Preliminary comparison of skin transcriptome from sheep with different wool fibre diameters

Context Wool is one of the most important animal fibres for the textile industry, and its diameter directly affects its economic value. However, the molecular mechanisms underlying wool fibre diameter (FD) in sheep have not been fully elucidated. Aims The aims of the work were to make an initial comparison of skin transcriptomes from sheep with wool of high and low FD, and to identify key genes affecting FD. Methods High-throughput RNA-Seq technology was employed to explore the skin transcriptome, using three sheep with fine wool (FD <21.0 μm) and three sheep with coarse wool (FD >27.0 μm). Key results We obtained 28 607 228 bp of clean sequence data, 78.9% (±3.8%) of which uniquely aligned to the reference genome across the six samples. In total, 19 914 mRNA transcripts were expressed (FPKM >0) in the six skin samples, among which were certain well-known genes involved in the skin–hair cycle, such as KRTAP7-1, KRT14, Wnt10b, Wnt2b, β-catenin and FGF5. Furthermore, 467 genes were significantly differentially expressed between the fine-wool and coarse-wool groups, including 21 genes with upregulated and 446 genes with downregulated expression in the sheep with lower FD. These differentially expressed genes were particularly enriched in the gene ontology processes related to lipid metabolism, skin development, differentiation and immune function (P < 0.05). The biological processes were involved in collagen catabolism, negative regulation of macromolecule metabolism, steroid hormone stimulation and lipid metabolism. A significant Kyoto Encyclopedia of Genes and Genomes pathway involving the metabolism of lipids and lipoproteins was also enriched, revealing that lipid metabolism might be one of the key factors affecting FD. The expression of these differentially expressed genes that were involved in the metabolism of lipids and lipoproteins pathway was verified by quantitative real-time PCR (qPCR). The correlation between the mRNA expression level from qPCR and RNA-Seq data was 0.999 (P < 0.001). Conclusions The 467 differentially expressed genes, especially those involved in lipid metabolism and immune function, may play key roles in wool follicle metabolism and the expression of wool FD. Implications This study provided valuable data for future studies aimed at elucidating the mechanisms that underlie wool follicle metabolism and wool FD. The work may also have implications for studies of the human hair follicle.