Cell and Developmental Biology Commons^™

A Novel Switch-Like Function Of Delta-Catenin In Dendrite Development, Ryan Baumert

Dissertations & Theses (Open Access)

The formation of neuronal networks in the brain is tightly regulated, and dependent on the morphology of dendrites, the branch-like signal-receiving structures extending from neurons. Disruptions in dendrite development, or dendritogenesis, can lead to the atypical neuronal connectivity associated with multiple neurodevelopmental diseases. My research addresses molecular processes that underlie dendritogenesis via analysis of a pair of novel interactions involving the protein delta-catenin.

In neurons, delta-catenin localizes to dendrites and synapses, where it functions in their development and maintenance. Structurally, delta-catenin possesses a central Armadillo domain and a C-terminal PDZ-binding motif. This motif associates with PDZ domain-containing proteins, and is …

Uncovering The Zeb1 Interactome To Identify Novel Regulators Of Metastatic Non-Small Cell Lung Cancer, Roxsan Manshouri

Dissertations & Theses (Open Access)

Non-small cell lung cancer (NSCLC) is the leading cause of cancer-related death in the United States, due in part to the robust affinity of lung cancer cells to metastasize. Understanding the processes that contribute to metastasis provides promise for the discovery of novel therapeutic targets. Epithelial-tomesenchymal transition (EMT) is a proposed model for the initiation of metastasis. During EMT cell adhesion and polarity is reduced, allowing epithelial cancer cells to dissociate from the primary tumor and invade distant organs. The transcription factor zinc finger E-box-binding homeobox 1 (ZEB1) has been reported to uniquely correlate with NSCLC disease progression and to …

The Role Of Membrane Domains In Protein And Lipid Sorting During Endocytic Traffic, Blanca B. Diaz-Rohrer

Dissertations & Theses (Open Access)

The lipid and protein composition of the plasma membrane (PM) must be tightly controlled to maintain cellular functionality, despite constant, rapid endocytosis. Because de novo synthesis of proteins and lipids is energetically costly, the cell depends on active recycling to return endocytosed membrane components back to the PM. For most proteins, the mechanisms and pathways of their PM retention remain unknown. The work presented here shows that association with ordered membrane microdomains is fully sufficient for PM recycling and that abrogation of raft partitioning leads to their degradation in lysosomes. These findings support a model wherein ordered membrane domains mediate …

The Gsk-3Β-Fbxl21 Axis Regulates Tcap Via Ubiquitin-Mediated Proteasomal Pathway In The Cytoplasm, Jiah Yang

Dissertations & Theses (Open Access)

Protein turnover is one of the most essential mechanisms controlling circadian rhythms. F-Box and Leucine Rich Repeat Protein21 (FBXL21) is a circadian E3 ligase which shows oscillatory mRNA transcripts and protein levels. It was previously found to perform subcellular compartment-specific E3 ligase activities targeting the core clock proteins CRYPTOCHROME(CRY)1/2. Here we identified a new sarcomeric target substrate, Telethonin(TCAP), which also shows circadian oscillation in its mRNA transcript and protein expression and, importantly, interaction with FBXL21 in an anti-phasic manner. Via computational and pharmacological tests, we identified Glycogen Synthase Kinase-3β(GSK-3β) as a regulator of FBXL21. Biochemical and molecular characterizations demonstrated that …

Ipsc Based Gene Correction And Disease Model Of A New Class Of Lgmd Due To Poglut1 Mutation, Jose Ortiz-Vitali

Dissertations & Theses (Open Access)

Recently, a novel class of muscular dystrophy has been discovered in a family due to autosomal recessive missense mutation in POGLUT1. Mutation of this enzyme leads to decreased O-glucosyltransferase activity and impaired Notch signaling, the pathways important for skeletal muscle stem cell (satellite cells) quiescence and activation. We hypothesize that reduced POGLUT1 activity and impaired Notch signaling is causative of this limb girdle muscular dystrophy through dysfunction of muscle stem cells and myogenic progenitors.

