Single-cell Transcriptomic And Chromatin Accessibility Analyses Of Dairy Cattle Peripheral Blood Mononuclear Cells And Their Responses To Lipopolysaccharide

The main components of peripheral blood mononuclear cells(PBMCs)include lymphocytes and monocytes.These cells are closely related to the body’s immunity.In the actual production of cattle,the infection of gram-negative bacteria is one of the main causes of severe inflammation.Inflammation may reduce the growth rate of cattle and increase the incidence rate and mortality rate of cattle,which will lead to economic losses.LPS(Lipopolysaccharide)is the main component of the outer membrane of gramnegative bacteria and the main pathogenic substance.Although many studies have been done on the immune response of cattle to LPS,there is still a lack of research on the LPS response of cattle PBMCs at the single cell level.In this study,four cattle PBMCs samples were analyzed for single cell transcriptome and chromatin accessibility.The main results are as follows:1.Using cell-specific marker genes,7 cell populations of different cell types were obtained from 26,141 single-cell RNA sequencing data of four cattle PBMCs samples that were treated with LPS at different times.In addition,two methods were used to verify the clustering results.2.By performing cell cycle,pseudo-time trajectory,regulatory network,gene coexpression network,gene ontology(GO),differentially expressed genes(DEG)and chromatin accessibility analysis,these immune cell types were annotated and studied.Their immune response to LPS.Research results show that LPS can induce host B cell proliferation and activation of monocytes,dendritic cells and macrophages through TLR4 receptor binding,thereby activating transcription factors such as NF-κB and promoting the production of pro-inflammatory cytokines and other factors Secretion,which initiates the innate and adaptive immune response.3.By integrating cell-type marker genes and DEGs included by LPS with large-scale GWAS of 45 complex traits in Holstein,we detected trait-relevant cell types and found LPS-induced DEGs were significantly associated with milk production,immune-relevant health and body conformation traits.4.By comparing them with human PBMCs samples to confirm their cell types.In summary,this study performed single cell transcriptome and chromatin accessibility analysis in cattle PBMCs,and demonstrated the types of immune blood cells and their response to LPS,which deepened the understanding of the response of cattle PBMCs to LPS.It provides a basis for finding the role of tissue / cell type in complex traits with economic value at the single cell level.