely toxicity of excess or aberrant globins, and therapeutic potential of induced or exogenous β-like globins. Reversed-phase high-performance liquid chromatography (HPLC) allows versatile and inexpensive globin quantification, but commonly applied protocols suffer from long run times, high sample requirements, or inability to separate murine from human β-globin chains. The latter point is problematic for in vivo studies with gene-addition vectors in murine disease models and mouse/human chimeras. This study demonstrates HPLC-based measurements of globin expression (1) after differentiation of the commonly applied human umbilical cord blood-derived erythroid progenitor-2 cell line, (2) in erythroid progeny of CD34+ cells for the analysis of clustered regularly interspaced short palindromic repeats/Cas9-mediated disruption of the globin regulator BCL11A, and (3) of transgenic mice holding the human β-globin locus. At run times of 8 min for separation of murine and human β-globin chains as well as of human γ-globin chains, and with routine measurement of globin-chain ratios for 12 nL of blood (tested for down to 0.75 nL) or of 300,000 in vitro differentiated cells, the methods presented here and any variant-specific adaptations thereof will greatly facilitate evaluation of novel therapy applications for β-hemoglobinopathies.

BCL11A mRNA Targeting by miR-210: A Possible Network Regulating γ-Globin Gene Expression

The involvement of microRNAs in the control of repressors of human γ-globin gene transcription has been firmly demonstrated, as described for the miR-486-3p mediated down-regulation of BCL11A. On the other hand, we have reported that miR-210 is involved in erythroid differentiation and, possibly, in γ-globin gene up-regulation. In the present study, we have identified the coding sequence of BCL11A as a possible target of miR-210. The following results sustain this hypothesis: (a) interactions between miR-210 and the miR-210 BCL11A site were demonstrated by SPR-based biomolecular interaction analysis (BIA); (b) the miR-210 site of BCL11A is conserved through molecular evolution; (c) forced expression of miR-210 leads to decrease of BCL11A-XL and increase of γ-globin mRNA content in erythroid cells, including erythroid precursors isolated from β-thalassemia patients. Our study suggests that the coding mRNA sequence of BCL11A can be targeted by miR-210. In addition to the theoretical point of view, these data are of interest from the applied point of view, supporting a novel strategy to inhibit BCL11A by mimicking miR-210 functions, accordingly with the concept supported by several papers and patent applications that inhibition of BCL11A is an efficient strategy for fetal hemoglobin induction in the treatment of β-thalassemia.

Eliminating HIV-1 Packaging Sequences from Lentiviral Vector Proviruses Enhances Safety and Expedites Gene Transfer for Gene Therapy

Lentiviral vector genomic RNA requires sequences that partially overlap wild-type HIV-1 gag and env genes for packaging into vector particles. These HIV-1 packaging sequences constitute 19.6% of the wild-type HIV-1 genome and contain functional cis elements that potentially compromise clinical safety. Here, we describe the development of a novel lentiviral vector (LTR1) with a unique genomic structure designed to prevent transfer of HIV-1 packaging sequences to patient cells, thus reducing the total HIV-1 content to just 4.8% of the wild-type genome. This has been achieved by reconfiguring the vector to mediate reverse-transcription with a single strand transfer, instead of the usual two, and in which HIV-1 packaging sequences are not copied. We show that LTR1 vectors offer improved safety in their resistance to remobilization in HIV-1 particles and reduced frequency of splicing into human genes. Following intravenous luciferase vector administration to neonatal mice, LTR1 sustained a higher level of liver transgene expression than an equivalent dose of a standard lentivirus. LTR1 vectors produce reverse-transcription products earlier and start to express transgenes significantly quicker than standard lentiviruses after transduction. Finally, we show that LTR1 is an effective lentiviral gene therapy vector as demonstrated by correction of a mouse hemophilia B model.

