Genetic mechanisms regulating the host response during mastitis

摘要

Mastitis is a very costly and common disease in thedairy industry. The study of the transcriptome fromhealthy and mastitic milk somatic cell samples usingRNA-Sequencing technology can provide measurementsof transcript levels associated with the immuneresponse to the infection. The objective of this studywas to characterize the Holstein milk somatic cell transcriptomefrom 6 cows to determine host response tointramammary infections. RNA-Sequencing was performedon 2 samples from each cow from 2 separatequarters, one classified as healthy (n = 6) and one asmastitic (n = 6). In total, 449 genes were differentiallyexpressed between the healthy and mastitic quarters(false discovery rate <0.05, fold change >±2). Amongthe differentially expressed genes, the most expressedgenes based on reads per kilobase per million mappedreads (RPKM) in the healthy group were associatedwith milk components (CSN2 and CSN3), and in themastitic group they were associated with immunity(B2M and CD74). In silico functional analysis wasperformed using the list of 449 differentially expressedgenes, which identified 36 significantly enriched metabolicpathways (false discovery rate <0.01), some ofwhich were associated with the immune system, suchas cytokine-cytokine interaction and cell adhesionmolecules. Seven functional candidate genes were selected,based on the criteria of being highly differentiallyexpressed between healthy and mastitic groupsand significantly enriched in metabolic pathways thatare relevant to the inflammatory process (GLYCAM1,B2M, CD74, BoLA-DRA, FCER1G, SDS, and NFKBIA).Last, we identified the differentially expressedgenes that are located in quantitative trait locus regionspreviously known to be associated with mastitis,specifically clinical mastitis, somatic cell count, andsomatic cell score. It was concluded that multiple geneswithin quantitative trait locus regions could potentiallyaffect host response to mastitis-causing agents, makingsome cows more susceptible to intramammary infections.The identification of potential candidate geneswith functional, statistical, biological, and positionalrelevance associated with host defense to infection willcontribute to a better understanding of the underlyinggenetic architecture associated with mastitis. Thisin turn will improve the sustainability of agriculturalpractices by facilitating the selection of cows with improvedhost defense leading to increased resistance tomastitis.