Small RNA-Seq analysis of liver tissues in AAV9-Tnnt2-Cre and AAV9-Tnnt2-Cre-miR122 injected mice

The cardiac troponin T (Tnnt2) promoter is broadly utilized for cardiac specific gene expression, particularly via adeno-associated virus (AAV)-based gene transfer. However, these vectors drive lower-level ectopic gene expression in other tissues, most notably in the liver. Whether the AAV-Tnnt2 vectors remain tissue-specific in applications sensitive to low or transient gene expression, such as gene editing, remains unclear. Inclusion of target sequences for microRNA-122, a highly expressed, liver-specific microRNA, in the AAV transgene's 3' untranslated region (3' UTR) markedly reduced ectopic transgene expression, genome editing and AAV integration in the liver. The heavily used AAV-Tnnt2 system exhibits liver leakiness that severely impairs the cardiac specificity of AAV-based genetic manipulation. This problem can be mitigated via miR122-mediated liver detargeting. Overall design: To investigate the impact of AAV-promotor-miR122 on the micro-RNA of murine livers.