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2016 Research Showcase
NB Abstracts
Abstract Title : Circular RNA in Neurodevelopment: Investigation into the Role of Rhabdomyosarcoma 2-Associated Transcript
Abstract : Advances in RNA detection technologies have revealed an abundance of circular RNAs present throughout the mammalian transcriptome. Their pervasiveness, conservation throughout evolution, enhanced stability, and specific expression indicate that these RNAs are subjected to regulation and serve a defined function. The developing brain has been revealed as a site of prominent circular RNA expression, particularly of genes implicated in neurogenesis. Rhabdomyosarcoma 2-associated transcript (RMST) is a multiexon long noncoding RNA (lncRNA) previously identified as host to the first identified trans-spliced long intergenic noncoding RNA, two microRNAs, as well as at least three other alternatively spliced isoforms. The nuclear-localized lncRNA RMST has recently been identified as necessary for neurogenesis, coregulating transcription of neurogenic genes with the transcription factor Sox2. RNA Sequencing of neural stem cells and neurons, derived from human induced pluripotent stem cells, led to our novel finding that the circular isoform of RMST is upregulated during neuronal differentiation. Here we aimed to validate the expression of circular RMST as predicted by RNA Sequencing. When compared to baseline expression during neural induction, quantitative real-time polymerase chain reaction (qPCR) revealed a significant 100-fold increase in circular RMST expression following 4 weeks of neuronal differentiation, and a significant 45-fold increase following 7 weeks of neuronal differentiation. This pattern of circular RMST expression, observed with RNA Sequencing and validated by qPCR, further supports the hypothesis that circular RNAs, such as RMST, play an important role in healthy neurodevelopment.
Abstract Title : Development of a High-Content Axon Regeneration Screening Assay
Abstract : The use of whole genome-wide transcriptional gene expression analysis has rapidly increased in the last decade. This method of acquiring data has the great potential to generate whole gene regulation and interaction profiles of injured and regenerating adult sensory neurons within an injury model in vivo. One of the major benefits but also challenges of big data approaches is the identification of hundreds to thousands of potential candidates, that ultimately have to be subjected to further screening methods. We made use of cost efficient lipid based transfection methods and commercially available low volume siRNA libraries to develop a rapid method of screening hundreds of candidates in a high-content cost-efficient manner. We investigated two widely used lipid based transfection reagents Lipofectamine 2000 and RNAiMAX and found that both transfection reagents lead to comparable gene silencing efficiencies in adult sensory neurons with minimal negative impact on cell survival. This method is optimized for screening in 384-well optical plates utilizing pooled siRNA libraries.
Abstract Title : Neural activation changes during a computerized attention modification program for social anxiety
Abstract : Computerized attention modification programs (AMP) utilize the probe detection task to alleviate symptoms of anxiety disorders. While AMPs have been empirically proven to match the efficacy of established pharmacological and psychological interventions, little is known about the underlying neural mechanisms. Previous studies have demonstrated attenuated activation in the amygdala, insula, anterior cingulate cortex and increased activation in the prefrontal cortex while viewing emotional faces following treatment. Increased prefrontal cortex activation post-treatment was also correlated with decreased anxious reactivity to a stressor. However, research has yet to examine brain response throughout the course of AMPs. This study will utilize functional magnetic resonance imaging (fMRI) to look at neural changes during AMP training in fourteen individuals with high social anxiety symptoms while they implicitly learn to orient their attention away from threatening stimuli. It is hypothesized that AMPs mediate anxious responses via top down brain processes in the previously implicated regions.
