scholarly journals Cellular and membrane properties of alpha and beta thalassemic erythrocytes are different: implication for differences in clinical manifestations

Blood ◽  
1989 ◽  
Vol 74 (6) ◽  
pp. 2194-2202 ◽  
Author(s):  
SL Schrier ◽  
E Rachmilewitz ◽  
N Mohandas
Keyword(s):  
Cell Density ◽  
Mechanical Stability ◽  
Membrane Properties ◽  
Beta Thalassemia ◽  
Normal Density ◽  
Beta Globin ◽  
Globin Chains ◽  
Alpha Thalassemia ◽  
Dynamic Rigidity ◽  
Membrane Skeletons

Abstract To define how excess unpaired alpha- and beta-globin chains in severe beta-thalassemia and severe alpha-thalassemia interacting with the membrane might alter cellular and membrane properties, we performed a series of biophysical and biochemical analyses on erythrocytes obtained from affected patients. Detailed analysis of cellular and membrane deformability characteristics showed that both forms of thalassemic erythrocytes have excess surface area in relation to cell volume and increased membrane dynamic rigidity. The deformability characteristics of thalassemic erythrocytes in hypertonic media differed significantly from that of normal erythrocytes of identical cell density. These findings suggest that dynamic rigidity of thalassemic erythrocytes is influenced not only by cytoplasmic viscosity determined by cell hemoglobin concentration but also by the extent and type of globin interacting with the membrane. In contrast to the above-noted similarities, major differences were noted in the mechanical stability of the alpha- and beta-thalassemic membranes and in their state of cell hydration. While the mechanical stability of alpha-thalassemic membranes was normal or marginally elevated, the stability of beta- thalassemic membranes was markedly decreased to half the normal value. Cell-density analysis showed that the alpha-thalassemic erythrocytes were uniformly less dense than normal, while beta-thalassemic erythrocytes had a broad-density distribution, with all populations having both lower and higher than normal density values, implying cellular dehydration in beta-thalassemia and not in alpha-thalassemia. Membrane-protein analysis revealed that excess globin chains were bound to the membrane skeletons of both alpha- and beta-thalassemic erythrocytes, with the highest amounts being found in membrane skeletons derived from erythrocytes of splenectomized individuals with beta-thalassemia intermedia. These data demonstrate that interaction of excess alpha- and beta-globin chains with membranes produces different cellular changes and suggest that the observed differences in the pathophysiology of alpha- and beta-thalassemias may be related to different cellular effects induced by the excess in beta- and alpha- globin chains.

scholarly journals Cellular and membrane properties of alpha and beta thalassemic erythrocytes are different: implication for differences in clinical manifestations

Blood ◽  
1989 ◽  
Vol 74 (6) ◽  
pp. 2194-2202 ◽  
Author(s):  
SL Schrier ◽  
E Rachmilewitz ◽  
N Mohandas
Keyword(s):  
Cell Density ◽  
Mechanical Stability ◽  
Membrane Properties ◽  
Beta Thalassemia ◽  
Normal Density ◽  
Beta Globin ◽  
Globin Chains ◽  
Alpha Thalassemia ◽  
Dynamic Rigidity ◽  
Membrane Skeletons

To define how excess unpaired alpha- and beta-globin chains in severe beta-thalassemia and severe alpha-thalassemia interacting with the membrane might alter cellular and membrane properties, we performed a series of biophysical and biochemical analyses on erythrocytes obtained from affected patients. Detailed analysis of cellular and membrane deformability characteristics showed that both forms of thalassemic erythrocytes have excess surface area in relation to cell volume and increased membrane dynamic rigidity. The deformability characteristics of thalassemic erythrocytes in hypertonic media differed significantly from that of normal erythrocytes of identical cell density. These findings suggest that dynamic rigidity of thalassemic erythrocytes is influenced not only by cytoplasmic viscosity determined by cell hemoglobin concentration but also by the extent and type of globin interacting with the membrane. In contrast to the above-noted similarities, major differences were noted in the mechanical stability of the alpha- and beta-thalassemic membranes and in their state of cell hydration. While the mechanical stability of alpha-thalassemic membranes was normal or marginally elevated, the stability of beta- thalassemic membranes was markedly decreased to half the normal value. Cell-density analysis showed that the alpha-thalassemic erythrocytes were uniformly less dense than normal, while beta-thalassemic erythrocytes had a broad-density distribution, with all populations having both lower and higher than normal density values, implying cellular dehydration in beta-thalassemia and not in alpha-thalassemia. Membrane-protein analysis revealed that excess globin chains were bound to the membrane skeletons of both alpha- and beta-thalassemic erythrocytes, with the highest amounts being found in membrane skeletons derived from erythrocytes of splenectomized individuals with beta-thalassemia intermedia. These data demonstrate that interaction of excess alpha- and beta-globin chains with membranes produces different cellular changes and suggest that the observed differences in the pathophysiology of alpha- and beta-thalassemias may be related to different cellular effects induced by the excess in beta- and alpha- globin chains.

