Aging is the most prevalent risk factor behind many common diseases such as cancer, cardiovascular disease, and various neurodegenerative diseases. The changes that take place with age are complex and affect most of the human body; age-related changes in gait, in particular, have been found to be associated with the onset of disease. While it is generally understood that there is an effect of aging on walking speed in humans, the mechanisms underlying age-related locomotor impairment have not yet been fully characterized. The focus of my research is using Drosophila melanogaster as a model to investigate such mechanisms. My hypothesis is that D. melanogaster exhibit similar age-related changes in gait as those seen in humans, which includes a decrease in walking velocity and duration, and a significant change in limb coordination over their lifespan. I followed cohorts of D. melanogaster over their lifespans and recorded videos of their walking in an arena. I then used these videos to study factors such as walking velocity and duration by analyzing the trajectories of each fly. In addition, I investigated more in-depth limb coordination of individual flies by analyzing the movement of each individual leg. Previous studies using D. melanogaster have found a significant decrease in climbing behavior with age, but have not looked at gait on a finer scale. Therefore, upon completion of this study, I expect to see a decrease in limb coordination and population walking velocity as the flies age. With the findings from this study, I hope to establish a foundation for how gait changes with age in D. melanogaster and to further use gait analysis to help predict the onset of disease and to distinguish between diseased and healthy flies.

Alzheimer’s Disease (AD) is a neurological disease that causes memory loss and neurodegeneration, and is one of the leading causes of death within the United States. Alzheimer’s is linked to the presence of neurofibrillary tangles within the brain, generated by hyperphosphorylation and aggregation of a protein called tau. However, the specific impact that tau has on biochemical pathways in neurons is largely unknown. My project attempts to fill this gap. I compared samples of wild type fruit flies, Drosophila melanogaster, with a strain which expresses the human tau gene in neurons. Despite the difference in human and fly brains, determining the affected biochemical pathway in flies could suggest similar effects in humans. I am using metabolomics, which quantifies the levels of approximately one hundred metabolites, to try to identify the biochemical pathways that are affected by expression of tau in the neurons. Head and body samples of these two fly strains were frozen at 12 days of age and assayed for a targeted set of metabolites. I analyzed these metabolome data using statistical methods in Python to search for potential differences between wild type and tau flies. Any metabolites found to be different will then be analyzed to see if they tend to represent similar biochemical pathways, allowing us to speculate about the effect of tau on those pathways, both in flies and humans. Future work aims to analyze fly brains and individual neurons, thus mapping the affected metabolic pathways more precisely. Importantly, metabolic pathways are often identical between organisms, allowing us to speculate on the effect tau has on similar pathways within humans, thus this work will inform our understanding of the mechanism of AD in humans.

In the brain, insulin acts to improve cognition and enhance memory. Exercise has likewise been shown to improve cognition and to decrease serum insulin levels in the periphery. Thus, we hypothesized that the cognitive benefits of exercise can be explained in part by increased insulin transport into the brain across the blood-brain barrier. Singly-housed male CD-1 mice had voluntary access to running wheels for twenty-four hours. Control, sedentary mice had access to locked running wheels for the same duration. At the end of this time, mice were anaesthetized and received an IV injection of 125I-insulin, which circulated 0.5-10 minutes, and then their brains were collected and measured for radioactivity. Compared to the sedentary control group, exercised mice experienced a significant increase in insulin uptake into the brain. We then repeated the study but allowed mice to run for two weeks. In this case, exercised mice experienced increased insulin transport in the olfactory bulb and hypothalamus, but not the brain as a whole. Taken together, these results suggest that exercise causes an increase in insulin transport across the blood-brain barrier, and the duration of exercise can affect where this enhanced transport occurs. Our findings provide insight into the link between physical activity and insulin kinetics. Future work should focus on mouse behavioral studies to determine if the physiological findings shown here correspond to an improvement in memory.