Abstract Title : Experience-dependent changes in NPAS4 driven BDNF subcellular localization
Abstract : Brain Derived Neurotrophic Factor (BDNF) is a member of the neurotrophin family of growth factors whose transcription is modulated by neuronal activity. BDNF regulates synaptic plasticity, synaptogenesis, memory formation, long-term potentiation and the differentiation and survival of neurons. BDNF is activity-dependent, creating increased expression in enriched environments. BDNF is a target gene of the inducible transcription factor NPAS4, which regulates inhibitory synapse number and function (Lin Y et al., 2008; Bloodgood et al., 2013). NPAS4 has been shown to regulate the homeostatic balance between synaptic excitation and inhibition (Lin et al., 2008) which in turn underlies neuronal plasticity. Specifically, NPAS4 expression results in an increase in somatic inhibition and a corresponding decrease in dendritic inhibition, through expression of activity-dependent genes (Bloodgood et al., 2013). The NPAS4 target gene BDNF is a candidate for mediating NPAS4-driven changes in somatic, but not dendritic inhibition (Lin Y et al., 2008). Through qPCR, NPAS4 has been shown to bind to three sites within the BDNF gene at P1 (promoter 1), I3 (intron 3) and P4 (promoter 4) (Bloodgood et al., 2013). Varying isoforms of BDNF localize differentially, possibly suggesting functional along with structural differences in these BDNF species that have yet to be fully described. Transcription of BDNF is differentially regulated by changing neuronal environments, and results in differential expression of isoforms, or different mRNA species containing differential exons of BDNF. Furthermore, it is unknown which BDNF isoforms are regulated by NPAS4, resulting in an activity-induced increase in somatic inhibitory synapse number. Here, we utilized the single-molecule in situ hybridization assay RNAscope to determine the localization of the family of BDNF isoforms in mouse hippocampal slices, and quantified the level of expression of the nine isoforms along the somato-dendritic axis of CA1 pyramidal neurons. We then utilized constitutive and conditional NPAS4 knockout mice to investigate which BDNF isoforms are regulated by NPAS4 expression.
Abstract Title : Brain-derived neurotrophic factor (BDNF)-elevating therapy for Huntington's Disease
Abstract : Deficiencies in brain-derived-neurotrophic-factor (BDNF) have been implicated in the pathogenesis of Huntington's disease (HD). The Thomas lab previously showed that Glatiramer acetate (GA; CopaxoneŽ), an FDA- approved drug used for the treatment of multiple sclerosis, could increase BDNF levels in cultured striatal cells. In this study we tested whether GA could improve disease symptoms in two different HD mouse models (CAG140 knock-in mice and N171-82Q transgenic mice), and whether GA could increase expression levels of BDNF in the brains of these mice. We treated HD mice with GA (25 mg/kg, s.c., 3 times per week; or 50 mg/kg 5 times per week) for up to 1 year, and found that GA caused significant improvement in motor symptoms in HD mice. These behaviors included the rotarod test, climbing test, and several measures of open field activity. GA treatment resulted in increased expression of BDNF transcripts I and IV in the cortex of CAG140KI mice, as measured by quantitative PCR analysis, normalized by the Hypoxanthine guanine phosphoribosyl transferase gene. Using an enzyme-linked immunosorbent assay (ELISA) for BDNF, we measured protein levels in different brain regions. We found small changes in BDNF protein expression induced by GA treatment. These findings suggest that glatiramer acetate may represent a useful therapeutic approach for HD. The excellent safety and tolerability record of this compound makes it an ideal candidate for drug repurposing efforts. ADDITIONAL PRESENTER: Jwan Nadhem
Abstract Title : Blockage in autophagic induction as a mechanism for ALS4 disease pathogenesis
Abstract : Autosomal dominant, gain-of-function mutations in the senataxin (SETX) gene cause a juvenile onset form of amyotrophic lateral sclerosis, known as ALS4. To determine the mechanistic basis of ALS4 motor neuron degeneration, we derived two different mouse models carrying human ALS4 mutations: (1) transgenic lines expressing the R2136H mutation in murine prion protein promoter expression constructs (PrP-SETX-wt & PrP-SETX-R2136H), and (2) a knock-in line containing the L389S substitution mutation at the mouse senataxin locus (SETX-L389S-KI). Characterization of these mice was performed using composite phenotype scoring, and by evaluating motor function through rotarod testing and stride length measurements. This analysis revealed that both mutant mouse lines develop a slowly progressive motor phenotype, with impaired rotarod performance, presence of hind limb clasping, and ledge test abnormalities. Autophagy is a cellular self-degradation pathway that is responsible for the turnover of misfolded proteins and damaged organelles, and has been implicated in a large number of neurodegenerative disorders, including ALS. To assess autophagy function in ALS4, we performed immunoblot analysis of p62 and detected an increase in p62 aggregation in primary cerebellar granule neurons from SETX L389S knock-in mice. In normal growth media and media treated with bafilomycin (a lysosomal inhibitor that blocks the final step of the autophagy pathway), cerebellar granule neurons from both SETX L389S knock-in mice and PrP-SETX-R2136H transgenic mice exhibit a reduction of LC3-II, a marker of autophagy pathway induction. Moreover, using a mCherry-GFP-LC3 lentivirus, we documented a blockage in autophagic induction and reduced autophagosomes in the SETX L389S knock-in mice. These findings suggest that autophagy pathway function may be compromised in ALS4.
