Transcriptome sequencing unveils a novel mechanism underlying breed distinctions between thin- and fat-tailed sheep

Tail fat in sheep (Ovis aries), has evolved mainly in response to cold weather for better energy storage. As things stand, too much tail fat in sheep can lead to a reduction in feed utilisation and is also unpopular with consumers due to the excessive fat content in the tail of sheep. Therefore, the need to find the mechanism of tail fat formation is obvious. In this study, we elected to utilise Kazakh sheep, prolific Suffolk sheep, and their hybrid F2 generation as research objects. Sheep transcriptome sequencing technology was employed to screen and explore target candidate genes related to sheep tail fat deposition. Comparison with RNA-seq data from fat-tailed and thin-tailed tissue, the LncRNA-mRNA-miRNA axis was identified as main functional pathway in the formation of fat in tail. Our results offer valuable insights into the fat deposition of sheep and provide a significant genomic resource for future genetic studies and the enhancement of genome-assisted breeding in sheep and other domestic animals. Three healthy adult Kazakh sheep (HUS) which is fat-tailed, F2 generation (F2) of crossbreeding between Kazakh (HUS) and Suffolk sheep (SFK) and adult Suffolk sheep, lean-tailed, of nearly the same age were selected and uniformly reared and managed. Tail tissue samples are collected in December when tail fat deposition is at its highest. Tail fat samples were collected in the shortest possible time using specially treated surgical instruments for RNA experiments (all from the same side), frozen in liquid nitrogen and stored in a refrigerator at -80℃ for back-up. RNA was extracted from tail tissues, and the samples underwent stringent quality control based on the following criteria. First, agarose gel electrophoresis was used to assess RNA integrity and detect potential DNA contamination. Second, RNA concentration and purity were preliminarily quantified. Finally, the integrity of RNA was accurately measured.