Lentiviral Transfer of γ-Globin with Fusion Gene NUP98-HOXA10HD Expands Hematopoietic Stem Cells and Ameliorates Murine β-Thalassemia

Recently, an engineered Homeobox-nucleoporin fusion gene, NUP98-HOXA10HD or NA10HD, was reported to expand and maintain murine hematopoietic stem cells (HSCs). We postulated that NA10HD would increase the number of human γ-globin-expressing cells to therapeutic levels. We developed a double gene lentiviral vector encoding both human γ-globin and NA10HD, which was used to transduce human peripheral blood CD34⁺ cells and increased engraftment 2- to 2.5-fold at 15 weeks post-transplantation in immunodeficient mice. In β-thalassemic mice transplanted with β-thalassemic HSCs transduced with the γ-globin/NA10HD vector, the number of fetal hemoglobin (HbF)-expressing cells was significantly increased after 3 months, leading to resolution of the anemia. Furthermore, the increases in HbF were maintained at 6 months and persisted after secondary transplantation. In addition, NA10HD enrichment of transduced HSCs led to HbF increases without affecting homeostasis of the white blood cell lineages. Our results suggest that NA10HD increases the number of γ-globin-transduced HSCs that engraft, leading to an elevated number of fetal hemoglobin-containing red cells. These effects of NA10HD provide an improved platform for testing of the therapeutic efficacy of novel globin vectors and provide further impetus to develop safe and effective methods for selective expansion of genetically modified cells.

Comparative genomics of canine hemoglobin genes reveals primacy of beta subunit delta in adult carnivores

Background

The main function of hemoglobin (Hb) is to transport oxygen in the circulation. It is among the most highly studied proteins due to its roles in physiology and disease, and most of our understanding derives from comparative research. There is great diversity in Hb gene evolution in placental mammals, mostly in the repertoire and regulation of the β-globin subunits. Dogs are an ideal model in which to study Hb genes because: 1) they are members of Laurasiatheria, our closest relatives outside of Euarchontoglires (including primates, rodents and rabbits), 2) dog breeds are isolated populations with their own Hb-associated genetics and diseases, and 3) their high level of health care allows for development of biomedical investigation and translation.

Results

We established that dogs have a complement of five α and five β-globin genes, all of which can be detected as spliced mRNA in adults. Strikingly, HBD, the allegedly-unnecessary adult β-globin protein in humans, is the primary adult β-globin in dogs and other carnivores; moreover, dogs have two active copies of the HBD gene. In contrast, the dominant adult β-globin of humans, HBB, has high sequence divergence and is expressed at markedly lower levels in dogs. We also showed that canine HBD and HBB genes are complex chimeras that resulted from multiple gene conversion events between them. Lastly, we showed that the strongest signal of evolutionary selection in a high-altitude breed, the Bernese Mountain Dog, lies in a haplotype block that spans the β-globin locus.

Conclusions

We report the first molecular genetic characterization of Hb genes in dogs. We found important distinctions between adult β-globin expression in carnivores compared to other members of Laurasiatheria. Our findings are also likely to raise new questions about the significance of human HBD. The comparative genomics of dog hemoglobin genes sets the stage for diverse research and translation.

Electronic supplementary material

The online version of this article (doi:10.1186/s12864-017-3513-0) contains supplementary material, which is available to authorized users.

One-Step Biallelic and Scarless Correction of a β-Thalassemia Mutation in Patient-Specific iPSCs without Drug Selection

Monogenic disorders (MGDs), which are caused by single gene mutations, have a serious effect on human health. Among these, β-thalassemia (β-thal) represents one of the most common hereditary hematological diseases caused by mutations in the human hemoglobin β (HBB) gene. The technologies of induced pluripotent stem cells (iPSCs) and genetic correction provide insights into the treatments for MGDs, including β-thal. However, traditional approaches for correcting mutations have a low efficiency and leave a residual footprint, which leads to some safety concerns in clinical applications. As a proof of concept, we utilized single-strand oligodeoxynucleotides (ssODNs), high-fidelity CRISPR/Cas9 nuclease, and small molecules to achieve a seamless correction of the β-41/42 (TCTT) deletion mutation in β thalassemia patient-specific iPSCs with remarkable efficiency. Additionally, off-target analysis and whole-exome sequencing results revealed that corrected cells exhibited a minimal mutational load and no off-target mutagenesis. When differentiated into hematopoietic progenitor cells (HPCs) and then further to erythroblasts, the genetically corrected cells expressed normal β-globin transcripts. Our studies provide the most efficient and safe approach for the genetic correction of the β-41/42 (TCTT) deletion in iPSCs for further potential cell therapy of β-thal, which represents a potential therapeutic avenue for the gene correction of MGD-associated mutants in patient-specific iPSCs.

