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2015 Research Showcase
NB Abstracts
Abstract Title : Correlation between the severity of several neurodegenerative diseases and the levels of the anti-aging protein Klotho.
Abstract : Klotho is an anti-aging protein that is known to regulate systemic homeostasis of calcium and phosphate. There is evidence that an overabundance of the Klotho protein in mammals significantly increases lifespan. It has also been shown that a deficiency of the protein in mice is correlated with a faster rate of neurodegeneration. Taking these published reports as preliminary mechanistic evidence for a role of klotho in disease, we hypothesize that Klotho will be present at lower levels in individuals suffering from more severe stages of neurodegenerative diseases such as Alzheimer?s disease (AD) and Parkinson?s disease (PD). Our work represents the first to test this hypothesis by studying Klotho protein levels in brain tissue of individuals diagnosed with varying degrees of either AD, PD, or both. To gain a more complete analysis, we also assayed klotho levels from CSF and plasma from well-characterized AD patients using high throughput bioassays.
Abstract Title : Evaluating Huntington?s Disease therapeutic targets for reduction of toxic huntingtin
Abstract : Huntington?s Disease (HD) is an unrelenting, late-onset, neurodegenerative disorder with no known cure. HD is caused by a CAG expansion in the huntingtin (htt) gene leading to a poly-glutamine expansion in the htt protein. Multiple diseases arise from poly-glutamine expansions, which are prone to aggregation of the altered protein. Throughout the disease?s progression, toxic protein aggregates overwhelm protective cellular functions such as autophagy, leading to cellular dysfunction prior to neuron death. In evaluating pharmacological target candidates for HD therapy, we first wanted to determine whether the candidates were expressed at high-enough levels in the brain for an impactful intervention. To assay this, immuno-blotting of brain tissues from a HD mouse model (BAC-HD - Bacteria Artificial Chromosome ? Huntington?s Disease) was done. Next, we took the candidate with the highest expression in the brain, and assessed its ability to induce autophagy. The next step will be to determine if increased autophagy by this candidate does, as predicted, lead to a reduction in toxic protein aggregation. A candidate that successfully reduces toxic protein aggregation may be an effective treatment not only for Huntington?s Disease, but also other poly-glutamine expansion diseases.
Abstract Title : Computational Extraction of Cellular Signals from Mouse Spinal Cord Imaging Data
Abstract : The spinal cord is the primary neurological link between the brain and other parts of our body. Cellular circuits within the spinal cord perform complex sensorimotor computations that influence what we sense and how we act, either directly or in communication with the brain. Despite the spinal cord?s crucial role in central nervous system function little is known about the cellular computations that underlie its actions. Fluorescence imaging allows optical recording of cellular activity from live mice. However, motion-induced image artifacts due to the animal?s cardiac and respiratory cycles, or muscular tone often corrupt optical recordings, particularly in the spinal cord. Here, we evaluated existing and developed new computational approaches to correct for motion artifacts and identify cellular signals automatically. We found that mutual information-based image registration followed by dimensional reduction, independent component analysis and image segmentation is effective in extracting cellular activity from mouse spinal cord calcium imaging data.
Abstract Title : Role of Reduced Protein Translation in Normal Neuronal Health and in Neurodegeneration
Abstract : A number of studies have begun to address the role of the mTOR signaling pathway in lifespan extension and neurodegeneration. In C. elegans, reduced protein translation significantly extends lifespan, a phenomenon corroborated by long-lived Ames dwarf mice. To establish a model system to study reduced protein translation and its effect in normal neuronal health, aging, and neurodegenerative disease, we have generated a neuronal stable cell line model and a mice model overexpressing eIF4E Binding Protein1 (4EBP1). Preliminary data show that primary cortical neurons from 4EBP1 overexpressing transgenic mice show better survival as compared to neurons from control littermates against conditions of stress that promotes cell death. More importantly, primary hippocampal neurons from 4EBP1 overexpressing mice shows lower cell death as compared to neurons from control littermates against α-synuclein preformed fibril mediated cytotoxicity (an in vitro model to study Parkinson?s). Reduced protein translation in both cell lines and primary cortical neurons also increases transcription levels of multiple genes important in maintaining mitochondrial health, such as genes involved in the glycolytic pathway and the reactive oxygen species pathway. Preliminary data also show that overexpression of 4EBP1 in stable cell lines and primary cortical neurons might also induce mitochondrial unfolded protein response.
