Molecular Genetics Commons^™

A Study Of The Snd1/Prmt5 Axis In Liver Cancer By Genetic Mouse Models, Tanner Wright, Tanner Wright

Dissertations & Theses (Open Access)

Arginine methylation is an essential post-translational modification (PTM) in cells. Protein arginine methyltransferase 5 (PRMT5) is the primary enzyme that catalyzes symmetric dimethyl arginine (SDMA) and requires methylosome protein 50 (MEP50) for stability and enzymatic activity which are necessary for life and development. Effector proteins bind different types of PTM’s to facilitate signaling. Staphylococcal nuclease Tudor domain containing 1 (SND1) is an effector that specifically binds SDMA via its single C-terminal Tudor domain. Both SND1 and PRMT5 have been implicated in hepatocellular carcinoma (HCC). SND1 has been confirmed as a driver of HCC using genetically engineered mouse models (GEMMs), though, …

Regulation Of De Novo And Maintenance Dna Methylation By Dnmt3a And Dnmt3b, Yang Zeng

Dissertations & Theses (Open Access)

DNA methylation (5-methylcytosine, 5mC) is essential for the regulation of gene expression and integrity of the mammalian genome. It occurs predominantly in the context of CpG dinucleotides to form a symmetrical pattern on both DNA strands, which allows DNA methylation patterns to be semi-conservatively maintained during DNA replication. There are two classes of DNA methyltransferases (DNMTs): DNMT3A and DNMT3B function primarily as de novo methyltransferases that establish DNA methylation patterns, whereas DNMT1 is the major enzyme responsible for maintaining DNA methylation patterns by converting hemi-methylated CpGs to fully methylated CpGs during DNA replication. Two accessory factors also play critical regulatory …

Functions Of The Trna Splicing Endonuclease And Other Adventures In Rna Processing, Jennifer Hurtig, Ambro Van Hoof

Dissertations & Theses (Open Access)

The tRNA splicing endonuclease (TSEN), has been studied for over three decades for its function in tRNA splicing. However, this enzyme has other functions that are just beginning to be characterized. Mutations in TSEN cause the neuronal disease pontocerebellar hypoplasia (PCH) that is characterized by atrophy of the cerebellum and pons, overall developmental failure, and usually results in death before adolescence. How mutations in TSEN cause these neuronal defects and disease is not understood. In yeast, TSEN has another essential function that is independent of tRNA splicing and is still unknown. In this thesis I strived to understand the other …

Unique Transcriptional Profiles Underlie Osteosarcomagenesis Driven By Different P53 Mutants, Dhruv Chachad

Dissertations & Theses (Open Access)

Missense mutations in the DNA binding domain of the Trp53 gene are characterized as structural (p53R172H) or contact (p53R245W) mutations based on their effect on the conformation of the protein. These mutations show gain-of-function activities such as increased metastatic incidence as compared to p53 loss, often mediated by their interaction with a repertoire of transcription factors. These interactions are largely context specific. In order to understand the mechanisms by which these mutations drive osteosarcoma progression, we created a mouse model, wherein either the p53 structural mutant p53R172H, or the contact mutant, p53R245W, are expressed specifically in …

Targeting Metabolic Alterations Associated With Smooth Muscle Α-Actin Pathogenic Variant Attenuates Moyamoya-Like Cerebrovascular Disease, Anita Kaw

Dissertations & Theses (Open Access)

Heterozygous pathogenic variants in ACTA2, encoding smooth muscle α-actin (α-SMA), predispose to thoracic aortic aneurysms and dissections. De novo missense variants disrupting ACTA2 arginine 179 (p.Arg179) cause a multisystemic disease termed smooth muscle dysfunction syndrome (SMDS), which is characterized by early onset thoracic aortic disease and moyamoya disease-like (MMD) cerebrovascular disease. The MMD-like cerebrovascular disease in SMDS patients is marked by bilateral steno-occlusive lesions in the distal internal carotid arteries (ICAs) and their branches. To study the molecular mechanisms that underlie the ACTA2 p.Arg179 variants, a smooth muscle-specific Cre-lox knock-in mouse model of the heterozygous Acta2 R179C variant, termed …

Genetic Analysis Of Rna Exosome Complex Cofactors, Luisa Orlando

Dissertations & Theses (Open Access)

