Restoration of correct βIVS2-654-globin mRNA splicing and HbA production by engineered U7 snRNA in β-thalassaemia/HbE erythroid cells.

Tiwaporn Nualkaew, Natee Jearawiriyapaisarn, Suradej Hongeng, Suthat Fucharoen, Ryszard Kole, Saovaros Svasti

Scientific reports 2019 May 21

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A cytosine to thymine mutation at nucleotide 654 of human β-globin intron 2 (βIVS2-654) is one of the most common mutations causing β-thalassaemia in Chinese and Southeast Asians. This mutation results in aberrant β-globin pre-mRNA splicing and prevents synthesis of β-globin protein. Splicing correction using synthetic splice-switching oligonucleotides (SSOs) has been shown to restore expression of the β-globin protein, but to maintain therapeutically relevant levels of β-globin it would require lifelong administration. Here, we demonstrate long-term splicing correction using U7 snRNA lentiviral vectors engineered to target several pre-mRNA splicing elements on the βIVS2-654-globin pre-mRNA such as cryptic 3' splice site, aberrant 5' splice site, cryptic branch point and an exonic splicing enhancer. A double-target engineered U7 snRNAs targeted to the cryptic branch point and an exonic splicing enhancer, U7.BP + 623, was the most effective in a model cell line, HeLa IVS2-654. Moreover, the therapeutic potential of the vector was demonstrated in erythroid progenitor cells derived from βIVS2-654-thalassaemia/HbE patients, which showed restoration of correctly spliced β-globin mRNA and led to haemoglobin A synthesis, and consequently improved thalassaemic erythroid cell pathology. These results demonstrate proof of concept of using the engineered U7 snRNA lentiviral vector for treatment of β-thalassaemia.

Citation

Tiwaporn Nualkaew, Natee Jearawiriyapaisarn, Suradej Hongeng, Suthat Fucharoen, Ryszard Kole, Saovaros Svasti. Restoration of correct βIVS2-654-globin mRNA splicing and HbA production by engineered U7 snRNA in β-thalassaemia/HbE erythroid cells. Scientific reports. 2019 May 21;9(1):7672