Abstract Title : Extreme binocular plasticity and dynamic strategy implementation sustains visual prey capture in cephalopod cuttlefish
Abstract : A fundamental goal in neuroscience is to understand how neurons cooperate to mediate and support goal-directed behaviors. Cuttlefish are highly visual creatures that anecdotally, was reported to undergo large shifts in eye position during its transition from prey to predator. Here we quantitatively evaluated if ocular convergence occurs in response to prey detection. We also asked whether such convergence is necessary for depth perception leading to successful prey capture. Finally, we explored how stereopsis deficient cuttlefish adapt to conditions of altered stereopsis, when survival (eating) was contingent on successful prey capture. Cuttlefish were hatched and maintained in our lab. Their eye movements during prey-capture behavior were analyzed via dual-angle, high-speed imaging (~1000 frames per second) and semi-automated eye tracking software. 3D coordinates were generated and subsequently used to calculate angle change between eyes throughout prey-capture. These recordings were also used to analyze tentacle dynamics (speed, angle and distance of attack). Necessity of binocularity/stereopsis for efficient prey-capture was tested by transiently blinding cuttlefish in one eye. Hunting episodes were also filmed after recovery of vision to the deprived eye. Multiple parameters of prey-capture were measured and compared to control animals. Control cuttlefish with sight in both eyes displayed 100% prey-capture success rates. Temporary suture of one eye significantly reduced the success rate to ~60%. Analysis of tentacle dynamics showed that cuttlefish deprived of vision in one eye tended to miscalculate prey distance, thus failing to capture their target. Removal of sutures restored sight in the deprived eye and the full ability to capture prey. Results from these experiments indicate binocular convergence and stereopsis are necessary for cuttlefish to accurately and efficiently capture prey. Interestingly, unilateral lid suture caused emergence of novel head movements during prey capture, which may sustain motion parallax and the remaining prey capture successes. We also discovered that cuttlefish can employ distinct prey distraction tactics depending on prey orientation during the stalking phase. Together these data indicate cuttlefish implement highly dynamic, rapidly updated strategies for successful visual prey capture. We are starting to make headway on the underlying neural circuits that support this extreme plasticity.
Abstract Title : Repurposing glatiramer acetate for Huntington's disease therapeutics.
Abstract : There is ample evidence that Huntington?s disease (HD) is linked to deficiency of striatal brain-derived neurotrophic factor (BDNF), which is essential to the development, function, and survival of neurons. Our study investigates the effects of an FDA-approved drug, glatiramer acetate (GA) or CopaxoneŽ , which is used in the treatment of multiple sclerosis. GA has been shown to increase BDNF levels in immune cells, and our previous studies found that GA could increase BDNF in striatal cells, as well. It is possible that increasing BDNF expression in affected cells will prevent or reduce HD phenotypes. In the current project, we tested whether chronic GA treatment could improve disease symptoms and elevate BDNF levels in an HD mouse model. We monitored HD phenotypes, such as motor dysfunction, cognitive ability, and behavioral changes, as well as BDNF expression in the brains of CAG140 knock-in HD mice in response to 18 weeks of GA treatment at a dose of 25 mg/kg. Slight motor skill improvement was seen in drug-treated homozygous HD mice compared to vehicle-treated mice in the climbing task, and improvements in cognition were observed in the T-maze test. There was minimal change in other behaviors, including rotarod and open field assessments. GA caused elevation of Bdnf mRNA, but no change in BDNF protein levels. These results revealed some beneficial effects of GA in the HD mice, but imply that a higher dosage of GA may be required for full therapeutic effects of drug treatment.