The RNA exosome complex is known to process and/or degrade many classes of RNA, including mRNA, rRNA, tRNA and snRNA, through its 3’-to-5’ exoribonuclease catalytic activity. The RNA exosome complex comprises a 9-unit core (exo-9), with six proteins making up a PH-Ring barrel and three proteins making up a S1-KH cap. The RNA exosome complex exo-9 core is inactive by itself and requires different cofactors in the nucleus and cytoplasm to perform different localized functions. This exo-9 core can associate with one or two catalytic subunits, including Rrp44/Dis3 and Rrp6 in yeast and DIS3 or DIS3L and RRP6/EXOSC10 in humans. …

Redox Sensing By Yeast Hsp70 Facilitates Modulation Of Protein Quality Control And The Cytoprotective Response, Alec Santiago

Dissertations & Theses (Open Access)

Neurodegenerative disease affects millions of Americans every year, through diagnoses such as Alzheimer’s, Parkinson’s, and Huntington’s diseases. One factor linked to formation of these aggregates is damage sustained to proteins by oxidative stress. Cellular protein homeostasis (proteostasis) relies on the ubiquitous Hsp70 chaperone family. Hsp70 activity has been previously shown to be modulated by modification of two key cysteines in the ATPase domain by oxidizing or thiol-modifying compounds. To investigate the biological consequences of cysteine modification on the Hsp70 Ssa1 in budding yeast, I generated cysteine null (cysteine to serine) and oxidomimetic (cysteine to aspartic acid) mutant variants of both …

Novel Regulators Of Cellular Secretion Alter The Tumor Microenvironment To Drive Metastasis, Rakhee Bajaj

Dissertations & Theses (Open Access)

Lung cancer is a highly aggressive disease responsible for ~25% of all cancer-related deaths, due in part to its proclivity to metastasize. Treating metastasis holds potential for improving patient survival but requires a deeper investigation into the underlying mechanisms. Some of these processes that can regulate metastasis are: (1) Oncogenic targets of epithelial micro-RNAs (miRNAs) are epigenetically de-repressed upon loss of the miRNAs during epithelial-to-mesenchymal transition (EMT) and in cancer. EMT confers plasticity and fitness to cancer cells promoting their survival through the metastatic cascade. This cascade and EMT are initiated by loss of the miRNA200 family (miR-200) and the …

Development Of The Ark Assay For Quantitating Dna- Protein Crosslink Accumulation And Fanconi Anemia Pathway Involvement In The Repair Process, Naeh Klages-Mundt

Dissertations & Theses (Open Access)

DNA-protein crosslinks (DPCs) are a common DNA lesion naturally arising in cells, wherein protein becomes covalently and irreversibly bound to the DNA. Given their excessive size, these adducts present a significant challenge to replication and transcription, thus requiring timely and efficient repair. However, the precise mechanisms involved with processing DPC removal remain unclear. Moreover, current methodologies to quantitate DPC accumulation and removal are restrained by a range of limitations. Here, we describe and discuss a new DPC detection assay – the ARK assay – capable of overcoming the limitations incurred by prior assays. The design, which uses dual chaotropic lysis …

Mutant Kras Alters Extracellular Vesicle Microrna Sorting In Pancreatic Cystic Neoplasms, Rachel L. Dittmar

Dissertations & Theses (Open Access)

Pancreatic ductal adenocarcinoma (PDAC) is among the deadliest cancers by organ site with a 5-year survival rate of just 10.8%. This is largely because most patients do not experience symptoms until the disease has already metastasized. The best hope to cure PDAC is surgery, which can only be done with a curative intent at an early stage when the disease is localized. There are no reliable circulating, body-fluid-based biomarkers to detect early stage PDAC or its precursor lesions in a timely manner for effective surgical intervention. When potential PDAC precursor lesions, such as mucinous pancreatic cysts are found, there are …

Deciphering The Role Of Hsp110 Chaperones In Diseases Of Protein Misfolding, Unekwu M. Yakubu

Dissertations & Theses (Open Access)

Molecular chaperones maintain protein homeostasis (proteostasis) by ensuring the proper folding of polypeptides. Loss of proteostasis has been linked to the onset of numerous neurodegenerative disorders including Alzheimer’s, Parkinson’s, and Huntington’s disease. Hsp110 is a member of the Hsp70 class of molecular chaperones and acts as a nucleotide exchange factor (NEF) for Hsp70, the preeminent Hsp70-family protein folding chaperone. Hsp110 promotes rapid cycling of ADP for ATP, allowing Hsp70 to properly fold nascent or unfolded polypeptides in iterative cycles. In addition to its NEF activity, Hsp110 possesses an Hsp70-like substrate binding domain (SBD) whose biological roles are undefined. Previous work …

