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External Awards for Research Training


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    The role of Neurexin in serotonin synaptic function and social behavior

    The goal of this proposal is to examine how presynaptic Neurexins (Nrxns) at serotonin (5-HT) synapses impact 5-HT signaling and social behavior. Extensive 5-HT axon terminal innervation throughout the brain corroborates 5-HT’s modulatory role in numerous behaviors including social behaviors, reward, emotion regulation, and learning and memory. Abnormal brain 5-HT levels and function are implicated in Autism Spectrum Disorder (ASD). While 5-HT therapeutics are often used to treat ASD, variable improvements in symptomatology require further investigation of 5-HT-mediated pathology. Many different genes contribute to increased ASD susceptibility and clinical presentation variability. Notably, synaptic dysfunction, specifically dysregulation of synaptic excitation and inhibition, remains a hallmark of ASD pathogenesis. Nrxns are presynaptic cell adhesion molecules that are well characterized in maintaining synapse function for proper neural circuit assembly. The three Nrxn genes transcribed from two promoters (α and β) express six principal Nrxn isoforms (αNrxn1-3, βNrxn 1-3). Additionally, mutations in Nrxn1 and Nrxn2 genes have been reported in ASD. In the current literature, the role of Nrxns at 5-HT synapses has yet to be investigated. Given that aberrant Nrxn and 5-HT function independently contribute to signaling pathology and social behavior impairments, it is critical to understand how Nrxn-mediated 5-HT neurotransmission participates in pathological mechanisms underlying the core deficits of ASD. Here, I will explore how 5-HT signaling mediated through Nrxns regulates social behaviors (Aim 1) and how Nrxns regulate 5-HT circuits relevant to social behaviors (Aim 2). Our group has created a novel mouse model in which the three Nrxn genes are selectively deleted in 5-HT neurons. My preliminary studies indicate that the loss of Nrxns at 5-HT synapses impairs social recognition memory and social reward preference. The hippocampus and nucleus accumbens, respectively, are crucial in these behaviors. In Aim 1, I will determine whether 5-HTergic Nrxns are critical for social behaviors through completion of social (and other complex) behavior studies. In addition, I will explore (i) if and (ii) how 5-HT is necessary for social behaviors using (i) 5-HT therapeutics to augment 5-HT function prior to social behavior studies and (ii) in vivo microdialysis to measure extracellular 5-HT levels during social behavior. In Aim 2, I will perform a mouse breeding and lentiviral rescue approach to determine whether specific Nrxns control social behavior. Furthermore, I will use immunohistochemical and electrophysiological approaches to identity how Nrxn proteins regulate excitatory and inhibitory synapse distribution and physiology. A close examination of Nrxns in 5-HT synaptic function is necessary to shed new light on social behavior disturbances in ASD.

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  • Samantha Tse, Pukkila-Worley Lab, Funding provided by National Institutes of Health

    Detection of intestinal pathogens through host surveillance of bacterial toxins

    Although commensal and pathogenic bacteria can be recognized by host pattern recognition receptors, intestinal epithelial cells target protective inflammatory responses towards pathogenic organisms through mechanisms that are incompletely understood. Additional mechanisms of pathogen sensing must exist that allow intestinal cells to target inflammatory defenses towards bona fide pathogens during an infection, and not harmless commensal bacteria. Pathogenic bacteria can express virulence determinants. Phenazine toxins are a family of redox active virulence determinants that are produced by a variety of human pathogens, including P. aeruginosa. P. aeruginosa can colonize the intestines of immunocompromised patients and cause fulminant septicemia and subsequent death. The mechanism by which intestinal epithelial cells detect P. aeruginosa, and whether this involves the surveillance of phenazine toxins, is not known. Nuclear hormone receptors (NHR) are transcription factors that program adaptive host responses following recognition of specific exogenous or endogenous ligands. In particular, HNF4⍺ is an NHR expressed in the intestine. In the model organism C. elegans, the HNF4⍺ homolog NHR-86 is required for the transcriptional activation of innate immune effector genes that protect against P. aeruginosa infection. The central hypothesis of this proposal is that intestinal epithelial cells detect infection through the surveillance of pathogen-derived phenazine toxins by NHR-86/ HNF4⍺, which directly activates protective anti-pathogen defenses in the intestinal epithelium. The following key preliminary findings support this central hypothesis: i) P. aeruginosa mutants that cannot make phenazine toxins do not activate C. elegans innate immune defenses; ii) synthetic phenazine toxins can activate immune genes; and iii) induction of immune genes by phenazine toxins is dependent on the expression of NHR-86/ HNF4⍺. In this proposal, Aim 1 will characterize the C. elegans immune response towards bacterial phenazine toxins, and Aim 2 will define the role of intestinal NHR-86/HNF4⍺ in detecting P. aeruginosa infection in C. elegans. The research proposed here will define a new concept of immune activation in intestinal epithelial cells and will also attribute a novel role for NHRs in pathogen sensing in the intestine. Insights from these findings may identify unexplored approaches for the development of anti-inflammatory and anti-infective therapies.

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    Discovery of a novel role of VPS13D in Autophagy

    Defects in autophagy, the self-degradation of cellular components, are linked to multiple disorders such as cancer, diabetes and neurodegenerative diseases. Autophagosomes, containing cargo marked for degradation, fuse with lysosomes to recycle cell resources, such as protein aggregates and damaged organelles. However, we know little about the mechanisms that regulate the association between autophagic cargoes and autophagosome formation. Here, I investigate the role of vps13d, an essential gene with relatively unknown function, in context-specific autophagy and cell death in the developing Drosophila intestine. Proteins that regulate autophagy and cell death are of particular interest given the roles they play in tumorigenesis. Previous studies of VPS13D identified a role in the clearance of mitochondria by autophagy, also known as mitophagy. Intriguingly, VPS13D also appears to be involved in dissolution of membrane contacts that are associated with autophagosome formation. Furthermore, little is known about the role of VPS13D in associating autophagy-bound cargo with the site of autophagosome formation, despite having links to the core autophagy machinery. I hypothesize that VPS13D facilitates context-dependent autophagy by associating ubiquitinated cargo with the autophagic machinery and disassembling membrane contact sites at the phagosome assembly site (PAS). Here I propose to determine if VPS13D functions as an autophagy receptor for ubiquitinated cargo and determine the relationship between VPS13D and membrane contact modulator Vacuole Membrane Protein 1 (VMP1). The association of VPS13D and mutations in other factors that regulate autophagic cargo recruitment with human disorders illustrates the importance of studying VPS13D function.

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  • Kevin O'Connor, Kelliher Lab, Funding Provided by National Institutes of Health

    Targeting dormant leukemia-initiating cells in T-cell acute lymphoblastic leukemia

    Therapy resistance is a major barrier to long term remission in pediatric T-cell acute lymphoblastic leukemia (T-ALL). The prognosis for children with relapsed or refractory disease is dismal. Leukemia-initiating cells (L-ICs) regenerate disease upon transplantation into mice. They also recapitulate the immunophenotypic complexity of the parent leukemia supporting that, as in normal hematopoiesis, there is a cellular hierarchy among leukemic cells. Our laboratory has previously demonstrated that the L-IC is a committed thymocyte progenitor and resides in the leukemic DN3 population, however, only a fraction of DN3 cells can give rise to disease. L-ICs rely on NOTCH1-induced MYC signaling for survival. Recent studies identified dormant, therapy resistant L-ICs in both murine models and T-ALL patient samples. The role of cell cycle restriction in L-IC latency is incompletely understood. In an effort to uncover pathways that govern L-IC function, we performed single cell RNA sequencing on thymocytes at varying stages of T-cell leukemogenesis using our transgenic Tal1/Lmo2 model. This approach identified a dormant DN3 cluster, marked by low Ki67 expression, which is observed in other murine T-ALL samples. Dormant DN3 cells exhibit high Notch1, but low Myc expression. The transcriptional signature of these cells shows enrichment of genes previously implicated in leukemia initiation or leukemia stem cell function. Dormant DN3 cells show enrichment of the non-canonical Wnt receptor Ryk, which is reported to maintain hematopoietic stem cell self-renewal by limiting proliferation and promoting quiescence. RYK is overexpressed in primary pediatric T-ALL and in Tal1/Lmo2-induced murine T-ALL compared to healthy thymus. This indicates that RYK may not be restricted to this rare subpopulation and moreover, there may be a therapeutic window for RYK inhibition in relapsed T-ALL. The central hypothesis of this proposal is that dormant DN3 cells are quiescent L-ICs that retain proliferative and differentiative capacity, which permits their therapy tolerance and subsequent expansion during relapse. This proposal will identify a gene signature of dormant DN3 cells and uncover the potential role of these cells in T-ALL relapse by evaluating their L-IC function and chemoresistance (Aim 1). Aim 2 will define the non-canonical WNT/RYK signaling network in T-ALL and uncover the role of these pathways in dormant DN3 cells and L-IC function by testing whether inhibition of RYK reduces the L-IC frequency of murine and patient T-ALL cells. Collectively, these studies will provide critical insight to TALL heterogeneity and will lay the foundation for development of L-IC targeted therapy for relapsed disease.