scholarly journals Globin-chain specificity of oxidation-induced changes in red blood cell membrane properties

Blood ◽  
1992 ◽  
Vol 79 (6) ◽  
pp. 1586-1592 ◽  
Author(s):  
SL Schrier ◽  
N Mohandas
Keyword(s):  
Membrane Damage ◽  
Membrane Skeleton ◽  
Material Behavior ◽  
Membrane Properties ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Globin Chain ◽  
Globin Chains ◽  
Alpha Globin

Abstract We have previously shown that excess unpaired alpha- and beta-globin chains in severe alpha- and beta-thalassemia interacting with the membrane skeleton induce different changes in membrane properties of red blood cells (RBCs) in these two phenotypes. We suggest that these differences in membrane material behavior may reflect the specificity of the membrane damage induced by alpha- and beta-globin chains. To further explore this hypothesis, we sought in vitro models that induce similar membrane alterations in normal RBCs. We found that treatment of normal RBCs with phenylhydrazine produced rigid and mechanically unstable membranes in conjunction with selective association of oxidized alpha-globin chains with the membrane skeleton, features characteristic of RBCs in severe beta-thalassemia. Methylhydrazine, in contrast, induced selective association of oxidized beta-globin chains with the membrane skeleton and produced rigid but hyperstable membranes, features that mimicked those of RBCs in severe alpha- thalassemia. These findings suggest that consequences of oxidation induced by globin chains are quite specific in that those agents that cause alpha-globin chain accumulation at the membrane produce rigid but mechanically unstable membranes, whereas membrane accumulation of beta- globin chains results in rigid but mechanically stable membranes. These in vitro experiments lend further support to the hypothesis that membrane-associated alpha- and beta-chains induce oxidative damage to highly specific different skeletal components and that the specificity of this skeletal damage accounts for the differences in material membrane properties of these oxidatively attacked RBCs and perhaps of alpha- and beta-thalassemic RBCs as well.

scholarly journals Globin-chain specificity of oxidation-induced changes in red blood cell membrane properties

Blood ◽  
1992 ◽  
Vol 79 (6) ◽  
pp. 1586-1592 ◽  
Author(s):  
SL Schrier ◽  
N Mohandas
Keyword(s):  
Membrane Damage ◽  
Membrane Skeleton ◽  
Material Behavior ◽  
Membrane Properties ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Globin Chain ◽  
Globin Chains ◽  
Alpha Globin

We have previously shown that excess unpaired alpha- and beta-globin chains in severe alpha- and beta-thalassemia interacting with the membrane skeleton induce different changes in membrane properties of red blood cells (RBCs) in these two phenotypes. We suggest that these differences in membrane material behavior may reflect the specificity of the membrane damage induced by alpha- and beta-globin chains. To further explore this hypothesis, we sought in vitro models that induce similar membrane alterations in normal RBCs. We found that treatment of normal RBCs with phenylhydrazine produced rigid and mechanically unstable membranes in conjunction with selective association of oxidized alpha-globin chains with the membrane skeleton, features characteristic of RBCs in severe beta-thalassemia. Methylhydrazine, in contrast, induced selective association of oxidized beta-globin chains with the membrane skeleton and produced rigid but hyperstable membranes, features that mimicked those of RBCs in severe alpha- thalassemia. These findings suggest that consequences of oxidation induced by globin chains are quite specific in that those agents that cause alpha-globin chain accumulation at the membrane produce rigid but mechanically unstable membranes, whereas membrane accumulation of beta- globin chains results in rigid but mechanically stable membranes. These in vitro experiments lend further support to the hypothesis that membrane-associated alpha- and beta-chains induce oxidative damage to highly specific different skeletal components and that the specificity of this skeletal damage accounts for the differences in material membrane properties of these oxidatively attacked RBCs and perhaps of alpha- and beta-thalassemic RBCs as well.

