The beta-thalassemias and sickle cell disease are severe congenital anemias that are caused by mutations that alter the production of the beta chain of hemoglobin. Allogeneic hematopoietic stem cell ...(HSC) transplantation is curative, but this therapeutic option is not available to the majority of patients. The transfer of a functional globin gene in autologous HCSs thus represents a highly attractive alternative treatment. This strategy, simple in principle, raises major challenges in terms of controlling the expression of the globin transgene, which ideally should be erythroid specific, differentiation-stage restricted, elevated, position independent, and sustained over time. Using lentiviral vectors, we have demonstrated that an optimised combination of proximal and distal transcriptional control elements permits lineage-specific, elevated expression of the beta-globin gene, resulting in therapeutic hemoglobin production and correction of anemia in beta-thalassemic mice. Several groups have now confirmed and extended these findings in various mouse models of severe hemoglobinopathies, thus generating enthusiasm for a genetic treatment based on globin gene transfer. Furthermore, globin vectors represent a general paradigm for the regulation of transgene function and the improvement of vector safety by restricting transgene expression to the differentiated progeny within a single lineage, thereby reducing the risk of activating oncogenes in hematopoietic progenitors. Here we review the principles underlying the genesis of regulated vectors for stem cell therapy.
Nonsense mutations, giving rise to UAA, UGA and UAG stop codons within the coding region of mRNAs, promote premature translational termination and are the leading cause of approx. 30% of inherited ...diseases, including cystic fibrosis, Duchenne muscular dystrophy and thalassaemia. For instance, in beta(0)39-thalassaemia the CAG (glutamine) codon is mutated to the UAG stop codon, leading to premature translation termination and to mRNA destabilization through the well-described NMD (nonsense-mediated mRNA decay). In order to develop an approach facilitating translation and, therefore, protection from NMD, aminoglycoside antibiotics have been tested on mRNAs carrying premature stop codons. These drugs decrease the accuracy in the codon-anticodon base-pairing, inducing a ribosomal read-through of the premature termination codons. Interestingly, recent papers have described drugs designed and produced for suppressing premature translational termination, inducing a ribosomal read-through of premature but not normal termination codons. These findings have introduced new hopes for the development of a pharmacological approach to the therapy of beta(0)39-thalassaemia. In this context, we started the development of a cellular model of the beta(0)39-thalassaemia mutation that could be used for the screening of a high number of aminoglycosides and analogous molecules. To this aim, we produced a lentiviral construct containing the beta(0)39-thalassaemia globin gene under a minimal LCR (locus control region) control and used this construct for the transduction of K562 cells, subsequently subcloned, with the purpose to obtain several K562 clones with different integration copies of the construct. These clones were then treated with Geneticin (also known as G418) and other aminoglycosides and the production of beta-globin was analysed by FACS analysis. The results obtained suggest that this experimental system is suitable for the characterization of correction of the beta(0)39-globin mutation causing beta-thalassaemia.
The beta -thalassemias and sickle cell disease are severe congenital anemias that are caused by the defective synthesis of the beta chain of hemoglobin. Allogeneic hematopoietic stem cell (HSC) ...transplantation is curative, but this therapeutic option is not available to the majority of patients. The transfer of a regulated beta -globin gene in autologous HCSs thus represents a highly attractive alternative treatment. This strategy, simple in principle, raises major challenges in terms of controlling transgene expression, which ideally should be erythroid-specific, differentiation stage-restricted, elevated, position-independent, and sustained over time. Using lentiviral vectors, we recently demonstrated that an optimized combination of proximal and distal transcriptional control elements permits lineage-specific and elevated expression of the beta -globin gene, resulting in therapeutic hemoglobin production and correction of anemia in beta -thalassemic mice. Several groups have now confirmed and extended these findings in various mouse models of severe hemoglobinopathies, thus generating enthusiasm for a genetic treatment based on globin gene transfer. Furthermore, globin vectors provide a paradigm for improving vector safety by restricting transgene expression to the differentiated progeny within a single lineage, thereby reducing the risk of activating oncogenes in hematopoietic progenitors. Here we review the principles underlying the genesis of regulated vectors for stem cell therapy.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, UILJ, UKNU, UL, UM, UPUK
In higher eukaryotes the mechanism controlling initiation of DNA replication remains largely unknown. New technologies are needed to shed light on how DNA replication initiates along the genome in ...specific regions. To identify the human DNA sequence requirements for initiation of replication, we developed a new method that allows selection of replication origins starting from large genomic regions of human DNA. We repeatedly isolated 15 new putative replication origins (PROs) from a human DNA region of 500 kb in which 17 genes have previously been characterized. Fine-mapping of these PROs showed that DNA replication can initiate at many specific points along actively transcribed DNA in the cell lines used for our selection. In conclusion, in this paper we describe a new method to identify PROs that suggests that the availability of initiation sites is dependent on the transcriptional state of the DNA.
Hemoglobinopathies are inherited genetic conditions that originate from a lack or malfunction of the adult hemoglobin protein. Thalassemia and other diseases associated with β-globin abnormal amino ...acid sequences—such as sickle cell disease (SCD) and hemoglobin E (HbE)—are some of the most common hemoglobinopathies. Severe anemia combined with complications that arise in the most affected patients raises the necessity for a cure to restore hemoglobin function. The current routine therapies for these conditions, namely transfusion and iron chelation, have significantly improved the quality of life in patients over the years, but still fail to address the underlying cause of the diseases. A curative option, allogeneic bone marrow (BM) transplantation, is available, but is limited by the availability of suitable donors and graft-versus-host disease (GVHD). Gene therapy offers an alternative approach to cure patients with hemoglobinopathies and aims at the direct recovery of the hemoglobin function via globin gene transfer. In the last two decades, gene transfer tools based on lentiviral vector development have been significantly improved, and proven curative in several animal models for SCD and thalassemia. As a result, clinical trials are in progress and three patients have been successfully treated with this approach. However, there are still frontiers to explore that might improve this approach: the stoichiometry between the transgenic hemoglobin and endogenous hemoglobin with respect to the different globin genetic mutations; donor cell sourcing, such as the use of induced pluripotent stem cells (iPSCs); and the use of safer gene insertion methods to prevent oncogenesis. This review will provide insights into the different lentiviral gene therapy approaches in mouse models and human cells; current and planned clinical trials; hurdles to overcome for clinical trials, such as myeloablation toxicity, insertional oncogenesis, and high vector expression; and future perspectives for gene therapy, including safe harbors, reactivation of fetal hemoglobin, and iPSC technology.
We have developed a methodology for identification and fine mapping of chromosome-specific transcripts. Combining digestion of DNA with different restriction enzymes, ligation to “bubble” linkers, ...and PCR amplification fromAluand “bubble” primers, we have synthesized human chromosome 1-specific sequences from DNA of a somatic cell hybrid, A9Neo1. After hybridization to human fetal brain cDNA, we could efficiently capture chromosome 1-specific cDNAs. The cDNAs were sequenced and used as probes in hybridizations to high-density filters containing the arrayed CEPH Mega-YAC library and to the arrayed cDNA library from infant brain made by B. Soares, which has been extensively sequenced. By this approach we have been able to select chromosome 1-specific cDNAs, to map them to chromosome 1 YAC contigs, and to identify and map corresponding longer cDNAs and ESTs.
PDF