CRISPR-Cas9 technology and its application in haematological disorders

The recent advent of the Clustered Regularly Interspaced Short Palindromic Repeats (CRISPR)-CRISPR associated protein 9 (Cas9) system for precise genome editing has revolutionized methodologies in haematology and oncology studies. CRISPR-Cas9 technology can be used to remove and correct genes or mutations, and to introduce site-specific therapeutic genes in human cells. Inherited haematological disorders represent ideal targets for CRISPR-Cas9-mediated gene therapy. Correcting disease-causing mutations could alleviate disease-related symptoms in the near future. The CRISPR-Cas9 system is also a useful tool for delineating molecular mechanisms involving haematological malignancies. Prior to the use of CRISPR-Cas9-mediated gene correction in humans, appropriate delivery systems with higher efficiency and specificity must be identified, and ethical guidelines for applying the technology with controllable safety must be established. Here, the latest applications of CRISPR-Cas9 technology in haematological disorders, current challenges and future directions are reviewed and discussed.

A validated cellular biobank for β-thalassemia

BACKGROUND

Cellular biobanking is a key resource for collaborative networks planning to use same cells in studies aimed at solving a variety of biological and biomedical issues. This approach is of great importance in studies on β-thalassemia, since the recruitment of patients and collection of specimens can represent a crucial and often limiting factor in the experimental planning.

METHODS

Erythroid precursor cells were obtained from 72 patients, mostly β-thalassemic, expanded and cryopreserved. Expression of globin genes was analyzed by real time RT-qPCR. Hemoglobin production was studied by HPLC.

RESULTS

In this paper we describe the production and validation of a Thal-Biobank constituted by expanded erythroid precursor cells from β-thalassemia patients. The biobanked samples were validated for maintenance of their phenotype after (a) cell isolation from same patients during independent phlebotomies, (b) freezing step in different biobanked cryovials, (c) thawing step and analysis at different time points. Reproducibility was confirmed by shipping the frozen biobanked cells to different laboratories, where the cells were thawed, cultured and analyzed using the same standardized procedures. The biobanked cells were stratified on the basis of their baseline level of fetal hemoglobin production and exposed to fetal hemoglobin inducers.

CONCLUSION

The use of biobanked cells allows stratification of the patients with respect to fetal hemoglobin production and can be used for determining the response to the fetal hemoglobin inducer hydroxyurea and to gene therapy protocols with reproducible results.

The potential of gene therapy approaches for the treatment of hemoglobinopathies: achievements and challenges

Hemoglobinopathies, including β-thalassemia and sickle cell disease (SCD), are a heterogeneous group of commonly inherited disorders affecting the function or levels of hemoglobin. Disease phenotype can be severe with substantial morbidity and mortality. Bone marrow transplantation is curative, but limited to those patients with an appropriately matched donor. Genetic therapy, which utilizes a patient's own cells, is thus an attractive therapeutic option. Numerous therapies are currently in clinical trials or in development, including therapies utilizing gene replacement therapy using lentiviruses and the latest gene editing techniques. In addition, methods are being developed that may be able to expand gene therapies to those with poor access to medical care, potentially significantly decreasing the global burden of disease.

Combining Single Strand Oligodeoxynucleotides and CRISPR/Cas9 to Correct Gene Mutations in β-Thalassemia-induced Pluripotent Stem Cells

β-Thalassemia (β-Thal) is one of the most common genetic diseases in the world. The generation of patient-specific β-Thal-induced pluripotent stem cells (iPSCs), correction of the disease-causing mutations in those cells, and then differentiation into hematopoietic stem cells offers a new therapeutic strategy for this disease. Here, we designed a CRISPR/Cas9 to specifically target the Homo sapiens hemoglobin β (HBB) gene CD41/42(-CTTT) mutation. We demonstrated that the combination of single strand oligodeoxynucleotides with CRISPR/Cas9 was capable of correcting the HBB gene CD41/42 mutation in β-Thal iPSCs. After applying a correction-specific PCR assay to purify the corrected clones followed by sequencing to confirm mutation correction, we verified that the purified clones retained full pluripotency and exhibited normal karyotyping. Additionally, whole-exome sequencing showed that the mutation load to the exomes was minimal after CRISPR/Cas9 targeting. Furthermore, the corrected iPSCs were selected for erythroblast differentiation and restored the expression of HBB protein compared with the parental iPSCs. This method provides an efficient and safe strategy to correct the HBB gene mutation in β-Thal iPSCs.