scholarly journals Characterization and comparison of the red blood cell membrane damage in severe human alpha- and beta-thalassemia

Blood ◽  
1992 ◽  
Vol 79 (4) ◽  
pp. 1058-1063 ◽  
Author(s):  
R Advani ◽  
S Sorenson ◽  
E Shinar ◽  
W Lande ◽  
E Rachmilewitz ◽  
...  
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Membrane Damage ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Cell Membrane Damage ◽  
Protein 4.1 ◽  
Globin Chains ◽  
Alpha Thalassemia ◽  
Alpha Globin

Abstract The aim of the present work was to understand the pathophysiology of the severe human thalassemias as represented by beta-thalassemia intermedia and hemoglobin (Hb) H (alpha-thalassemia) disease. We have previously shown that the material properties of the red blood cell (RBC) and its membrane differ in severe alpha- and beta-thalassemia, and we now show that this difference is probably caused by accumulation of alpha-globin chains at the cytoskeleton in beta-thalassemia, whereas beta-globin chains are associated with the cytoskeleton in alpha- thalassemia. In both alpha- and beta-thalassemia, some of these globin chains have become oxidized as evidenced by loss of the free thiols. Furthermore, there is similar evidence of oxidation of protein 4.1 in beta-thalassemia, whereas beta-spectrin appears to be subject to oxidation in alpha-thalassemia. These observations support the idea that the association of partly oxidized globin chains with the cytoskeleton results in oxidation of adjacent skeletal proteins. The abnormality of protein 4.1 in beta-thalassemia is consistent with a prior observation, and is also in accord with the known importance of protein 4.1 in maintenance of membrane stability, a property that is abnormal in beta-thalassemic membranes.

scholarly journals Characterization and comparison of the red blood cell membrane damage in severe human alpha- and beta-thalassemia

Blood ◽  
1992 ◽  
Vol 79 (4) ◽  
pp. 1058-1063 ◽  
Author(s):  
R Advani ◽  
S Sorenson ◽  
E Shinar ◽  
W Lande ◽  
E Rachmilewitz ◽  
...  
Keyword(s):  
Blood Cell ◽  
Red Blood Cell ◽  
Membrane Damage ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Cell Membrane Damage ◽  
Protein 4.1 ◽  
Globin Chains ◽  
Alpha Thalassemia ◽  
Alpha Globin

The aim of the present work was to understand the pathophysiology of the severe human thalassemias as represented by beta-thalassemia intermedia and hemoglobin (Hb) H (alpha-thalassemia) disease. We have previously shown that the material properties of the red blood cell (RBC) and its membrane differ in severe alpha- and beta-thalassemia, and we now show that this difference is probably caused by accumulation of alpha-globin chains at the cytoskeleton in beta-thalassemia, whereas beta-globin chains are associated with the cytoskeleton in alpha- thalassemia. In both alpha- and beta-thalassemia, some of these globin chains have become oxidized as evidenced by loss of the free thiols. Furthermore, there is similar evidence of oxidation of protein 4.1 in beta-thalassemia, whereas beta-spectrin appears to be subject to oxidation in alpha-thalassemia. These observations support the idea that the association of partly oxidized globin chains with the cytoskeleton results in oxidation of adjacent skeletal proteins. The abnormality of protein 4.1 in beta-thalassemia is consistent with a prior observation, and is also in accord with the known importance of protein 4.1 in maintenance of membrane stability, a property that is abnormal in beta-thalassemic membranes.

scholarly journals Molecular analysis of beta zero-thalassemia intermedia in Sardinia

Blood ◽  
1989 ◽  
Vol 74 (2) ◽  
pp. 823-827 ◽  
Author(s):  
R Galanello ◽  
E Dessi ◽  
MA Melis ◽  
M Addis ◽  
MA Sanna ◽  
...  
Keyword(s):  
Nonsense Mutation ◽  
Frameshift Mutation ◽  
Globin Gene ◽  
Thalassemia Major ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Thalassemia Intermedia ◽  
Mild Phenotype ◽  
Beta Globin Gene ◽  
Alpha Thalassemia

