# CircVPS13C Promotes Intramuscular Adipogenesis via MiR-5606-X-ECHDC3 Axis in Yaks (Bos grunniens)

## TL;DR

This study identifies a circular RNA, circVPS13C, that promotes fat formation in yaks by interacting with miR-5606-x and ECHDC3, offering new insights into intramuscular fat regulation in this low-fat animal species.

## Contribution

The study reveals a novel circRNA-mediated regulatory axis (circVPS13C/miR-5606-x/ECHDC3) involved in intramuscular adipogenesis in yaks.

## Key findings

- circVPS13C is a cytoplasmic circRNA that regulates intramuscular adipogenesis in yaks.
- circVPS13C promotes differentiation and inhibits proliferation of yak preadipocytes via the miR-5606-x/ECHDC3 axis.
- miR-5606-x and ECHDC3 have opposing roles in intramuscular adipogenesis.

## Abstract

Although large-scale studies and potential pathways of genes on intramuscular fat (IMF) in livestock have been reported, research on circRNAs in yaks—a unique, low-IMF-content animal species that is native to the Qinghai–Tibetan Plateau—is still lacking. Based on previous high-throughput sequencing results on longissimus dorsi with different IMF content, a novel circRNA encoded by the VPS13C gene (designated as circVPS13C) was found to exhibit significant differential expression. Here, we systematically characterized the function and mechanism of circVPS13C on IMF deposition in yaks by adopting a series of experiments. Sequencing, RNase R processing, and nucleoplasmic separation experiments confirmed the circular structure feature of circVPS13C, and it was predominantly distributed in the cytoplasm. Furthermore, these experiments demonstrated that circVPS13C was mainly distributed in the cytoplasm. The circVPS13C/miR-5606-x/ECHDC3 axis was constructed through ceRNA network analysis and validated by dual-luciferase reporter and rescue experiments. Furthermore, the function of these three potential regulators during IMF deposition was investigated through CCK-8, BODIPY, Oil Red O staining, and qRT-PCR analyses, and results showed that both circVPS13C and miR-5606-x promoted the differentiation and inhibited the proliferation of yak intramuscular preadipocytes, while the function of ECHDC3 was the opposite. In conclusion, circVPS13C could act as a competitive endogenous RNA (ceRNA) sponge to sequester miR-5606-x, thereby relieving the inhibitory effect of miR-5606-x on ECHDC3.