Abstract Title : The Role of the Auditory Cortex in Associative Fear Learning
Abstract : Auditory fear conditioning is a classic example of associative learning. In mice, pairing a tone (conditioned stimulus, CS) with a mild tail shock (unconditioned stimulus, US) leads to a long-lasting fear response to the CS alone. Associative fear conditioning is dependent on the amygdala, a temporal lobe structure responsible for emotional learning and memory. However, the sensory circuits underlying auditory fear conditioning are unclear. For example, auditory information is transmitted to the amygdala via two pathways; while the subcortical auditory thalamus provides a direct connection, the amygdala also receives higher order input via the auditory cortex. Here, we aim to determine the role of the auditory cortex in auditory fear learning. Mice were conditioned to two tones at different frequencies, one paired with a tail shock (CS+), and the other without (CS-). After training the mice demonstrated a fear response to the CS+, but not the CS-. To determine if the cortex plays a role in discriminative fear learning, we took advantage of optogenetic tools to acutely silence auditory cortex during retrieval of the fear memory. Cortical silencing impaired discrimination of the CS+ and CS- tones, indicating a role for the auditory cortex in memory retrieval. We next wish to examine the activity of the cortico-amygdala projecting cells during memory retrieval. To address this, we are using in vivo 2-photon imaging and selective expression of the optical activity indicator GCaMP6s. To selectively label amygdala-projecting neurons in auditory cortex we inject a retrograde cre virus, canine adenovirus 2 (CAV 2), into the amygdala, which expresses cre recombinase in neurons projecting to the amygdala. By subsequently injecting a cre-dependent, GCaMP6s viral vector in auditory cortex, we can restrict expression of the activity indicator specifically to cells projecting to the amygdala. We will take advantage of this approach to chronically image sound-evoked activity of this cell population before and after learning. Learning-related changes in response properties of auditory cortex neurons would suggest that cortical plasticity could contribute to associative learning. ADDITIONAL PRESENTER: Mandy Lai
Advisor : DR. YISHI JIN
Abstract Title : Understanding roles of microtubule cytoskeleton in synapse formation and maintenance
Abstract : Microtubules (MTs) are filaments in the cell, made of polymers of α- and β-tubulins. MTs aid in the structural integrity of the cell, and act as highways for molecular transport.  MTs are also dynamic structures, and transition between intervals of polymerization and de-polymerization. In neurons, MT dynamics is essential for normal axonal growth, synapse formation, and maintenance. Regulation of MT dynamics is achieved in part by interactions between the external surface of MTs and microtubule-associated proteins (MAPs). Here, we use an α-tubulin mutant in C. elegans (tba-1(gf)) to identify MAPs essential for normal synapse formation. tba-1(gf) is a glycine-to-arginine change in the C-terminal domain of α-tubulin, likely disrupting MAP binding and normal regulation of MT dynamics. tba-1(gf) animals are uncoordinated and have fewer, irregularly formed synapses. We performed an unbiased forward genetic screen using the chemical mutagen ethyl methanesulfonate, and isolated several mutants that mitigated uncoordinated movement of tba-1(gf) animals. Following characterization of these suppressor mutants after outcrossing, we identified one mutant that suppressed both the behavioral and synaptic defects of tba-1(gf) animals. We are determining the identity of the gene affected by this suppressor mutant, using whole-genome-sequencing analyses. We are also investigating the relative levels of expression of tba-1 at various genomic loci in an attempt to understand its transcriptional regulation. Elucidating how MAPs interact with α-tubulin will further our understanding of debilitating neurodevelopmental disorders such as lissencephaly, a condition in which patients have causative mutations in TUBA1A, the human homolog of tba-1.