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    Mechanism of epigenetic inheritance in a mouse model of acute paternal stress

    Epigenetic inheritance is a process by which parental exposure to environmental factors influences offspring phenotype. This field of investigation has wide-ranging implications for human health. Epidemiologic studies have shown that exposure of parents or grandparents to starvation, trauma, cigarette smoke, or other stressors alters offspring susceptibility to cardiovascular disease, obesity, lung disease, or other conditions. Research with animal models has mirrored these findings and offers tools for disentangling the underlying mechanisms of epigenetic information transfer from parent to offspring. Such research has been greatly enabled by recent technological advances, including next generation sequencing and fundamental discoveries like microRNA biology. In vitro fertilization experiments demonstrate that sperm carry sufficient information to propagate epigenetic phenotypes across generations, and research with these paternal epigenetic inheritance models has identified sperm-associated small non-coding RNAs (sncRNA) as carriers of information from father to offspring. I have established an epigenetic inheritance model in which paternal influenza infection, with virus elimination and disease recovery prior to mating, results in an adaptive attenuation of disease severity (significantly decreased weight loss) in response to influenza infection in offspring, as well as a maladaptive altered glucose metabolism. While these phenotypes are robust, the underlying mechanism of information transfer to offspring remains to be determined. In preliminary experiments to address the mechanism I have found that influenza infection alters sperm-associated sncRNA. This proposal addresses the hypothesis that influenza virus-induced changes in sperm-associated sncRNA populations alter embryo development resulting in offspring metabolic and immune phenotypes. Aim 1 elucidates the underlying epigenetic inheritance mechanism through kinetic analysis of sperm sncRNA and early embryo development. Aim 2 determines the specificity of the offspring epigenetic inheritance phenotype to the paternal stressor both directly by challenging with a non-cross reactive strain of influenza virus, and indirectly by further metabolic phenotyping to determine if paternal influenza infection alters glucose homeostasis and liver gene expression in the offspring in ways similar to other paternal stressors. This research will provide valuable insight into the mechanism underlying epigenetic inheritance, and do so within the context of a novel epigenetic inheritance model with direct relevance to human health.

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    Investigating the role of MS4As during Alzheimer's disease

    Alzheimer’s Disease (AD) is the most common neurodegenerative disease in the world and the 6th leading cause of death in the United States. Despite significant effort, current AD therapies are highly limited in both number and efficacy. Hope for new therapeutic interventions has emerged from recent genome-wide association studies (GWAS), which have identified genes whose mutations are linked to altered AD susceptibility. One of the strongest and most reproducible genetic associations with altered AD risk are members of the Membrane Spanning 4a (MS4A) gene family. In fact, current genetic data suggest that MS4A polymorphisms account for approximately 10% of all AD cases. However, a limited understanding of MS4As has hindered the development of therapies targeting these proteins. Single cell transcriptional profiling has revealed that the Ms4a genes genetically linked to AD are selectively expressed in a subset of microglia, the resident innate immune cells of the central nervous system. Furthermore, MS4A-positive subsets of microglia display a phenotype similar to microglia seen in neurodegenerative disease states, necessitating inquiry into the role of MS4As in microglia. We found that Ms4a-positive microglia are enriched for phagocytic machinery versus Ms4a-negative microglia, and animals deficient for individual Ms4a family members have significantly reduced expression of genes important for phagocytosis compared to wild-type (WT) animals. Microglial phagocytosis is a dynamic process by which brain debris, dying cells, unwanted synaptic connections, and toxic molecules are eliminated and disruption of this process is thought to underlie numerous neurological disorders, including AD. Thus, this proposal will test the hypothesis that MS4As regulate microglial phagocytosis and alter AD pathogenesis. To test this hypothesis, aim 1 will examine microglia phagocytosis of synapses, dead neurons, and amyloid-beta 42- one of the neurotoxic, pathogenic agents of AD- both in vitro and in vivo using Ms4a-deficient and WT microglia. These experiments will characterize the role of MS4As in microglia, and provide insight into how MS4As affect microglial phagocytosis. Aim 2 will investigate the role of MS4As in AD pathogenesis. Although GWAS studies have strongly linked MS4A polymorphisms to AD susceptibility, the role of MS4A genes in AD is unknown. Some MS4A alleles confer AD protection while others increase AD susceptibility, and MA4A polymorphisms are often located in non-coding regions of these genes. To investigate whether MS4As are protective against or contributive toward AD, mice that are homozygous deficient for individual Ms4a family members will be crossed to the 5XFAD mouse model of AD and pathological features of AD, including behavioral defects in memory, amyloid beta plaque formation, microgliosis, neuronal loss, and synapse elimination will be assessed. Together, these aims will provide fundamental new insight into the role of MS4As in AD and contribute to the development of therapeutic approaches targeting MS4A receptors.

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    Characterization of MS4A Chemoreceptive Function

    As animals explore their environment, they encounter millions of chemical signals that must be correctly interpreted to identify food and mates and to avoid predation. In mammals, the majority of this chemical information is detected by the sensory neurons of the olfactory system, (OSNs), which express more than one thousand distinct olfactory receptors (ORs), specialized chemoreceptors that sense volatile, chemical odorants. While many of these receptors have been molecularly defined, how they function to elicit appropriate behavioral responses remains largely unclear (i.e., how does a mouse know to run away from a cat and toward a piece of cheese). This proposal outlines a series of experiments aimed at taking advantage of the opportunities offered by the olfactory system to begin to characterize the mechanisms by which chemosensory information is detected and processed to generate specific, stereotyped behavioral responses. We have recently identified a new family of olfactory receptors encoded by the Ms4a family of genes, which our preliminary experiments suggest are required to mediate innate avoidance responses to stimuli such as predator-derived odorants that signify danger to the animal. However, how MS4A receptors function to elicit these behaviors is largely unknown, which significantly impairs our understanding of how the olfactory system interprets relevant sensory stimuli to elicit appropriate behavioral responses. To begin to elucidate MS4A chemoreceptor function, in Aim 1 I will use mutagenesis, electrophysiology, and calcium imaging to determine how MS4As bind ligands and signal their presence. In Aim 2, I will use ex vivo and in vivo preparations as well as mouse behavioral assays to determine the contribution of MS4As to transducing predator odor presence into appropriate innate avoidance responses. Together, the experiments proposed here will characterize a novel family of odorant receptor and how it signals the presence of ethologically relevant odors. Broadly speaking, these studies seek to illuminate basic principles of olfaction, provide insight into mammalian chemosensation, and shed light on the neural pathways associated with sensory perception.

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    The Influence of Spatial Proximity to Sterile Syringe Sources and Secondary Syringe Exchange on HCV Risk Among Rural People Who Inject Drugs

    The current U.S. opioid epidemic has fueled an increase in injection drug use and, in turn, an alarming surge in new hepatitis C virus (HCV) infections. Between 2010 and 2015, the incidence of HCV increased by 294% nationally, driven primarily by a rise in injection drug use and risky injection behavior – namely syringe sharing. This growing epidemic has disproportionately affected young people who inject drugs (PWID) in rural communities. There is an urgent need to implement tailored and effective harm reduction strategies to rural PWID who are disproportionately impacted by HCV. Although research has shown that syringe services and pharmacy syringe sales (i.e sterile syringe sources) are associated with a reduction in injection-mediated risks and HIV transmission, the evidence for whether these services reduce HCV risk among PWID remains mixed. This proposal will applying the risk environment model to evaluate the influence of sterile syringe sources on the HCV risk environment. Specifically, this proposal will evaluate whether spatial proximity to sterile syringe sources and receptive secondary syringe exchange are associated with HCV serostatus among rural PWID. The aims are: (1) To evaluate the association between road network distance to the nearest sterile syringe source (SSP or pharmacy that sells nonprescription syringes) and HCV serostatus; (2) To use egocentric social network analysis to evaluate the association between receptive secondary syringe exchange and HCV serostatus; (3) to explore and unpack rural PWIDs’ perceptions of and experiences with syringe acquisition and syringe sharing practices through in-depth interviews. These findings could help inform the development of future harm reduction interventions in rural New England, a region of the country that has been particularly hard hit by the opioid epidemic and related HCV infections.

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    Pathogen sensing by nuclear hormone receptors in C. elegans intestinal epithelial cells

    The mechanisms of pathogen sensing and immune effector induction in intestinal epithelial cells are not completely understood. Disruption in the mechanisms of pathogen sensing and immune homeostasis in intestinal epithelial cells can lead to dysbiosis and inflammation, as well as susceptibility to bacterial infection. Key insights into intestinal epithelial cell immunity and host-pathogen interactions have been made using the nematode C. elegans. Nematodes mount innate immune defenses against bacterial infection via conserved immune pathways, but the mechanisms of pathogen detection are unknown in this organism. In nematodes, the family of nuclear hormone receptors (NHRs) has dramatically expanded compared to other metazoans. NHRs are ligand-gated transcription factors that sense endogenous and exogenous signals to induce adaptive transcriptional responses. The C. elegans genome encodes 274 NHRs, of which 260 are homologs of human HNF4α. HNF4α is a key NHR involved in inflammatory bowel disease, though the mechanism through which HNF4α mediates inflammatory bowel disease in humans is unknown. The central hypothesis of this proposal is that C. elegans HNF4α homologs are an ancient family of pathogen sensors whose evolutionary expansion in C. elegans was driven by their function in detecting diverse pathogens. The following key findings support this hypothesis: (i) The nuclear hormone receptor, NHR-86/HNF4α, senses the cellular environment and activates C. elegans intestinal immune defenses; (ii) NHR-86/HNF4α is required for pathogen resistance and immune response towards the gram positive human pathogen E. faecalis; and (iii) A different C. elegans HNF4α homolog is required for pathogen defense and immune effector regulation against the gram negative pathogen P. aeruginosa. In this proposal, Aim 1 will define the role of C. elegans NHR-86/HNF4α in pathogen detection and immune effector induction during E. faecalis infection using a combination of transcriptomics, ChIP- sequencing, tissue-specific rescue and genetic epistasis. Aim 2 will characterize the function of a separate C. elegans HNF4α homolog in pathogen sensing during P. aeruginosa infection. The approach includes: transcriptomics, global NHR binding site identification, tissue specific rescue, and P. aeruginosa genetics. Collectively, these studies will characterize a fundamentally new paradigm of immune activation, which will solve a major conundrum of how pathogens are sensed in C. elegans. These findings will also establish NHRs as evolutionarily ancient pathogen sensors. Ultimately, the expectation is that detailed dissection of this mechanism will shed light on the role of HNF4α in mammalian pathogen sensing and inflammatory bowel disease.