Abstract Title : Alpha-synuclein: Its relation with the Alzheimer's Disease
Abstract : Alzheimer?s disease (AD) is one of the leading causes of death in U.S. population and is characterized neuropathologically by beta-amyloid plaques and neurofibrillary tangles. In order to further understand co-morbidity in AD and to facilitate early detection we analyzed whether levels of the protein α-synuclein was measured. Although α-synuclein is best known for its role in Parkinson?s disease (PD), it may also serve as a disease marker for AD. We used high throughput bioassays and Western blotting to measure levels of α-synuclein in blood and CSF and from the brains of twelve patients: a normal individual for control, three PD patients, and eight AD patients with different severities. Although we will be finalizing our work over the next month, our preliminary results demonstrate that α-synuclein is a common pathology between AD and PD and may be useful as a biomarker for multiple neurodegenerative diseases.
Abstract Title : Individual differences in methamphetamine self-administration model methamphetamine-addicted phenotype and are associated with differential cell death in dentate gyrus of the hippocampus
Abstract : The hippocampus is important for the relapse stage of addiction, and maladaptive patterns of methamphetamine intake result in altered levels of neurogenesis in the dentate gyrus during withdrawal. Individual differences in methamphetamine intake during extended-access self-administration were used to model the methamphetamine-addicted phenotype. These individual differences allowed us to test whether specific patterns of methamphetamine-intake differentially altered the number of cells undergoing apoptosis in the dentate gyrus of the hippocampus. Male outbred albino Wistar rats were trained to self-administer methamphetamine intravenously 6 hr/day for 17 sessions (FR 1 schedule, 0.05mg/kg per infusion). Rats with higher levels of methamphetamine intake (high responders, n = 15) exhibited escalating patterns of methamphetamine intake across the 17 sessions. The rats with lower levels of methamphetamine intake (low responders, n = 13) maintained a stable pattern of intake without escalation during extended access. After three weeks of withdrawal, high responders demonstrated greater latency to extinguish drug-seeking behavior, greater drug-context-induced reinstatement and greater cue-induced reinstatement, indicating higher propensity for drug relapse compared with low responders. After reinstatement session, animals were euthanized and brain tissue was processed for immunohistochemistry and hippocampal sections were processed for AC3 (activated caspase-3; apoptosis marker) immunohistochemistry. Stereological analysis of cell numbers in the dentate gyrus resulted in an increase in expression of AC3 in low responders compared to controls and high responders. These findings suggest that methamphetamine addiction is related specifically to differential alterations in cell death factors in the hippocampus, and these alterations may be able to modulate methamphetamine-seeking behavior.
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 : Hippocampal Anatomical Changes Accompanying Memory Impairments in a Chronic Model of Temporal Lobe Epilepsy
Abstract : Temporal lobe epilepsy (TLE) is the most common type of epilepsy in adults, and is characterized by recurrent, spontaneous seizures. In addition to seizures, memory deficits often emerge, suggesting that the networks that underlie learning and memory are not functioning properly. One such network is the dentate gyrus of the hippocampus, which is thought to mediate pattern separation (the process of separating similar experiences). In human TLE, neuron loss in the hilus of the dentate gyrus and granule cell axon reorganization are commonly observed. However, it is unknown when these structural changes occur during the disease progression or whether they lead to functional impairments. We hypothesize that anatomical changes and memory deficits occur early, before the appearance of recurrent seizures.To test this, rats were given kainate to induce epilepsy and then were tested on a behavioral pattern separation task during the period of epileptogenesis (before spontaneous seizures). If our hypothesis is correct, dentate dependent pattern separation tasks could be used as a biomarker of epileptogenesis and preventative treatment could be started.
