Systems Biology Commons^™

Identification And Characterization Of Novel Immune Modulating Genes In Parkinson's Disease, Kathleen Chaundy Paul Murphy

Dartmouth College Ph.D Dissertations

Parkinson’s disease (PD) is a progressive age-related neurodegenerative disorder characterized by both motor and non-motor symptoms. The poorly understood prodromal period, decades-long progression, and disease-phenotype heterogeneity continue to impede the development of preventive and curative therapies. A growing appreciation of immune system changes during the progression of PD suggests that evaluating peripheral immune cells may help identify signatures relevant to disease etiology. We aimed to expand our understanding of the peripheral immune compartment in PD via two lines of investigation: (1) by employing single-cell RNA sequencing to profile the transcriptomes of peripheral blood mononuclear cells (PBMCs) from a cohort of …

Drifting Neurons, Stable Geometry: Population Representations Of Instrumental Behavior In The Dorsomedial Striatum, Arati Sharma

Dartmouth College Ph.D Dissertations

The brain reliably supports learned behaviors over long periods of time despite continual biological changes that alter the activity of individual neurons, and the connections between them. For learned behaviors to persist, the information stored in neural populations must remain accessible even when the activity of individual neurons changes. Understanding how the brain achieves this is a fundamental challenge in neuroscience. The dorsomedial striatum (DMS) is critical for instrumental behavior, encoding information about actions, outcomes, and their relationships. Although extensive work has characterized the role of the DMS during learning and performance, less is known about how task-related information is …

Deconstructing Systemic Sclerosis Heterogeneity: From Patient Subtypes To Pathogenic Fibroblasts, Rezvan Parvizi

Dartmouth College Ph.D Dissertations

This thesis advances heterogeneity as the central barrier both to interpreting therapeutic response and to identifying the molecular regulators that drive fibrosis in systemic sclerosis (SSc). In SSc, heterogeneity is manifest at every level at which the disease can be measured: clinically, in the variable extent of skin and organ involvement; molecularly, in the distinct gene-expression programs that distinguish otherwise comparable patients; and cellularly, in the diverse fibroblast populations from which the fibrotic signal ultimately arises.

Leveraging longitudinal skin transcriptomics from a large cohort treated with mycophenolate mofetil (MMF), the first study demonstrates that intrinsic molecular subtypes are dynamic rather …

Emergence Of Heterogeneity In Bacteria During Antibiotic Exposures, Mirjana Stevanovic

Dartmouth College Ph.D Dissertations

Bacterial populations exposed to antibiotics often exhibit phenotypic heterogeneity, with individual cells displaying distinct responses with fates ranging from survival to arrest or death. The emergence of this heterogeneity is largely driven by feedback mechanisms mediated by the interactions between antibiotic action, gene regulation, and cellular metabolism. These responses unfold in dynamic environments where conditions such as nutrient availability and drug concentration fluctuate over time and space. Yet, these complex interactions and their role in shaping population-level outcomes during drug responses remain poorly understood. Using tetracycline resistance in E. coli as a model system, this thesis focuses on how these …

Hierarchical Lineage Tracing To Unravel Mechanisms Of Cancer Treatment Resistance, Rachel Danielle Saxe

Dartmouth College Ph.D Dissertations

Cancer cells adapt to treatment, leading to the emergence of clones that are more aggressive and resistant to anti-cancer therapies. We have a limited understanding of the development of treatment resistance as we lack technologies to map the evolution of cancer under the selective pressure of treatment. To address this, we developed a hierarchical, dynamic lineage tracing method called FLARE (Following Lineage Adaptation and Resistance Evolution). We use this technique to track the progression of acute myeloid leukemia (AML) cell lines through exposure to Cytarabine (AraC), a front-line treatment in AML, in vitro and in vivo. We map distinct cellular …

Metabolite Analysis To Understand Factors Limiting Microbial Fermentation At High Substrate Concentrations, Bishal D. Sharma

Dartmouth College Ph.D Dissertations

Clostridium thermocellum, a thermophilic anaerobic bacterium, holds promise as a biocatalyst for conversion of lignocellulosic biomass into biofuels. This microbe has been subjected to various metabolic engineering strategies, including the deletion of genes encoding secondary fermentation products such as H₂, formate, acetate, and lactate, as well as the expression of heterologous genes to redirect carbon flux toward ethanol production. Despite these efforts, achieving economically viable ethanol titers remains a challenge. We hypothesized that studying how intracellular metabolite concentrations change as fermentation stops could reveal metabolic bottlenecks or regulatory mechanisms limiting ethanol production at high titers. However, metabolomics studies at …