Abstract Title : Nicotine-mediated neuroprotection of dopamine neurons and neurotransmitter switching
Abstract : This research is aiming to investigate the potential involvement of nicotine in the neurotransmitter switching effect observed in the nigrostriatal pathway, as nicotine was found to produce neuroprotective effects. Extensive research has found out the inverse correlation between smoking and the incidence of Parkinson's disease (PD) (Ritz et al., 2007). PD is known to be caused by a massive loss of dopaminergic neurons in the substantia nigra pars compacta, leading to symptoms such as tremor, rigidity and bradykinesia (Hirsch et al., 1988; Quik et al., 2012). Subsequent studies have been performed to investigate the effect of nicotine in the substantia nigra. Evidence suggests that nicotine has neuroprotective effects when administered before and during nigrostriatal damage in rats and monkey (Huang et al., 2010). Also, it is hypothesized that there is a reserve pool of neurons in the substantia nigra. The results of retrograde tracing and anterograde electrical stimulation in the substantia nigra demonstrate that the dopamine expressing neurons in the substantia nigra pars compacta are not the only neurons projecting to the striatum. Besides the thalamus, the GABAergic neurons in the substantia nigra pars reticulata also project to the striatum (Hontanilla et al., 1996). Furthermore, a previous study on MPTP-treated macaques provides an evidence that the new striatal dopamine-expressing neurons in the substantia nigra are formed by the phenotypic shift of pre-existing non-dopaminergic cells (Tande, 2006). Our hypothesis is that nicotine can induce this phenotypic shift that triggers the neurotransmitter switching from non-dopaminergic to dopamine-expressing neurons.
Abstract Title : Using GCaMP6S to detect changes in activity of beta amyloid in cell cultures
Abstract : Alzheimer's disease (AD) affects the infrastructure of neuronal networks by leading to loss of neuronal connections and cell death. The beta-amyloid peptide is believed to be the molecular cause of AD although it is not fully understood how. We used a precursor to amyloid beta, C99, to overexpress this peptide in hippocampal dissociated cell cultures. We used GCaMP6s, a calcium indicator, to detect changes in activity between control cells and cells overexpressing A. GCaMP6S has been developed and tested to reliably detect action potentials by detecting changes in intracellular calcium concentrations. Using confocal microscopy, we quantified the change in fluorescence to see the difference in neuronal activity between cells overexpressing beta-amyloid and control cells. We predict that elevated levels of beta-amyloid, will decrease neuronal activity. GCaMP6s is able to detect the effects of increased and decreased activity of beta-amyloid in cells to control peptides in a various conditions which could provide more tools for research in AD. ADDITIONAL PRESENTER: Zachary Carrico
Abstract Title : Role of Myelin Basic Protein in the Autoimmune Basis of Neuropathic Pain
Abstract : Neuropathic pain (NP) from peripheral nerve injury is a debilitating condition currently without effective treatments. Following nerve injury, Myelin Basic Protein (MBP), an integral component of myelin, is proteolyzed into smaller fragments. Several of these degraded (d)MBP fragments induce NP. Understanding the pathways responsible for generation and activity of dMBP in NP can translate to the development of effective novel therapeutics. In this study, we hypothesized that dMBP is transported axonally from the site of peripheral nerve injury towards the central nervous system. A chronic constriction injury to sciatic nerve was utilized to induce NP in rats. The formation of dMBP in sciatic nerve segments was measured using conformation-specific antibody by immunoblotting and immunofluorescent imaging. Preliminary results support the hypothesis that dMBP released at the peripheral injury site is transported axonally along the damaged nervous system to sustain the chronic state of NP.
