Thus, we validated a safe and effective procedure for β-globin gene transfer in thalassemia patient CD34(+) HPCs, which we will implement in the first US trial in patients with severe inherited globin disorders.
β-Thalassemia, a hereditary blood disorder caused by reduced or absent synthesis of the β-globin chain of hemoglobin, is characterized by ineffective erythropoiesis, and can manifest as nontransfusion-dependent thalassemia (NTDT) or transfusion-dependent thalassemia (TDT).
A common mutation causing thalassemia in Mediterranean populations is an amber (UAG) nonsense mutation at the 39th codon of the human beta-globin gene, the beta-39 mutation.
It has previously been demonstrated that the self-inactivating γ-globin lentiviral vector GGHI can significantly increase fetal hemoglobin (HbF) in erythroid cells from thalassemia patients and thus improve the disease phenotype <i>in vitro.</i> In the present study, the GGHI vector was improved further by incorporating novel enhancer elements and also pseudotyping it with the baboon endogenous virus envelope glycoprotein BaEVRless, which efficiently and specifically targets human CD34<sup>+</sup> cells.
DNA analysis of the α2 globin gene identified a novel mutation (namely Hb Nakhon Ratchasima), GCC (Ala)→GTC (Val) at codon 63 in trans to the α(+)-thalassemia (3.7-kb deletion).
Hematological parameters were compared with those of patients with compound heterozygote for other α-globin variants and α<sup>0</sup>-thalassemia previously documented.
DNA sequencing identified a CTT (Leu) to TTT (Phe) mutation at codon 91 corresponding to the Hb Grey Lynn (Vientiane) [α91(FG3)Leu>Phe (α1) on α1-globin gene and a C deletion between codons 36 and 37 on α2-globin gene causing α(+)-thalassemia.
Epsilon gamma delta beta (εγδβ)<sup>0</sup> - thalassemia is a very rare disorder that results from large deletions in the β-globin gene cluster which abolish all regional globin chain gene expression from that allele.
Herein are results obtained in use of lentiviral vectors to insert a gamma-globin gene into murine stem cells with phenotypic correction of the thalassemia phenotype.
These results, without undermining the strength of BCL11A as a silencer of the γ globin gene, suggest that the LCR background, by governing the state of BCL11A binding to this region, plays a more significant role in determining the thalassemia phenotype than the level of BCL11A protein expression, that might be influenced by single nucleotide polymorphisms in intronic regions of the BCL11A gene.
In addition the activated δ-globin gene gives rise to a robust increase of the hemoglobin level in β-thalassemic mice, effectively improving the thalassemia phenotype.
This paper reports a Sardinian patient, who was a compound heterozygote for silent beta-thalassaemia and high Hb A2 beta o-thalassaemia with the clinical phenotype of mild thalassaemia intermedia; alpha globin gene mapping showed a single alpha globin gene deletion.
In addition the activated δ-globin gene gives rise to a robust increase of the hemoglobin level in β-thalassemic mice, effectively improving the thalassemia phenotype.
However, α-globin genotyping should be carried out in samples with positive IC strip as positive reactivity was also observed in homozygous α(+)-thalassemia carriers who have 2 trans α-globin gene deletions.
The analysis of a number of cases of beta-globin thalassemia and hereditary persistence of fetal hemoglobin (HPFH) due to large deletions in the beta-globin locus has led to the identification of several DNA elements that have been implicated in the switch from human fetal gamma- to adult beta-globin gene expression.
Homozygous inactivation of the endogenous alpha- or beta-globin genes in mice results in corresponding thalassemic syndromes that are uniformly fatal in utero.
The most prevalent molecular defect was the deletion of 3 alpha-globin structural genes most commonly the (--/-alpha 3.7) genotype (83.6%) and rarely the (--/-alpha 4.2) genotype (1.4%), followed in decreasing order of incidence by the combination of deletion alpha zero-thalassemia and initiation codon mutation of the alpha 2-gene (--/alpha NcoI alpha = 9.8%), deletion alpha zero-thalassemia and pentanucleotide deletion of IVS-I of the alpha 2-globin gene, (--/alpha HphI alpha = 3.3%) deletion alpha zero-thalassemia and initiation codon mutation of the alpha 1-gene (--/alpha alpha NcoI = 1.3%), a homozygous state for initiation codon mutation of the alpha 2-gene (alpha Nco alpha/alpha NcoI alpha = 0.7%).
This finding demonstrates that the genetic combination leading to the more/less degree of alpha- to non-alpha-globin chains imbalance is indeed the cause of the severe/mild thalassemia phenotype.