Ryan M. O'Connell, Ph.D. - US grants

DESCRIPTION (provided by applicant): MicroRNAs (miRNAs) have quickly emerged as important regulators of mammalian physiology owing to their precise regulation of critical protein coding genes. Importantly, perturbations in expression or function of specific miRNAs has been linked to a plethora of human pathological conditions including cancer, autoimmunity, cardiovascular disease and neurodegeneration. Although miRNA gene deletion in mice via homologous recombination has led to an improved understanding of how they function during times of health and disease, there remains a fundamental need to manipulate miRNA genes and their target binding sites in the human germ line. This would allow for the study of their biology in man, and may be a strategic means by which miRNAs can be targeted therapeutically to combat human disease. We propose to develop a novel approach to activating, repressing or disrupting human miRNA genes in vivo by engineering TALE proteins that will function as transcription factors or nucleases that specifically target miRNA genes or their binding sites in the 3'UTRs of key target mRNAs. We will focus on targeting human miRNA---155, an oncomiR involved in regulating immune responses, and miR---146a, a tumor suppressor miRNA that inhibits inflammatory responses. Following proper targeting and disruption of these miRNAs or their binding sites in the 3' UTRs of relevant target mRNAs, a series of functional assays will be carried out to assess the roles of human miR---155 and miR---146a in regulating immune responses and cancer phenotypes. Beyond these two miRNAs, this approach will be compatible with any human miRNA making it a powerful, specific and versatile technology that has not yet been used to study miRNAs.

? DESCRIPTION (provided by applicant): Chronic, low-grade inflammation is a contributing factor to most age-related human diseases. However, the molecular mechanisms that sustain chronic inflammatory responses during aging remain poorly understood making it difficult to treat this deleterious condition. Over the past few years, studies have indicated that mammalian noncoding microRNAs (miRNAs) regulate a variety of acute inflammatory responses in young mice. We hypothesize that miRNAs also play critical roles in gauging inflammation during the aging process. Consistent with this, removal of miR-146a has recently been shown to cause an age-dependent inflammatory disease that recapitulates many aspects of chronic inflammation in patients, including progression to life-shortening disorders like cancer. We have used the miR-146a-/- model to identify and study other miRNAs that promote age-related inflammation, and have determined that miR-155 is necessary for disease to emerge in the miR-146a-/- mouse model. We have also found that miR-155 is required for spontaneous accumulation of T follicular helper cells, autoantibody production and the subsequent tissue inflammation that emerges in middle-aged miR-146a-/- mice. Further, we also have preliminary data indicating a T cell-intrinsic role for miR-155 as it promotes chronic inflammation in miR-146a-/- mice. We will carry out a research plan to determine which downstream phenotypes in miR-146a-/- are dependent on miR-155 function in T cells, and also determine the specific contribution by Tfh cells. The molecular mechanism by which miR-155 instructs Tfh cell development in miR-146a-/- mice will also be investigated. Furthermore, we will extend our studies into the clinic and determine if miR-155 and Tfh cell levels correlate with other markers of chronic, low-grade inflammation in healthy middle aged patients. Taken together, our research plan will provide valuable insight into the mechanisms underlying chronic inflammation, and determine whether miR-155 and Tfh cells are promising therapeutic targets with the potential to reduce chronic, low-grade inflammation and the myriad of diseases that stem from this pathological condition.

Abstract Mammalian microRNAs are critical regulators of several human diseases. As a result, therapeutic manipulation of miRNAs in diseased tissues has emerged as a promising approach to combating human disorders, and has had success in some settings. Yet, effective delivery of miRNAs or their inhibitors to many cell and tissue types continues to be a major challenge, and this underscores the need for improved methods of small RNA delivery to relevant cell types. Recent reports have demonstrated that miRNAs can be released from cells in small lipid vesicles called exosomes. In turn, the exosomes can deliver miRNAs to recipient cells, and this system is thought to constitute a novel form of intercellular communication. This process includes an endogenous miRNA delivery mechanism that is largely uncharacterized, yet could provide valuable insights into how therapeutic miRNA delivery can be improved and how inflammatory responses are regulated. Our preliminary data demonstrate that mouse bone marrow derived dendritic cells (BMDCs) produce exosomes that contain specific miRNAs, including the inflammatory regulators miR-155 and mIR-146a, that can be delivered to recipient immune cells and subsequently mediate target knockdown both in vitro and in vivo. This results in an altered response to endotoxin both in vitro and in vivo, which provides experimental evidence that exosome-transferred miRNAs provide a novel layer of regulating inflammation. Further, we have also been able to successfully load specific miRNA mimics into exosomes and demonstrate that they can be delivered to recipient cells in a functionally relevant manner. As a result of these findings, we hypothesize that exosomal miRNAs play novel regulatory roles during physiologically relevant inflammatory responses, and that through an improved understanding of this process, exosomes can ultimately be coopted to deliver specific miRNA cocktails in a therapeutically relevant manner. We will carry out the following specific aims to test these predictions. First, we will define the process of exosomal miRNA delivery to immune cells. Next, we will determine the functional relevance of exosomal miRNAs during inflammation using radiation chimeras and Rab27a/b DKO mice with impaired exosome production. Finally, we will engineer custom exosomes and test their impact on inflammatory disease. Together, this project will shed light on how exosome transfer of miRNAs is regulated, determine the role of this system during physiologically relevant inflammation, and begin to understand the translational potential of this novel process.

