Sodium Butyrate and Valproic Acid as Splicing Restoring Agents in Erythroid Cells of b-Thalassemic Patients

Background: b-Thalassemia is a common autosomal recessive disorder in human caused by a defect in b-globin chain synthesis. The most common mutations causing b-Thalassemia have been found to be splicing mutations. Most of which activate aberrant cryptic splicing/sites without complete disruption of normal splicing. IVSI-110 mutation, a common splicing mutation, leads to a 90% reduction of normal b-globin synthesis and lead to blood transfusion dependency in the homozygote forms. However, modulation of splicing can be achieved by activation or suppression of transacting factors such as SR (Serine, Arginine) amino acids and hnRNPs (Heterogeneous ribonucleoprotein particle) through drugs. Objectives: The aim of this study was to investigate the effects of NaBu, isoBu and VPA drugs on restoration of splicing of IVSI-110 b-Thalassemia pre-mRNA in human. Materials and Methods: Primary erythroid cells derived from IVSI-110 b-Thalassemia patients were cultured ex vivo and differentiated in the presence of 0.5 and 1 mM of Na-Butyrate (NaBu), 0.5 mM Isobutyramide (isoBu) and 100 mM Valproic acid (VPA). RT- PCR analysis was used to evaluate the effect of the drugs in correction of normal splicing in b-globin mRNAs. Results: Following treatment with NaBu, isoBu and VPA, the level of normal b-globin mRNA in Primary erythroid cells derived from IVSI-110 b-Thalassemia patients, increased 1.7, 1.5, 1.4 fold, respectively relative to normal b-globin mRNAs. Higher splicing restoration was achieved by NaBu, a histone deacetylase inhibitor, known to upregulate the expression of splicing factors.  Conclusion: The results highlighted the therapeutic potential of splicing modulation for genetic diseases caused by splicing mutations.