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    Investigating sliding clamps and their contribution to genome stability

    All cells must replicate their genome once per cell cycle. To ensure proper duplication, cells integrate hundreds of factors that copy, surveil, and repair our genetic information. Proliferating Cell Nuclear Antigen [PCNA] and Rad9-Rad1-Hus1 [9-1-1] are ring-shaped clamps that act as master “conductors” that regulate many of the factors that replication and maintain our DNA. PCNA is a homotrimeric ring that coordinates the replisome during DNA synthesis to work in tandem with DNA repair, chromatin remodeling, and cell cycle progression. When cells experience dsDNA breaks, they use the heterotrimeric clamp 9-1-1 to coordinate specific “SOS” repair factors. The collaborate efforts of both clamps are critical for genome stability. Many cancers are linked to inappropriate clamp coordination and changes in their expression. Because sliding clamps are central to many oncogenic pathways, we must address how they regulate themselves and their client partners. This proposal aims to address the following questions about sliding clamps: 1) How do sliding clamps coordinate their various partners? 2) Does the time sliding clamps spend on DNA influence genome stability? and 3) What determines site-specific loading of sliding clamps? I propose a multidisciplinary approach to address these questions about sliding clamps by investigating two-disease causing PCNA variants [PCNA-S228I [serine to isoleucine] and PCNA-C148S [cysteine to serine]] and the loading mechanism of 9-1-1. I hypothesize that sliding clamps control genome integrity via site-specific loading, proper partner interactions, and residence-time on DNA. I further hypothesize that PCNA-S228I and PCNA-C148S disrupt genome integrity by either promoting premature DNA dissociation or disrupting partner interactions. Finally, I hypothesize that the Rad17 subunit alters the clamp loader structure to specifically load the 9-1-1 clamp at sites of DNA damage. In aims 1 and 2, I will use PCNA-S228I and PCNA-C148S to address how clamps “choose” their partners and regulate their time on DNA. I will use x-ray crystallography, unfolding experiments, and a series of functional assays to determine how each variant compromise genome stability. In aim 3, I will determine the loading mechanism of clamp 9-1-1 to address how clamps are loaded to specific sites in the genome. I will use cryo-electron microscopy and a series of anisotropy experiments to capture the different states of 9-1-1 loading. Collectively, our work will help in the development of sliding clamp specific chemotherapeutics and tumor diagnostics.

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    Investigating the role of B cells in pulmonary fibrosis resulting from STING gain-of-function autoinflammation

    Pulmonary lung fibrosis is a poorly understood process that can arise in pediatric patients with gain-of-function mutations that disrupt the regulation of the cytosolic double stranded DNA sensing pathway, cGAS-STING. This project will define the role that B cells play in mediating lung fibrosis in a mouse model of STING gain-of- function autoinflammation that recapitulates a human disease known as STING Associated Vasculopathy with onset in Infancy (SAVI). The expectation is that the results of these studies will offer insights into the mechanisms by which B cell contribute to fibrotic lung disease and assess, using murine models, whether targeting B cells is a valid strategy for prophylactically treating lung fibrosis.

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    Tissue-specific modulation of Apolipoprotein E in neurodegeneration

    Alzheimer’s Disease (AD) and Amyotrophic Lateral Sclerosis (ALS) are multifaceted, progressive neurodegenerative conditions that place a monumental burden on patients, providers, and the public healthcare system. No disease-modifying treatments are currently available for either AD or ALS. Although the etiology of each disease is well studied, strategies targeting characteristic features of disease pathogenesis— e.g., beta-amyloid in AD—show limited clinical efficacy. Identification of novel targets that modify progression of neurodegeneration is needed for innovative therapeutic development across neurodegenerative disorders. AD and ALS are caused by genetic and environmental factors that alter downstream pathways like lipid homeostasis. A critical player in systemic and central nervous system (CNS) lipid transport, that is also implicated in the onset and progression of neurodegeneration, is <em>apolipoproteinem> E (ApoE). Genetic deletion of ApoE reduces neuropathology in mice, but also causes atherosclerosis. Thus, despite its implication in disease, the diverse functionality of ApoE in its distinct biological “pools” (i.e. systemic and CNS) makes it a challenging therapeutic target. Reducing individual ApoE pools may circumvent this issue. However, the independent effects of systemic or CNS ApoE silencing on neurodegenerative diseases are unclear. The goal of this proposal is to determine the relationship between systemic and CNS ApoE pools, and their effects on disease progression in AD and ALS mice. The project will take advantage of chemically-stable, self- delivering small interfering RNAs (siRNAs) that enable sustained, <em>tissue-specificem> silencing of target mRNA. GalNAc-siRNAs specifically deliver to liver (site of systemic ApoE production), and divalent (Di)-siRNAs deliver throughout the brain and spinal cord after intra-cerebroventricular (ICV) injection. With guidance from Drs. Anastasia Khvorova (siRNA chemistry), Robert Brown (ALS), Evgeny Rogaev (AD models), Andrew Tapper (animal behavior), and Thomas Smith (neuropathologist), GalNAc- and Di-siRNA will be used to silence hepatic and CNS ApoE, respectively, and the effects on CNS and systemic ApoE pools, and AD and ALS phenotypes, will be examined. In Aim 1, GalNAc-siRNA targeting ApoE will be subcutaneously injected into mice. In Aim 2, Di-siRNA targeting ApoE will be delivered to the CNS via ICV injection. Both aims will utilize the APP/PSEN1 mouse model of AD and the SOD1G93A mouse model of ALS, and will measure systemic and CNS ApoE and cholesterol levels, and AD and ALS neuropathology and behavior two months post injection. These studies will advance the understanding of how ApoE pools interact in the context of neurodegeneration, and the effects on disease progression. Such findings will inform strategies for safe and effective therapeutic targeting of ApoE in AD, ALS, and age-related neurodegenerative disorders.

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  • Ariel Beccia, Lapane Lab, Funding provided by National Institute on Minorty Health and Health Disparities

    Intersectionality of Sexual Orientation, Gender Expression, and Weight Status on Risk of Disordered Eating Behaviors

    A glaring sexual orientation-related disparity is in the prevalence of disordered eating behaviors (DEBs), including severe calorie restriction, self-induced vomiting, laxative and diet pill use, and binge-eating. One in three sexual minority young people (lesbian, gay, bisexual, and other non-heterosexual individuals) engage in DEBs, a seven-fold higher odds than their heterosexual peers. There are considerable health consequences associated with these behaviors, such as metabolic and reproductive health issues, substance use, depression, and suicidality. However, research on DEBs lags behind that on other sexual orientation-related health disparities, with critical gaps including failing to consider both within-group diversity in risk and the upstream social determinants of the observed disparities. Importantly, experiencing multiple forms of social disadvantage has been shown to increase risk of eating-related pathologies, including DEBs. Gender nonconforming and higher-weight (i.e., overweight/obese) statuses are especially relevant dimensions of disadvantage to consider, as these groups experience high levels of appearance-based discrimination and may use DEBs as dangerous body-modification practices to cope. Sexual minorities who experience further marginalization through membership in these groups may encounter unique and/or compounding social stressors that exacerbate risk. Examining the intersectionality of sexual orientation, gender expression, and weight status is thus critical to addressing these research gaps. Using the Growing Up Today Study (GUTS), a national longitudinal cohort study of over 27,000 participants (~20% of whom are sexual minorities), the aims of this proposal are to: 1) Quantify the intersectional effects of sexual orientation, gender expression, and weight status on risk of DEBs among young adults; 2) Quantify the effects of interpersonal-level determinants (bullying victimization, weight-based harassment) on risk of DEBs by sexual orientation, and evaluate differences by gender expression and/or weight-status; and 3) Quantify the effects of structural-level determinants (discriminatory social conditions, state policies) on risk of DEBs by sexual orientation, and evaluate differences by gender expression and/or weight-status. The National Academy of Medicine’s 2011 landmark report on sexual minority health stressed the importance of adopting an intersectional framework for disparities research to inform the development of inclusive health equity efforts. Applying this lens through leveraging novel statistical methods will further understanding of a critically understudied sexual minority health issue and help identify high-risk subgroups and modifiable contextual risk factors. A tailored training plan accompanies this proposal and outlines the steps required to advance the Applicant’s career as an independent researcher focused on intersectional health disparities research.

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  • Emily Agnello, Kelch Lab, Funding provided by National Science Foundation

    Elucidating the structural and mechanistic features of a thermophilic bacteriophage

    As the most abundant and deadliest entities on earth, bacteriophage play an essential role in many biological environments. While there are well-developed phage model systems that have informed our understanding of phage in the past 60 years, these systems have structural limitations. Here, we use a unique thermophilic siphovirus, P74-26, with extraordinary strength and stability to fill in the knowledge gaps that remain and take a closer look at some of the fascinating abilities of a phage that developed under the evolutionary pressure of a hot spring. Double-stranded DNA (dsDNA) viruses, which include bacteriophage along with herpesviruses, adenoviruses, use a powerful ATPase motor to pump their genome into an immature structure called the procapsid. Genome loading leads to immense internal pressure, resulting in a conformational change from a spherical particle to an expanded, pressurized icosahedron. The extreme stability of P74-26 despite high temperature and pressure makes it a novel tool for elucidating the intricacies of phage assembly and thermodynamics. In this study, we will combine cryo-EM, SEC-multi angle light scattering, and mass spectrometry to examine physical and mechanistic aspects of P74-26. A structure of the uniquely long phage tail tube will provide perspective into the mechanism of DNA ejection and possible evolutionary advantages for such length. Additionally, we have found that the major capsid protein spontaneously assembles, allowing us to create a controlled system for determining the essential components for viral head stability.