Abstract Older adults are prone to experience periods of muscle disuse resulting in muscle atrophy and weakness. Moreover, muscle recovery following a disuse event is impaired in older adults. Therefore, a high priority in the face of a rapidly growing aging population is a need to further understand the cellular mechanisms behind impaired muscle regrowth with aging. Macrophages and other immune cell populations (e.g., T-cells) are of critical importance to optimally restore muscle size following a period of disuse, however, their role under such conditions in aging skeletal muscle has surprisingly not been elucidated. Therefore, using a well-established mouse model of muscle disuse and regrowth, we have produced compelling preliminary data demonstrating impaired muscle regrowth in aged mice and this is accompanied by an altered macrophage immune response and recruitment in skeletal muscle during recovery. In the current proposal, we have proposed to conduct an extensive time course of the muscle macrophage (and other immune cells) response in old and young mice during recovery from disuse. We will also determine if inhibiting macrophage recruitment in young mice will result in a phenotype characteristic of old mice during recovery from disuse. We will utilize combined unique approaches of FACS and single cell RNA sequencing to extensively address these questions. These data will be foundational for additional mechanistic studies investigating upstream mediators of macrophage and other immune cell responses during recovery from disuse while also using novel immunotherapies to optimize muscle recovery in older muscle.

Neuroimmunology is a rapidly growing field of research that touches a number of critical human diseases including multiple sclerosis, epilepsy, spinal cord injury, and viral encephalopathies. Traditionally, researchers have been trained in either neuroscience or immunology whereas the Neuroimmunology Training Program at the University of Utah seeks to develop and train the next generation of researchers in both fields with a cross- disciplinary approach focused on the interplay between the immune and nervous systems during disease. This application is the result of ongoing collaborations between high caliber faculty on campus who recognized the need to develop a training program specific to the challenges of neuroimmunology. This application requests support for 4 pre-doctoral trainees who will be selected from an outstanding pool of candidates within our relevant graduate programs. The Neuroimmunology Training Program at the University of Utah will formally bring together 17 faculty members from across the neuroimmunology research spectrum to participate in mentorship, program-wide meetings, workshops, and boot camps to share expertise and further develop the neuroimmunology field. The training program will be overseen by two faculty directors and a steering committee focused on selecting and supporting trainees who are highly likely to exhibit continued success within the diverse field of neuroimmunology research. Selected trainees will be expected to participate in specialized training in quantitative literacy, statistical analysis, and scientific rigor and reproducibility within the context of neuroimmunology research. Given the exceptional training track record of our faculty, available and unique resources to support research and robust institutional support, the Neuroimmunology Training Program will provide and outstanding opportunity for trainees to develop intellectually, advance and optimize their thesis research projects, create a valuable network of colleagues, and prepare for a highly successful research career focused on the crossroads of immunology and neuroscience.

Project Summary Macrophages play an important role during inflammatory diseases such as colitis, being able to both promote and suppress inflammation depending on the context. Therefore, understanding ways to control macrophage behavior is important for understanding how to modulate inflammatory responses. Two biological regulators that play a critical role in macrophage identity and functional capacity are microRNAs (miRNAs) and metabolism. How these two major regulators of cellular function interact with each other has been a topic of recent interest. While several studies have explored how miRNAs regulate metabolic pathways, far fewer have explored how metabolism regulates miRNA expression and function. Our preliminary data indicate that glutaminolysis is a major regulator of miRNA expression in macrophages. One cluster of miRNAs that appears to be significantly impacted by glutaminolysis is the miR125a/miR99b/Let7e cluster, which is significantly reduced upon blockade of glutaminolysis. Based on our preliminary results, the transcription factor Hif1a appears to be a key link between glutaminolysis and miR125a/miR99b/Let7e cluster transcription. To build upon these promising preliminary re- sults, we will use biochemical approaches and newly developed transgenic mouse models to begin to examine how and why glutaminolysis regulates the expression of this prominent miRNA cluster. Further, we will utilize a mouse model of colitis to study this novel regulatory mechanism in the context of inflammatory disease. Results from this work will shed new light on how miRNAs are regulated by cellular metabolism in the innate immune system. These results will both fill a major gap in our knowledge of immune regulation, and inform the develop- ment of new therapeutic approaches aimed at modulating miRNAs to combat human disease.