To test this, we have used iPSCs for disease modeling and rescue experiments. Using a CRISPR based gene targeting method, we aimed to correct the point …

Deubiquitinating Enzymes Promote Cancer Progression And Metastasis Via Regulating Protein Stability, Zhenna Xiao

Dissertations & Theses (Open Access)

Deubiquitinating enzymes (DUBs, also called deubiquitinases) are enzymes that remove monoubiquitin or polyubiquitin chains from target proteins. DUBs have critical roles in cell homeostasis and signal transduction, as they regulate protein degradation, subcellular localization, and protein-protein interaction. Deregulation of DUBs contributes substantially to tumor formation and progression, and therefore targeting DUBs may be a promising cancer therapy strategy. My dissertation focuses on identifying the DUBs of EZH2 and SNAI1, two proteins critical for cancer progression and metastasis, and establishing these DUBs as promising anti-cancer targets.

EZH2, the catalytic component of the PRC2 complex, silences gene transcription by histone methylation. High …

Fasting Reduces Intestinal Radiotoxicity Enabling Dose-Escalated Radiotherapy For Pancreatic Cancer, Marimar De La Cruz Bonilla

Dissertations & Theses (Open Access)

Surgical resection is the only potentially curative treatment for pancreatic cancer, but only 15-20% of patients have resectable tumors. In unresectable cases, stereotactic body radiotherapy (SBRT) may be used to give tumor-directed radiotherapy (RT). Unfortunately, this can cause severe gastrointestinal (GI) toxicity due to proximity of the pancreatic head to the duodenum. Protecting the intestine from the toxic side-effects of radiation may enable dose-escalation that could achieve more effective local control of disease. We and others have previously shown that a fast of 24 hours protects mice from lethal doses of the DNA-damaging agent etoposide. In this study, we demonstrate …

Gcn5 Loss Impacts Myc-Driven Cancer In Mice And Human Cells, Aimee Farria

Dissertations & Theses (Open Access)

GCN5 is the catalytic subunit in the acetyltransferase module of SAGA and ATAC, multiprotein complexes involved in the modification of histone and nonhistone proteins. GCN5 is most recognized as a co-activator of gene transcription. The SAGA complex is recruited to chromatin by transcription factors such as MYC and E2F1 where GCN5 acetylates H3K9 leading to a more open and accessible chromatin structure. Previous research has demonstrated that GCN5 also acetylates MYC, a protein that amplifies the expression of cancer-promoting genes and is frequently dysregulated in cancer, increasing its stability. Our lab has found there is a significant overlap in the …

Modeling Cancer Using Li-Fraumeni Syndrome Patient-Derived Induced Pluripotent Stem Cells, Ruoji Zhou

Dissertations & Theses (Open Access)

Li-Fraumeni syndrome (LFS) is an autosomal dominant disease caused by germline mutations in the gene TP53, which predispose individuals to a wide range of malignancies, including osteosarcoma and breast cancer. In the previous study, our group developed a novel disease model platform by reprograming LFS patients' fibroblasts to induced pluripotent stem cells (iPSCs), and further differentiate these iPSCs into mesenchymal stem cells (MSCs) then to osteoblasts (OBs), the cells from which osteosarcomas originate. Interestingly, LFS iPSC-derived osteoblasts recapitulated the osteosarcoma phenotype, creating “a bone tumor in a dish”. This “tumor in a dish” platform proved that LFS is an …

An Oxanthroquinone Derivative Disrupts Ras Plasma Membrane Localization And Function By Inhibition Of Acylpeptide Hydrolase And Perturbation Of Sphingomyelin Metabolism, Lingxiao Tan

Dissertations & Theses (Open Access)

Oncogenic RAS proteins are commonly expressed in human cancer. To be functional, RAS proteins must undergo post-translational modification and localize to the plasma membrane (PM). Therefore, compounds that prevent RAS PM targeting have potential as putative RAS inhibitors. Here we examined the mechanism of action of oxanthroquinone G01 (G01), a recently described inhibitor of KRAS PM localization. We show that G01 mislocalized HRAS and KRAS from the PM with similar potency and disrupted the spatial organization of RAS proteins remaining on the PM. G01 also inhibited recycling of epidermal growth factor receptor and transferrin receptor, but did not impair internalization …

The Role Of Gene Expression Noise In Mammalian Cell Survival, Kevin Farquhar

Dissertations & Theses (Open Access)

Drug resistance and metastasis remain obstacles to effective cancer treatment. A major challenge contributing to this problem is cellular heterogeneity. Even in the same environment, cells with identical genomes can display cell-to-cell differences in gene expression, also known as gene expression noise. Gene expression noise can vary in magnitude in a population or in fluctuation time scales, which is influenced by gene regulatory networks.