Npsd4: A New Player In Sumo-Dependent Dna Repair, Erin Atkinson

Dissertations & Theses (Open Access)

The human genome is under constant threat from sources of damage and stress. Improper resolution of DNA damage lesions can lead to mutations, oncogene activation, and genomic instability. Difficult-to-replicate-loci present barriers to DNA replication that, when not properly resolved, lead to replication fork stalling and collapse and genomic instability.

DNA damage and replication stress trigger signaling cascades potentiated by multiple types of post-translational modifications, including SUMOylation. Through proteomic analysis of proteins involved in SUMOylation following DNA damage, our lab identified an uncharacterized protein that we named New Player in SUMO-dependent DNA damage repair 4 (NPSD4). Through an additional proteomic screen, …

Understanding The Pathogenesis Of Renal Medullary Carcinoma, Melinda Soeung

Dissertations & Theses (Open Access)

Renal medullary carcinoma (RMC) is a lethal cancer that predominantly affects young individuals with sickle cell trait (SCT). It is not currently understood why RMC only affects certain individuals with SCT. We found that patients with RMC more frequently participated in high-intensity exercise than matched controls. Using mouse models of SCT, we demonstrated the significant increase of renal hypoxia in the right kidney following high- but not moderate-intensity exercise. We also demonstrated in cell culture studies that SMARCB1 is ubiquitinated for proteasome-mediated degradation in hypoxia, and the re-expression of SMARCB1 leads to compromised proliferation in renal cells specifically in the …

Epithelial Memory Of Resolved Inflammation Limits Tissue Damage While Promoting Pancreatic Tumorigenesis, I-Lin Ho

Dissertations & Theses (Open Access)

Inflammation is a major risk factor for pancreatic ductal adenocarcinoma. When occurring in the context of pancreatitis, mutations of KRAS accelerate tumor development. We discovered that long after its complete resolution, a transient inflammatory event primes pancreatic epithelial cells to subsequent transformation by oncogenic KRAS. Upon recovery from acute inflammation, epithelial cells of the pancreas display an enduring adaptive response associated with sustained transcriptional and epigenetic reprogramming. Such adaptation enables the prompt reactivation of acinar-to-ductal metaplasia (ADM) upon subsequent inflammatory events, thus efficiently limiting tissue damage via rapid decrease of zymogen production. We propose that since activating mutations of KRAS …

Targeting Plasma Membrane Phosphatidylserine Content To Inhibit Oncogenic Kras Function, Walaa E. Kattan

Dissertations & Theses (Open Access)

The small GTPase KRAS, which is frequently mutated in human cancers, must be localized to the plasma membrane (PM) for biological activity. We recently showed that the KRAS C-terminal membrane anchor exhibits exquisite lipid-binding specificity for select species of phosphatidylserine (PtdSer). We therefore investigated whether reducing PM PtdSer content is sufficient to abrogate KRAS oncogenesis. Oxysterol-related binding proteins ORP5 and ORP8 exchange PtdSer synthesized in the ER for phosphatidylinositol-4-phosphate (PI4P) synthesized in the PM. We show that depletion of ORP5 or ORP8 reduced PM PtdSer levels, resulting in extensive mislocalization of KRAS from the PM. Concordantly, ORP5 or ORP8 depletion …

Understanding The Role Of Arglu1 In Interferon Signaling Activation In Breast Cancer, Phuoc Nguyen

Dissertations & Theses (Open Access)

In the U.S., the highest number of new cancer cases belongs to breast cancer in women, and this cancer also bears the second-highest death rate in women. Despite significant progress in breast cancer treatment that has been made in the past several decades, innovative and efficient therapies are still needed to eradicate this deadly disease. Novel cancer immunotherapy with immune checkpoint blockade (ICB) could induce long-lasting responses and improve survival in hard-to-treat malignancies. Regrettably, only a fraction of breast cancer patients respond to this highly promising strategy. To improving ICB therapy in breast cancer treatment, IFN signaling induction is a …

Functions Of Dcp2 And Ski7 In Mrna Degradation, Minseon Kim, Ambro Van Hoof

Dissertations & Theses (Open Access)

Posttranscriptional gene regulation is essential to maintain gene expression fidelity. This is partially achieved by mRNA decay. When no longer required, mRNA is degraded by two alternative pathways. The decapping enzyme Dcp2 removes the 5` <sup>m7</sup>G cap of mRNAs, allowing Xrn1 to degrade the mRNA from the 5` end. Alternatively, mRNA is degraded from the 3` end by the RNA exosome.

