# EIF4A3‐Induced Circular RNA circSnd1 Promotes Muscle Atrophy and Muscle Ageing by Stabilizing EEF1A1

## TL;DR

This study identifies a circular RNA called circSnd1 that promotes muscle atrophy and aging by stabilizing a protein involved in translation.

## Contribution

The study discovers circSnd1 as a novel circular RNA involved in muscle atrophy and aging, and reveals its stabilization mechanism involving EEF1A1.

## Key findings

- circSnd1 is upregulated in multiple muscle atrophy models and aged muscle in humans and mice.
- circSnd1 promotes muscle atrophy and aging by stabilizing EEF1A1 through interaction with FAT10.
- Inhibiting circSnd1 ameliorates muscle atrophy in cellular and mouse models.

## Abstract

Muscle atrophy is a common complication of ageing, and many chronic conditions, lacks defined therapeutic interventions. It is still mostly unknown how circular RNAs contribute to muscle atrophy.

circRNA sequencing and quantitative real‐time PCR were performed to detect the changed circRNAs in muscle atrophy models and aged muscle. Then the gain‐of‐function and loss‐of‐function experiments were used to investigate the function of circSnd1 in muscle atrophy and muscle ageing. Furthermore, we used RIP‐MS and RIP assay to determine the downstream and upstream mechanism of circSnd1 in muscle atrophy.

Here, we characterized the function and mechanism of highly species‐conserved circRNA derived from staphylococcal nuclease and Tudor domain containing 1 gene (named circSnd1) in muscle atrophy. CircSnd1 is upregulated in many types of muscle atrophy models in both in vivo and in vitro (all p < 0.01). Meanwhile, circSnd1 is also higher expressed in aged muscle in humans (+2.2‐fold, n = 5, p < 0.05), mice (+43.96%, n = 6, p < 0.05) and myotubes (+42.21%, n = 6, p < 0.05). Functional analyses show that circSnd1 promotes muscle atrophy and muscle ageing at the cellular level and mouse level while repressing it ameliorates multiple types of muscle atrophy (all p < 0.05). Mechanistically, the RNA binding protein eukaryotic translation initiation factor 4A3 (EIF4A3) can bind to the intron flanking sequence of circSnd1 to induce circSnd1 cyclization and increase circSnd1 expression in muscle atrophy. In addition, circSnd1 promotes the binding between human HLA‐F adjacent transcript 10 (FAT10) and eukaryotic translation elongation factor 1 alpha 1 (EEF1A1). FAT10 competes with ubiquitin for binding with EEF1A1, which decreases the ubiquitination of EEF1A1 and stabilizes the protein level of EEF1A1 in muscle cells to promote atrophy.

We have identified circSnd1 as a novel circRNA that promotes muscle atrophy and highlighted its potential as a novel therapeutic target.