Transcriptome Analysis Reveals Candidate Genes Regulating the Skin and Hair Diversity of Xinji Fine-Wool Sheep and Tan Sheep

The hair follicle is a complex mini-organ in the skin that undergoes organ induction, morphogenesis, and regeneration. However, the accurate molecular mechanism of skin and hair diversity regulation is still elusive. The sheep is an animal model that can be used to further explore the mechanisms of skin and hair diversity. In this study, we carried out a transcriptomic analysis of the mRNA expression in the skin of Xinji fine-wool sheep at different growth stages (3 and 12 months old) and 12-month-old Tan sheep and explored the transcripts’ relationship with hair follicle growth. A total of 1327 mRNAs and 67 transcription factors were identified to be differentially expressed in the different breeds and during different periods of skin development. The differentially expressed genes were enriched in GO terms represented by system development, multicellular organism development, animal organ development, and skin development, and three KEGG pathways typified those governing differences in skin structure. Combining protein–protein interaction networks of skin development (GO:0043588) and functional annotation, nine important candidate genes, namely, LAMA5 , OVOL1 , SRF , DHCR24 , NGFR , SMO , CDSN , HOXC13 , and KDF1 , and many core genes with minor effects were confirmed to be associated with hair follicle development. Furthermore, members of the zf-C2H2 and homeobox transcription factor families, which were identified to play a crucial role in producing finer and denser wool, were mainly upregulated in 12-month-old Xinji fine-wool sheep when compared with expression in 12-month-old Tan sheep and 3-month-old Xinji fine-wool sheep. This study revealed the major–minor gene interactions in the developmental pathway and provided ideas for an in-depth understanding of the genetic structure and gene regulation in the skin/hair growth process.