Comparison of miRNA expression profiles in pituitary-adrenal axis between Beagle and Chinese Field dogs after chronic stress exposure

A review on microRNA detection and expression studies in dogs

MicroRNAs (miRNAs) are small non-coding RNAs that function by post-transcriptional regulation of gene expression. Their stability and abundance in tissue and body fluids makes them promising potential tools for both the diagnosis and prognosis of diseases and attractive therapeutic targets in humans and dogs. Studies of miRNA expression in normal and disease processes in dogs are scarce compared to studies published on miRNA expression in human disease. In this literature review, we identified 461 peer-reviewed papers from database searches using the terms "canine," "dog," "miRNA," and "microRNA"; we screened 244 for inclusion criteria and then included a total of 148 original research peer-reviewed publications relating to specific miRNA expression in canine samples. We found an overlap of miRNA expression changes between the four groups evaluated (normal processes, non-infectious and non-inflammatory conditions, infectious and/or inflammatory conditions, and neoplasia) in 39 miRNAs, 83 miRNAs in three of the four groups, 110 miRNAs in two of the three groups, where 158 miRNAs have only been reported in one of the groups. Additionally, the mechanism of action of these overlapping miRNAs varies depending on the disease process, elucidating a need for characterization of the mechanism of action of each miRNA in each disease process being evaluated. Herein we also draw attention to the lack of standardization of miRNA evaluation, consistency within a single evaluation method, and the need for standardized methods for a direct comparison.

MicroRNA and Messenger RNA Expression Profiles in Canine Mammary Gland Tumor

Canine mammary gland tumor (CMT) is the most frequently diagnosed neoplasm in intact female dogs. As prognosis depends on the malignancy of tumors and metastasis levels, early and accurate diagnosis are crucial for prolongation of life expectancy. The genetic similarity of dogs with humans in addition to environmental and physiological similarities make them ideal models for the study of cancer. In this study, we analyzed differentially expressed microRNAs followed by RNA-Seq to investigate the alterations in mRNA levels based on the malignancy (benign, malignant) and the biopsy locations (tumors, surrounding normal tissues). We identified multiple breast cancer-related genes regardless of malignancy. We found cfa-miR-503 to be the only miRNA that showed altered expression in response to malignancy in CMTs. Although further validation is needed, cfa-miR-503 could be used as a potential diagnostic biomarker as well as a potential RNA-based anti-tumor drug in malignant CMTs.

Hippocampal glucocorticoid receptor and microRNA gene expression and serum cortisol concentration in foxes selected for behavior toward humans

In many cases, stress reactivity is one of the important bases of aggressive behavior. It appears as if reduced stress reactivity underlies an abrupt decrease in aggression towards man in domesticated animals. However, the mechanisms of this reduction have yet to be resolved. In this work, we used an experimental domestication model, the silver fox selected for many years for the response to humans to study cortisol stress reactivity in tame and aggressive foxes in response to immobilization in human arms. Additionally, these behavioral fox groups were explored for one of the important mechanisms of glucocorticoid negative feedback, the expression of the glucocorticoid receptor gene (NR3C1) in a portion of the dorsal hippocampus. In recent years, attention has been paid to differences in miRNA expression patterns between animals with different behavior and stress reactivity, as well as to miRNA regulation under stress. The same applies to NR3C1 mRNA as well. That is why we performed a miRNA-seq analysis on a portion of the fox dorsal hippocampus. It has been demonstrated that immobilization in human arms leads to significantly higher stressinduced cortisol levels in aggressive than tame foxes. At the same time, no differences have been found between hippocampal NR3C1 gene expression and the pattern of miRNA expression. Thus, reduced stress reactivity in foxes during selection for the absence of aggressive responses and for the presence of emotionally positive responses to humans does not seem to be associated with important mechanisms of regulation such as alterations in hippocampal NR3C1 gene expression or microRNA-mediated silencing.