While decapping by Dcp2 is a critical step in mRNA decay, its physiological function has been unclear. Null mutations of Saccharomyces cerevisiae DCP2 have been reported to be lethal in some studies but slow-growing in others. In this …

Rare Variant Association Studies In Crohn’S Disease And Colorectal Cancer: Methods And Applications, Jiun-Sheng Chen

Dissertations & Theses (Open Access)

Genetic factors account for a substantial portion of Crohn’s disease and colorectal cancer (CRC) risk. Patients with Crohn’s disease, a condition that causes chronic inflammation of the gastrointestinal tract, are at increased risk of colorectal cancer morbidity and mortality. Genome-wide association studies using single marker approaches have identified loci responsible for these diseases, but disease susceptibility from rare variants is incompletely understood. This dissertation includes three chapters, two association studies for Crohn’s disease and CRC, and a statistical method to improve the power of statistical tests.

For Crohn’s disease, we performed targeted sequencing of 101 genes in 205 children with …

P53 Drives A Transcriptional Program That Elicits A Non-Cell-Autonomous Response And Alters Cell State In Vivo, Sydney Moyer

Dissertations & Theses (Open Access)

Cell stress and DNA damage activate the tumor suppressor p53, triggering transcriptional activation of a myriad of target genes. The molecular, morphological, and physiological consequences of this activation remain poorly understood in vivo. We activated a p53 transcriptional program in mice by deletion of Mdm2, a gene which encodes the major p53 inhibitor. By overlaying tissue-specific RNA-sequencing data from pancreas, small intestine, ovary, kidney, and heart with existing p53 ChIP-sequencing, we identified a large repertoire of tissue-specific p53 genes and a common p53 transcriptional signature of seven genes which included Mdm2 but not p21. Global p53 activation …

A Context-Forward In Vivo Functional Genomics Platform For Target Discovery And Establishing Vulnerability Context In Pancreatic Cancer, Johnathon Rose, Johnathon Lynn Rose

Dissertations & Theses (Open Access)

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive malignancy with a very poor patient prognosis (5-year survival of ≤ 7%). While transcriptional profiling has aided in the classification of this disease into at least two broader subtypes, this alone has so far been insufficient to inform on more nuanced patterns of oncogenic dependency. We hypothesized that a more comprehensive and granular characterization of PDAC disease diversity is required to establish relevant context for targeted therapy. To this end, we sought to establish an integrated platform to: i) more comprehensively characterize differential oncogenic signaling across our tumor models, and ii) establish …

Artificial Intron Technology To Generate Conditional Knock-Out Mice, Amber N. Thomas-Gordon

Dissertations & Theses (Open Access)

Genetic engineering has been re-shaped by the invention of new tools in modern biotechnology in a way that offers precision and efficiency in modifying the genome at a single nucleotide level and/or allowing precise control of gene expression. Such gene manipulation brings about significant findings and revelations in comprehending more about embryonic development, cellular and physiological functions, and disease pathology. Current methods used to produce conditional knockouts have limitations on conditional allele placement and modification varies among genes in different organisms. Thus, a system for generating conditional alleles with fidelity remains a challenge. My goal was to examine an approach …

P53r245w Mutation Elicits Metastatic Phenotype In Pten Deficient Prostate Cancer, Ky Pham

Dissertations & Theses (Open Access)

Trp53 mutations are the most frequent genetic alterations in prostate cancer and are associated with more aggressive disease and worse overall survival. The majority of Trp53 mutations in prostate cancer are missense mutations, resulting in amino acid substitutions with profound effect. In addition to the loss of wild type function, missense mutations in Trp53 result in a gain-of-function (GOF) phenotype. This GOF phenotype confers biologic advantages to the tumor cells, enabling them to metastasize and invade distant organs. In this study, we generated mice carrying a conditional prostate-specific p53R245W mutant and Pten deletion to access the role of this common …

Higher Order Chromosome Organization And Recombination Dynamics Of Meiotic Prophase I In Mouse Spermatocytes, Rhea Kang