Abstract In this study we have carried out alpha- and beta-globin gene analysis and defined the beta-globin gene polymorphisms in a group of patients with thalassemia intermedia of Sardinian descent. A group of patients (109) with thalassemia major of the same origin served as control. Characterization of the beta-thalassemia mutation showed either a frameshift mutation at codon 6 or a codon 39 nonsense mutation. We found that homozygotes for the frameshift mutation at codon 6 or compound heterozygotes for this mutation and for the codon 39 nonsense mutation develop thalassemia intermedia more frequently than thalassemia major. The frameshift mutation at codon 6 was associated with haplotype IX that contains the C-T change at position -158 5′ to the G gamma globin gene implicated in high gamma chain production and thus the mild phenotype. In patients' homozygotes for codon 39 nonsense mutation, those with thalassemia intermedia more frequently had the two- gene deletion form of alpha-thalassemia, or functional loss of the alpha 2 gene as compared with those with thalassemia major. In a few siblings with thalassemia major and intermedia, the thalassemia intermedia syndrome correlated with the presence of the -alpha/-alpha genotype. No cause for the mild phenotype was detected in the majority of patients who had not inherited either haplotype IX or alpha- thalassemia.

scholarly journals Oxidative damage and erythrocyte membrane transport abnormalities in thalassemias

Blood ◽  
1994 ◽  
Vol 84 (1) ◽  
pp. 315-320 ◽  
Author(s):  
O Olivieri ◽  
L De Franceschi ◽  
MD Capellini ◽  
D Girelli ◽  
R Corrocher ◽  
...  
Keyword(s):  
Oxidative Damage ◽  
Membrane Transport ◽  
Blood Cells ◽  
Experimental Models ◽  
Beta Thalassemia ◽  
Human Red Blood Cells ◽  
Globin Chains ◽  
Alpha Thalassemia ◽  
Normal Human ◽  
Increased Activity

Abstract Oxidative damage induced by free globin chains has been implicated in the pathogenesis of the membrane abnormalities observed in alpha and beta thalassemia. We have evaluated transport of Na+ and K+ in erythrocytes of patients with thalassemias as well as in two experimental models that use normal human red blood cells, one for alpha thalassemia (methylhydrazine treatment, alpha thalassemia like) and one for beta thalassemia (phenylhydrazine treatment, beta thalassemia like). With the exception of the Na-K pump, similar alterations in membrane transport were observed in thalassemia and thalassemia-like erythrocytes. These were: increased K-Cl cotransport, Na-Li countertransport and reduced Na-K-Cl cotransport. The Na-K pump was reduced in thalassemia-like cells, whereas it was increased in severe alpha thalassemia and in beta thalassemia cells. The increased K- Cl cotransport activity could be observed in light and dense fractions of beta-thalassemic cells. K-Cl cotransport in thalassemic and thalassemia-like erythrocytes was partially inhibited by [(dihydro- indenyl) oxy] alkanoic acid and completely abolished by dithiothreitol. Thus, oxidative damage represents an important factor in the increased activity of the K-Cl cotransport observed in thalassemias, and of the K+ loss observed in beta-thalassemia erythrocytes.

scholarly journals Investigating Zeta Globin Gene Expression to Develop a Potential Therapy for Alpha Thalassemia Major

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 3-4
Author(s):  
Georgia L. Gregory ◽  
Beeke Wienert ◽  
Marisa Schwab ◽  
Billie Rachael Lianoglou ◽  
Roger P. Hollis ◽  
...  
Keyword(s):  
Board Of Directors ◽  
Globin Gene ◽  
Thalassemia Major ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Wild Type ◽  
Advisory Committees ◽  
Alpha Thalassemia ◽  
Alpha Globin ◽  
Zeta Globin Gene