Abstract Title : LncRNA in Lithium Treatment of Type 1 Bipolar Disorder
Abstract : Long noncoding RNAs (lncRNAs), RNAs longer than 200 nucleotides in length that do not code for proteins, have been implicated in various neuropsychiatric disorders including schizophrenia and Huntington?s disease, among others. With the advent of gene therapies and the increasing importance of noncoding RNA (ncRNA) in epigenetic regulation, lncRNA may provide a key in determining new prognostic markers and therapeutic targets for these disorders. Investigation into current literature has shown that although the role of other ncRNA such as microRNA has been widely studied, little is known about the role lncRNA in he neurons of neuropsychiatric, and in particular type 1 bipolar disorder (BD1), patients. Various studies have shown the efficacy of lithium treatment in BD1 patient samples, but few have examined the mechanism behind the therapy. There is thus a clear gap in knowledge concerning the role of lncRNA in BD1, which further investigation may help to clarify. We hypothesize that differentially expressed lncRNA regulate BD1 and its treatment by lithium through the CRMP2 pathway.
Abstract Title : Profiling Epigenetic Alterations in Neurodegenerative Diseases: Histone Modification Alterations
Abstract : Epigenetic mechanisms, involving DNA methylation and histone post-translational modifications, alter gene expression without changing DNA sequences. Recently, they have been found to play an important role in brain function and in the pathology of the most prevalent neurodegenerative disorders: Alzheimer's disease (AD), Parkinson's disease (PD), and Dementia with Lewy Bodies (DLB). On one end of the neurodegenerative spectrum, AD is the most common cause of dementia, with its manifestation marked with progressive loss in memory and cognitive functions. On the other side is PD, the second most common neurodegenerative disease, notably characterized by motor impairments. Bridging the two diseases is DLB, which is the second most common cause of dementia, but in addition to attention and cognitive deficits as AD, symptoms also include mild Parkinson's-like features. Interestingly, a previous study from the Desplats Lab analyzing the expression of gene encoding chromatin modifier enzymes in the frontal cortex of AD, PD, and DLB patients revealed that histone modifications were the most affected functional groups in these neurodegenerative disorders. Here, we investigate whether these changes in the transcription of chromatin remodeling enzymes affect the actual pattern of histone modification. We discovered a significant decrease in the levels of tri-methylation of histone H3 on lysine 27 (H3K27me3) and significant increase in the levels of tri-methylation of histone H3 on lysine 9 (H3K9me3) in both PD and DLB compared to controls. We additionally identified a significant decrease in levels of histone phosphorylation and significant increase in levels of histone acetylation in PD alone compared to controls. Our results exemplify how similar alterations in a subset of histone modifications are common specifically for DLB and PD (both characterized by a-synuclein accumulation) or PD alone, while differing from AD. These patterns of epigenetic deregulation specific to dementia and non-dementia related neurodegenerative diseases underscores particular epigenetic signatures that may potentially aid in differential diagnosis as biomarkers or identification of novel targets of therapy.
Advisor : JING WANG
Abstract Title : A Drosophila Pheromone Circuit Described by an Incoherent Feed Forward Circuit Motif
Abstract : The Drosophila pheromone cis?vaccenyl acetate (cVA) elicits different behaviors depending upon the environmental context. In a mating context, fed females are highly attracted to males and are drawn to the cVA pheromone found in the male cuticle. Detection of cVA is first triggered through the Or67d odorant receptor neuron (ORNs) in the Drosophila antenna. Information is then delivered to two populations of projection neurons (PNs): the DA1 lateral PNs, and the DA1 ventral PNs. We hypothesized that the unique DA1 circuit design can be described by an incoherent feedforward circuit motif which is comprised of two parallel circuits activated by cVA with opposing effects on behavioral odor attraction. We tested this model by first observing female flies bred to have either the DA1 lateral or ventral PNs silenced. We then observed their responses towards a mixture of a food odor with cVA. When the DA1 lateral PNs were silenced, we observed an enhanced attraction towards the odor mixture. When the DA1 ventral PNs were silenced, we observed a decreased attraction towards the odor mixture. We next observed fly behavioral responses to cVA alone. In flies with the DA1 lateral PNs silenced, we observed no effect on behavioral attraction to the pheromone. Thus, the incoherent feedforward circuit model appears to be useful in describing female fly responses to a mixture of a food odor with cVA, but does not account for behavioral responses to cVA alone in female flies. Thus, fly behavioral responses to cVA can be described by the incoherent feed forward circuit motif only in a context dependent manner.