Dissertations & Theses (Open Access)

Meiotic recombination is required for parental chromosomes to find each other (pairing/synapsis) and to exchange genetic information thus allowing faithful segregation of chromosomes and the production of haploid gametes. At the start of meiotic prophase I, meiotic chromosomes organize into loop arrays that extrude out of the chromosome axis. Then, a large number of programmed double-strand breaks (DSBs) are formed at specific chromosomal locations or “hotspots” on parental chromosomes, which are repaired by homologous recombination (HR). HR produces either crossovers, which result in the exchange of flanking markers between homologs, or noncrossovers, which are short regions ofgene conversion to the …

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 …

Sequence-Specific Gene Correction Of Cystic Fibrosis Airway Basal Cells, Varada Anirudhan

Dissertations & Theses (Open Access)

Cystic fibrosis (CF) is a lethal monogenic disease resulting from mutations in the CFTR gene which encodes a protein involved in regulating anion trans-epithelial transport. A three-base deletion in CFTR (termed as ΔF508 mutation), wherein CFTR protein is misfolded leading to its pre-mature degradation in the endoplasmic reticulum (ER), is the most common cause of this debilitating disease. Since CFTR is expressed in multiple body systems, CF affects different organs, but lung pathology is the greatest cause of death in affected patients. We achieved site-specific gene correction with an efficiency of ~10 % in CF airway basal cells homozygous for …

The Role Of Tumor Suppressor Dear1 In The Acquisition Of Mammary Stem/Progenitor Cell Properties, Uyen Le

Dissertations & Theses (Open Access)

Breast cancer is the most commonly diagnosed cancer in women in America. Ductal carcinoma in situ (DCIS), one of the earliest pre-invasive forms of invasive ductal carcinoma (IDC), has a 30-50% risk of progressing to IDC. Understanding the mechanisms regulating progression from DCIS to IDC would help identify biomarkers to stratify patients at higher risk of progression or metastasis. Cumulative literature suggests the earliest phase of dissemination from the primary tumor is driven by the epithelial-mesenchymal transition (EMT) program. DEAR1 is a tumor suppressor gene which is mutated, undergoes loss of heterozygosity in breast cancer, and is downregulated in DCIS …

Mechanism Of Incorporation And Repair Of Uracil At Highly Transcribed Genes In Saccharomyces Cerevisiae, Norah Auma Owiti

Dissertations & Theses (Open Access)

Recombination and mutagenesis are elevated by high levels of transcription. The correlation between transcription and genome instability is largely explained by the topological and structural changes in DNA and the associated physical obstacles generated by the transcription machinery. However, such explanation does not directly account for the unique types of mutations originating from the non-canonical residues such as uracil, which are also elevated at highly transcribed regions. Apurinic/Apyrimic or Abasic (AP) sites derived from uracil excision, accumulate at a higher rate in actively transcribed regions of the genome in S. cerevisiae and are primarily repaired by base excision repair (BER) …

Investigating The Roles Of Tap63 And Tap73 In Cutaneous Squamous Cell Carcinoma And Lung Adenocarcinoma, Andrew J. Davis

Dissertations & Theses (Open Access)

TP63 and TP73 (which encode p63 and p73, respectively) are highly conserved transcription factors with important roles in development and tissue homeostasis. Similar to their homolog, p53, both p63 and p73 have been shown to mediate tumor suppression in multiple tissue types. Interestingly, however, both genes are expressed as multiple isoforms, which appear to have different and, in many cases, antagonistic functions. Through the use of isoform-specific null alleles of p63 and p73 our lab and others have shown that the full-length N-terminal isoforms of p63 and p73 (referred to as TAp63 and TAp73, respectively) exhibit distinct functions in development, …

Trim24 In Normal & Malignant Hematopoiesis, Justin Shaw

Dissertations & Theses (Open Access)

Treatment for acute myeloid leukemia (AML) has changed little in the past four decades. For the majority of AML patients, current treatment options include chemotherapy and allogeneic stem cell transplants, which also involves high-dose chemotherapy or radiation treatment. These options have little success in the long-run, as only an estimated 26% of patients survive five years post-diagnosis. In efforts to address this low survival rate, interest has increased for targeting epigenetic pathways in AML. This focus stems from the discovery that AML is frequently driven by blockades on hematopoietic stem cell differentiation, which involves a series of coordinated epigenetic changes. …