Etv2 is an endothelial-specific ETS transcription factor that is essential for endothelial differentiation and vascular morphogenesis in vertebrates. However, etv2 expression dynamics during development and the mechanisms regulating it are poorly understood. I found that etv2 transcript and protein expression are highly transient during zebrafish vascular development, with both expressed early during development and then subsequently downregulated. Inducible knockdown of Etv2 in zebrafish embryos prior to mid-somitogenesis, but not later, causes severe vascular defects, suggesting a role for Etv2 in specifying angioblasts from the lateral mesoderm. I further demonstrate that the 3’UTR of etv2 is post-transcriptionally regulated in part by the let-7 family of microRNAs. Ectopic expression of let-7a represses endogenous Etv2 transcript and protein expression with a concomitant reduction in endothelial cell gene expression. Additionally, overexpressed Etv2 in HEK293T cells is ubiquitinated and degraded by the proteasome. Accordingly, endogenous zebrafish Etv2 protein is rapidly degraded in the presence of the translation inhibitor cycloheximide in vivo. Taken together, our results suggest that etv2 acts during early development to specify endothelial lineages and is subsequently downregulated through post-transcriptional and post-translational mechanisms, to allow normal vascular development to proceed.

A variety of diseases lead to the atrophy and/or death of skeletal muscle. To better understand the molecular mechanisms that mediate these processes, I have taken advantage of the intersegmental muscles (ISMs) of the tobacco hawkmoth Manduca sexta, which undergo sequential programs of atrophy and programmed cell death at the end of metamorphosis. ISM death is mediated by changes in gene expression and numerous cell-death associated transcripts have been identified. MicroRNAs (miRs) are small (~22 nucleotide) non-coding RNAs that bind to sequences in messenger RNAs (mRNAs) and either cause translational arrest or mRNA degradation. To test the hypothesis that developmentally regulated miRs may control the stability and/or translatability of target mRNAs in the ISMs, putative mRNA targets for the test miRs have been identified and their 3’ untranslated region (UTR) have been cloned into a dual luciferase reporter plasmid. The microRNA mir-92b binds to the 3’ UTR of the Small Cytoplasmic Leucine Rich repeat Protein (SCLP) mRNA. Expression of miR-92b declines during development and SCLP expression increases with the commitment to die. I found that the miR-92b inhibits luciferase mRNA translation (spectrophotometric plate assays), but does not lead to transcript degradation (quantitative polymerase chain reaction; qPCR). miR-92 plays a survival role in several mammalian tissues and is repressed in two types of cardiomyopathy. Consequently, understanding how miRs regulate mRNA translation and stability may provide a better understanding of the regulation of muscle atrophy and death as well as provide novel tools for diagnostics or therapeutics.

Indiana University-Purdue University Indianapolis (IUPUI) / A hallmark of diabetes is the loss of physical or functional Beta (β) cell mass. Maladaptive intrinsic β cell responses to islet inflammatory stress may exacerbate diabetes development, suggesting that β cells themselves may not be innocent bystanders in diabetes development. MicroRNAs (miRNAs), small RNAs that repress mRNA translation, serve as important regulators of β cell development and function. β cell microRNA 21 (miR-21) is increased in models of diabetes and I have identified Hypoxia Inducible Factor 1 Subunit Alpha (Hif1a) as a regulator of β cell miR-21. However, β cell effects of miR-21, remain poorly defined. To define the effects of miR-21, an in silico analysis of predictive targets of miR-21 identified multiple targets associated with maintenance of β cell identity, including the SMAD Family Member 2 (Smad2) mRNAs in the Transforming Growth Factor Beta 2 (Tgfb2) pathway. Based on this, I hypothesized that β cell miR-21 induces dysfunction via loss of β cell identity. To test this, I developed a tetracycline-on system of miR-21 induction in clonal β cells and human islets, as well as novel transgenic zebrafish and mouse models of inducible β cell specific miR-21 overexpression. β cell miR-21 induction increased aldehyde dehydrogenase (aldh1a3), but reduced expression of transcription factors associated with β cell identity, and glucose stimulated insulin secretion (GSIS), consistent with β cell dedifferentiation and dysfunction. Predicted targets Tgfb2 and Smad2 were reduced by miR-21 overexpression and confirmed to directly bind miR-21 using streptavidin-biotin pulldown. In vivo models of β cell miR-21 induction exhibited hyperglycemia, increased glucagon expression, and decreased insulin expression. These findings implicate miR-21- mediated reduction of mRNAs regulating β cell identity as a contributor to β cell dedifferentiation and dysfunction during islet inflammatory stress. / 2022-05-19

