Integration of bulk and single-cell RNA sequencing reveals dynamic changes in epidermal cells

The epidermis and its appendages serve as key systems in stem cell biology. However, despite extensive research, the dynamic changes in these structures and the regulatory mechanisms governing cell behavior during the hair follicle cycle remain incompletely understood. In this study, we employed bulk and single-cell RNA sequencing to investigate the molecular regulation of yak epidermal cell populations across the anagen, catagen, and telogen phases. Through bulk transcriptomics screening, the hub genes potentially involved in the hair follicle cycle of yaks were identified. Single-cell RNA sequencing further revealed the temporal and spatial dynamics of 14 different cell populations in the hair follicle cycle, and reconstructed the trajectory of epidermal cell differentiation. We also found a large overlap of gene modules in the hair follicle microenvironment. Differential gene enrichment analysis of different branches further revealed that the function of hair follicle stem cells is closely related to their spatial location in tissues and their ability to adhere to the basement membrane. Our study not only provides valuable resources for understanding the molecular pathways of the time axis and spatial axis of the hair follicle cycle but is also highly important for future yak breeding.