Abstract / Summary
Circular RNAs (circRNAs) act as critical regulators of hair follicle development, but how they mediate phenotypic divergence of hair growth in cashmere goats remains largely unclear. In this study, skin transcriptome analysis was conducted to screen differentially expressed circRNAs (DE circRNAs) in Jinlan cashmere goats. Skin samples were obtained from two fleece phenotypes, namely coarse hair longer than cashmere (CHLC) and coarse hair shorter than cashmere (CHSC), at three hair follicle developmental stages: anagen (AN), catagen (CA), and telogen (TE). We identified 35, 84, and 115 DE circRNAs at the three developmental stages by comparing the two fleece phenotypes. GO and KEGG enrichment analyses revealed that the host genes of these phenotype-associated DE circRNAs exhibited distinct stage-specific functional signatures during hair follicle development, suggesting their potential roles in the formation of divergent fleece traits. GO terms and pathways enriched in the anagen stage primarily participate in substance transport and energy metabolism to support follicular cell proliferation and hair shaft morphogenesis, represented by BP terms including cation transport and transmembrane transport, and KEGG pathways such as carbon metabolism and lysine degradation. Catagen-related functional modules are associated with cell growth cessation and immune homeostasis to facilitate follicular remodelling. These modules are typified by BP terms for regulation of cellular process and biological regulation, along with KEGG pathways including the cell cycle and Ras signalling pathways. The telogen-specific functions focused on structural stability and maintenance of internal homeostasis to reserve follicle regenerative potential, corresponding to BP terms involving DNA metabolic process, as well as KEGG pathways including homologous recombination and tight junction. Beyond stage-specific regulation, shared GO terms and pathways across three stages formed a coordinated regulatory system to ensure orderly hair follicle cycle transition. Signal transduction and signaling were two core shared signaling terms across the AN and CA stages. Ubiquitin mediated proteolysis was co-enriched during AN and CA stages, and lysine degradation was commonly enriched in AN and TE stages. Several key pathways, such as tight junction and PI3K-Akt signaling pathway, were shared by CA and TE stages. Furthermore, ceRNA network analysis in catagen uncovered four hub candidate genes (TRIM32, IL34, IDUA, and SLC16A3). They are closely involved in follicle stem cell homeostasis, hair structural remodelling, and skin follicle development. Collectively, this study characterizes the circRNA-regulated regulatory network governing cyclic hair follicle development in cashmere goats, providing a theoretical basis and genetic resources for follicle mechanism research and cashmere molecular breeding.