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    Elucidating premature translation termination in Cystic Fibrosis

    A leading cause of Cystic Fibrosis (CF) is premature termination codons (PTCs) in the cystic fibrosis transmembrane conductance regulator (CFTR) gene. Suppression of translation termination at PTCs—i.e. PTC readthrough—to restore full-length CFTR protein may be a treatment strategy. Yet, current PTC readthrough drug candidates for CF are toxic (e.g. aminoglycosides) or ineffective (e.g. ataluren). Efficacy of PTC readthrough depends on efficiency of translation termination at the PTC. Thus, manipulating the molecular mechanisms of CFTR PTC termination to lower efficiency may improve PTC readthrough efficacy. However, strategies for such manipulations are limited in the absence of a detailed understanding of translation termination on CFTR PTCs. In the current model for normal termination, eukaryotic Release Factors 1 and 3 form a complex (eRF1•eRF3) that releases a newly synthesized protein from the ribosome. eRF1 recognizes a tetra-nucleotide stop codon at the end of an open reading frame, and catalyzes peptidyl-tRNA hydrolysis. Poly-A binding protein (PABP), which binds at 3′ ends of mRNA, recruits eRF3 and enhances termination efficiency. However, it remains unclear how PABP, eRF1, eRF3, and the tetra-nucleotide stop codon recognize the PTC to produce truncated CFTR protein. The goal of this proposal is to determine the biochemical and structural mechanism of translation termination. With guidance from Dr. Andrei Korostelev (expert in biochemical and structural mechanisms of translation), Dr. Allan Jacobson (expert in premature translation termination and PTC read-through), Dr. Phillip Zamore (RNA biochemist), Dr. Chen Xu (cryo-EM instrumentalist), and Dr. Nikolaus Grigorieff (expert in cryo-EM method development), release assays will be optimized to study the efficiency of translation termination mediated by eukaryotic release factors, and ensemble time-resolved (ENTIRE) cryo-EM will be used to capture structural intermediates of enzymatic reactions. Aim 1 will use defined mammalian translation systems to measure the individual effects of stop codon context, eRF1•eRF3, and PABP on the termination efficiencies (kcat/KM) of CFTR PTCs and the true stop codon. Aim 2 will visualize how the ribosome terminates on CFTR PTC G542X in its natural sequence context using ENTIRE cryo-EM. Collecting data at multiple time points will identify conformational changes and interactions between mRNA sequence, eRF1•eRF3, and PABP during termination. To reveal the termination mechanism on CFTR PTCs, structures and their progression intermediates will be compared with those recorded on the true CFTR stop codon. If successful, this study will reveal key molecular determinants of CFTR PTC termination, and may inform strategies to induce PTC readthrough for CF treatment.

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    Dissecting ADAM10 function in microglia-mediated synapse elimination

    The goal of this proposal is to dissect the molecular signaling between microglia and neurons that regulates synapse elimination in response to changes in sensory experience. Despite compelling evidence that microglia, the resident brain macrophages, play important roles in eliminating synapses in development and disease, the precise neuron-to-microglia molecular signaling that drives this process is poorly understood. I recently discovered a signaling pathway necessary for microglia-mediated synapse elimination by utilizing the well-described circuitry of the mouse barrel cortex circuit as a model to manipulate sensory experience and dampen neuronal activity. Here I found microglia robustly engulf synapses in the barrel cortex following either whisker lesioning or trimming, and that this engulfment is dependent on the microglial CX3CR1 receptor and its canonical neuronal ligand, CX3CL1, but not complement. Using single-cell RNAseq I also found that neuronal Cx3cl1 was not differentially regulated in the cortex following whisker removal, but the protease Adam10, known to cleave membrane-bound CX3CL1 into a soluble form, is increased following lesioning. Importantly, pharmacological inhibition of ADAM10 resulted in synapse elimination defects that phenocopied CX3CR1 and CX3CL1-deficient mice. These data suggest that post-translational modification of neuronal CX3CL1 by ADAM10 is required to regulate microglial synapse elimination in the cortex following whisker removal. Several exciting new questions have now arisen, which I will tackle in this proposal: 1) What is the cellular source of ADAM10 and is it localized to synapses (Aim 1)? 2) Do other subcortical synapses within the barrel circuit remodel via ADAM10-CX3CL1-CX3CR1 signaling and does this differ between whisker lesioning and trimming (Aim 2)? I hypothesize ADAM10 is derived from layer IV excitatory neurons to regulate microglia- mediated synapse remodeling and that ADAM10 signaling is specific for cortical synapse rewiring after whisker trimming and lesioning, but not for sub-cortical synapse remodeling. To test this hypothesis, I have acquired powerful in vivo molecular genetic tools to manipulate ADAM10 function in specific cells. I have also developed collaborations to learn and perform cutting-edge whole tissue clearing by iDISCO to assess structural remodeling of entire circuits. Finally, I have a strong mentoring team that includes my mentor Dr. Dorothy Schafer with expertise in microglial function within neural circuits, my co-mentor Dr. Andrew Tapper with expertise in structural and functional mapping of brain circuits, and collaborators with expertise in iDISCO. Together, I am in a strong position to molecularly dissect how ADAM10 modulates neuron-microglia signaling necessary for remodeling brain circuits. This could be highly relevant for neurodegenerative disease where microglial dysfunction, synapse loss, and ADAM10 have been implicated. In the process, I will receive training in a variety of microscopy and molecular genetic approaches that will provide a foundation for my future career as an independent principle investigator at an academic institution focused on dissecting functions for glial cells within neural circuits.

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    Investigating how the conserved ZNFX-1 protein regulates epigenetic inheritance and germline immortality in Caenorhabditis elegans

    Germ cell immortality is essential for fertility and for species survival. To proliferate indefinitely, germ cells depend on mechanisms that maintain genome integrity and epigenetic programs. In animals, small RNAs that interact with Argonaute proteins of the PIWI family—called piRNAs—serve as a vanguard of transcriptome and epigenome integrity in the germline, by identifying and silencing transposable elements and by regulating germline gene expression. In many animals, piRNAs are essential for germline health. Defective piRNA biogenesis or function activates transposon expression and mobility, increases DNA damage, disrupts germ cell development, and reduces fertility. In Caenorhabditis elegans, small RNA pathways with opposing activities collaborate to maintain germ cell survival and fertility. Recent studies identified ZNFX-1 as a regulator of epigenetic inheritance in worms. ZNFX- 1 is a highly conserved UPF1-like helicase with C-terminal NF-X1-type zinc finger domains. znfx-1 mutants activate epigenetically silenced reporters, and in some cases they silence normally active reporters, indicating that ZNFX-1 balances opposing epigenetic programs. The targeting pattern of small RNAs redistributes in znfx- 1 mutants, suggesting that ZNFX-1 determines the origin of small RNAs required for silencing and anti-silencing pathways. Preliminary data also show that znfx-1 null mutations cause a mortal germline phenotype at elevated temperatures, suggesting that ZNFX-1 maintains balanced epigenetic signals essential for germline immortality. This proposal seeks to use genetic, computational, and biochemical approaches to test the hypothesis that ZNFX-1 is recruited to targets and identifies sites of small RNA biogenesis. Studies in Aim 1 will determine how ZNFX-1 regulates small RNA biogenesis by identifying how and where it binds to target transcripts, and if it unwinds or moves along RNA. Studies in Aim 2 will determine how ZNFX-1 regulates germline immortality by identifying functional domains of ZNFX-1, potentially redundant proteins with homologous domains, and small RNA and transcriptome features of germline immortality. These studies will reveal how animals transmit heritable epigenetic information and how epigenetic pathways maintain germ cell immortality. In addition, the proposed research will provide training in genetics and epigenetics, quantitative biochemistry, and computational approaches, and prepare the fellow for a postdoc in computational and systems biology and a future career as an independent investigator.

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    Integrin Regulation of Mammary Gland Development

    The mammary epithelium is composed of diverse cell populations that are responsible for regulating key processes in mammary gland development, especially lactation. Alveolar progenitor (AP) cells are partially differentiated stem cells that produce alveolar/milk-producing cells and these cells have recently been implicated as cells of origin in breast cancer. Through analysis of published single cell RNA-seq data, integrin β4, a protein known to function primarily in basal mammary epithelial cells to maintain structural integrity of the gland, was found to be expressed in the AP population. This unexpected result suggests that β4 plays a novel role in the AP population and may regulate dynamic processes within the developing mammary gland. This goal of this proposal is to understand the functional role of β4 in the AP cells of the nulliparous and lactating mammary gland and elucidate the mechanism by which β4 regulates this population. Preliminary studies have revealed that β4 expression is necessary to promote progenitor potential of the AP cells and identified LacdiNAc, a novel glycosylation modification, on β4 that we hypothesize is essential for its localization in lipid rafts that promotes its function in the AP population. Using an AP cell culture model as well as a Cre-lox mouse model to conditionally knock out β4 from the AP population, the function of β4 in the AP population will be assessed in vitro and in the virgin and lactating mammary gland. Also, glycomics analyses and biochemical approaches will identify novel glycans on β4 and help in understanding how LacdiNAc affects function of β4 in the AP population. This approach will further our understanding of the novel role of β4 in the AP population and a new mechanism involving LacdiNAc-β4 localization to lipid rafts to regulate alveolar differentiation. These studies have to potential to define novel mechanisms that regulate the AP population during normal mammary gland development as well as breast cancer progression.

