Blood microRNAomes profiling reveals signatures of lameness phenotypes in feedlot cattle
Creators: Li, Wentao
Publisher: name: University of Alberta Library
Year: 2022

<p>Maintaining the health of feedlot beef cattle is essential because diseases are directly associated with economic losses and animal welfare. Lameness is an important health issue in feedlot cattle. However, the molecular mechanisms behind cattle lameness have not been well studied. Moreover, there are different types of lameness with various causes, and visual diagnosis methods may not differentiate them, leading to misdiagnosis and ineffective treatment. Recent evidence has demonstrated that circulating microRNAs (miRNAs) in biological fluids can reflect the changes in the physiological status and biological processes in the tissues/organs, which can be used as biomarkers for disease diagnosis. Therefore, this thesis research aimed to characterize miRNA profiles in the whole blood of beef cattle using RNA-sequencing and to determine whether they were different between healthy (HC) and lame beef cattle with different lameness phenotypes, including digital dermatitis (DD), foot rot (FR), toe tip necrosis (TTN) and foot rot &amp; digital dermatitis combined (FRDD). In the first study (Chapter 2), although profiles of blood total miRNAs were not significantly different between healthy and lame cattle, 4 and 12 miRNAs were exclusively expressed in healthy and lameness phenotypes, respectively. In addition, 3, 7, 6, and 14 miRNAs were differentially expressed (FDR &lt; 0.05, and log2 fold change &lt; -1 or &gt; 1)) in the blood of DD, FR, TTN, and FRDD cattle when compared to that of healthy cattle. Further RT-qPCR validation analysis of 6 selected miRNAs, including three lameness phenotype-specific miRNAs (DD-specific: bta-miR-2904; FR-specific: bta-miR-200a; and TTN-specific: bta-miR-483) and three differentially expressed miRNAs (bta-miR-6119-3p, down-regulated in all lameness phenotypes; bta-miR-133a, up-regulated in the FR and TTN group; and bta-miR-1, up-regulated in the TTN group) confirmed that bta-miR-133a was highly expressed in the TTN group compared with HC and bta-miR-483 was highly expressed in the TTN group compared with FR as detected based on RNA-seq. Moreover, predicted functions of all differentially expressed miRNAs revealed that they were involved in functions of inflammation response and muscle cell development. The second study compared the temporal expression of miRNAs in the whole blood collected for three weeks after lameness diagnosis and treatment (DD, TTN, and FRDD) to identify the relationship between miRNA temporal expression changes and lameness recovery patterns. The comparison of blood miRNA profiles between recovered and unrecovered lame cattle revealed that some miRNAs (bta-miR-1 and bta-miR-206 in the DD and FRDD groups, respectively) were only expressed in the blood of unrecovered cattle and vice versa. The predicted functions of those uniquely and differentially expressed miRNAs in unrecovered cattle were mainly related to bacterial infection and muscle cell self-repair. Further time-series analysis revealed miRNAs with specific expression-changing patterns over three weeks following the first assessment for each lameness phenotype. The miRNAs identified in the patterns may involve functions related to infection and inflammatory response during the treatment period. In summary, the comparative miRNAome analysis revealed that the blood miRNAs might affect the functions related to muscle and immune functions of cattle as a result of varied pathogenesis of different lameness phenotypes. The two miRNAs: bta-miR-133a and bta-miR-483, are potential markers for TTN, which warrant future research on their functions and validation using large populations.</p>