THE ROLE OF DENDRITIC BDNF TRANSCRIPTS ON ALTERED INHIBITORY CIRCUITRY IN AGING AND DEPRESSION

Low neurotrophic support and a GABA deficit have been suggested as mechanisms underlying structural and functional abnormalities of the brain in depressed subjects. A parallel downregulation of brain-derived neurotrophic factor (BDNF) and GABA function-related genes including somatostatin (SST), a marker of GABA interneurons targeting the dendritic compartment of pyramidal cells, has been consistently observed during normal aging and in major depression. Here, translational research combining cell culture, animal and human postmortem studies has been conducted in search of a possible link between BDNF and GABA interneurons. I found that dendritic-targeting interneuron markers displayed a higher BDNF dependency compared to other GABAergic genes in BDNF-knockdown mice. To explore the nature and extent of the biological components linking BDNF and SST, we analyzed the top 200 genes positively correlated with BDNF expression in the human brain and found that age-related BDNF reduction may induce synaptic alterations which are likely responsible for age-associated cognitive decline. Interestingly, SST and the α5 subunit of GABAA receptor (GABRA5), a subunit considered to be enriched in the post-synaptic compartment of SST (+) interneurons, are included in the top 200 genes, with GABRA5 displaying the highest correlation with BDNF expression among ~ 300,000 probes examined with the arrays. These data suggest that the synaptic target of SST (+) interneurons, the distal dendrite, may act as a bridge between BDNF and SST. Therefore, we hypothesized that MDD is associated with reduced dendritic BDNF which results in low BDNF supply to SST (+) interneurons. Indeed, 3’ untranslated region (UTR)-containing-BDNF mRNA, which is known to migrate to the distal dendrites of pyramidal cells, showed downregulation in the dorsolateral prefrontal cortex (dlPFC) of depressed subjects and medial prefrontal cortex of stressed mice. Furthermore, such changes were closely linked to changes in dendritic-targeting interneuron markers. Knockdown of BDNF long 3’ UTR was sufficient to induce dendritic shrinkage, depressive-/anxiety-like behavior, and SST downregulation. Finally, pharmacological potentiation of TrkB prevented the development of depression-like behaviors following chronic stress in rodents. Together, I provide a mechanistic link between the GABA and neurotrophic hypotheses of major depression, which data indicate may be through dysfunctional dendritic-targeting interneuron populations

Characterization of Vacuolating cytotoxin A binding to sphingomyelin in Helicobacter pylori pathogenesis

The main objective of my research project is to characterize vacuolating cytotoxin A (VacA) from Helicobacter pylori binding to an important host cell membrane lipid, sphingomyelin (SM). Previously, our laboratory showed that plasma membrane SM is important for the toxin biological activity, cell surface binding, and toxin-receptor direct interactions suggesting that SM is a receptor for VacA. Moreover, recent findings from our laboratory showed that R552, W603, and R647 of VacA are important that when changed to alanine, resulting in decreased SM-dependent VacA activity in gastric epithelial cells. However, the molecular basis of SM-VacA interactions remains unknown. My research focuses molecular on the detailed molecular mechanism by which these three residues of VacA interact with SM in SM-dependent toxin cellular activities. I will evaluate the hypothesis that R552, W603, and R647 on VacA facilitate its SM binding by interacting with the phosphorylcholine head group of SM. To test this hypothesis, I will conduct site-directed mutagenesis analysis to evaluate the specific properties of the three residues (R552/W603/R647) that are important for SM-dependent toxin cellular activities. I will evaluate the prediction that VacA interacts with SM through pi-cation interactions between the aromatic ring of tryptophan and choline moiety of head group of SM and ionic interactions between positively charged arginine residues and negatively charged phosphate moiety of SM. Testing this prediction, I am evaluating the toxin cellular activity of charge conservative and non-conservative single substitution mutations in the three residues. The results of this study will provide the framework for the molecular interactions behind VacA-SM interactions.Ope

Graphene Sheets Stabilized on Genetically Engineered M13 Viral Templates as Conducting Frameworks for Hybrid Energy-Storage Materials

Utilization of the material-specific peptide–substrate interactions of M13 virus broadens colloidal stability window of graphene. The homogeneous distribution of graphene is maintained in weak acids and increased ionic strengths by complexing with virus. This graphene/virus conducting template is utilized in the synthesis of energy-storage materials to increase the conductivity of the composite electrode. Successful formation of the hybrid biological template is demonstrated by the mineralization of bismuth oxyfluoride as a cathode material for lithium-ion batteries, with increased loading and improved electronic conductivity.National Institute for International Education (Korea) (Korean Government Scholarship Program)United States. Army Research Office (Institute for Collaborative Biotechnologies (ICB))National Institutes of Health (U.S.) (Materials Research Science and Engineering Centers program

Age-Related Gene Expression in the Frontal Cortex Suggests Synaptic Function Changes in Specific Inhibitory Neuron Subtypes

