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- Genre: Masters Thesis
- Member of: Theses and Dissertations
Description
Alzheimer’s disease (AD) is one of the most prevalent neurodegenerative diseases worldwide, with no effective treatments or preventions. Evidence suggests that environmental factors, including dietary nutrients, contribute to the etiology of AD. Choline is an essential nutrient found in many common foods. Choline is produced endogenously, but not at levels sufficient for healthy metabolic function and thus requires dietary supplementation. Literature shows that ~90% of Americans do not meet the adequate intake threshold for dietary choline consumption and therefore are dietary choline-deficient. While dietary choline supplementation throughout life has been shown to have significant health benefits, such as reducing AD pathology and improving cognition in a mouse model of AD, the impacts of dietary choline deficiency are unknown. Experiments were designed to understand the effects of dietary choline deficiency in healthy, non-transgenic mice (NonTg) and in the 3xTg-AD mouse model of AD. From 3 to 12 months of age, mice received either adequate choline (ChN) in the diet or were put on a choline-deficient (Ch-) diet. A Ch- diet leads to significant weight gain throughout life in both the NonTg and 3xTg-AD mice, with AD mice showing a greater increase. Additionally, impaired glucose metabolism, which is a risk factor for AD, was induced in both NonTg Ch- and 3xTg-AD Ch- mice. Interestingly, Ch- induced cardiomegaly in 3xTg-AD mice and elevated markers of cardiac dysfunction in NonTg mice to similar levels in 3xTg-AD mice. Finally, Ch- exacerbated amyloid-β plaque pathology and tau hyperphosphorylation in the hippocampus and cortex of 3xTg-AD mice. Proteomic analyses revealed Ch- induced changes in hippocampal proteins associated with postsynaptic receptor regulation, microtubule stabilization, and neuronal development, as well as well-known AD-associated proteins (MAPT, BACE1, MECP2, CREBBP). Proteomic analyses also revealed Ch- induced changes of plasma proteins associated with secondary pathologies of AD including inflammation, immune response insulin metabolism, and mitochondrial dysfunction (SAA1, SAA2, IDE, HSPD1, VDAC-1, VDACE-2). Taken together, these data suggest that dietary choline deficiency induces system-wide cellular and molecular dysfunction associated with AD across several pathogenic axes, through proteomic changes not only in the hippocampus but also in the plasma.
ContributorsDave, Nikhil (Author) / Velazquez, Ramon (Thesis advisor) / Piras, Ignazio (Committee member) / Mastroeni, Diego (Committee member) / Arizona State University (Publisher)
Created2022
Description
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.
ContributorsChua, Wan Rong (Author) / Lifshitz, Jonathan (Thesis advisor) / Balmer, Timothy (Thesis advisor) / Velazquez, Ramon (Committee member) / Arizona State University (Publisher)
Created2023
Description
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.
ContributorsKizeev, Gabrielle (Author) / Balmer, Timothy (Thesis advisor) / Newbern, Jason (Committee member) / Velazquez, Ramon (Committee member) / Arizona State University (Publisher)
Created2023
Description
Frontotemporal dementia (FTD) is a neurodegenerative disease that causes deterioration of the frontal and temporal lobe. Detection is pivotal in preventative care, but current screening methods are not sensitive enough to detect early-stage disease. Synapse loss has been implicated as an early contributor to neurodegeneration and subsequent atrophy. Fluorine-18 fluorodeoxy-glucose (18[F]-FDG) positron emission tomography (PET) is a noninvasive imaging biomarker method frequently used as a surrogate measure for synaptic activity in the brain. PET scans using 18[F]-FDG tracers were performed on progranulin (GRN) knockout mice (Grn-/-), a commonly used mouse model of FTD. Interestingly, 18[F]-FDG PET at both, 9 months and 11 months, two time points considered early symptomatic in the Grn-/- mouse model, did not detect significant changes in synaptic activity, suggesting that no synapse loss has occurred yet at these early stages of FTD in this model. After the last PET scan, the imaging data were validated via fluorescent immunostaining for pre- and post-synaptic marker proteins SV2 and PSD95, respectively. Quantifications in several brain regions, including the frontal cortex, did not reveal any significant differences in protein expression, supporting the lack of aberrant 18[F]-FDG tracer uptake measured via PET. Additional examinations for activated microglia, a known aspect of FTD pathology recently observed in end Grn-/- mice, did not reveal microglia activation as measured via CD68 immunostaining. These data suggest that Grn-/- mice at 9 and 11 months do not exhibit synaptic dysfunction in the frontal cortex when measured via 18[F]-FDG PET or immunostaining of pre- and postsynaptic marker proteins SV2 and PSD95.
ContributorsWeisman, Hannah (Author) / Sattler, Rita G (Thesis advisor) / Mastroeni, Diego (Committee member) / Velazquez, Ramon (Committee member) / Arizona State University (Publisher)
Created2022
Description
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.
ContributorsHouchins, Nicole (Author) / Medina, David (Thesis advisor) / Velazquez, Ramon (Thesis advisor) / Tseng, Jui-Heng (Committee member) / Arizona State University (Publisher)
Created2024