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    Characterizing effects of sperm- and oocyte-derived epigenetic factors on early embryonic gene expression and offspring metabolic function

    Metabolic diseases such as obesity have become significant health risks affecting one-third of the population worldwide and can have devastating complications. It is therefore imperative to understand the causes of metabolic disease predisposition in order to develop preventative strategies. Extensive genetic studies have failed to explain this ongoing epidemic. However, parents pass on not only genetic information, but also epigenetic factors, which can be modified in response to environmental stimuli, and can then affect gene expression. If information about parental environment can be recorded in the germline, it has the potential to be transmitted to the zygote and impact offspring health. This concept remains controversial in mammals and represents a large knowledge gap in the field of embryology. Previous work in the lab has demonstrated that sperm from fathers fed a low protein diet carry tRNA fragments and microRNAs that can modify gene expression in the embryo. Therefore, in Aim 1, sperm-derived RNAs will be purified and microinjected into parthenogenetically-activated oocytes, or parthenotes, which lack any paternal genetic content. Transcriptomic profiles of injected parthenotes will be acquired by single-embryo RNA-Seq to characterize resulting alterations to the embryonic transcriptome. Maternal transmission of epigenetic information has not been characterized to the same extent as the paternal side. Therefore, in Aim 2 a similar dietary paradigm will be utilized to address the question of whether information about maternal diet can be carried in oocytes and result in changes to the embryonic transcriptome. In vitro-fertilized embryos from mothers fed low protein, high fat, or control diet will be sequenced by single-embryo RNA-Seq. These embryos will be transferred to foster mothers to produce adult offspring, which will then be assessed for glucose tolerance and insulin resistance. The use of in vitro fertilization in this paradigm will ensure that any changes observed in the embryo originate from the oocyte and not from nutrient exchange during gestation. Completion of this research will elucidate effects of paternal and maternal epigenetic factors carried by gametes on the embryonic transcriptome. This work will be completed at the University of Massachusetts Medical School under the sponsorship of Dr. Oliver Rando. The fellowship training plan includes training in embryological techniques, such as microinjection and immunofluorescent staining of lineage markers, as well as metabolic phenotyping of adult mice. Opportunities to gain experience in science communication include participation in departmental seminars and local and national conferences. Furthermore, career development workshops are provided by the university, in addition to teaching and mentoring of first-year graduate students.

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  • Denis Lafontain, Dekker Lab, Funding provided by National Institutes of Health

    Stability of the folded genome

    Perturbations in normal gene expression arising from defects in genome organization can lead to cellular dysfunctions linked to aging and various disease states. The mammalian genome is generally organized into chromosomes, compartments, topological associating domains (TADs) and loops. Although TAD and loop formation have been extensively studied, little is known about the processes that drive nuclear compartment formation. It has been proposed that microphase phase separation drives the association of genomic domains of similar chromatin state, resulting in the formation of either type A (active chromatin) or B (inactive chromatin) compartments. However, identifying factors involved has been limited by a lack of tools capable of quantifying the biophysical properties driving this phenomenon. Mammalian heterochromatin protein 1 (HP1) α and HP1β bind constitutive heterochromatin and are known to facilitate the bridging of nucleosomes, suggesting that these proteins play a key role in heterochromatin compartmentalization. Although a recent study has demonstrated that heterochromatin compaction is independent of HP1α, work from our collaborators suggest that this protein is required to stabilize interactions between heterochromatic loci. Interestingly, HP1 proteins and several of their interacting partners can bind RNAs. Independent of HP1 function, specific RNA transcripts are known to play important roles in the formation and maintenance of spatial genome organization and perhaps microphase separation, notably at nucleoli, speckles, and the inactive X chromosome of female cells. We recently developed liquid chromatin Hi-C (LC-Hi-C), which allows quantification of chromatin interaction stability measurements genome-wide. Briefly, isolated nuclei are subject to in situ restriction digestion. Digestion of the genome into a specific fragment size distribution results in the loss of low density/unstable interactions whereas higher density/stable interactions are maintained, which is quantifiable by genome-wide chromosome conformation capture (Hi-C). This technique reveals that the dissolution kinetics of chromatin interactions vary widely between A and B compartments as well as compartmental substructures. The development of “in situ LC-HiC” in Aim 1 will allow stability measurement on mitotic chromosomes, streamline the existing protocol and allow the study of smaller cell populations. Aim 2 will assess contributions of (HP1) α and HP1β to stability of heterochromatic interactions. In Aim 3, LC-Hi-C will allow identification of genomic regions destabilized by RNA depletion. Candidate factors contributing to stability will then be identified using in situ chromatin-associated RNA sequencing (iMARGI) and validated by perturbation followed by LC-Hi- C. Taken together, this study aims to measure the dynamics of chromatin interactions and to provide new mechanistic insight as to how the genome is organized throughout the cell cycle.

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    Feasibility of Smartwatches for Atrial Fibrillation Detection in Older Adults

    Atrial fibrillation (AF) is a cardiac rhythm abnormality that currently affects over 6 million Americans. This statistic is expected to double over the next decade given the increasing prevalence of AF risk factors such as advanced age and obesity. Atrial fibrillation confers a 5-fold risk of ischemic stroke, but can be treated effectively with anticoagulation therapy. Despite the efficacy of available treatment options, 1 in 5 patients with AF present with stroke as their initial manifestation of the arrhythmia. This is attributable to the significant challenge in diagnosing AF due to its episodic and sometimes asymptomatic nature. Existing AF monitoring strategies are burdensome or costly and invasive, and thus have low patient adherence and satisfaction. Recently, commercially available wrist-based wearable devices, or smartwatches, have shown to be accurate for AF detection, and may represent a promising tool for identifying AF. However, commercial devices are not primarily designed for use by older adults for arrhythmia detection, and there is a significant research gap in the feasibility of using smartwatches for arrhythmia detection in this population. Furthermore, no previous research has investigated the potential for implementation and integration of smartwatches into the healthcare system and infrastructure. Using data collected from the in-house randomized control trial Pulsewatch, and by conducting qualitative assessments in usability and implementation, this proposal addresses the evidence gap in the feasibility of smartwatches for AF detection with three specific aims: 1) to evaluate individual-level factors associated with adherence of using a smartwatch for AF detection, 2) to explore patient characteristics associated with acceptability of smartwatches and identify specific usability challenges and nuances for older adults, and3) to identify barriers and facilitators of implementing smartwatches for use in a clinical setting. We approach the problem with a user-centered focus and apply rigorous and systematic scientific methods in completing these aims. Knowledge generated from this proposal will provide future researchers and stakeholders with practical evidence in the potential use of smartwatches for detection of AF.

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  • Yiyang Yuan, MPH, MS, Lapane Lab, Funding Provided by National Institutes of Health

    Concurrent trajectories of physical frailty and cognitive impairment among nursing home residents and community-dwelling older adults

    Physical frailty, characterized by decreased physiologic reserve and increased vulnerability to stressors, and cognitive impairment, ranging from mild impairment to dementia, often co-occur in older adults. Both are associated with considerable adverse health outcomes, high healthcare costs, and substantial caregiver burden, and are highly prevalent in U.S. community-dwelling older adults. However, for older adults receiving long-term care in nursing homes, data is scarce on the prevalence of the two conditions over their stay. Community-based studies suggest the heterogeneous clinical presentation of physical frailty, which may have implications for its management. It is unknown if such heterogeneity is similar in older nursing home residents and if it is influenced by cognitive impairment. Further, physical frailty and cognitive impairment share risk factors and predict the future onset of one another but the mechanism of this complex interplay remains unclear. Lastly, depression is strongly correlated with both conditions, yet findings regarding the impact of antidepressants on the progression of physical frailty and cognitive impairment are inconsistent. This proposed F99/K00 project seeks to address these gaps by two specific aims with population, longitudinal data, and advanced statistical methods. Aim 1 (dissertation research) focuses on older nursing home residents and will describe the prevalence of physical frailty and cognitive impairment; identify subgroups of physical frailty and examine the variation of subgroups by cognitive impairment levels, and delineate the developmental trajectories of physical frailty and cognitive impairment and examine the correlations between trajectories. Aim2 (post-doctoral research) expands to older adults in the community and will assess the reciprocal association between physical frailty and cognitive impairment; quantify the impact of cumulative exposure to antidepressants on trajectories of physical frailty, cognitive impairment, and depressive symptoms; and examine the effect of depressive symptoms as a mediator of physical frailty on cognitive impairment with causal mediation analysis. Methodological innovations include the use of latent class analysis, group-based trajectory models, structural equation models (autoregressive cross-lagged panel analysis; autoregressive latent trajectory model), and causal mediation. This proposal is directly relevant to the growing aging population in the U.S., including those residing in the nursing homes and those living in the community, since it uses the national nursing home database Minimum Data Set 3.0 (Aim 1) and the nationally representative Health and Retirement Study linked to Medicare Part D Drug Event Files and the Harmonized Cognitive Assessment Protocol (Aim 2). This project will shed light on the concurrent progression of age-related physical and cognitive conditions. Results will inform future work to develop diagnostic tools and prediction models to facilitate timely identification of older adults at risk for accelerated functional decline and implement care tailored to older adults’ needs to effectively delay the onset of negative health outcomes, enhance the quality of life, and foster healthy longevity.

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    Replication-independent DNA methylation dynamics during post-testicular sperm maturation

    It has become apparent that sperm are extensively remodeled during epididymal transit, with ongoing changes to the protein and RNA content of maturing sperm. In addition, an increasing number of studies have shown that epigenetic information is modified during the process of sperm maturation. During the first year of my PhD studies, I have discovered that cytosine methylation patterns are surprisingly dynamic during sperm maturation in the epididymis. Using whole genome bisulfite sequencing (WGBS), I identified widespread changes in DNA methylation as sperm move from the testes through the caput, corpus, and cauda of the epididymis. Given that sperm are a highly methylated and condensed cell type, it is surprising and novel that epididymal transit results in any DNA methylation reprogramming of sperm. I aim to address the question of how DNA methylation changes occur between different sperm populations. My approach is to recapitulate maturation-associated cytosine methylation dynamics in vitro to understand the mechanism by which these changes are occurring. Resolving what these changes mean for potential offspring and determining the mechanisms and factors leading to changes in methylation will have significant implications for both assisted reproduction, and for understanding how a father's environment impacts his children's well being.

