Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disease characterized by the deterioration of both upper and lower motor neurons in the brain, brain stem, and spinal cord. Multiple missense mutations have been connected to ALS, including mutations in the Matr3 gene. Matrin-3 is an RNA and DNA-binding protein encoded by the Matr3 gene. Normally found in the nuclear matrix, Matrin-3 plays several roles vital to RNA metabolism, including splicing, mRNA transport, mRNA stability, and transcription. The most common Matr3 mutation identified in familial ALS (fALS) patients is the S85C mutation, but the mechanisms through which it contributes to ALS pathology remain unknown. This makes mouse models particularly useful in elucidating pathological mechanisms, having the potential to serve as preclinical models for therapeutic drugs. For this thesis project, an ALS mouse model for the Matr3 S85C mutation was created, specifically generating a CRISPR/Cas9 mediated knock-in mouse model containing the Matr3 S85C mutation expressed under the control of the endogenous promoter. The Matr3S85C/S85C mice displayed significant phenotypic differences, such as reduced size, impaired motor coordination, and shortening of lifespan. Moreover, the Matr3S85C/S85C mice exhibited ALS-like pathology in both the muscle and central nervous system (CNS). Muscle pathology included decreased muscle fiber size and Matrin-3 loss. CNS pathology included selective neurodegeneration, Matrin-3 loss, neuroinflammation, and reduction of N6-methyladenosine (m6A) RNA modifications. Bulk RNA sequencing (RNA-seq) revealed significant differential gene expression in the Matr3S85C/S85C mice compared to Matr3+/+ mice, with synaptic pathways being particularly affected. Overall, the Matr3 S85C mutation induced both phenotypic effects and ALS-like pathology in vivo.

Dementia is a disease affecting many individuals worldwide resulting in neurological deficits. The most common form of dementia known as Alzheimer’s Disease (AD) is the 6th leading cause of death in the United States. The disease is defined by neuron loss, the presence of intracellular tau protein (tubulin associated unit) neurofibrillary tangles (NFT), and extracellular amyloid- (Aβ) plaques. For this study, our aim was to understand the staging system used based off of the disease progression, called Braak Staging. Our hypothesis is that as disease progresses, marked by Braak stages, different brain regions will begin to show differential expressions of various biological dysregulations. Molecular dysfunctions of early disease will be precursors to later disease dysfunctions. The outcomes of our study indicated there were several molecular dysfunctions in early disease with tau pathology not present in the region yet.

Alzheimer’s disease (AD) is projected to increase, and understanding risk and protective factors could help mitigate this increase. Deficits in Choline, a B-like vitamin, intake or issues with endogenous choline production can lead to an increased risk for AD development. To better understand the effects of endogenous choline through the lifespan in the context of Alzheimer pathology, Male and Female 3xTg-AD and NonTg mice, were aged to 16.81 ± 0.13 months. Body weight, food consumption data, and blood plasma samples were collected across the lifespan. A behavioral battery, that consisted of Rotarod, Elevated Plus Maze, and Intellicage, was performed to assess differences across a range of tasks. Hippocampal and cortical tissue were collected to assess pathology. Overall, 3xTg-AD mice had lower choline levels than NonTg at multiple timepoints and Males had higher choline than Females. Furthermore, 3xTg-AD Females had higher levels of both Aβ and Tau pathology than their Male counterparts. In the Intellicage, Females made fewer Percent of Correct Responses during Place Preference. Together these findings show that choline levels through the lifespan, impact the severity of pathology between Males and Female 3xTg-AD mice and behavioral differences between the 3xTg-AD and NonTg mouse models.

This thesis explores the nature of Type II diabetes and Alzheimer’s disease to better understand their symptoms, treatments, and the factors that lead to further development; with a specific focus on the role that diet plays. Alternate connections outside of diet, including amyloidosis and inflammation, are additionally analyzed, but the focus remains on introducing diets that may be helpful in terms of preventative measures and controlling symptoms of diseases. Two major diets investigated are the Mediterranean diet and DASH, and why these diets are better suited for overall health, in comparison to a diet based primarily in high-fat or ultra-processed foods. This paper integrates information from scientists, medical professionals, and even personal testimony from a diabetic patient. This thesis will recommend legislation to better regulate ultra-processed foods based on the current models of the US FDA and the EU, and will further recommend better education implementation discussing healthier diets and overall disease prevention. Despite the current research and statistics outlined on these two diseases, with their respective connections to diet, deeper investigation and analysis remains to be done so we may better understand diet-disease links.

