Title: MicroRNA content in milk exosomes as a phenotypic indicator of Staphylococcus aureus infection in the bovine mammary gland Authors
Submitted to: BARC Poster Day
Publication Type: Abstract Only
Publication Acceptance Date: April 15, 2014
Publication Date: April 23, 2014
Citation: Jiajie, S., Kshama, A., Schroeder, S.G., Reinhardt, T.A., Lippolis, J.D., Sonstegard, T.S. 2014. MicroRNA content in milk exosomes as a phenotypic indicator of Staphylococcus aureus infection in the bovine mammary gland. BARC Poster Day, Poster 61, pp. 73. Technical Abstract: Previous gene mapping research to understand the host genetic response to mammary infection based on somatic cell score has been unsuccessful due to the poor correlation of this confounding trait with mastitis, a disease costing the dairy industry an estimated $2 billion in annual costs. Recently, miRNAs have been identified in many body fluids, including serum and plasma, saliva, urine, milk, and cell culture supernatants, and that the unique expression patterns of miRNAs in various body fluids may serve as non-invasive or minimally invasive biomarkers for various diseases. MicroRNAs (miRNAs) are a family of ~22 nucleotide small RNA molecules that bind primarily to the 3’UTR of target mRNAs to repress their translation and accelerate their decay, and can regulate up to 30% of all expressed transcripts. The goals of this study were to identify if microRNAs could be detected from milk samples, and if so, determine which miRNAs were associated with or induced by bacterial infection of the mammary gland. Exosomes were harvested from aseptically collected milk of 4 mid-lactation Holstein cows in an uninfected state or 2 days post-infection with a controlled dose of S. aureus, one of the main infective agents that causes mastitis. Total RNA was extracted from these membranous vesicles (30~100 nm in diameter) of endocytic origin and small RNA libraries were constructed for next generation sequencing. Over 76.44 million sequencing reads were produced from 8 libraries and analyzed by genome alignment to identify 720 different expressed miRNAs. The top 10 most prevalent miRNAs in both control and infected replicates accounted for approximately 80% of all aligned reads, with the remaining differentially expressed miRNAs showing much lower expression. Six miRNAs (Bta-miR-101, -142-5p, -183, -2285g-3p, -223 and -99a-5p) were found to be differentially present in exosomes during infection (p<0.05), and these small RNA transcripts will serve as target molecules to develop potential diagnostic tests that can be used to detect early stages of bacterial infection of the mammary gland. Such information can then be used to generate phenotypic data in diary resource populations to investigate genome methods for genetic improvement to incidence of mastitis.