Objective: In this study, we used gapmer-type antisense oligonucleotides (ASOs) containing amido-bridged nucleic acid (AmNA). ASO, short single-stranded stretches of DNA or RNA with complementary sequence of their target mRNA, is one of the most commonly used strategy for silencing gene expression. AmNA is a novel locked nucleic acid (LNA) analogue based on a cyclic amide structure, which shows high nuclease resistance and binding affinities towards complementary strands.

The aim of this study is to investigate the effectiveness in downregulation of SNCA, administering ASO to SNCA transgenic mouse models.

Background: α-synuclein (aSyn) plays important roles in the pathogenesis of Parkinson’s disease (PD). Both missense mutations and increased copy number of the SNCA gene encoding aSyn cause early onset autosomal dominant PD.

Though previous studies have shown that nucleic acid therapies inhibit SNCA expression in some animal models, there still remain issues in both effectiveness and sustainablity.

Methods: We transfected ASOs which have 50 different sequences encoding SNCA’s mRNA to human embryonic kidney cells 293. Total RNA from the cells was extracted 1 day after transfection, reverse transcribed, and evaluated SNCA expression by quantitative PCR. We determined “the best” sequence of the 50 ASOs.

Then, we injected the ASO intracerebroventricularly to human SNCA transgenic mice. Seven days after injection, we extracted RNA from striatum and evaluated SNCA expression by quantitative PCR, similarly. Thirty days after injection, protein was also extracted, and the level of aSyn was determined by ELISA. As the behavioral test, we gave several 1cm-pieces of spaghetti noodles to human SNCA transgenic mice which had motor deficit (Line 61), and evaluated the number of bites per gnawing episode and the frequency (pasta gnawing test).

Results: The mice which were injected the AmNA-ASO showed significantly reduction of SNCA expression and the level of aSyn in the striatum. The result of pasta gnawing test indicated that the ASO-treated group significantly improve motor function better than non-treated group.

Conclusions: We revealed that gapmer AmNA-ASO downregulates SNCA expression, and improve motor function of the PD animal model. We think this nucleic acid medicine has the potential to treat PD.

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MDS Abstracts - https://www.mdsabstracts.org/abstract/antisense-oligonucleotides-containing-amido-bridged-nucleic-acid-downregulate-snca-expression-and-improve-motor-function-in-parkinsons-disease-mouse-models/