Advisor : DR. JING WANG
Abstract Title : Neuromodulation of Drosophila Mushroom Body Circuits by Hunger and Satiety
Abstract : Starvation induces shifts in neural circuit function that flexibly coordinate the behavior of an organism with its metabolic status. In Drosophila melanogaster , different changes in olfactory behavior and circuits after food deprivation emerge on different timescales. Early starvation (6-24 hrs) leads to enhanced olfactory sensitivity and enhanced food odor search behavior. Severe starvation (48 hrs+) leads to an additional increase in the intensity of food search behavior and increased locomotion. Our preliminary data indicates severe starvation leads to critical changes in the local circuits in the mushroom body (MB), a multimodal, higher order olfactory neuropil. Both intrinsic and extrinsic MB neurons undergo changes in excitability as the duration of starvation increases and are critical for changes in odor search behavior after severe starvation, but not early starvation. Thus, as the duration of starvation increases, the number of neural resources allocated towards appetitive behavior appear to increase as well. ADDITIONAL PRESENTERS: Joseph Ayoub, Wilson Tan
Advisor : DR. BRIAN HEAD
Abstract Title : Caveolin-1 Regulation of DISC1 and Synaptic Proteins as a Potential Mechanistic Target for Schizophrenia
Abstract : Schizophrenia is a debilitating neuropsychiatric disorder manifested in early adulthood. Disrupted-In-Schizophrenia-1 (DISC1) is a promising candidate gene for schizophrenia. Caveolin-1 (Cav-1) is implicated in neuronal signal transduction and plasticity. Here we examined the role of Cav-1 in mediating DISC1 and synaptic proteins expression in neurons in vitro and the hippocampus in vivo.
Abstract : Hydrocephalus is one of the most common neurological diseases of newborns and young children in which the accumulation of cerebrospinal fluid (CSF) causes the build-up of pressure within the ventricles. As the condition progresses, irreversible brain damage inevitably occurs. Deficient memory and cognitive processing worsen as rapid expansion of skull disrupts the development of the normal head. While there is no cure, there are treatments involving a surgical insertion of a cerebral shunt into a ventricle to drain excess fluid and relieve pressure on the brain. This is an ongoing procedure that can lead to serious complications such as infections, headaches, and hemorrhage. Previous papers have shown that LPA-mediated signaling plays a significant role in the development of hydrocephalus. Here we examined the receptor-mediated phenomenon and figured out which LPA receptor is attributable to morphological effects of the brain. The studies of LPA in mouse model suggest potential preventative therapeutics, and less invasive and more effective treatment.
Abstract Title : Elucidating the Brainstem Circuitry Responsible for Mediating Motor Control of the Distal Forelimb
Abstract : Two brainstem systems that are postulated to mediate direct control of peripheral musculature from corticospinal neurons are the rubrospinal and reticulospinal tracts, which originate from the red and reticular nuclei, respectively. Our studies have utilized a viral intersectional approach to target genetically encoded axonal tracers to specific subsets of brainstem populations projecting to lower cervical segments responsible for the control of distal musculature. Our results demonstrate that these two key brainstem nuclei possess unique patterns of innervation to the spinal cord and are likely to modulate very distinct aspects of behavior. Ongoing studies will use the viral intersectional system to target retrograde transynaptic tracers (rabies virus) to specific subsets of reticulo and rubrospinal projections to identify monosynaptic inputs driving these neurons. Together, these studies will provide greater insight into the synaptic circuitry responsible for mediating fine motor control of the forelimb.
