Identification and Characterization of Circular RNAs in Association With the Deposition of Intramuscular Fat in Aohan Fine-Wool Sheep.

Le Zhao,Xinming Duan,Fuhui Han,Jianning He,Lei Wang,Feng Guo,Lisheng Zhou,Xiaojing Hao,Lirong Liu,Nan Liu

doi:10.3389/fgene.2021.759747

Abstract

Aohan fine-wool sheep (AFWS) is a high-quality fine-wool sheep breed that supplies wool and meat. Research is needed on the molecular mechanism behind intramuscular fat (IMF) deposition that greatly improves mutton quality. The widely expressed non-coding RNA is physiologically used in roles such as competitive endogenous RNA (ceRNA) that includes circular RNAs (circRNAs). Although circRNAs were studied in many fields, little research was devoted to IMF in sheep. We used the longissimus dorsi muscle of 2 and 12-month-old AWFS as research material to identify circRNAs related to IMF deposition in these sheep by RNA-seq screening for differentially expressed circRNAs in the two age groups. A total of 11,565 candidate circRNAs were identified, of which the 104 differentially expressed circRNAs in the two age groups were analyzed. Enrichment analysis was performed using Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes. The enriched pathways included lipid transport (GO:0006869), negative regulation of canonical Wnt signaling pathway (GO:0090090), fat digestion and absorption (ko04975), and sphingolipid metabolism (ko00600). The differentially expressed circRNAs included ciRNA455, circRNA9086, circRNA7445, circRNA4557, and others. The source genes involved in these pathways might regulate IMF deposition. We used the TargetScan and miRanda software for interaction analysis, and a network diagram of circRNA-miRNA interactions was created. CircRNA455-miR-127, circRNA455-miR-29a, circRNA455-miR-103, circRNA4557-mir149-5p, and circRNA2440-mir-23a might be involved in the IMF deposition process. The targeting relationship of circRNA4557-miR-149-5p was verified by a dual-luciferase reporter assay. The RT-qPCR results of seven randomly selected circRNAs were consistent with the sequencing results. This study provides additional information on circRNA regulation of IMF deposition in AFWS and is a useful resource for future research on this sheep breed.

Highlights

We evaluated the intramuscular fat (IMF) content of 2, 4, 6, and 12-month-old Aohan fine-wool sheep (AFWS)
Based on the Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, we identified pathways with more enriched genes that might be related to IMF deposition
Intramuscular fat has an important influence on meat quality

Summary

Introduction

With the improvement in the standard of living, the demand for meat products has increased. The IMF content is a factor determining meat quality. The research on its genes is important, as it could help improve its meat quality. Only by clarifying the factors that affect meat quality and gene regulation mechanisms can we make effective choices. Mutton’s quality is affected by the IMF deposition (Scollan et al, 2017). IMF gene regulation research is of great significance. Current research shows that a variety of molecules are involved in IMF regulation. Glycerolipid metabolism and the fatty acid degradation pathway might contribute to the differences in IMF deposition (Liu et al, 2019). Many studies have recently shown that circRNAs play an important role in IMF. CircRNA has been shown to adjust IMF content and improve meat quality (Wang et al, 2020)

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Discussion

Conclusion