Computational Drug Repositioning And 3d Skin-Like Tissues Identify Anti-Fibrotic Targets For Systemic Sclerosis (Ssc), Dillon Popovich

Dartmouth College Ph.D Dissertations

Systemic Sclerosis (SSc) is a rare autoimmune disease characterized by dermal and internal organ fibrosis, including heart, lungs, and gastrointestinal tract, and autoantibody formation. Although disease etiology is currently unknown, like other autoimmune diseases, SSc likely develops due to environmental factor exposure in genetically susceptible individuals. Fibrotic diseases are notoriously difficult to treat. Coupled with the autoimmune aspect, SSc is difficult to study scientifically due to the lack of complex disease models that can recapitulate the immune-fibrotic axis of the disease. Due to this, there are only two FDA approved medical treatments for SSc approved for symptomatic treatment of SSc …

Quantitative Proteomic Strategies To Determine Substrate Specificities Of Phosphoprotein Phosphatases, Hieu Trung Nguyen

Dartmouth College Ph.D Dissertations

Reversible phosphorylation is a crucial regulatory mechanism of cellular signaling pathways. Being the most prevalent post-translational modification (PTM) in the cells, with over 75% of all proteins detected to be phosphorylated, phosphorylation regulates a significant number of important cellular processes that have implications in various diseases. Phosphorylation is carried out by protein kinases, which have been extensively studied. However, the opposite reaction, carried out by protein phosphatases, has lagged significantly, exposing a gap of knowledge that is required to be investigated to delineate the kinase-substrate-phosphatase relationship. Phosphoprotein phosphatase family (PPPs), containing seven members of phospho-Serine (pS) and phospho-Threonine (pT) phosphatases, …

Cytokine Activity Estimation And Receptor Abundance Approximation With Multimodal Scrna-Seq/Cite-Seq Data., Azka Javaid

Dartmouth College Ph.D Dissertations

Single-cell RNA-sequencing (scRNA-seq) data enables individual cell resolution quantification of messenger RNA. While revolutionary for revealing key cell type and cell phenotype-specific heterogeneity, scRNA-seq data has important statistical challenges. First, scRNA-seq data is usually more sparse and second, it is more variable than bulk transcriptomics data. Given these challenges, more intuitive and interpretive statistical and computational methods are needed to develop appropriate solutions. Here, we detail the development of three techniques to perform receptor abundance estimation and cytokine activity estimation for scRNA-seq data. While SPECK (Surface Protein abundance Estimation using CKmeans-based clustered thresholding) and STREAK (gene Set Testing-based Receptor abundance …

Targeting Cholinergic Signaling In Glioblastoma, Sumyuktha Vijay Anand

Dartmouth College Ph.D Dissertations

Primitive stem cell-like populations that are prone to malignant transformation reside in the brain throughout adulthood. My lab’s reports and many others have characterized subsets of glioma cells reminiscent of adult stem-like cells implicating them rational candidates for cell-targeted therapies. Emerging evidence suggests that the neurotransmitter microenvironment influences these stem-like cells during glioma progression providing an inroad to study neuromodulators in glioma. Some glioma stemlike cells share characteristics with adult tissue oligodendrocyte progenitor cells. Primitive cells of the oligodendroglial lineage express muscarinic acetylcholine receptors (mAChRs), and their “stemness” is maintained by the acetylcholine (ACh) neurotransmitter. Here, I conduct transcriptomic, electrophysiological, …

Regulation Of The Wnt/Wingless Receptor Lrp6/Arrow By The Deubiquitylating Complex Usp46, Zachary T. Spencer

Dartmouth College Ph.D Dissertations

The evolutionarily conserved Wnt/Wingless signal transduction pathway is critical for the proper development of all animals and implicated in numerous diseases in adulthood. Upon binding of the Wnt/Wingless ligand, a cascade of events culminates in inactivation of the destruction complex, a negative regulator of the pathway, and the subsequent formation of singalosomes which mediate pathway activation. A critical component of signalosome formation is the Wnt/Wingless receptor LRP6/Arrow. Upon canonical pathway activation, LRP6/Arrow undergoes activation via phosphorylation by several kinases and complexes with another Wnt/Wingless receptor Frizzled, along with several cytoplasmic components. While many studies have investigated the regulatory mechanisms of …