Abstract Title : Mapping the Neural Circuitry of Ventral Pallidal Neurons in Different Subtypes of Depressive Behaviors
Abstract : Nearly 10% of adults are diagnosed with Major Depressive Disorder (MDD) over their lifetimes, yet current therapeutics are not fully effective and often require long-term treatment. A significant obstacle to treating MDD is that patients exhibit a wide range of symptoms from anhedonia and social withdrawal to anxiety. Though these symptoms have been well documented, little is known of the neural circuitry underlying these behaviors. Particularly, do different circuitries underlie discrete behavioral symptoms of depression? To model depression, we use the social defeat stress (SDS) model in mice to elicit similar behavioral phenotypes as MDD in humans. Using a multifaceted strategy of virus-mediated circuit tracing, immunohistochemistry, and behavior, we have identified the parvalbumin (PV) ventral pallidal circuit as a necessary component underlying depressive-like behavior in mice. The high amount of heterogeneity in the ventral pallidum (VP) requires a thorough characterization of its cell-type specific circuitry. First, using a viral tracer to label efferent axons and sites of synaptic contact (AAV-DIO-synapTAG), we find that PV neurons in the VP project to the ventral tegmental area (VTA) and the lateral habenula (LHb). Next, we combined AAV-DIO-synapTAG injections with rabies virus as a retrograde transneuronal tracer to further characterize the circuit. Immunohistochemistry suggests that these projections from the presynaptic sites of the VP are likely excitatory. Lastly, the functional contributions of PV VP neurons were investigated using a Cre-dependent virus expressing tetanus toxin (TNxT) to silence the neurons by locally prevent neurotransmitter release. TNxT treatment revealed that the knockout of PV VP neurons in mice resulted in more resilience to SDS, as measured by the social interaction, tail suspension, and force swim behavioral assays. These experiments reveal an integral circuit mediating depressive behavior in mice and identify putative downstream targets important for these effects. A growing understanding of the neural circuitry responsible for SDS can translate to further knowledge of MDD and more targeted, more effective treatments. ADDITIONAL PRESENTER: Daniel Knowland
Abstract Title : Effects of Nerve Stretch on Axonal Structure
Abstract : Peripheral nerves exist throughout the body to allow for movement and sensation. The length of nerves throughout the arms and legs demonstrate variable deformation when stretched. Peripheral nerves can stretch more in joint regions (e.g. elbow and knee) than in non-joint regions (e.g. calf). It is unknown why joint regions are more flexible than non-joint regions. Previous studies have shown that there is not a significant difference between tissues among these regions. Axonal structures have not been examined closely in the joint and non-joint regions in the nerves. We used the median nerve and the sural nerve as model nerves to understand regional differences in regional responses to stretch. The median nerve, which contains both motor and sensory neurons, is a mixed nerve in the arm. The sural nerve, which contains purely sensory neurons, is a branch of the sciatic nerve and runs down the gastrocnemius calf muscle. Thus, we can examine how stretch affects both motor and sensory classes of neurons, and ultimately motor and sensory function. Furthermore, stretching the sural nerve can potentially effect sensation. Previous studies have shown that axons can undulate, so that they unravel before they are actually stretched. We hypothesize that axon frequency and amplitude, or the waviness, can vary in both joint and non-joint regions as well as vary when the nerve is stretched. To observe axonal structure during stretch, we imaged nerves in mice that expressed fluorescence exclusively in neurons through the expression of the brainbow gene (which creates the fluorescence) and the cre gene driven under the Thy-1 promoter (which provides neuronal specificity). These genes were examined because they allow the nerves to fluoresce under confocal microscopy to distinguish axonal structures. Imaging was performed using confocal microscopy, which allowed us to optically section the nerves without the need of physical cross-sections. Nerves were imaged with and without stretch and results were compared via one-way ANOVA. Initial results suggest that joint regions in the median nerves are more deformed than non-joint regions.
Abstract Title : Neural Differentiation of Rat Embryonic Stem Cells
Abstract : Embryonic stem cells (ESCs) and ESC-derived neural stem cells (ES-NSCs) are promising potential therapies for repair of spinal cord injury (SCI). Rat ES-NSCs were therefore tested in vitro and in vivo for their ability to differentiate into the neurons and glia necessary for SCI repair. Rat ESCs were driven toward an NSC fate. Midway through the differentiation protocol, the cells tested positive for NSC markers and negative for pluripotency markers, confirming successful derivation of ES-NSCs. Some of these intermediate cells were allowed to complete differentiation in vitro, and eventually expressed markers of neurons and glia, confirming their progression beyond the NSC stage. In contrast, cells grafted into sites of rat SCI continued to express NSC markers nestin and vimentin, and failed to differentiate into neurons and glia. Thus, although successful differentiation of ES-NSCs was achieved in vitro, further experimentation is required to attain in vivo differentiation of ES-NSCs in SCI.