Abstract Title : Human neural stem cell grafts in spinal cord injury: integration and maturation
Abstract : Neural stem cells (NSCs) hold potential as therapy for spinal cord injury (SCI). We previously reported that grafts of human pluripotent NSCs in sites of severe SCI in rodents formed neuronal relays and mediated functional recovery. In the current study using a monkey model of SCI, we have replicated the anatomical components of our rodent study (graft survival, integration with the host cord, and profuse, long-distance axon growth) and assessed graft maturation and differentiation. We hypothesized that grafted human NSCs have a timecourse of maturation that mimics normal human development. Consistent with this hypothesis, at longer times after grafting, cell number and cell size increased, and cell density decreased. These analyses will help determine timepoints for behavioral analysis and optimal conditions for NSC grafting in future studies, which will aid the translation of NSC therapy to human clinical trials.
Abstract Title : Visual stimulation as a strategy to regenerate retinal ganglion cell axons after injury
Abstract : Retinal ganglion cell (RGC) axons in the adult mammalian visual system do not regenerate after injury, leading to permanent deficits in vision. The failure of RGC axon regeneration remains a considerable scientific and clinical problem, especially in the case of optic nerve diseases like glaucoma. Regeneration of the adult optic nerve and restoration of visual perception would ultimately require RGC axons to regrow, navigate to the correct targets, and reform functional synapses in the appropriate visual subcortical nuclei. In order to study RGC axon regeneration in vivo, we used the optic nerve crush lesion model. For three weeks, animals were treated with passive visual stimulation involving moving, high-contrast sinusoidal gratings alternating between vertical, horizontal, and orthogonal orientations. Our data show that daily visual stimulation of injured RGCs in adult mice triggers RGC axon regeneration past the optic nerve lesion site. Our results suggest a role for visual stimulation in the regeneration of RGC axons after injury. Because there are currently no clinically satisfactory ways to regenerate the damaged optic nerve, further studies will focus on elucidating a better understanding of the role of visual stimulation in RGC axon regeneration and its possible therapeutic role in the recovery of lost vision.
Abstract Title : Charcot Marie Tooth Disease Type 2B: Study of a Mouse Knockin Model of Rab7V162M
Abstract : Charcot-Marie-Tooth disease subtype 2B (CMT2B) is a debilitating hereditary sensory neuropathy associated with autosomal dominant point mutations (L129F, K157N, N161T/I, V162M) in Rab7, a small monomeric GTPase that regulates endocytic trafficking. Currently the pathogenic mechanism is unknown and no effective treatments are available. Although strong evidence has shown that these Rab7 mutants behave as constitutively active mutants i.e. gain of function, studies in Drosophila suggest these CMT2B mutations cause a loss of function for Rab7. To resolve this controversy, we have generated a knockin mouse model of Rab7V162M and obtained human patient fibroblasts that harbor Rab7V162M. We will test the hypothesis that hyper-activated Rab7 mutant(s) causes down-regulation of NGF/TrkA trophic signaling and induces peripheral sensory neuropathy in CMT2B.
Abstract Title : Detecting underlying white matter pathology in Temporal Lobe Epilepsy
Abstract : Patients with refractory temporal lobe epilepsy (TLE) often show hippocampal atrophy as well as degeneration to white matter tracts within the medial temporal lobe. Past research has reported that diffusion tensor imaging (DTI) can detect underlying white matter changes in TLE by measuring water anisotropy within tissue. DTI protocols are effective at determining diffusion within a patient, but are limited in comparison studies due to the questionable validity of standard registration algorithms. Registration of patient scans and subsequent analysis of cohorts by standard linear algorithms may not lead to valid conclusions. Tract-Base Spatial Statistics (TBSS) is a registration algorithm which resolves this concern by utilizing nonlinear registration in combination with an alignment-invariant representation of fractional anisotrophy (FA) tracts. In this study, we examined whole brain DTI maps in 26 patients with TLE and 20 age-matched controls. We used extracted FA maps in combination with TBSS processing to create and analyze voxelwise maps of FA. Our results suggests that DTI in combination with TBSS confirms tracts identified in previous studies and that it may provide new information for understanding white matter pathology in TLE.
