Dissertation Defense Announcement
To:  The George Mason University Community

Candidate: Kshama Aswath

Program: PhD in Bioinformatics & Computational Biology



Date:   Monday April 20, 2015

Time:   4:00 p.m.

Place:  George Mason University
             Fairfax Campus<http://www.gmu.edu/resources/welcome/Directions-to-GMU.html>

             Research I Bldg., Room 161



Title: "Exosomal Small RNA Survey of Bovine Milk: Discovery of Small RNA Signatures Across Bacterial Infections of the Bovine Mammary Glands"
Committee Chair: Dr. Donald Seto
Dissertation Director: Dr. Tad Sonstegard
Committee Members:  Dr. Jason Kinser, Dr. Lakshmi Matukumalli
A copy of the dissertation is available in the Mercer Library.  All are invited to attend the defense.
ABSTRACT:
Mastitis, an endemic disease, affects the mammary glands of the milk producing cows and contributes to an annual two billion dollars loss to the U.S. dairy economy (Hogeveen, Huijps, & Lam, 2011). Many bacterial pathogens, for example, Streptococcus uberis, Staphylococcus aureus and Escherichia coli, if left undetected and untreated at sub-clinical stages, for example, can cause infections of the mammary glands in the dairy cattle that may manifest into an endemic disease like Mastitis (Barkema, Green, Bradley, & Zadoks, 2009). Mastitis negatively affects  the quality and quantity of milk production in the dairy cattle (De Vliegher, Fox, Piepers, McDougall, & Barkema, 2012)  and extensive use of antibiotics to treat this disease can have possible implications on human health, which, in turn pose a threat to consumer safety. Recent research has shown the potential of circulating miRNAs as non-invasive biomarkers in disease diagnosis and monitoring (Zen & Zhang, 2012).  miRNAs present in the milk are shown to be selectively packaged into exosomes, a type of extracellular micro vesicles secreted by various cells (Valadi et al., 2007). This study aims at profiling the lactation related bovine milk miRNAs under two days post-infection with S. uberis and S. aureus bacterial inoculations, across nine Holstein-Friesian cattle.
This study is a part of a three pronged study of Mastitis in cattle initiated at National Animal Disease Center (NADC) (Ames, Iowa). Proteomic study was performed at NADC, Agricultural Research Services (ARS), USDA (Ames, Iowa).  A transcriptomics study was performed at the level of mRNA at Teagasc, Animal and Bioscience Research Department, Grange ( Dunsany, County Meath, Ireland ) by Dr. David Lynn's group and miRNA study was performed at ARS / USDA (Beltsville, MD).
Exosomal pellets collected from pre and post infections were used for the RNA extraction and sequencing of miRNA reads was performed using the Next Generation Sequencing (NGS) technology on the Illumina Genome Analyzer IIIx. A host of current bioinformatics tools were implemented in the data analysis. A total of 75.76 million reads were analyzed across S. aureus infections and 309 different types of miRNAs were profiled. Under S. uberis infections, a total of 59.52 million reads were analyzed and a total of 109 unique types of miRNAs are profiled. Differential expression analysis revealed 16 miRNAs under S. uberis infection over the controls, while 35 miRNAs were differentially expressed under S. aureus infections over the controls. This novel information of exosomal small RNA profiles, in the bovine milk, provides a comprehensive list of  bovine miRNAs and other small RNA signatures across healthy and (bacterial) infections of the mammary glands in dairy cattle. These miRNA profiles could prove to be a key to the development of  molecular markers in the future, specifically in the early (sub-clinical) detection of an endemic disease like Mastitis.
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