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    Exploiting RNAi-based silencing of Myc and metabolic vulnerabilities to prevent relapse afer Kras inhibition in lung cancer

    Lung cancer is the leading cause of cancer-related death, accounting for approximately 1.3-million deaths worldwide. The most common type of lung cancer, non-small cell lung cancer (NSCLC), is frequently associated with oncogenic mutations in KRAS, a GTPase that regulates cell growth and division. Oncogenic KRAS mutations constitutively activate Kras protein and result in rapid cell division, even in the absence of growth signals, and thus play a critical role in tumor formation and maintenance. Genetic inactivation of oncogenic Kras reduces tumor size and metastatic potential, but Kras-independent tumors eventually recur and are more aggressive. Preliminary studies suggest that Kras-independent relapse may be mediated by the proto-oncogene, MYC. The MYC mRNA is a known target of the microRNA miR-34a, and treatment with ectopic miR-34a delays Kras-independent relapse. The goal of the proposed project is to understand the roles of Myc and miR-34a in Kras-independent tumor relapse in a mouse model of NSCLC. Aim 1 will investigate the role of miR-34a in delaying relapse. Endogenous levels of miR-34a will be quantified during tumor growth and regression, and during Kras-independent relapse. CRISPR/Cas9 genome editing will be used to mutate the miR-34a binding site in the Myc 3’ untranslated region to test whether miR-34a delays relapse by directly silencing Myc. Findings from this aim will provide insight into the use of microRNA-mediated inhibition as a potential therapeutic strategy to target Myc. Aim 2 will investigate how Myc controls relapse and glucose metabolism in Kras-independent NSCLC cells and mice. To achieve this, a novel doxycycline inducible dual shRNA system will be used to co-silence Kras and Myc expression in vitro. Using the seahorse bioanalyzer system, glucose metabolism will be monitored in both Kras-silenced and Kras/Myc co-silenced NSCLC cells to identify metabolic vulnerabilities of tumors. Using a mouse model of NSCLC, tumor burden will be monitored after Kras and Kras/Myc co-silencing. This aim will result in a novel dual shRNA based strategy to establish the efficacy of co-silencing Myc and Kras as a therapeutic strategy to induce tumor regression and prevent relapse in NSCLC. Taken together, findings from this study will elucidate mechanisms of tumor relapse induced by Kras silencing and identify regulators of tumor development, maintenance, and relapse. Ultimately, this work will aid in the creation of novel therapeutic strategies to improve NSCLC patient outcomes.

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    Mechanism of cdk4 diabetes rescue in IRS2 knockout mice

    Type 2 Diabetes (T2D) is a major public health issue in the United States with approximately 9.3% of the population suffering from the disease. Additionally, 86 million people have prediabetes and the economic impact is staggering, with 1 in 10 health care dollars being spent on T2D and its complications. T2D results from insulin resistance and reduced beta cell mass; thus, strategies to increase functional beta cell mass are critical goals for diabetes research. Although it is well established (from rodent models) that increased beta cell mass results from enhanced beta cell proliferation, new research suggests that beta cell dedifferentiation also contributes to reduced beta cell function. Some proteins involved in the G1/S transition of the cell cycle, especially Cdk4, are critical for the maintenance of beta cell proliferation and mass. Insulin receptor substrate 2 knockout (Irs2 KO) mice develop diabetes due to peripheral insulin resistance and reduced beta cell mass, and we previously found that in vitro re-expression of cyclin D2, which activates Cdk4, rescues the loss of proliferation in beta cells lacking Irs2. Therefore, we hypothesized that expression of a constitutively active form of Cdk4 (Cdk4 R24C) might be able to rescue the diabetic phenotype of Irs2 KO mice. Intriguingly, preliminary results suggest that Cdk4 R24C is able to completely rescue not only beta cell mass, but also insulin secretion and beta cell differentiation. Interestingly, recent studies show that the Cdk4 kinase plays many roles independently of its known activity in the cell cycle. Therefore, the goal of this proposal is to determine the mechanisms behind this rescue and determine what atypical roles cdk4 plays in the beta cell. In Aim 1, we will determine how Cdk4 rescues beta cell proliferation, focusing on both the canonical Cdk4-Rb- E2F pathway, and will also identify novel Cdk4 interactors in the beta cell using BioID. In Aim 2, we will determine if Cdk4 R24C rescues 1st or 2nd phase insulin secretion in Irs2 KO islets using both islet perifusion and hyperglycemic clamps studies. We will also perform molecular studies to determine whether the KATPase Kir6.2, which was previously reported to be a target of the Cdk4-Rb-E2F1 pathway, is increased and is sufficient to rescue insulin secretion in Irs2 KO islets. Finally, in Aim 3 we will explore how Cdk4 R24C is able to restore beta cell differentiation markers. This is surprising and interesting, since it goes against the data showing that when beta cells proliferate they lose differentiation markers, and I think the most likely explanation is that Cdk4 is having effects unrelated to its cell cycle actions. I will investigate how Cdk4 rescues Pdx1 expression, with a focus on FoxO1 and PPARγ, two transcription factors that regulate Pdx1 expression. Using in silico analyses and reading the primary literature, I found that both contain Cdk4 consensus phosphorylate sites. Therefore, I will determine whether Cdk4 acts via either or both of these to maintain beta cell differentiation. If Cdk4 plays atypical roles as a kinase to influence multiple aspects of beta cell biology, this may lead to better therapeutic options for preserving beta cell mass, function and differentiation in T2D.

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  • Jordan L. Smith, Xue Lab, Funding provided by National Cancer Institute

    Investigating YAP1 control of differentiation and metabolism in Hepatoblastoma

    Hepatoblastoma (HB), the most common pediatric primary liver tumor, affects children from infancy to five years of age. Surgical resection with adjuvant chemotherapy has saved many young lives. However, the five-year survival rate remains at 70%, and is worse for children with unresectable tumors. Meeting the clinical need for HB-targeted therapies requires a better understanding of how HB tumors are formed and maintained. The transcriptional co-regulator YAP1 is hyper-activated in 79% of HB cases, and recent studies suggest that YAP1 and the Wnt/β-catenin pathway act together to initiate HB tumors. But is YAP1 required to maintain HB tumorigenesis? Preliminary studies using a conditional mouse model of HB—driven by doxycycline-inducible hyperactive YAP1S127A and constitutively active β-catenin—suggest that YAP1 is essential for tumor maintenance. In the presence of doxycycline, YAP1 is expressed, and mice develop HB tumors; withdrawing doxycycline turns off YAP1, resulting in >90% tumor regression within 10 weeks. Transcriptional analyses revealed that hepatocyte differentiation factors and liver metabolic genes were induced in regressing tumors.

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    Integrin Function in Breast Cancer Initiation

    Breast cancer is the most common cancer diagnosis in women and is also one of the leading causes of cancer-related mortality in women who suffer from this condition. Tumors that originate in the breast consist of heterogeneous populations of cells. Breast cancer stem cells (BSCSs) are a subtype of tumor cells that have properties similar to normal, tissue stem cells such as the ability to divide slowly and give rise to differentiated cellular lineages. Furthermore, BCSCs have been implicated in tumor initiation, therapy resistance and metastasis to distant organs. Given this information, a greater understanding of the biological processes that sustain BCSCs will lead to the development of novel agents directed against this chemo- and radio-resistant population of tumor cells. The proposed work will explore the role of the α6 integrin splicing variants, α6Aβ1 and α6Bβ1, in the genesis of BCSCs, specifically addressing the mechanism of activation of the TAZ transcriptional coactivator. Integrins are a family of cell surface receptors that function in signal transduction and adhesion to the extracellular matrix. The α6Aβ1 integrin variant is expressed in differentiated, epithelial breast cancer cells and inhibits the acquisition of stem cell properties Conversely, the α6Bβ1 integrin variant is expressed in BCSCs and promotes tumor initiation by activating the Hippo signaling pathway transducer TAZ. TAZ has previously been shown to be important in the functioning of BCSCs, but the mechanism is unknown. Therefore, elucidating the relationship between the α6 integrin splicing variants and TAZ activation will provide insight into mechanisms of breast cancer progression. This proposal will use a cellular and molecular biology approach to establish the mechanism by which TAZ is suppressed in the α6Aβ1 expressing non-stem breast cancer cell population (Aim 1). Biochemical studies will also be undertaken with the purpose of connecting mechanisms of TAZ inactivation with classical Hippo pathway signaling in the non-stem breast cancer cell population (Aim 2). In summary, the studies included in this proposal will increase the understanding of integrin regulation of BCSCs. Our results can provide rationale in designing future targeted therapies for treatment resistant subtypes of breast cancer.

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    Defining the Rules for Designing Fully Chemically Modified siRNAs to Treat Genetically Linked Central Nervous System Disorders

    Small interfering RNA (siRNA) therapeutics are a promising class of drugs for the treatment of genetic disorders. Chemical modification of siRNA is necessary for delivery to the central nervous system, but may hinder the efficacy of some siRNAs. This project will define the relationships between siRNA sequence, chemical modification patterns, and efficacy to streamline the development of clinically-relevant siRNAs capable of treating genetically-defined neurological disorders.