microRNAs (miRNAs) are a class of noncoding RNAs that regulate gene expression. This class of 18-25 nucleotide-long non-coding RNAs has been found to play critical roles in the modulation of a wide spectrum of cellular processes including immunity, development, and metabolism. They modulate their interactions by binding to the 3’ untranslated region of the target messenger RNA to mediate the repression of gene expression. Given their emerging critical roles in the regulation of biological processes, it is not surprising that miRNAs play a significant part in modulating host-virus interactions. Viruses are obligate parasites that hijack the host cellular machinery and processes to promote their life cycle and their propagation. Emerging evidence suggests that miRNAs add an extra regulatory layer to fine-tune viral pathogenesis. This offers novel opportunities not only to delineate the crosstalk between the host and the virus but also allows for the development of novel therapeutics and the identification of novel potential biomarkers of viral infection. Herein, we examine the roles of various miRNAs in the modulation of host-virus interactions. In this thesis, we identify a polycistronic miRNA cluster (miR-183, miR-96, and miR-182) to possess antiviral properties against RNA viruses by augmenting innate immune responses to viral infection. We as well identify miR-383 to possess novel antiviral potential against Dengue virus (DENV), through its targeting of PLA2G4A, a pro-viral host factor essential for the production of infectious particles. Finally, we examine miR-185’s role in the modulation of SARS-CoV-2 infection where we show that miR-185’s regulation of fatty acid and cholesterol metabolism suppresses the virus’s entry and propagation in lung and liver cells. Collectively, the findings in this thesis demonstrate the critical role that miRNAs play in the modulation of host-virus interaction through modifying the host’s cellular environment essential for the regulation of viral pathogenesis.

MicroRNAs are small RNA molecules that could possibly play a major role in fertility. In the experiment, spermatozoa were extracted from bovine followed by an extraction of total RNA. Bovine spermatozoa were extracted from two bulls of different fertility, high and low fertility. An expression array was done to compare the expression levels of the microRNAs. It was shown that thousands of microRNAs are present in bovine spermatozoa but only a small amount was significantly expressed. The microRNAs from low fertility bulls were more highly expressed than those in high fertility bulls. A Bioanalyzer gel was used to confirm the results of the microarray data. The microRNAs were present in the bull’s spermatozoa at 25 nucleotides. The functions of the significantly expressed microRNAs are not known but there is a great possibility that their functions affect fertility.

