Comparison of the Relative Quantities of γ-mRNAs and Fetal Hemoglobin in SS Patients with Different Haplotypes

Abstract

We have studied the relative levels of γ-mRNA [%γ/(γ + β)], ^Gγ- and ^Aγ-mRNAs [%^Gγ/(^Gγ + ^Aγ)], hemoglobin (Hb) F, and the ^Gγ and ^Aγ chains in some 50 patients with sickle cell anemia (SS) and with different haplotypes. As expected, the Hb F levels varied greatly and were high in patients with the Saudi Arabian-Indian haplotype. Similarly, the ^Gγ values varied greatly (from 19.5 to 76.5%) and depended on the haplotypes. A rare haplotype, named Mor, was found in 3 SS patients, 1 of whom was a homozygote Mor/Mor; this haplotype is associated with the lowest ^Gγ value (19.5% in the homozygote) and with a C→T mutation at position –202 of the ^Aγ promoter. The levels of γ-mRNA roughly parallel those of Hb F, but older patients have increased levels of mRNA, which appears not to be efficiently translated into Hb F. Similar observation have been reported for other hemoglobinopathies such as δβ-thalassemia heterozygotes and Hb Lepore heterozygotes. The relative quantity of ^Gγ-mRNA was closely related to that of the ^Gγ chain in the 15 patients who were studied; the ^Gγ- to ^Aγ-mRNA ratio did not change with age.

Therapeutic levels of fetal hemoglobin in erythroid progeny of β-thalassemic CD34+ cells after lentiviral vector-mediated gene transfer

“…25 For transduction, CD34 ϩ cells grown for approximately 48 hours in expansion medium were transferred to RetroNectin-coated 24-well plates (50 g/cm 2 ; Fisher Scientific) at a concentration of 2 ϫ 10 5 to 4 ϫ 10 5 cells/mL in media supplemented with protamine sulfate (10 g/mL) and incubated overnight with vector particles (multiplicity of infection [MOI], [5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20]. The next day, cells were returned to the expansion medium with an aliquot (1000 cells/mL) mixed with semisolid methylcellulose medium supplemented with human cytokines (H4434, StemCell Technologies) to assess multilineage colony-forming potential and gene transfer efficiency.…”

“…[9][10][11][12] Similarly, SCD patients with HPFH or those with certain ␤-globin locus haplotypes that are associated with increased HbF can demonstrate markedly reduced disease manifestations. 13,14 These observations suggested the therapeutic potential of genetic modification of autologous HSCs to enhance HbF. Indeed, we and others have used lentiviral vectors encoding a human ␥-globin gene for HSC gene transfer to successfully correct murine models of ␤-thalassemia intermedia and SCD through high-level HbF expression.…”

Utility of family studies in diagnosing abnormal hemoglobins/thalassemic states

“…The latter is a well known entity, especially in the Indian subcontinent as the Arab-Indian HbS variant is known to have a high HbF level ~ 10-25%. 9 HbS -β thalassemia cases are known to have HbF levels around 5-15% 1 . Both Cases 5 and 6 showed high Hb F values, 27.6% and 15.7% with peaks in the S window -62.2% and 77.8% respectively (Fig.…”

Effect of hydroxyurea on G gamma chain fetal hemoglobin synthesis by sickle-cell disease patients

“…More recently, mRNA analysis strengthened these data. Sickle-cell anemia patients with Senegal and Saudi Arabia-India haplotypes had higher percentages of γ mRNA than Benin, Bantu or Cameroon types (8).…”