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    Smoking Cessation in Persons with Mental Health Conditions: Exploring the Role of Family and Friends

    Ruth L. Kirschstein National Research Service Award (NRSA) Individual Predoctoral Fellowship to Promote Diversity in Health-Related Research (Parent F31-Diversity). Smokers with mental health conditions (MHC) have increased risk of dying from lung and cardiovascular disease. The smoking rate among people with MHC greatly exceeds the rate in the general adult population. Although, these smokers are interested in quitting, their quit rates are much lower than the general population. Factors that act as quitting barriers for these smokers, include pro-smoking social norms and attitudes/behaviors of social network members, underuse of pharmacotherapies and behavioral strategies, and inconsistent treatment of tobacco dependency of mental health providers. Thus, leading researchers have called for innovative approaches to address smoking disparities in people with MHC. Family/peer-based behavioral interventions can be an innovative and effective approach to target smokers with MHC for several reasons. Family/peers influence smoking behaviors, and their importance in health behavior change is well-established. Families/peers are often a principal resource for persons with MHC in seeking and accessing health services. A small but consistent body of literature suggests that family/peers may influence the cessation behavior of smokers with MHC. Family /peers could augment other cessation interventions such as adoption of pharmacotherapies. However, interventions that attempt to harness family/peer support for long-term smoking cessation have underperformed. Knowledge gaps exist in our understanding of the mechanisms through which family/peers affect smoking behaviors, as well as how to involve family/peers in smokers’ cessation efforts. Guided by the social influence domain, as outlined in the Theoretical Domains Framework, my dissertation will address these knowlegde gaps. My specific aims are to: 1) prospectively examine the effect of family/peer influences on smoking cessation among smokers with MHC using data from the Population Assessment of Tobacco and Health (PATH study), a nationally representative survey of US non-institutionalized individuals in which participants are interviewed annually, 2) evaluate relationships between smokers’ characteristics, family/peer influences, and smoking cessation among smokers with MHC using Structural Equation Models, and 3) qualitatively explore social and clinical barriers and facilitators to smoking cessation and inclusion of family/peer support among smokers with MHC and mental health care providers. This work in combination with the proposed training will facilitate my development into an independent research scientist committed to conducting research focused on tobacco prevention and control. I will be supported by an outstanding mentoring team with expertise in all the relevant areas: smoking cessation, mental health, implementation science, and biostatistics. My research directly addresses NHLBI’s objective of better understanding the causes of population health differences and identifying strategies to effectively address these differences.

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    Microglia-derived neuroactive cytokines governing neural circuit excitatory-inhibitory balance

    Elaborate mechanisms exist to establish and maintain the appropriate balance of excitation and inhibition (E/I balance) in the brain. Defects in E/I balance are hypothesized to underlie many core clinical symptoms seen in ASD including repetitive behaviors and seizures. Concomitant with E/I imbalance are increased markers of inflammation in the periphery and brain. Central to this inflammation are microglia, a resident macrophage of the central nervous system. Whether microglial inflammatory state drives E/I imbalance in neuropsychiatric disease remains a critical open question. In this proposal, I will leverage my primary mentor’s (Schafer) expertise in using mouse models to study microglia function at synapses with my co- mentor’s (Frazier) expertise as a physician scientist studying neuroinflammatory processes in ASD patients to explore whether microglia-derived cytokine signaling modulates E/I balance. I will use a mouse model with altered inflammatory cytokine signaling to assess how microglial inflammatory cytokine production modulates neuronal excitability (aim1). Next, I will use human ASD functional imaging data and data from patient serum to identify pro-inflammatory cytokines that are dysregulated in ASD patients and assess how these ASD-specific cytokines affect E/I balance in our mouse models (aim2). To start, I already have one candidate TNF􏰀-alpha. The results from these experiments will help to identify novel targets for treating ASD with inflammatory modulation.

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    A chemical biology approach to studying the role of SARM1 in a novel neuronal degradative pathway

    The novel NAD glycohydrolase, SARM1, is an active executioner in progressive axonal and neuronal degeneration1. This type of degeneration, termed Wallerian degeneration, defines a number of diseases, including neuropathies, traumatic brain injury and neurodegenerative diseases, yet no therapies exist. In fact, prior to the discovery of SARM1’s role in triggering Wallerian degeneration, the process was believed to occur passively. SARM1’s causal role in Wallerian degeneration demonstrates that it is an attractive therapeutic target that could prevent disease progression. However, the design of therapeutics targeting SARM1 is limited by the dearth of knowledge surrounding its inherent NADase activity. In order to evaluate SARM1’s therapeutic efficacy and design potential SARM1 inhibitors, the proposed research will study its structure, enzymatic mechanism and cellular activity. Solving the structure by leveraging the benefits of crystallography and cryoEM, determining the enzymatic mechanism via a series of assays and analyzing the in vivo activity with activity-based probes will fill in important gaps. Revealing these properties would enable the design of SARM1 inhibitors that could ultimately treat Wallerian-type diseases. Moreover, demystifying the role SARM1 plays in neurodegeneration would also allow for a better understanding of these disease types, the enzymatic capabilities of toll/interleukin receptor (TIR) domains and the involvement of NADases in numerous disease states.

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    Amelioration of Beta-hemoglobinopathies by efficient precise deletion of the +58 BCL11A enhancer using orthogonal Cas9-Cas9 chimeras

    Project Summary β-Thalassemia and sickle cell disease (SCD) are severe inherited anemias that result in defective β-globin expression. A common feature shared between both disorders is that the diseases can be mitigated by the production of fetal hemoglobin (HbF). Current treatments for both disorders are mainly supportive and focus on alleviating disease complications. However, management of these β-hemoglobinopathies is expensive, restrictive, lifelong, and associated with significant side effects. Currently, allogeneic hematopoietic stem cell therapy is the only curative treatment for β-hemoglobinopathies. However, finding human leukocyte antigen (HLA)-matched donors is highly challenging. Gene editing approaches that alter the expression of HbF should improve the health and quality of life of individuals with β-hemoglobinopathies. The goal of this project is to develop efficient, accurate, and safe CRISPR gene editing approaches as a universal treatment for β-hemoglobinopathies. Typically, a nuclease (SpyCas9) and guide RNA (gRNA) target a specific region (+58 enhancer of BCL11A) and creates a double-stranded break. Small insertions or deletions (InDels) are created when imprecise repair of the DNA break occurs, resulting in inactivation of the target gene or functional element. Current therapeutic editing approaches for β-hemoglobinopathies at the BCL11A locus focus on the mutagenesis of a single GATA1 recognition sequence within the +58 enhancer in CD34+ hematopoietic stem and progenitor cells (HSPCs), limiting the scope of their potential impact. This project will harness our recently developed Cas9-Cas9 fusion chimera, which is able to produce segmental deletions with defined junctions (precise deletions) at a higher efficiency than standard Cas9 nucleases. Furthermore, Cas9-Cas9 fusions are able to effectively target suboptimal PAM sequences, and thus these nucleases have a broader targeting range than standard SpyCas9. These properties make Cas9- Cas9 fusions ideal for the deletion of therapeutically relevant regulatory elements, such as the +58 enhancer of BCL11A. Our preliminary studies show that ribonucleoprotein (RNP) complexes of these Cas9-Cas9 fusions targeting this locus are functional in CD34+ HSPCs and result in robust induction of HbF. In Aim 1, I will define deletion products within the +58 enhancer that facilitate the maximum induction of HbF in erythroid model systems and optimize the Cas9-Cas9 fusions to efficiently and specifically produce these precise deletions with minimal collateral damage to the genome. In Aim 2, optimized Cas9-Cas9 fusion protein-sgRNA complexes will be delivered into CD34+ HSPCs and HbF induction levels will be quantified in erythroid progeny. Treated CD34+ cells will be engrafted into immunodeficient mice to measure engraftment potential and persistence of editing in long-term hematopoietic stem cells (LT-HSCs). The genome-editing tools generated from the proposed work will provide a path to improved autologous HSC therapies that will impact the lives of individuals affected by β-hemoglobinopathies.

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    Gq Receptor Regulation of Striatal Dopamine Transporters

    Dopamine (DA) neurotransmission is vital for behaviors such as movement and reward, as well as, cognitive functions including mood, learning and memory. Several neuropsychiatric disorders are linked to alterations in DA signaling including Attention Deficit Hyperactivity Disorder (ADHD), schizophrenia, Parkinson's disease, and addiction. The DA transporter (DAT) is imperative for temporal and spatial control of DA signaling. DAT is located at the presynaptic terminal of DAergic neurons and facilitates the termination of DAergic transmission by rapidly clearing released DA. DAT is the primary target of addictive and therapeutic psychostimulants, which compete for DA binding and block uptake through the transporter, preventing DA clearance and leading to the hyper-locomotive and rewarding behaviors associated with drug use. Given that DAergic signaling is highly sensitive to DAT function, understanding the molecular mechanisms that control DAT function and availability is a critical missing piece of the puzzle in understanding DAergic neurotransmission and dysfunction in DA- related disorders. Over two decades of research support that DAT surface expression is acutely regulated by endocytic trafficking. Protein kinase C (PKC) activation with phorbol esters stimulates DAT internalization and thereby decreases DAT surface expression and function. Although considerable progress has been made to define the molecular mechanisms governing basal and PKC-regulated DAT trafficking, there are significant gaps in our understanding of this process in bona fide DAergic terminals. It is not clear how DAT is regulated in response to the endogenous presynaptic receptors that are activated upstream of PKC, such as Gq-coupled receptors, and how the complex signal events stemming from Gq receptor activation integrate to acutely control DAT surface expression. It is additionally unknown whether regulated DAT trafficking is region-specific, or whether altered DAT surface expression impacts DAergic signaling in the striatum. The proposed studies will leverage chemogenetic receptors to test how Gq activation impacts DAT surface levels in a cell- autonomous manner, in both dorsal and ventral striatum. We will capitalize on a novel conditional, inducible, in vivo gene silencing approach to determine the endocytic mechanisms that are required for Gq-mediated DAT trafficking, by both chemogenetic and endogenous presynaptic receptors. We will further employ ex vivo fast- scan cyclic voltammetry to investigate how presynaptic DAT trafficking impacts DA signaling. I anticipate that at the completion of these studies, we will have gained a more in-depth understanding of the complex mechanisms underlying DAT regulation at presynaptic DAergic terminals, and its potential influence on synaptic DA homeostasis.

