Construction Of Single Cell Transcription Map Of Yak Hair Follicle And Its Cycle Transition Analysis

The complex mixed hair coat structure and the seasonal growth of the villi of the yak will help it survive in the cold and high altitude areas.As a micro-organ produced by villus,hair follicles continue to experience three stages of telogen,anagen and catagen.The continuous regeneration cycle of hair follicles is a very complex process,involving the interaction of different types of hair follicle cells to jointly regulate the formation of hair follicle structure.Single cell RNA sequencing(scRNA-seq)technology can highlight cell heterogeneity at the single cell level of different tissues and organs.Therefore,studying the relationship between the diversity of cell types in hair follicles and the morphogenesis of hair follicles,and the regulation of different cell types in hair follicles,provide a scientific basis for analyzing the functional diversity of cells in hair follicles.In order to explore the molecular regulation of periodic conversion of yak hair follicles,this study collected skin tissue samples from the scapula of yaks and prepared single cell suspension for scRNA-seq.The transcription profiles of hair follicle cells in anagen and catagen,telogen and anagen were constructed.The main cell groups were identified by using known marker molecules.The morphogenesis process of hair follicles from anagen to catagen,telogen to anagen was analyzed by t-distributed stochastic neighbor embedding clustering,uniform manifold approximation and projection clustering,gene ontology and pseudo-time series analysis,and the molecular pathways of main cell types were described.The main results are as follows:1.In order to analyze the cell heterogeneity during hair follicle morphogenesis,scRNA-seq was performed on the three stages of yak hair follicle telogen,anagen and catagen,and the number of cells reached 30,000.Based on the Seurat function,the data set was quality-controlled,and the genes of each cell and the total number of nCount＿RNA in the three periods were detected.2.A total of 19 cell clusters were obtained from the anagen and catagen,and 8 major cell populations were identified,and the obtained cell molecular characteristics were further enriched.The results showed that epidermal cell lines,inner root sheath(IRS)and hair shaft(HS)cells were mainly involved in the transition from anagen to catagen.The enrichment results showed that the cell-specific expression genes were significantly enriched in epidermal development,epithelial cell differentiation and wound healing.3.Through pseudotime trajectory analysis,the differentiation trajectory of epidermal and dermal cell lineages in the hair follicle cycle and the expression changes of major cell pseudo-time genes during the transition from the anagen to the catagen were described.The specialization process of epidermis to HS and IRS cells was described.LHX2,KRT25 and KRT71 genes were highly expressed during the specialization of HS and IRS,and these genes were similar to the expression results in mouse HS and IRS specialization.4.The main cell types of yak hair follicles during the transition from telogen to anagen were screened and identified at the single cell level.The main cell types such as HS,IRS and dermal papilla(DP)cells were obtained by uniform manifold approximation and projection clustering.Based on pseudo-temporal analysis,the differentiation trajectory of DP cells was successfully constructed.This paper systematically expounds the changes of gene expression in the process of DP cell specialization,and reveals the key genes and functions involved in the fate of DP cells.In summary,this study described the process of differential gene expression over time during the differentiation of dermal cell lineage and epidermal cell lineage in the anagen and catagen of yak hair follicle cycle transition from the single cell level.The main cell types were identified,and the fate specialization of the main cell types was demonstrated.At the same time,a single cell transcriptome map during the hair follicle transition of the telogen and anagen was constructed,and the DP cell lineage differentiation trajectory was constructed.The DP cell population during the hair follicle transition of the telogen and anagen was analyzed more systematically and comprehensively.Different types of cells in the hair follicle cycle were analyzed by scRNA-seq,which provided theoretical and data support for the growth and development of yak hair follicle cycle.