Currently, it is unclear how gene expression noise from gene regulatory networks contributes to drug survival outcomes in mammalian cells. An isogenic cell line with a noise-modulating genetic system tuned to the same mean is required. …

Il-6/Jak1 Drives Pd-L1 Phosphorylation And Glycosylation To Promote Cancer Immune Evasion, Li-Chuan Chan

Dissertations & Theses (Open Access)

Glycosylation of immune receptors and ligands, such as T-cell receptor (TCR), major histocompatibility complex (MHC), and co-inhibitory molecules, regulates immune signaling activation, antigen presentation, and immune surveillance. Recent studies revealed that the glycan structures of co-inhibitory molecules are required for receptor-ligand interaction, a critical feature for activating cancer immune evasion. However, it is unclear how oncogenic signaling initiates glycosylation of co-inhibitory molecules to induce immunosuppression. Here we show interleukin (IL)-6-activated Janus kinase 1 (JAK1) phosphorylates programmed death-ligand 1 (PD-L1)-Tyr112, leading to the recruitment of endoplasmic reticulum (ER)-associated N-glycosyltransferase, STT3A, which catalyzes the glycosylation of PD-L1, contributing to its stability. A …

Genetic Counselor Utilization And Interpretation Of Somatic Tumor Testing In Evaluation For Lynch Syndrome, Danielle Williams

Dissertations & Theses (Open Access)

Lynch syndrome (LS) is a hereditary cancer predisposition syndrome characterized by increased risk for colorectal and uterine cancers. Individuals with pathogenic variants in the mismatch repair (MMR) genes (MLH1, MSH2/EPCAM, MSH6, PMS2) are diagnosed with LS and subsequently recommended to proceed with high risk screening protocols to increase prevention and early detection of LS-related cancers. Various tumor studies can help identify those at high risk for LS, but sometimes create uncertainty with discordant screening and germline results, leading to unexplained mismatch repair deficiency (UMMRD). Somatic testing of the MMR genes has created opportunities for resolving …

Thiol-Based Misfolding: Linking Redox Balance To Cytosolic Proteostasis, Ford Amy

Dissertations & Theses (Open Access)

The eukaryotic cytosolic proteome is vulnerable to changes in proteostatic and redox balance caused by temperature, pH, oxidants and xenobiotics. Cysteine-containing proteins are especially at risk as the thiol side chain is subject to oxidation, adduction and chelation by thiol-reactive compounds. All of these thiol-modifiers have been demonstrated to induce the heat shock response and recruit protein chaperones to sites of presumed protein aggregation in the budding yeast Saccharomyces cerevisiae. However, endogenous targets of thiol stress toxicity responsible for these outcomes are largely unknown. Furthermore, I hypothesize proteins identified as redox-active are prone to misfolding and aggregation by thiol-specific …

Platiscity Of C. Elegans Germline Stem Cells Under Nutritional And Metabolic Stress, Kenneth Trimmer

Dissertations & Theses (Open Access)

Stem cells are integral for tissue maintenance and fertility. Therefore, understanding how stem cells are regulated under stress is imperative. When confronted with acute starvation, stem cells must conserve energy and metabolites to cope with the lack of an external source. Caenorhabditis elegans germline stem cells (GSCs) are an excellent model for studying stem cell properties and regulation as they can divide throughout the life of the organism. While GSCs are an adult stem cell population, their cell cycle structure more closely mimics mouse and human embryonic stem cells with short G1 and long S phases. In this thesis, I …

Cross-Presentation Is A Source Of Tumor Antigens For Multiple Myeloma Immunotherapy, Alexander A. Perakis

Dissertations & Theses (Open Access)

Cross-presentation is an essential bridge between the innate and adaptive arms of the immune system where antigen presenting cells (APCs) prime cytotoxic T cell responses. We have recently identified cross-presentation as a mechanism by which solid tumors present exogenous antigens. We therefore hypothesized that multiple myeloma would be capable of cross-presentation as these cells are derived from B cells, known APCs. We explored the capacity of multiple myeloma to cross-present PR1, a human leukocyte antigen (HLA)-A2 nonameric peptide that is derived from neutrophil elastase (NE) and proteinase 3 (P3), and the ability to treat multiple myeloma using PR1-targeting immunotherapies. Here …