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    Fluorescent visualization of complement-dependent pannexin activity in microglia

    The goal of this project is fluorescently visualize ATP release and extracellular accumulation at the surface of stimulated microglia. The development of this innovative technology has the potential to enable spatiotemporal imaging of microglial extracellular signaling. For this project, I am exploiting the presence of the cell's glycocalyx to attach ATP-sensitive biosensors at the sites of ATP accumulation. There are two aims to this project: 1) to synthesize a novel, polyhistidine binding moiety that covalently modifies the glycocalyces of living cells and binds recombinant biosensors to measure ion and metabolite efflux and accumulation; 2) to visualize and measure ATP release from pannexin channels in C5a stimulated microglia. The completion of these aims will yield a transformative set of chemical-biological tools and methodologies to investigate the physiology and pathophysiology of pannexin-dependent activity in glia, and potentially in living animals.

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    Modeling Down Syndrome Neural Phenotypes with Chromosomal Silencing

    Down syndrome (DS), or trisomy 21, is the leading genetic cause of intellectual disability in children, with approximately 1 in 700 live births carrying an extra copy of chromosome 21. Compared to less common single gene disorders, DS pathogenesis is still poorly understood. Treatment for DS would require either identification of molecular pathways to target with conventional therapies or, potentially, chromosomal therapy to silence the many possibly disruptive genes on the trisomic chromosome. One window of therapeutic intervention lies in the Alzheimer’s disease pathology that almost all DS patients suffer from in middle age. Recently, the extra chromosome has been silenced in an inducible manner by targeted insertion of a transgene for the XIST gene into human induced pluripotent stem cells (iPSC). XIST normally silences one X chromosome in females, providing a natural mechanism of dosage compensation. Chromosomal silencing in DS cells provides a powerful isogenic and isoepigenetic model for studying DS pathology and marks the first step towards the goal of chromosomal therapy for DS patients. The proposed work will investigate the effect of silencing the extra chromosome on DS iPSC-derived neuronal cells, investigating both DS and Alzheimer- specific phenotypes. Aim 1: In order to investigate the effect that chromosomal silencing has on DS neural phenotypes in vitro, iPSCs will be differentiated into neurons using conventional two-dimensional neuronal culturing techniques and three-dimensional organoids. Cerebral organoids are a recently-developed tool that have been shown to be a useful model for human brain development, and have been used to study disorders of brain development. Neurons derived from iPSCs with two and three functional copies of Chr.21 will be compared for phenotypes that DS neural cells are thought to possess. These include an increased glia:neuron ratio, altered dendritic spine morphology, and altered mitochondrial morphology. Three-dimensional cultures will be used to investigate less well-explored pathologies such as alterations in cortical lamination. This aim will also address the important therapeutic question of whether post-mitotic cells can support chromosomal silencing. Aim 2: The same chromosomal silencing system will be used to investigate Alzheimer’s-associated neuronal phenotypes. These include intra and extracellular amyloid deposition as well as intracellular hyperphosphylated tau deposition. Due to its relatively late onset compared to general intellectual disability, the Alzheimer’s disease component of DS is most suitable for therapeutic intervention. Studying the effect of chromosomal silencing on Alzheimer’s phenotypes provides a strong model for Alzheimer’s pathogenesis while also bringing this novel strategy one step closer to therapeutics. This proposal seeks to utilize a novel chromosomal silencing technique to better model human neural phenotypes in DS and associated AD.

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  • Alec K. Gramann, Ceol Lab, Funding provided by National Institutes of Health

    Targeting BMP signaling to treat advanced melanoma and suppress therapeutic resistance

    Melanoma is the leading cause of skin cancer death in the United States, with the 5-year survival rate of 20% for patients with advanced disease. Despite improvements in therapy, many patients receive minimal survival benefit and often develop resistance to standard-of-care therapies. Furthermore, a population of patients exist who do not have the appropriate mutations or tumor characteristics to be eligible for new targeted and immunotherapies. In order to provide adequate treatment options for patients who develop resistance or are ineligible for current cutting-edge therapies, new therapeutic targets must be identified. Our lab has discovered a novel melanoma oncogene, growth differentiation factor 6 (GDF6), a secreted bone morphogenetic protein (BMP) ligand that promotes melanoma by regulating expression of specific neural crest factors, which has the dual effect of preventing differentiation and suppressing apoptosis9. In addition to these specific factors, we found GDF6 more broadly promotes a gene expression signature that mimics that of the embryonic neural crest. Neural crest identity has previously been identified as a key feature involved in melanoma initiation, progression, and therapeutic resistance. Our studies show knockdown of GDF6 suppresses expression of many of these neural crest genes. Taken together, these data indicate GDF6 is an optimal target for melanoma therapy. As a secreted extracellular protein, GDF6 is amenable to targeting by antibodies. We produced a panel of monoclonal antibodies to target the C-terminal binding region of GDF6 and developed multiple in vitro and in vivo assays to assess candidate antibodies with the most potent action against GDF6 and evaluate their effectiveness as potential melanoma therapeutics. I hypothesize that a subset of antibodies will effectively block GDF6 activity leading to increase differentiation and cell death of melanoma cells in vitro and in vivo. I further hypothesize that blocking GDF6 will suppress neural crest identity in melanoma cells, leading to less aggressive tumor cell characteristics and sensitizing previously resistant cells to standard-of-care therapy. I will evaluate a pre- screened panel of 42 monoclonal antibodies for in vitro and in vivo activity against GDF6 in melanoma cells to identify top candidates with the most potent activity, in parallel with characterizing pharmacokinetic and dynamic properties of the antibodies in vivo. I will further characterize the effects of GDF6 inhibition by these antibodies on neural crest expression profiles and key features of advanced melanoma such as therapeutic resistance, invasiveness, and anchorage independent growth. Additionally, I will analyze potential combinatorial therapies in vitro and in vivo to assess changes in pathway activity for known therapeutic resistance mechanisms. Results of this study will identify lead candidate anti-GDF6 antibodies for first-in-human (FIH) studies and provide appropriate pre-clinical safety data for submission of an FIH application. Furthermore, these data will provide broad insight into the tumorigenic features that are connected to neural crest identity and the result of reversing neural crest characteristics in established melanomas.

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    C. elegans as a model for host-microbe-drug interactions

    The bacteria that live in our body (microbiota) help us metabolize different nutrients and chemicals from our diet, including the medications we take. Thus, these bacteria can influence our response to treatments, like chemotherapy, by converting drugs into more or less toxic forms. Understanding the mechanisms by which bacteria influence our response to drugs is critical to design better treatments that maximize therapeutic effects and minimize adverse effects. The nematode C. elegans and its bacterial diet provide a suitable model to explore host-microbe drug interactions because both host and microbe are amenable to high throughput drug screening and genetic screening. I propose to use the nematode C. elegans as a model to study host-microbe-drug interactions in cancer chemotherapy drugs. In Aim 1, I will test ~ 200 cancer chemotherapy drugs for developmental or fecundity phenotypes in C. elegans animals fed two different bacteria. Additionally, I will test the role of active bacterial metabolism in the observed host-microbe-drug interactions. Then, I will use genetic screening and metabolomics, in the host and in the bacteria, to characterize the mechanisms responsible for the observed drug response. In summary, this project will generate a set of host and bacterial genes that contribute to the response to cancer chemotherapeutic agents.

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  • Alec K. Gramann, Ceol Lab, Funding provided by Melanoma Research Foundation

    Examining BMP signaling as a regulator of neural crest identity during melanoma initiation and progression

    In many types of cancer, less differentiated tumors are more strongly associated with a poor patient prognosis. These tumors tend to be more aggressive: they have higher proliferation rates, a greater propensity for invasion and metastasis, and increased resistance to therapy compared to more differentiated tumors. Less differentiated tumors, by their nature, share characteristics with their embryonic cells of origin. In melanoma, these less differentiated tumors are associated with a neural crest identity that is acquired during early stages of tumor initiation and is present through tumor progression. Previous studies have shown that acquisition of a neural crest identity is a necessary step during initiation of early melanoma lesions and supports fundamental properties of aggressive tumors such as invasion and metastasis. However, the mechanisms of generating a neural crest identity are unknown. Recently, our lab has identified growth differentiation factor 6 (GDF6) as a novel melanoma oncogene. GDF6, a bone morphogenetic protein (BMP) ligand, is recurrently amplified in both human and zebrafish melanomas, and expressed in tumors but not normal melanocytes. We have shown GDF6 acts to prevent differentiation and suppress apoptosis in established melanomas, both in vitro and in vivo. Additionally, we have found that GDF6 regulates expression of multiple neural crest and melanocyte factors previously implicated in melanoma. Upon knockdown of GDF6, we observed downregulation of select neural crest factors coupled with upregulation of melanocyte differentiation factors, leading to melanoma cell differentiation and ultimately cell death. These results suggest that GDF6 plays a role in regulating oncogenic neural crest identity. Here, we look to identify the role of GDF6 and BMP signaling in establishing a neural crest identity during melanoma initiation and explore oncogenic characteristics imparted by GDF6 during melanoma progression. I hypothesize that GDF6-depenent BMP signaling acts to initiate a neural crest identity in melanomas to promote tumor initiation and aggressive tumor characteristics. I further hypothesize that loss of BMP activity leads to differentiation (and in tumors death of differentiating cells), making GDF6 an attractive target for differentiation therapy in melanoma.

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