miRNA Expression Associated with HbF in Saudi Sickle Cell Anemia.

Background and Objectives: Sickle cell anemia (SCA) is a hereditary monogenic disease due to a single ß-globin gene mutation that codes for the production of sickle hemoglobin. Its phenotype is modulated by fetal hemoglobin (HbF), a product of γ-globin genes. Exploring the molecules that regulate γ-globin genes at both transcriptional and translational levels, including microRNA (miRNA), might help identify alternative therapeutic targets. Materials and Methods: Using next-generation sequencing we identified pre-miRNAs and mature miRNA expression signatures associated with different HbF levels in patients homozygous for the sickle hemoglobin gene. The involvement of identified miRNAs in potential SCD-related pathways was investigated with the DIANA TOOL and miRWalk 2.0 database. Results: miR-184 were most highly upregulated in reticulocytes. miR-3609 and miR-483-5p were most highly downregulated in sickle cell anemia with high HbF. miR-370-3p that regulates LIN28A, and miR-451a which is effective in modulating α- and ß- globin levels were also significantly upregulated. miRNA targeted gene pathway interaction identified BCL7A, BCL2L1, LIN28A, KLF6, GATA6, solute carrier family genes and ZNF genes associated with erythropoiesis, cell cycle regulation, glycosphingolipid biosynthesis, cAMP, cGMP-PKG, mTOR, MAPK and PI3K-AKT signaling pathways and cancer pathways. Conclusions: miRNA signatures and their target genes identified novel miRNAs that could regulate fetal hemoglobin production and might be exploited therapeutically.

Genome-based therapeutic interventions for ß-type hemoglobinopathies.

For decades, various strategies have been proposed to solve the enigma of hemoglobinopathies, especially severe cases. However, most of them seem to be lagging in terms of effectiveness and safety. So far, the most prevalent and promising treatment options for patients with ß-types hemoglobinopathies, among others, predominantly include drug treatment and gene therapy. Despite the significant improvements of such interventions to the patient's quality of life, a variable response has been demonstrated among different groups of patients and populations. This is essentially due to the complexity of the disease and other genetic factors. In recent years, a more in-depth understanding of the molecular basis of the ß-type hemoglobinopathies has led to significant upgrades to the current technologies, as well as the addition of new ones attempting to elucidate these barriers. Therefore, the purpose of this article is to shed light on pharmacogenomics, gene addition, and genome editing technologies, and consequently, their potential use as direct and indirect genome-based interventions, in different strategies, referring to drug and gene therapy. Furthermore, all the latest progress, updates, and scientific achievements for patients with ß-type hemoglobinopathies will be described in detail.

Lentiviral vector ALS20 yields high hemoglobin levels with low genomic integrations for treatment of beta-globinopathies.

Ongoing clinical trials for treatment of beta-globinopathies by gene therapy involve the transfer of the beta-globin gene, which requires integration of three to four copies per genome in most target cells. This high proviral load may increase genome toxicity, potentially limiting the safety of this therapy and relegating its use to total body myeloablation. We hypothesized that introducing an additional hypersensitive site from the locus control region, the complete sequence of the second intron of the beta-globin gene, and the ankyrin insulator may enhance beta-globin expression. We identified a construct, ALS20, that synthesized significantly higher adult hemoglobin levels than those of other constructs currently used in clinical trials. These findings were confirmed in erythroblastic cell lines and in primary cells isolated from sickle cell disease patients. Bone marrow transplantation studies in beta-thalassemia mice revealed that ALS20 was curative at less than one copy per genome. Injection of human CD34+ cells transduced with ALS20 led to safe, long-term, and high polyclonal engraftment in xenograft experiments. Successful treatment of beta-globinopathies with ALS20 could potentially be achieved at less than two copies per genome, minimizing the risk of cytotoxic events and lowering the intensity of myeloablation.

Production and Transduction of a Human Recombinant ß-Globin Chain into Proerythroid K-562 Cells To Replace Missing Endogenous ß-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. ß-Thalassemias are severe congenital hemoglobinopathies, characterized by deficiency or reduced production of the adult ß-globin chain. The resulting imbalance of α-/ß-globin chains of adult hemoglobin (α2ß2) 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 ß-globin chain in fusion with the TAT peptide and successfully transduced it into human proerythroid K-562 cells, deficient in mature ß-globin chain. Notably, the produced human recombinant ß-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-ß-globin protein interacts with the endogenous native α-like globins to form hemoglobin α2ß2-like tetramers to a limited extent. Our findings provide evidence that recombinant TAT-ß-globin is transmissible into proerythroid K-562 cells and can be potentially considered as an alternative protein therapeutic approach for ß-thalassemias.

Wake-up Sleepy Gene: Reactivating Fetal Globin for ß-Hemoglobinopathies.

Disorders in hemoglobin (hemoglobinopathies) were the first monogenic diseases to be characterized and remain among the most common and best understood genetic conditions. Moreover, the study of the ß-globin locus provides a textbook example of developmental gene regulation. The fetal γ-globin genes (HBG1/HBG2) are ordinarily silenced around birth, whereupon their expression is replaced by the adult ß-globin genes (HBB primarily and HBD). Over 50 years ago it was recognized that mutations that cause lifelong persistence of fetal γ-globin expression ameliorate the debilitating effects of mutations in ß-globin. Since then, research has focused on therapeutically reactivating the fetal γ-globin genes. Here, we summarize recent discoveries, focusing on the influence of genome editing technologies, including CRISPR-Cas9, and emerging gene therapy approaches.

Recent Progress on Genetic Diagnosis and Therapy for ß-Thalassemia in China and Around the World.

Thalassemia is a recessive monogenic hematological disease associated with reduced amounts of functional hemoglobin caused by mutations/deletions in at least one of the globin genes. This disease has attracted significant attention throughout the years in terms of genetic diagnosis and developments in gene and cell therapy. Here, recent progress is reviewed in the genetic diagnosis and development of therapeutics for thalassemia, particularly ß-thalassemia, in China and around the world.