Introduction: Alpha globin mutations are very common worldwide, and the severity of resulting anemia depends on the number and type of mutated alleles. While the 4 gene mutation (alpha thalassemia major, ATM) was previously deemed fatal except in rare cases, emerging evidence indicates that survival to birth and good postnatal outcomes are possible with in utero transfusions. We hypothesized that the embryonic zeta globin gene, which is expressed early in gestation prior to alpha globin, may compensate for the lack of alpha globin and that induction of zeta globin after it has naturally been silenced may become a new therapy for patients with ATM. Methods: We evaluated mutations in the UCSF international registry of patients with ATM to understand factors related to patient survival with and without in utero transfusions. We then engineered Human Umbilical Cord Derived Erythroid Progenitor Cells (HUDEP-2 cells) carrying the common SEA alpha globin deletion, in which zeta globin expression is preserved (H-SEA), as well as those on which the zeta globin genes were deleted (HBZ-/-) using CRISPR-Cas9. We evaluated the expression of alpha and zeta globins using qPCR, Western blot, and flow cytometry. We generated lentiviral vectors expressing zeta globin under the control of beta-globin promoters to examine changes in both zeta and alpha globin in a dynamic way. Results: None of the registry patients who survived to birth spontaneously (n=11) had a mutation that involves a concomitant deletion in zeta globin (such as the -FIL, -THAI, or -MEDII mutation), while alpha globin mutations extending into the zeta globin gene were found in 14 of 37 (38%) patients who were diagnosed prenatally, suggesting that the presence of zeta globin may play a role in the ability to survive to birth without fetal therapy. Interestingly, we found that H-SEA clones express higher levels of zeta globin than WT cells, as illustrated by quantitative real-time PCR (Fig 1A), Western blot (Fig 1B) and flow cytometry (Fig 1C). These cells also developed beta globin dimers due to excess unpaired beta-globin chains, as demonstrated by Western blotting with and without reducing agents, indicating that they are an appropriate cell model for ATM. We next generated HUDEP-2 clones lacking zeta globin (HBZ KO) and transduced these clones with lentiviral vectors expressing high levels of zeta globin (lenti-zeta) (Fig 1D). Western blotting revealed that increasing the levels of zeta globin in these cells resulted in decreased expression of alpha globin, suggesting reciprocal control between these genes (Fig 1E). Most importantly, we saw a reduction in toxic beta-globin dimers in H-SEA cells expressing high levels of zeta-globin after transduction with lenti-zeta, suggesting that zeta globin could functionally replace the missing alpha-globin (Fig 1 F,G). To understand transcriptomic differences in H-SEA cells that may result in increased zeta globin expression, we performed bulk RNA sequencing of wild type and H-SEA clones. We confirmed that zeta expression is significantly upregulated in H-SEA compared to wild type (log2 fold change of 4.25, p=2.24E-38). Pathway analysis of differentially expressed genes is ongoing. Conclusions: Our international patient registry suggests that expression of zeta globin may play a role in the spontaneous survival to birth in a subset of patients. Zeta globin expression is increased in the setting of H-SEA cells in vitro, and restoration of zeta expression by lentivirus results in a reduction of toxic beta globin dimers in these ATM cells. Furthermore, expressing zeta globin at high levels in H-WT cells decreased alpha globin expression, suggesting a reciprocal regulation of these two genes. This concept is similar to the relationship between fetal gamma and adult beta globins which has been exploited for therapeutic editing approaches in patients with beta-thalassemia. At this point, the natural repressor of zeta globin is not yet known, but our data suggests that a strategy of upregulating zeta globin could potentially be developed to mimic the ongoing trials of using the BCL11A repressor to induce gamma globin in patients with beta thalassemia and sickle cell disease. Disclosures Wienert: Integral Medicines: Current Employment. Kohn:Allogene Therapeutics: Consultancy, Membership on an entity's Board of Directors or advisory committees; Orchard Therapeutics: Consultancy, Patents & Royalties, Research Funding. MacKenzie:Acrigen: Membership on an entity's Board of Directors or advisory committees; Ultragenyx: Research Funding.

Alpha Hemoglobin Stabilizing Protein (AHSP) Optimizes Hemoglobin A Synthesis by Maintaining a Pool of Viable Alpha Globin Subunits.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 650-650
Author(s):  
Xiang Yu ◽  
Yi Kong ◽  
Louis C. Dore ◽  
Anne M. Katein ◽  
John K. Choi ◽  
...  
Keyword(s):  
In Vitro Translation ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Fully Depleted ◽  
Alpha Thalassemia ◽  
Gene Ablation ◽  
Mutant Strains ◽  
Alpha Globin