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The global incidence of overweight and obese individuals has skyrocketed in the past few decades resulting in a new health epidemic. In 1980, 5% of males and 8% of females were categorized as obese; by 2008 these values doubled equating to half a billion adults worldwide. This surge of overweight and obese individuals has driven a dramatic increase in people afflicted with metabolic disorders. As such, the term "metabolic syndrome" (MetS) has been coined to describe several interrelated metabolic risk factors which often present in concert. Specifically, metabolic syndrome refers to the presence of at least three of the following five conditions: central obesity, elevated triglycerides, diminished high density lipoprotein (HDL) cholesterol, hypertension, and insulin resistance (IR). MetS is a major health concern due to its ability to increase the likelihood of cardiovascular disease (CVD), diabetes, and other life-threatening ailments. In light of this growing medical epidemic, we have concentrated our efforts in evaluating the role of microRNA-155 (miR-155) in MetS development. MicroRNAs are a newly defined class of small, non-coding RNA which contain the unique ability to regulate gene expression through RNA interference. As a result of this ability, microRNAs can mediate a wide variety of cellular processes. In order to evaluate the function of miR-155 in MetS, we established a novel miR-155-/-/ApoE-/- (DKO) mouse model. Coupling this model with the use of normal rodent or high fat diets allowed us to investigate how states of caloric balance and surplus affected the manifestation of the individual MetS components. We found that male and female DKO mice fed a high fat diet had significantly augmented body masses of 18% and 10% respectively, when compared to ApoE-/- counterparts on the same diet. Evaluation of this phenotype with body composition analysis revealed an 18% and 46% increase in body fat percentage among the male DKO mice on normal and high fat diets, respectively. This trend was also observed in female DKO mice, albeit to a lesser extent. This phenotype was further substantiated by the observation of augmented gonadal white adipose tissue pad mass within male and female DKO mice fed either chow. This equated to a 43% and 112% increase in male mice and a 45% and 57% augmentation in female mice for normal and high fat chow diets, respectively. In light of our findings, we also evaluated how miR-155 impacted glucose and insulin sensitivity. We found levels of insulin to be augmented by 181% and 148% in male DKO mice on normal and high fat diets, respectively. Furthermore, we found these mice to be euglycemic. These observations suggest that DKO mice are IR but capable of compensating for their insensitivity with elevated insulin production. Due to the tight association between MetS and the development of non-alcoholic fatty liver disease (NAFLD) as well as CVD, we felt it prudent to investigate the manifestation of these conditions. We found elevated hepatic mass of 40% and 13% in male and female DKO mice on high fat chow. Furthermore, hepatic discoloration was seen in these mice prompting us to perform in-depth histological evaluation which revealed widespread steatosis, a hallmark of NAFLD. Meanwhile, investigation of atherosclerosis, the key underlying cause of most CVDs, unexpectantly revealed diminished development. Due to the complex nature of atherosclerosis it is tough to explain the exact reason for this observation. Independent reports have shown that miR-155 plays a critical role in the development, maturation, or activation of B-cell, T-cells, macrophages, and dendritic cells. As a result, decreased immune cell infiltration may be the root cause for the observed decline in atherosclerosis. Taking into account our observations of obesity, IR, and NAFLD in conjunction with independent findings of blood pressure mitigation by miR-155, we feel confident in reporting that miR-155 is a vital factor in preventing MetS and NAFLD development. Despite this, we surprisingly found atherosclerosis development to be diminished in these mice suggesting a pro-inflammatory role in atherogenesis. This duality highlights the complex and ambiguous nature of miRNAs. In light of this, further evaluations should be conducted to gain additional insight into these pathologies and hopefully the development of novel therapeutics. / Pharmacology

Yes / Background - Previous studies have demonstrated that a number of HOX genes, a family of transcription factors with key roles in early development, are up-regulated in head and neck squamous cell carcinoma (HNSCC) and other cancers. The loci of several Homeobox (HOX) genes also contain microRNAs (miRs), including miR-196a. Methods - Global miR expression and expression of all 39 HOX genes in normal oral keratinocytes (NOKs), oral pre-malignant (OPM) and HNSCC cells was assessed by expression microarray and qPCR and in tissues by immunohistochemistry (IHC) and qPCR of laser microdissected (LCM) tissues. Expression of miR196a and HOXB9 was reduced using anti-miR-196a and siRNA, respectively. Expression microarray profiles of anti-miR196a and pre-miR196a transfected cells were compared to parental cells in order to identify novel targets of miR- 196a. Putative miR196a targets were validated by qPCR and were confirmed as binding to the 3’UTR of miR196a by a dual luciferase reporter assay combined with mutational analysis of the miR-196a binding site. Results - miR-196a and HOXB9 are highly expressed in HNSCC compared to NOKs, a pattern also seen in HNSCC tissues by HOXB9 IHC and qPCR of miR-196a in LCM tissue. Knock-down of miR-196a expression decreased HNSCC cell migration, invasion and adhesion to fibronectin, but had no effect on proliferation. Furthermore, knock-down of HOXB9 expression decreased migration, invasion and proliferation but did not alter adhesion. We identified a novel primary mRNA transcript containing HOXB9 and miR196a-1 as predicted from in-silico analysis. Expression array analysis identified a number of miR196a targets, including MAMDC2 and HOXC8. We confirmed that MAMDC2 is a novel miR-196a target using a dual luciferase reporter assay with the effect abolished on mutation of the binding site. Conclusions - These results show that miR-196a and HOXB9 are overexpressed, perhaps co-ordinately, as HNSCC develops and exert a pro-tumourigenic phenotype in HNSCC and OPM cells.