The Roles of CircRNAs in Regulating Muscle Development of Livestock Animals

Abstract

The muscle growth and development of livestock animals is a complex, multistage process, which is regulated by many factors, especially the genes related to muscle development. In recent years, it has been reported frequently that circular RNAs (circRNAs) are involved widely in cell proliferation, cell differentiation, and body development (including muscle development). However, the research on circRNAs in muscle growth and development of livestock animals is still in its infancy. In this paper, we briefly introduce the discovery, classification, biogenesis, biological function, and degradation of circRNAs and focus on the molecular mechanism and mode of action of circRNAs as competitive endogenous RNAs in the muscle development of livestock and poultry. In addition, we also discuss the regulatory mechanism of circRNAs on muscle development in livestock in terms of transcription, translation, and mRNAs. The purpose of this article is to discuss the multiple regulatory roles of circRNAs in the process of muscle development in livestock, to provide new ideas for the development of a new co-expression regulation network, and to lay a foundation for enriching livestock breeding and improving livestock economic traits.

Keywords: circRNAs; co-expression regulatory network; livestock animals; muscle development; transcription and translation.

FIGURE 1

The biogenesis mechanisms and biological roles of circular RNAs. (A) Lariat-driven circularization. (B) Intron pairing–driven circularization. (C) RBP-mediated circularization. (D) Repetitive MIR-mediated circularization. (E) EML4-ALK fusion gene–mediated circularization. (F) SLC34A2-ROS1 fusion gene–mediated circularization. (G) Interfering with gene-mediated circularization that regulates transcription. (a) CircRNAs can sponge miRNAs. (b) A few circRNAs containing the m⁶A motif or IRES can encode functional proteins. (c) CircRNAs splice with linear RNA to promote the expression of mRNA. (d) EIciRNA can interact with U1 small nuclear ribonucleoproteins and then increase the transcription of their host genes by binding with RNA pol II; ciRNA, and the RNA pol II complex can directly interact and play a role in regulating parental gene transcription. (e) CircRNAs can be translated into peptides or proteins. (f) CircRNA in some nuclei is involved in histone modification. (g) Mitochondrial-derived circRNA can regulate the entry of proteins into mitochondria under the interaction of TOM40 and PNPASE. CiRNA, Circular intronic RNA; EcircRNA, Exonic circRNA; EIciRNA, Exon–intron circRNA; RBP, RNA-binding protein; RNA pol II, RNA polymerase II.

FIGURE 2

CircRNAs involved in muscle development and their function. Schematic representation of the role of circRNAs in muscle proliferation and differentiation. The diagram shows various circRNAs that regulate the proliferation and differentiation of myoblasts. The circRNAs are represented in red.