# Short 2′-O-methyl/LNA oligomers as highly-selective inhibitors of miRNA production in vitro and in vivo

## TL;DR

Researchers developed a new method to selectively inhibit specific miRNA family members by targeting their precursor sequences, enabling the study of their unique functions.

## Contribution

A novel strategy using 2′-OMe/LNA oligomers to selectively inhibit miRNA production from specific precursors is introduced.

## Key findings

- 2′-OMe/LNA-ASOs targeting pre-miRNA apical regions selectively inhibit miRNA-5p production in Xenopus.
- The approach was successfully applied to the human miR-16 family, showing its broad applicability.
- The method allows efficient and specific manipulation of miRNA expression in vitro and in vivo.

## Abstract

MicroRNAs (miRNAs) that share identical or near-identical sequences constitute miRNA families and are predicted to act redundantly. Yet recent evidence suggests that members of the same miRNA family with high sequence similarity might have different roles and that this functional divergence might be rooted in their precursors' sequence. Current knock-down strategies such as antisense oligonucleotides (ASOs) or miRNA sponges cannot distinguish between identical or near identical miRNAs originating from different precursors to allow exploring unique functions of these miRNAs. We here develop a novel strategy based on short 2′-OMe/LNA-modified oligonucleotides to selectively target specific precursor molecules and ablate the production of individual members of miRNA families in vitro and in vivo. Leveraging the highly conserved Xenopus miR-181a family as proof-of-concept, we demonstrate that 2′-OMe/LNA-ASOs targeting the apical region of pre-miRNAs achieve precursor-selective inhibition of mature miRNA-5p production. Furthermore, we extend the applicability of our approach to the human miR-16 family, illustrating its universality in targeting precursors generating identical miRNAs. Overall, our strategy enables efficient manipulation of miRNA expression, offering a powerful tool to dissect the functions of identical or highly similar miRNAs derived from different precursors within miRNA families.

Graphical Abstract