Abstract Title : Brain-derived neurotrophic factor (BDNF)-elevating therapy for Huntington's disease
Abstract : Deficiencies in brain-derived-neurotrophic-factor (BDNF) have been implicated in the pathogenesis of Huntington's disease (HD). The Thomas lab previously showed that Glatiramer acetate (GA; CopaxoneŽ), an FDA- approved drug used for the treatment of multiple sclerosis, could increase BDNF levels in cultured striatal cells. In this study we tested whether GA could improve disease symptoms in two different HD mouse models (CAG140 knock-in mice and N171-82Q transgenic mice), and whether GA could increase expression levels of BDNF in the brains of these mice. We treated HD mice with GA (25 mg/kg, s.c., 3 times per week; or 50 mg/kg 5 times per week) for up to 1 year, and found that GA caused significant improvement in motor symptoms in HD mice. These behaviors included the rotarod test, climbing test, and several measures of open field activity. GA treatment resulted in increased expression of BDNF transcripts I and IV in the cortex of CAG140KI mice, as measured by quantitative PCR analysis, normalized by the Hypoxanthine guanine phosphoribosyl transferase gene. Using an enzyme-linked immunosorbent assay (ELISA) for BDNF, we measured protein levels in different brain regions. We found small changes in BDNF protein expression induced by GA treatment. ADDITIONAL PRESENTER: Taylor Howell
Abstract Title : Neurotransmitter Plasticity After Chronic Social Defeat
Abstract : The underlying mechanism that allows one to experience and cope with social stress is a complex and ill-defined process that may play a substantial role in the development of stress-associated neuropsychiatric conditions. Part of the response to social stress may include the recently discovered phenomena of neurotransmitter respecification in which a stressful stimulus causes a neuron to synthesize and secrete a different neurotransmitter than the one expressed before stimulus exposure (Dulcis et al., 2013). In this project rats were exposed to an aggressor to serve as a model for social stress. Following social defeat, neurotransmitter levels in various brain nuclei were quantified. The susceptible rat group, compared to resilient and control, displayed substantial neurotransmitter plasticity in the Dorsal Raphe, an area associated with processing the stress response. Current studies are investigating the molecular identity of neurons that undergo neurotransmitter plasticity by testing various neurotransmitters and transcription factors expressed in the Dorsal Raphe nucleus of rats before and after undergoing social defeat. These changes may highlight the differences between various individual's ability to cope with stress, which can provide further insight into the mechanisms behind stress-related mood disorders and lead to increased efficiency of treatments.
Advisor : DR. JING WANG
Abstract Title : Tracing Neural Circuits: Making a Version of the CaLexA Reporter System with a Higher Sensitivity to Calcium
Abstract : Genetically encoded activity reporter systems allow us to identify and label active neurons in a model organism. Tracing neural circuits and elucidating the neurons responsible for various olfactory mechanisms is integral to our laboratory's approach and much of this depends upon activity reporter systems. The CaLexA transcriptional activity reporter system uses a modified NFAT protein as well as a reporter gene such as GFP, (induced by the LexA/LexAop system) to label populations of active neurons. In the CaLexA system, the import of a modified version of the NFAT to the nucleus of a cell occurs upon sustained rise in intracellular calcium. This import of NFAT initiates the transcription of reporter genes such as GFP. We made a version of the CaLexA reporter with higher sensitivity to calcium. This was done by altering the calcineurin-binding site on the NFAT molecule, by site directed mutagenesis. The goal of constructing a more sensitive version of the CaLexA system is to detect relatively lower levels of neuronal activity in an organism. We now plan to express the original and more sensitive versions of the CaLexA systems in Drosophila brains, in order to compare the intensity of neuronal activity detected by each version of the CaLexA system.
Advisor : DR. FRED GAGE
Abstract Title : In vivo 2-photon imaging of adult born dentate granule cells
Abstract : The growth and refinement of dendritic arbors are crucial steps in the formation of neuronal circuits; however, the processes that regulate dendrite morphogenesis are not yet fully understood. Some neuronal types undergo transient dendritic branch overgrowth, followed by extensive pruning. Here we studied the development of adult-born dentate granule cells (DGCs) in the mouse hippocampus using in vivo 2-photon imaging, following nascent dendrites over a period of several weeks. By knocking-down the expression of different proteins using shRNA we were able to study the effect of various molecular pathways on dendrite growth and pruning, thus obtaining novel insights on the process of dendrite morphogenesis.