Enteric alpha defensins, such as human defensin 5 (HD5), are antimicrobial peptides secreted by Paneth cells in the lumen of the small intestine as part of the innate immune response. Defensin activity effectively inhibits many bacterial and viral pathogens during infection. However, not all pathogenic human viruses are neutralized in the presence of defensins. For example, among the seven human adenovirus (HAdV) species, infections of certain serotypes are enhanced by HD5, while other serotypes are inhibited. Our goal is to identify the molecular determinants that confer HAdV neutralization or enhancement by HD5. We have previously identified regions of the three major capsid proteins that form the outside of the virus, hexon, penton base, and fiber, as key determinants. We identified these determinants through rational design and the creation of chimeric viruses in which we swapped portions of the three major capsid proteins between two serotypes with opposite HD5-dependent phenotypes. From these data, we have created a model of the enhancement and neutralization mechanisms. To further test these models, I am creating a panel of chimeric HAdVs by swapping capsid components from additional HAdV species and serotypes. I will study the concentration-dependent effect of HD5 on each chimera’s infectivity compared to the wild type viruses, which will uncover new mechanistic detail and allow us to create a more generalized model.

  My research focuses on ‘tauopathy’—the pathological effects of misfolding of the tau protein—using the fruit fly, Drosophila melanogaster, as a model system. In particular, I am interested in how the expression of tau affects locomotive function. Tau is a protein found in both humans and flies that is associated with stabilizing neuronal microtubules. However, under certain physiological conditions, human tau proteins form neurotoxic aggregates in the brain. This neuronal damage leads to dementia, a hallmark of Alzheimer’s Disease (AD). Aging comes with a multitude of age-related functional deficits, including decline in locomotor function. Some individuals with AD pathology are never diagnosed, however, because the cognitive impairment they experience is not sufficient for a clinical diagnosis of dementia, the most common symptom of AD. Consequently, it is imperative we understand AD as more than dementia. I study the climbing abilities of transgenic tau and control flies through negative geotaxis assays. Negative geotaxis refers to the tendency of flies to move vertically upward when startled. For my project, I am measuring the climbing performance of the flies to see the effects of tau on locomotor function as flies age. I hypothesize that the neurotoxic tau aggregates that form will interfere with neural activity involved in the flies’ motor function, resulting in decreased climbing performance. This research holds an abundance of biomedical implications and a capacity to better the lives of many. By using motor function to flag at-risk individuals early in their lives, they have the opportunity to participate in preclinical AD clinical trials that may prevent them from developing AD pathology later on. It is important that we, as a scientific community, strive to better understand the effects of aging and tauopathies, as it is through this understanding we can provide elderly individuals with care that transforms their quality of life.

Mycobacterium tuberculosis (Mtb) is a bacterium that kills nearly 2 million people annually and continues to be a large threat to the health of individuals around the world. T-cells play a key role in the immune response to Mtb infection, but there is still much we do not understand about their role in mediating protection. CD4 and CD8 are glycoproteins found on the surface of T cells. CD4 and CD8 T-cells recognize glycolipids associated with the bacterium, such as glucose monomycolate (GMM), that are presented by the cell-surface glycoprotein CD1b on a human antigen presenting cell. I am focused on identifying the T-cell receptor (TCR) of a T-cell line from the Rhesus Macaque species. Using newly validated CD1b tetramers, I sorted for T-cells that can bind to the GMM lipid antigen using flow cytometry. The tetramer is made up of four CD1b molecules which present the antigen and bind to T-cells that have a matching receptor. I used various molecular techniques such as RNA extraction, 5’ RACE PCR (a procedure for amplification of nucleic acid sequences using a messenger RNA template), and in fusion cloning to determine the TCR gene sequence of the alpha and beta chain regions. By identifying the sequence of a T-cell receptor in the Rhesus Macaque species we will be expanding our knowledge of how T cells recognize Mtb lipids in non-human primates. Since we have previously published that CD1d-restricted TCRs are very similar between NHP (non-human primates) and humans, we expect the same is true here. We can use tetramers and the NHP model to understand how lipid-specific T cells are important for controlling Mtb.