This thesis explores the nature of Type II diabetes and Alzheimer’s disease to better understand their symptoms, treatments, and the factors that lead to further development; with a specific focus on the role that diet plays. Alternate connections outside of diet, including amyloidosis and inflammation, are additionally analyzed, but the emphasis remains on introducing diets that may be helpful in terms of preventative measures and controlling symptoms of diseases. Two major diets investigated are the Mediterranean diet and DASH, and it will be discussed why these diets are better suited for overall health, in comparison to a diet based primarily in high-fat or ultra-processed foods. This paper integrates information from scientists, medical professionals, and even a personal testimony from a diabetic patient. This thesis will recommend legislation to better regulate ultra-processed foods based on the current models of the United States FDA and the EU and will further recommend better education implementation discussing healthier diets and overall disease prevention. Despite the current research and statistics outlined on these two diseases, with their respective connections to diet, deeper investigation and analysis remains to be done in order to better understand diet-disease links.

Neuroinflammation contributes significantly to the pathogenesis of Alzheimer’s and Parkinson’s diseases. However, the inflammatory pathways contributing to neurodegeneration are not well understood. Moreover, there is a need to identify changes in inflammatory signaling that may occur early in disease progression to identify potential targets for therapeutic intervention. An important step towards addressing this need is understanding how the extracellular vesicles (EVs) released by microglia can be detected in the periphery. For microglia, phagocytic macrophages, and CD 14+ monocytes share many genes and membrane- bound proteins, and there is currently no method to distinguish microglia EVs from those generated by macrophages or monocytes. Therefore, this study aims to identify membrane-bound proteins unique to microglia EVs to enable their reliable isolation. Liquid-chromatography tandem mass spectrometry analysis was used to detect proteins in the EVs from both normal and disease-associated human stem-cell differentiated microglia (iMGL), and human induced pluripotent stem cell-derived CD 14+ monocytes and macrophages. We identified 23 proteins unique to the microglial EVs, eight of which localize to the membrane and may be potential targets for isolation. This investigation also used RNA sequencing to gain insight into the contents of DAM-like and control iMGL EVs and of microglia and white blood cells in Alzheimer’s disease. We propose that the contents of microglial EVs isolated from peripheral compartments will provide crucial insight for understanding the current inflammatory state of CNS microglia. This approach could provide a means to track changes in microglial activation over time, which is critical for understanding the progression of neuroinflammatory diseases like Alzheimer's and Parkinson's. Additionally, it may offer insights into potential therapeutic targets for modulating neuroinflammation.

Synaptosomes are isolated nerve terminals that contain pre- and post-synapticproteins and can be used to model functionally intact synapses. While the quantification and characterization of synaptosomes have been used to study neurological conditions and diseases, relatively few studies have included the use of flow cytometry in the quantification and analytical processes. As such, this study highlights the use of flow cytometry in the synaptosomal quantification process and describes the adaptation of a previously performed synaptic flow protocol to find the optimal concentrations, protein- to-antibody ratios and gating strategies that meet the goals of this and future studies. To validate the protocol, three independent experiments measuring different treatments – traumatic brain injury (TBI), neurodevelopment, and ketamine - on synaptosomal quantity were conducted and compared to pre-existing literature. Despite the high standard deviation values between certain sample replicates, the synaptic flow protocol was validated by the right-skewed nature of the frequency distribution of the standard deviations between sample replicates and that most of the deviations fell below 40% of the maximum variance value. Further analysis showed significant differences (p < 0.05) between the ketamine and TBI groups compared to the control group while no significant differences were observed between the neurodevelopment (P30) group. This study validates the use of flow cytometry in synaptosomal quantification while providing insight to the potential of the synaptic flow protocol in future TBI and psychoplastogen studies.

The cerebellum predicts and corrects motor outputs based on sensory feedback for smoother and more precise movements, thus contributing to motor coordination and motor learning. One area of the cerebellum, the vestibulocerebellum, integrates vestibular and visual information to regulate balance, gaze stability, and spatial orientation. Highly concentrated within the granule cell layer of this region is a class of excitatory glutamatergic interneurons known as unipolar brush cells (UBCs) that receive input from mossy fibers and synapse onto multiple granule cells and other UBCs. They can be divided into ON and OFF subtypes based on their responses to synaptic stimulation. Prior research has implicated ON UBCs in motor dysfunction, but their role in motor coordination, balance, and motor learning is unclear. To test the hypothesis that ON UBCs contribute to motor coordination and balance, a transgenic mouse line (GRP-Cre) was used to express the GqDREADD (Gq designer receptors exclusively activated by designer drugs) hM3Dq in a subset of ON UBCs in the cerebellum to disrupt their electrical activity. In a second set of experiments, a Cre-dependent caspase 3 AAV (adeno-associated virus) viral vector was injected into the nodulus of the vestibulocerebellum of GRP-Cre mice to selectively ablate a subset of ON UBCs in the region and test whether they were necessary for motor learning. Motor coordination and balance were assessed using the rotor-rod and balance beam in young mice, and the forced swim test was used to assess vestibular function in older mice. Activity levels, anxiety, gross locomotion, and exploration in young mice were assessed using the open field. The results show that neither motor coordination and balance, nor motor learning, were impaired when the ON UBCs were disrupted or ablated in young mice. However, disruptions affected climbing behavior in older mice during the forced swim test, suggesting an age-dependent effect of ON UBCs on vestibular function.

