miR-122-loaded Argonaute2 complex targeting engineered miR-122 binding sites in AARS2 mRNA 3′UTR (miR-122/AGO2-AARS2-3'UTR)

The miR-122-loaded Argonaute2 (AGO2) complex targeting engineered miR-122 binding sites in the AARS2 mRNA 3'UTR represents a synthetic regulatory mechanism employed in gene therapy to achieve tissue-specific transgene expression. Alanyl-tRNA synthetase 2 (AARS2) is a nuclear-encoded mitochondrial enzyme essential for protein synthesis within mitochondria; mutations in the AARS2 gene lead to severe disorders such as leukoencephalopathy with thalamic involvement and high lactate (LTBL) and hypertrophic cardiomyopathy (Götz et al., 2011). To treat these conditions, gene therapy vectors, typically Adeno-associated virus (AAV), are used to deliver a functional AARS2 gene. However, systemic delivery often leads to high expression in the liver, which can cause hepatotoxicity or trigger an immune response against the transgene product. By incorporating binding sites for the liver-specific microRNA-122 (miR-122) into the 3'UTR of the AARS2 mRNA, the endogenous AGO2-RISC machinery in hepatocytes can identify and silence the transgene (Xie et al., 2011). This detargeting strategy ensures that AARS2 protein production is restricted to non-hepatic target tissues, such as the central nervous system or heart, thereby enhancing the safety profile of the therapeutic intervention (Jopling, 2012; Meister, 2013).

Other names

miR-122-regulated AARS2 mRNAAGO2-miR-122-AARS2 complexmiR-122T-AARS2miR-122-detargeted AARS2 transgene

The miR-122-loaded AGO2 complex recognizes and binds to complementary sequences (miR-122 binding sites) engineered into the 3'UTR of the AARS2 mRNA. This recruitment leads to the degradation of the mRNA transcript or the inhibition of its translation, specifically in the liver where miR-122 is highly expressed (Jopling, 2012; Meister, 2013).