Artificially designed transcription activator-like effector (TALE) proteins fused to a transcription activation domain (TAD), such as VP64, are able to activate specific eukaryotic promoters. They thus provide a good tool for targeted gene regulation as a therapy. However, the efficacy of such agent in vivo remains to be demonstrated since the majority of studies have been done in cell culture. We produced an AAV9 coding for a TALEfrat#8 containing 13 repeat-variable di-residues (RVDs) able to bind to the proximal promoter of human frataxin (FXN) gene. This TALEfrat#8 was fused with a 3XFLAG at its N-terminal and a VP64 TAD at its C-terminal and driven by a CAG promoter. This AAV9_3XFLAG-TALEfrat#8-VP64 was injected intra-peritoneally to 9 days old and 4 months old YG8R mice. One month later, heart, muscle and liver were removed and their FXN mRNA and FXN protein were analyzed. The results show that the AAV9_3XFLAG-TALEfrat#8-VP64 increased the FXN mRNA and FXN protein in the three organs studied. These results corroborate our previous in vitro studies in the FRDA human fibroblasts 1. Our study indicates that an AAV coding for a TALE protein coupled with a TAD may be used to increase gene expression in vivo as a possible treatment not only for FRDA but also for other haploinsufficiency diseases.

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