Genome-wide expression profiling of the human brain has revealed genes that are differentially expressed across the lifespan. Characterizing these genes adds to our understanding of both normal functions and pathological conditions. Additionally, the specific cell-types that contribute to the motor, sensory and cognitive declines during aging are unclear. Here we test if age-related genes show higher expression in specific neural cell types. Our study leverages data from two sources of murine single-cell expression data and two sources of age-associations from large gene expression studies of postmortem human brain. We used nonparametric gene set analysis to test for age-related enrichment of genes associated with specific cell-types; we also restricted our analyses to specific gene ontology groups. Our analyses focused on a primary pair of single-cell expression data from the mouse visual cortex and age-related human post-mortem gene expression information from the orbitofrontal cortex. Additional pairings that used data from the hippocampus, prefrontal cortex, somatosensory cortex and blood were used to validate and test specificity of our findings. We found robust age-related up-regulation of genes that are highly expressed in oligodendrocytes and astrocytes, while genes highly expressed in layer 2/3 glutamatergic neurons were down-regulated across age. Genes not specific to any neural cell type were also down-regulated, possibly due to the bulk tissue source of the age-related genes. A gene ontology-driven dissection of the cell-type enriched genes highlighted the strong down-regulation of genes involved in synaptic transmission and cell-cell signaling in the Somatostatin (Sst) neuron subtype that expresses the cyclin dependent kinase 6 (Cdk6) and in the vasoactive intestinal peptide (Vip) neuron subtype expressing myosin binding protein C, slow type (Mybpc1). These findings provide new insights into cell specific susceptibility to normal aging, and suggest age-related synaptic changes in specific inhibitory neuron subtypes

Identification of a novel gene regulating amygdala-mediated fear extinction.

Recent years have seen advances in our understanding of the neural circuits associated with trauma-related disorders, and the development of relevant assays for these behaviors in rodents. Although inherited factors are known to influence individual differences in risk for these disorders, it has been difficult to identify specific genes that moderate circuit functions to affect trauma-related behaviors. Here, we exploited robust inbred mouse strain differences in Pavlovian fear extinction to uncover quantitative trait loci (QTL) associated with this trait. We found these strain differences to be resistant to developmental cross-fostering and associated with anatomical variation in basolateral amygdala (BLA) perineuronal nets, which are developmentally implicated in extinction. Next, by profiling extinction-driven BLA expression of QTL-linked genes, we nominated Ppid (peptidylprolyl isomerase D, a member of the tetratricopeptide repeat (TPR) protein family) as an extinction-related candidate gene. We then showed that Ppid was enriched in excitatory and inhibitory BLA neuronal populations, but at lower levels in the extinction-impaired mouse strain. Using a virus-based approach to directly regulate Ppid function, we demonstrated that downregulating BLA-Ppid impaired extinction, while upregulating BLA-Ppid facilitated extinction and altered in vivo neuronal extinction encoding. Next, we showed that Ppid colocalized with the glucocorticoid receptor (GR) in BLA neurons and found that the extinction-facilitating effects of Ppid upregulation were blocked by a GR antagonist. Collectively, our results identify Ppid as a novel gene involved in regulating extinction via functional actions in the BLA, with possible implications for understanding genetic and pathophysiological mechanisms underlying risk for trauma-related disorders

Sex-Dependent Anti-Stress Effect of an alpha 5 Subunit Containing GABA(A) Receptor Positive Allosteric Modulator

Rationale: Current first-line treatments for stress related disorders such as major depressive disorder (MDD) act on monoaminergic systems and take weeks to achieve a therapeutic effect with poor response and low remission rates. Recent research has implicated the GABAergic system in the pathophysiology of depression, including deficits in interneurons targeting the dendritic compartment of cortical pyramidal cells. Objectives: The present study evaluates whether SH-053-2'F-R-CH3 (denoted "alpha 5-PAM"), a positive allosteric modulator selective for (alpha 5-subunit containing GABA(A) receptors found predominantly on cortical pyramidal cell dendrites, has anti stress effects. Methods: Female and male C57BL6/J mice were exposed to unpredictable chronic mild stress (UCMS) and treated with alpha 5-PAM acutely (30 min prior to assessing behavior) or chronically before being assessed behaviorally. Results: Acute and chronic alpha 5-PAM treatments produce a pattern of decreased stress induced behaviors (denoted as "behavioral emotionality") across various tests in female, but not in male mice. Behavioral Z-scores calculated across a panel of tests designed to best model the range and heterogeneity of human symptomatology confirmed that acute and chronic alpha 5-PAM treatments consistently produce significant decreases in behavioral emotionality in several independent cohorts of females. The behavioral responses to alpha 5-PAM could not be completely accounted for by differences in drug brain disposition between female and male mice. In mice exposed to UCMS, expression of the Gabra5 gene was increased in the frontal cortex after acute treatment and in the hippocampus after chronic treatment with alpha 5-PAM in females only, and these expression changes correlated with behavioral emotionality. Conclusion: We showed that acute and chronic positive modulation of alpha 5 subunit containing GABA(A) receptors elicit anti-stress effects in a sex-dependent manner, suggesting novel therapeutic modalities

EVIDENCE INFORMED STRATEGIES TO ENHANCE THE USE AND EXPERIENCE OF HEALTHCARE BY HOMELESS INDIVIDUALS

The purpose of this thesis was to provide evidence informed strategies through online modules and in-class testimonial for healthcare providers treating the homeless individuals. There has been an increase of 0.7% of homeless population in the last year in America (“Homelessness in America: Overview of Data and Causes”, 2018). Additionally, the individuals facing homelessness have greater risks for morbidities and mortalities due to the lack of safe environment. Many individuals find it difficult to obtain medical attention from lack of intimate care in the hospital and lack of resources, such as transportation and insurance. The health care providers, too, feel that they do not know enough about homelessness to educate the individuals on further treatment. Implementing online training programs for nurses working in the emergency department to utilize resources and referrals and to educate on background of homelessness would provide nurses with necessary evidence-based information needed to guide them in providing care to homeless individuals