The process of brain development is magnificently complex, requiring the coordination of millions of cells and thousands of genes across space and time. It is therefore unsurprising that brain development is frequently disrupted. Numerous genetic mutations underlying altered neurodevelopment have been identified and aligned with behavioral changes. However, the cellular mechanisms linking genetics with behavior are incompletely understood. The goal of my research is to understand how intracellular kinase signaling contributes to the development of ventrally derived glia and neurons. Of particular interest are GABAergic interneurons in the cerebral cortex, as GABAergic disruption is observed in multiple neurodevelopmental disorders including epilepsy, schizophrenia, and autism spectrum disorders. In addition, I investigated how kinase signaling influences the number and distribution of ventral born oligodendrocyte lineage cells to gain insight into white matter abnormalities observed in developmental disorders. This work primarily investigates the mitogen associated protein kinase (MAPK) signaling cascade, which is ubiquitously expressed but is particularly important for brain development. Hyperactive MAPK signaling causes RASopathies, a group of neurodevelopmental disorders where affected individuals often exhibit learning disability. MAPK haploinsufficiency, such as in 16p11.2 deletion syndrome, also results in intellectual disability. In both cases, the cells driving cognitive dysfunction are unknown. Using genetically modified mouse models, I found that hyperactivation of MAPK signaling disrupts a subtype of GABAergic neurons that express parvalbumin, though the same cells are resilient to MAPK deletion. In contrast, somatostatin expressing neurons require MAPK for normal development but are less responsive to hyperactivation. Oligodendrocyte lineage cells have a bidirectional response to MAPK signaling, where hyperactivating MAPK increases cell number and deletion reduces glial number. MAPK signaling activates several hundred downstream cues, but one of particular interest to this work is called Liver Kinase B1 (LKB1). LKB1 is a protein kinase which can regulate cell proliferation, survival, and metabolism. Here, I discovered that LKB1 is necessary for the development of parvalbumin expressing neurons. Collectively, these data identify disruption to certain ventral derivatives as a candidate pathogenic mechanism in neurodevelopmental conditions.

Glyphosate is the most heavily used herbicide worldwide and recent reports indicate that it may have deleterious neurological and neurodegenerative effects on human health. Here I demonstrate that glyphosate can infiltrate the brain in a dose-dependent manner in mice sub-acutely exposed to 125, 250, or 500 mg/kg/day. I also establish that glyphosate elicits a neuroinflammatory response in both the cortex and hippocampus, marked by elevation of tumor necrosis factor α (TNFα), and causes transcriptomic dysregulation of key genes involved in oligodendrocyte proliferation, maturation, and myelination. Given that both the hippocampus and the cortex are critical for learning and memory, and are affected in Alzheimer’s disease (AD), I investigate how 50 or 500 mg/kg chronic glyphosate exposure influences locomotion, anxiety-like behavior, and cognition in the APP/PS1 mouse model of AD. Results show that while glyphosate did not influence weight, appearance, locomotion, or anxiety-like behavior, learning acquisition is impaired in the place preference and reaction time tasks following 500mg/kg chronic exposure. Additionally, I report a strong increase in water consumption in glyphosate-exposed mice, demonstrating that chronic glyphosate exposure induces polydipsia. To ascertain whether glyphosate influences AD pathogenesis, I examine neuropathological changes following chronic daily oral exposure to 50 or 500 mg/kg glyphosate. Post-mortem analysis of amyloid-beta (Aβ) in APP/PS1 hippocampal and cortical tissue show that 50 or 500 mg/kg of glyphosate elevates soluble and insoluble Aβ1-40 and Aβ1-42 in both sexes, with females showing higher levels. Further analysis of cortical TNFα levels in chronically exposed APP/PS1 mice and littermate controls confirms a neuroinflammatory response. I report no differences in amyloid precursor protein (APP) processing pathway components, CA1 NeuN+ neuronal number, relative density of Iba1+ microglia in the hippocampus, or relative density of MBP+ oligodendrocytes in the fimbria. I also show that 50mg/kg chronic glyphosate exposure elevates hemoglobin A1c levels, indicating disruptions in glucose metabolism that may be tied to polydipsia. Collectively, these results indicate that glyphosate crosses the blood-brain barrier, induces a neuroinflammatory response, and exacerbates amyloid pathology. Ultimately, these findings provide important insight into the concerns surrounding the neurological implications of glyphosate exposure.