Human induced pluripotent stem cells for monogenic disease modelling and therapy

Recent and advanced protocols are now available to derive human induced pluripotent stem cells (hiPSCs) from patients affected by genetic diseases. No curative treatments are available for many of these diseases; thus, hiPSCs represent a major impact on patient' health. hiPSCs represent a valid model for the in vitro study of monogenic diseases, together with a better comprehension of the pathogenic mechanisms of the pathology, for both cell and gene therapy protocol applications. Moreover, these pluripotent cells represent a good opportunity to test innovative pharmacological treatments focused on evaluating the efficacy and toxicity of novel drugs. Today, innovative gene therapy protocols, especially gene editing-based, are being developed, allowing the use of these cells not only as in vitro disease models but also as an unlimited source of cells useful for tissue regeneration and regenerative medicine, eluding ethical and immune rejection problems. In this review, we will provide an up-to-date of modelling monogenic disease by using hiPSCs and the ultimate applications of these in vitro models for cell therapy. We consider and summarize some peculiar aspects such as the type of parental cells used for reprogramming, the methods currently used to induce the transcription of the reprogramming factors, and the type of iPSC-derived differentiated cells, relating them to the genetic basis of diseases and to their inheritance model.

Quality of life, clinical effectiveness, and satisfaction in patients with beta thalassemia major and sickle cell anemia receiving deferasirox chelation therapy

Objectives:

There is a need to remove excess iron with iron chelation therapy (ICT) to avoid the serious clinical sequelae associated with iron overload in patients with beta thalassemia major (BTM) and sickle cell anemia (SCA). Due to the effects of the diseases and their treatments, ICT is still a major reason for unsatisfactory compliance. The aim of this single-center observational study was to evaluate the quality of life, clinical effectiveness, and satisfaction in pediatric and adult patients with BTM and SCA receiving deferasirox (DFX) chelation therapy.

Methods:

In this study, 37 pediatric and 35 adult patients with BTM or SCA receiving DFX for at least 6 months participated. Upon receipt of Informed Consent Form, Case Report Form, Demographic Data Collection Form, Child Health Questionnaire-Parent Form, Life Quality Survey Short Form-36, and ICT Satisfaction Survey were used to obtain data for the effectiveness of ICT and parameters that may affect compliance to treatment and life quality of the participants.

Results:

As a main index for the effectiveness of DFX chelation therapy, serum ferritin levels were higher than the normal values in the patients receiving DFX. The increased ferritin levels were also associated with hematological and biochemical abnormalities. Our findings regarding quality of life and satisfaction with DFX chelation therapy indicated that the patients with BTM or SCA had lower scores. Overall, problems with treatment regimen and side effects appeared to be common causes of poor compliance to DFX chelation therapy.

Conclusions:

Our findings suggest that health care providers should be aware of the importance of monitoring iron load with timely initiation of DFX chelation therapy and ongoing adjustments to chelation regimens and/or transfusion methods to decrease hospitalizations and improve compliance to ICT of the patients with BTM and SCA.

Clinical Effect and Mechanism of Yisui Shengxue Granules in Thalassemia Patients with Mild, Moderate, or Severe Anemia

Yisui Shengxue granules, which is a Chinese traditional medicine, can increase hemoglobin, red blood cells, and Ret of thalassemia patients with mild, moderate, and severe anemia and thus relieve clinical anemia symptoms. Studies on mechanism found that Yisui Shengxue granules can increase the proliferation ability of hematopoietic stem cells. Emodin promoted colony forming of hematopoietic stem cells. Yisui Shengxue granules can increase the activity of GSH-PX in bone marrow blood and decreased the severity of inclusion bodies on the cytomembrane of RBCs. YSSXG attenuated anemia symptoms in patients with thalassemia mostly by increasing the proliferation of hematopoietic stem cells and decreasing the hemolysis of RBCs.

Gene therapy for hemoglobin disorders - a mini-review

Gene therapy by either gene insertion or editing is an exciting curative therapeutic option for monogenic hemoglobin disorders like sickle cell disease and β-thalassemia. The safety and efficacy of gene transfer techniques has markedly improved with the use of lentivirus vectors. The clinical translation of this technology has met with good success, although key limitations include number of engraftable transduced hematopoietic stem cells and adequate transgene expression that results in complete correction of β0 thalassemia major. This highlights the need to identify and address factors that might be contributing to the in-vivo survival of the transduced hematopoietic stem cells or find means to improve expression from current vectors. In this review, we briefly discuss the gene therapy strategies specific to hemoglobinopathies, the success of the preclinical models and the current status of gene therapy clinical trials.