Abstract AHSP binds alpha hemoglobin (Hb) to maintain its structure and limit its prooxidant activities. In addition, AHSP binds and stabilizes apo-alpha globin, which lacks heme. Previously, we demonstrated that Ahsp−/− mice exhibit hemolytic anemia with Hb precipitation in erythroid cells. Through interbreeding of mutant strains, we also showed that loss of AHSP exacerbates beta thalassemia. Together, these studies indicate that AHSP participates in Hb homeostasis and may act to neutralize potentially toxic excess alpha globin that is known to accumulate in normal erythroid precursors, and to a greater extent, in beta thalassemic ones. However, additional functions for AHSP may exist. In particular, AHSP-alpha globin complexes may also promote HbA synthesis. To test this, we depleted the pool of excess alpha globin in Ahsp−/− mice by interbreeding with alpha thalassemic ones. Compared to mice with either mutation alone, compound mutants missing both AHSP and one alpha globin allele (genotype Ahsp−/− //alpha globin*α/αα) exhibited more severe erythroid defects, including worsened anemia, hypochromia, Hb instability and ineffective erythropoiesis. Pulse-labeling of double-mutant reticulocytes showed that alpha to beta globin synthetic ratios were unaffected by loss of AHSP, but precipitation of both alpha and beta nascent chains into cell membranes was strongly enhanced. These data indicate that AHSP is important for erythropoiesis and Hb production even when alpha globin is not produced in excess. In vitro translation studies using wheat germ extracts showed that recombinant AHSP present during the synthesis of alpha globin improved its ability to become incorporated into HbA. Moreover, AHSP conferred protease resistance to nascent alpha globin, suggesting enhanced folding into the native state. Further supporting this interpretation, circular dichroism studies showed that AHSP accelerated refolding of purified denatured alpha Hb. Finally, through pulse labeling of reticulocytes followed by isoelectric focusing of soluble cytosolic fractions, we identified transient pools of free alpha Hb and AHSP-alpha Hb in vivo and showed that Ahsp gene ablation fully depleted both pools. Together, our studies indicate that AHSP acts as a molecular chaperone to promote alpha globin folding and stability prior to its incorporation into HbA. In addition, it is possible that alterations in AHSP gene function or expression could modulate alpha thalassemia severity in patients.

Gene Therapy for Beta-Thalassemia: Preclinical Studies on Human Cells.

Blood ◽  
2006 ◽  
Vol 108 (11) ◽  
pp. 5473-5473
Author(s):  
Giuliana Ferrari ◽  
Emanuela Roselli ◽  
Francesca Tiboni ◽  
Erica Biral ◽  
Sarah Marktel ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Genetically Modified ◽  
Beta Thalassemia ◽  
Beta Globin ◽  
Hematopoietic Stem ◽  
Molecular Defects ◽  
Globin Chains ◽  
Number Of Patients ◽  
Cd34 Cells ◽  
The Impact

Abstract Gene therapy for beta-thalassemia is based on the transplantation of genetically-modified autologous hematopoietic stem cells (HSC) into patients affected by the severe form of disease. The genetic treatment of the hemoglobinopathies poses the general challenge of efficient level of gene transfer into HSC and high and persistent transgene expression, in the differentiated progeny of a genetically modified stem cell. The validation of a gene therapy approach to thalassemia requires to obtain results of gene correction in a broad number of patients’ cells, since different molecular defects in the beta-globin gene lead to the clinical phenotype. The heterogeneity in the molecular defects and in the proportion of alpha and non-alpha (beta, gamma and delta) chains will represent a key element to set a threshold in the amount of vector-derived beta-chain required to correct a thalassemic phenotype. Additionally, the impact of some biological parameters, such as the degree of BM erythroid hyperplasia, the BM subpopulations proportion and the apoptotic index, on the successful correction of thalassemic phenotype needs to be studied in the perspective of clinical translation. In order to address these issues, we collected samples from BM aspirates and isolated CD34+ cells from 25 beta+ and beta0 thalassemic patients, characterized by different genotypes and biochemical profiles of globin chains synthesis. A novel, erythroid specific LV expressing human beta-globin from a minimal promoter enhanced by only 2 LCR elements (HS2 and HS3) was used to transduce BM derived CD34+ cells at high efficiency (>80%). The efficacy of the beta-globin LV in correcting the human thalassemic phenotype was tested in an in vitro model of erythropoiesis and in the human-mouse hematological chimera. Upon transduction, normal level of HbA expression was achieved in erythroblastic cultures and BFU-E, associated with a progression towards erythroid maturation, which was impaired in mock-transduced thalassemic cells. Molecular analysis showed proviral integrity, with no detectable rearrangements and an average proviral copy number of 2.4. Analysis of specific globin chains proportion and contribution to phenotype correction in the context of different genotypes is under evaluation.

Sign in / Sign up

Export Citation Format

Share Document