title: Next generation sequencing reveals the expression of a unique miRNA profile in response to a gram-positive bacterial infection.
abstract: MicroRNAs (miRNAs) are short, non-coding RNAs, which post-transcriptionally regulate gene expression and are proposed to play a key role in the regulation of innate and adaptive immunity. Here, we report a next generation sequencing (NGS) approach profiling the expression of miRNAs in primary bovine mammary epithelial cells (BMEs) at 1, 2, 4 and 6 hours post-infection with Streptococcus uberis, a causative agent of bovine mastitis. Analysing over 450 million sequencing reads, we found that 20% of the approximately 1,300 currently known bovine miRNAs are expressed in unchallenged BMEs. We also identified the expression of more than 20 potentially novel bovine miRNAs. There is, however, a significant dynamic range in the expression of known miRNAs. The top 10 highly expressed miRNAs account for >80% of all aligned reads, with the remaining miRNAs showing much lower expression. Twenty-one miRNAs were identified as significantly differentially expressed post-infection with S. uberis. Several of these miRNAs have characterised roles in the immune systems of other species. This miRNA response to the Gram-positive S. uberis is markedly different, however, to lipopolysaccharide (LPS) induced miRNA expression. Of 145 miRNAs identified in the literature as being LPS responsive, only 9 were also differentially expressed in response to S. uberis. Computational analysis has also revealed that the predicted target genes of miRNAs, which are down-regulated in BMEs following S. uberis infection, are statistically enriched for roles in innate immunity. This suggests that miRNAs, which potentially act as central regulators of gene expression responses to a Gram-positive bacterial infection, may significantly regulate the sentinel capacity of mammary epithelial cells to mobilise the innate immune system.
authors.affiliation: Animal and Bioscience Research Department, Animal and Grassland Research and Innovation Centre, Teagasc, Grange, Dunsany, County Meath, Ireland.
authors.forename: Nathan
authors.initials: N
authors.lastname: Lawless
authors.forename: Amir B K
authors.initials: AB
authors.lastname: Foroushani
authors.forename: Matthew S
authors.initials: MS
authors.lastname: McCabe
authors.forename: Cliona
authors.initials: C
authors.lastname: O'Farrelly
authors.forename: David J
authors.initials: DJ
authors.lastname: Lynn
mesh_terms: D000818:Animals; D002417:Cattle; D002478:Cells, Cultured; D002874:Chromosome Mapping; D004847:Epithelial Cells / Q000382:microbiology; D005260:Female; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial; D016908:Gram-Positive Bacterial Infections / Q000235:genetics* / Q000662:veterinary; D059014:High-Throughput Nucleotide Sequencing; D054884:Host-Pathogen Interactions; D007113:Immunity, Innate; D008321:Mammary Glands, Animal / Q000382:microbiology; D008414:Mastitis, Bovine / Q000235:genetics* / Q000382:microbiology; D035683:MicroRNAs / Q000378:metabolism*; D017423:Sequence Analysis, RNA; D013291:Streptococcus
chemical_list: D035683:MicroRNAs