Towards in vivo amplification: Overcoming hurdles in the use of hematopoietic stem cells in transplantation and gene therapy

With the advent of safer and more efficient gene transfer methods, gene therapy has become a viable solution for many inherited and acquired disorders. Hematopoietic stem cells (HSCs) are a prime cell compartment for gene therapy aimed at correcting blood-based disorders, as well as those amenable to metabolic outcomes that can effect cross-correction. While some resounding clinical successes have recently been demonstrated, ample room remains to increase the therapeutic output from HSC-directed gene therapy. In vivo amplification of therapeutic cells is one avenue to achieve enhanced gene product delivery. To date, attempts have been made to provide HSCs with resistance to cytotoxic drugs, to include drug-inducible growth modules specific to HSCs, and to increase the engraftment potential of transduced HSCs. This review aims to summarize amplification strategies that have been developed and tested and to discuss their advantages along with barriers faced towards their clinical adaptation. In addition, next-generation strategies to circumvent current limitations of specific amplification schemas are discussed.

The therapeutic potential of genome editing for β-thalassemia

The rapid advances in the field of genome editing using targeted endonucleases have called considerable attention to the potential of this technology for human gene therapy. Targeted correction of disease-causing mutations could ensure lifelong, tissue-specific expression of the relevant gene, thereby alleviating or resolving a specific disease phenotype. In this review, we aim to explore the potential of this technology for the therapy of β-thalassemia. This blood disorder is caused by mutations in the gene encoding the β-globin chain of hemoglobin, leading to severe anemia in affected patients. Curative allogeneic bone marrow transplantation is available only to a small subset of patients, leaving the majority of patients dependent on regular blood transfusions and iron chelation therapy. The transfer of gene-corrected autologous hematopoietic stem cells could provide a therapeutic alternative, as recent results from gene therapy trials using a lentiviral gene addition approach have demonstrated. Genome editing has the potential to further advance this approach as it eliminates the need for semi-randomly integrating viral vectors and their associated risk of insertional mutagenesis. In the following pages we will highlight the advantages and risks of genome editing compared to standard therapy for β-thalassemia and elaborate on lessons learned from recent gene therapy trials.

Development and characterization of K562 cell clones expressing BCL11A-XL: Decreased hemoglobin production with fetal hemoglobin inducers and its rescue with mithramycin

Induction of fetal hemoglobin (HbF) is considered a promising strategy in the treatment of β-thalassemia, in which production of adult hemoglobin (HbA) is impaired by mutations affecting the β-globin gene. Recent results indicate that B-cell lymphoma/leukemia 11A (BCL11A) is a major repressor of γ-globin gene expression. Therefore, disrupting the binding of the BCL11A transcriptional repressor complex to the γ-globin gene promoter provides a novel approach for inducing expression of the γ-globin genes. To develop a cellular screening system for the identification of BCL11A inhibitors, we produced K562 cell clones with integrated copies of a BCL11A-XL expressing vector. We characterized 12 K562 clones expressing different levels of BCL11A-XL and found that a clear inverse relationship does exist between the levels of BCL11A-XL and the extent of hemoglobinization induced by a panel of HbF inducers. Using mithramycin as an inducer, we found that this molecule was the only HbF inducer efficient in rescuing the ability to differentiate along the erythroid program, even in K562 cell clones expressing high levels of BCL11A-XL, suggesting that BCL11A-XL activity is counteracted by mithramycin.

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K562 clones were described with integrated copies of a BCL11A-XL expressing vector.

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B-Cell lymphoma/leukemia 11A-XL (BCL11A-XL) levels inversely correlate with the extent of hemoglobin induction.

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Mithramycin induces γ-globin genes even in K562 clones expressing high levels of BCL11A-XL.

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K562(BCL11A-XL) clones might be useful in identifying fetal hemoglobin inducers acting on BCL11A.

5p deletions: Current knowledge and future directions

Disorders resulting from 5p deletions (5p-) were first recognized by Lejeune et al. in 1963 [Lejeune et al. (1963); C R Hebd Seances Acad Sci 257:3098-3102]. 5p- is caused by partial or total deletion of the short arm of chromosome 5. The most recognizable phenotype is characterized by a high-pitched cry, dysmorphic features, poor growth, and developmental delay. This report reviews 5p- disorders and their molecular basis. Hemizygosity for genes located within this region have been implicated in contributing to the phenotype. A review of the genes on 5p which may be dosage sensitive is summarized. Because of the growing knowledge of these specific genes, future directions to explore potential targeted therapies for individuals with 5p- are discussed. © 2015 Wiley Periodicals, Inc.