Treatment of β⁶⁵⁴ -thalassaemia by TALENs in a mouse model

This study explored whether TALENs-mediated non-homologous end joining (NHEJ) targeting the mutation site can correct the aberrant β-globin RNA splicing, and ameliorate the β-thalassaemia phenotype in β⁶⁵⁴ mice.

TALENs vectors targeted to the human β-globin gene (HBB) IVS2-654C >T mutation in a mouse model were constructed and selected to generate double heterozygous TALENs⁺ /β⁶⁵⁴ mice. The gene editing and off-target effects were analysed by sequencing analysis. β-globin expression was identified by RT-PCR and Western blot analysis. Various clinical indices including haematologic parameters and tissue pathology were examined to determine the therapeutic effect in these TALENs⁺ /β⁶⁵⁴ mice.

Sequencing analysis revealed that the HBB IVS2-654C >T point mutation was deleted in over 50% of the TALENs⁺ /β⁶⁵⁴ mice tested, and off-target effects were not detected. RT-PCR and Western blot analysis confirmed the expression of normal β-globin in TALENs⁺ /β⁶⁵⁴ mice. The haematologic parameters were significantly improved as compared with their affected littermates. The proportion of nucleated cells in bone marrow was considerably decreased, splenomegaly with extramedullary haematopoiesis was reduced, and significant decreases in iron deposition were seen in spleen and liver of the TALENs⁺ /β⁶⁵⁴ mice.

These results suggest effective treatment of the anaemia phenotype in TALENs⁺ /β⁶⁵⁴ mice following deletion of the mutation site by TALENs, demonstrating a simple and straightforward strategy for gene therapy of β⁶⁵⁴ -thalassaemia in the future.