Generation and molecular characterization of a transgenic mouse line carrying a mutated human IVS-I-6 thalassemia beta-globin gene

In β-thalassemias, mutations of the β-globin gene or its regulatory regions cause absence (β°) or reduced (β+) synthesis of β-globin chains, associated with a corresponding excess of the complementary α-globins. More than 200 mutations of the β-globin gene have been described. Mouse models for the different mutations causing thalassemia are very important to test in vivo the activity of novel mutation-specific therapeutic approaches. The IVSI-6 mutation is the most frequent in the middle-east region and recurrent in Italy and Greece. This mutation leads to the activation of three criptic splicing sites, which generate three aberrantly spliced RNAs. Generation of a mouse that expresses such mutation could supply a model to test new compounds and therapies for these populations of patients. In this study we report the production and characterization of a transgenic mouse line carrying a human β-globin gene containing the IVS-I-6 thalassemia point mutation. The major contribution of our work is the development of a transgenic TG-β-IVS-I-6 mouse, which: (a) displays a tissue specific expression of the transgene, fully overlapping with that of the endogenous murine β-globin gene; (b) as expected produces normally spliced human β-globin mRNA, giving rise to β-globin production and formation of a human-mouse tetrameric chimeric hemoglobin βm2βh2,and more importantly, (c) exhibits in blood cells presence of the unspliced aberrant β-globin-IVS-I-6 RNA. Therefore, the TGβ- IVS-I-6 mouse might be used as an in vivo model to characterize the effects of antisense ODN targeting the criptic site responsible for the generation of aberrantly spliced human β-globin RNA sequences.