The seasonal development dynamics of the yak hair cycle transcriptome
Abstract Background: Mammalian hair play an important role in mammals' ability to adapt to changing climatic environments. The seasonal circulation of yak hair helps them adapt to high altitude but the regulation mechanisms of the proliferation and differentiation of hair follicle (HF) cells during development are still unknown. Here, using time series data for whole genome expression profiles and hormone contents, we systematically analyzed the mechanism regulating the periodic expression of hair development in the yak and reviewed how different combinations of genetic pathways regulate HF development and cycling. Results: This study used high-throughput RNA sequencing to provide a detailed description of global gene expression in 15 samples from five developmental time points during the yak hair cycle. A total of 11,666 genes were found to be involved in the hair cycle. According to clustering analysis and the morphological features we observed, we found that these 15 samples could be significantly grouped into three phases, which represent different developmental periods in the hair cycle. A total of 2,316 genes were identified in these three consecutive developmental periods and their expression patterns could be divided into 9 clusters; GO annotation and KEGG pathway enrichment were performed on these differentially expressed genes (DEGs), showing that the three periods have distinctive functions in the seasonal hair cycle. The regulatory network of related signaling factors highlighted the interaction and dynamic expression of key DEGs during the seasonal hair cycle. Through co-expression analysis, we revealed a number of modular hub genes highly associated with hormones that may play unique roles in hormonal regulation of events associated with the hair cycle. Conclusions: Our results revealed the molecular mechanisms and developmental regulatory networks of the seasonal hair cycle in the yak and filled a gap in the current research field. The findings will be valuable in further understanding the alpine adaptation mechanism in the yak, which is important in order to make full use of yak hair resources and promote the economic development of pastoral plateau areas. Keywords: Hair cycle, Seasonal development, Transcriptome, Yak