# Transcriptome Sequencing Unveils a Novel Mechanism Underlying Breed Distinctions Between Thin- and Fat-Tailed Sheep

## TL;DR

This study identifies genes and regulatory pathways involved in fat deposition in sheep tails, which could help improve sheep farming efficiency.

## Contribution

The study reveals a novel lncRNA-mRNA-miRNA regulatory axis involved in tail fat deposition in sheep.

## Key findings

- Five core genes (BDH1, EPHX1, BCAT2, FASN, ACACA) are highly expressed in fat-tailed sheep and linked to fatty acid synthesis.
- 189 lncRNAs and three miRNAs regulate genes involved in lipid transport and droplet formation.
- qRT-PCR confirmed the high expression of key genes in fat-tailed sheep.

## Abstract

Background: Sheep (Ovis aries) tail fat serves as a crucial energy reserve for adapting to harsh environments. However, excessive deposition can reduce farming efficiency and product quality. Elucidating the regulatory mechanisms of tail fat deposition is of great significance for genetic improvement in sheep. Methods: In this study, transcriptome sequencing was conducted on tail fat tissues from fat-tailed Kazakh sheep (KAZ), thin-tailed Suffolk sheep (SFK), and their F2 hybrid sheep (CSH) (3 individuals per group). Subsequently, qRT-PCR validation, Enrichr, and KEGG database analyses were performed to investigate the molecular pathways involved in tail fat deposition. Results: High-quality clean reads were obtained from sequencing, with a genome alignment rate ranging from 76.15% to 79.43% and good data reproducibility. Differential expression analysis revealed multiple differentially expressed genes (DEGs) between KAZ and CSH groups, KAZ and SFK groups, as well as SFK and CSH groups. Five core candidate genes (BDH1, EPHX1, BCAT2, FASN, ACACA) were identified, all enriched in the fatty acid synthesis pathway and highly expressed in fat-tailed sheep, which was confirmed by qRT-PCR. Additionally, 189 lncRNAs were identified to collectively regulate target genes (e.g., FABP family, AGPAT2), along with three common differentially expressed miRNAs (novel_120, novel_171, novel_440) targeting genes enriched in lipid transport and lipid droplet formation pathways. Conclusions: This study confirms that the lncRNA-mRNA-miRNA regulatory axis is a key pathway in tail fat formation, providing important theoretical support and molecular targets for genetic improvement of ovine tail fat deposition traits.