Advisor : JING WANG
Abstract Title : Screen for neurons involved in innate olfactory attraction behavior in Drosophila
Abstract : The ability to make decisions is dependent on assigning attractive and aversive values to different stimuli. Flies show robust innate attraction and aversion behaviors to different odors. What neural circuits in the brain make one like or dislike a particular odor? We addressed this question using an high throughput olfactory four-field paradigm, which quantifies odor attraction in fruit flies. Candidate GAL4 driver lines that targeted different regions of the Drosophila brain were silenced to see if any were critical for behavioral attraction. Two lines emerged from our behavioral screen-- X102 and Pr-GAL4. We subsequently crossed X102 and Pr-GAL4 flies with UAS-shibire(ts) to silence those neurons. Our data showed that during testing both Pr-Gal4/Shi(ts) and X102/Shi(ts) flies showed increased attraction to a food odor compared to control flies. It is of interest that both X102 and Pr-Gal4 drivers target neurons in the lateral horn, a brain region theorized to mediate innate olfactory behaviors. Thus, our data supports this popular theory.
Abstract Title : Profiling Of Npas4 Expression In the Hippocampus
Abstract : Npas4 plays an important role in transcriptional regulation of inhibitory synapse development. In addition, in vivo learning induces Npas4 expression . The spatial and temporal dynamics of Npas4 expression in different sub-regions of the hippocampus is unexplored thus far but interesting to study, considering each region is known to process information differently. For instance, CA1 is responsible for pattern completion, while Dentate Gyrus is responsible for pattern separation. However, the time course of Npas4 expression in hippocampal sub-regions as a function of the amount of activity induction remains unknown and will be analyzed by this project. We will use disinhibition with a GABAA blocker, picrotoxin, as our method of activity induction in organotypic slices to probe this important question.
Abstract Title : Delivery of a Constitutively Active Mutant Of The Netrin-1 Receptor, Deleted in Colorectal Cancer (DCC), to Promote Corticospinal Tract Regeneration Following Spinal Cord Injury.
Abstract : Millions are currently living with traumatic spinal cord injury (SCI), resulting in paralysis and sensory loss that can last a patient?s lifetime. One of the most important tracts affected by SCI is the corticospinal tract (CST), responsible for fine motor control. To date, attempts to enhance CST regeneration have met with very limited success.We have recently reported successful implementation of neural stem cell (NSC) grafts for severe SCI (Lu et al., Cell 2012). These grafts exhibit excellent survival and proliferate into mature neurons, sending long-distance axonal projections throughout the CNS. Most importantly, NSC grafts form functional relays between supraspinal neurons and sites below the lesion. Morever, we have demonstrated, for the first time, moderate CST regeneration into this NSC graft; however, no functional improvement on motor tasks was observed. Hence, our ultimate goal is to combine this permissive cellular substrate with gene therapy that can enhance the intrinsic regenerative capacity of CST neurons.Deleted in Colorectal Cancer (DCC) is a Netrin-1 receptor that enhances axon outgrowth upon homodimerization. We hypothesize that overexpressing DCCdp1, a constitutively active, pro-growth form of DCC, in CST neurons will enhance regeneration into NSC grafts placed in sites of SCI. To test our hypothesis we have generated novel AAV viral constructs with super-folder GFP reporters, and we are currently validating the effects of these on neurite outgrowth in vitro. We will assess the effects of DCCdp1 overexpression on CST regeneration in vivo by transducing cortical motor neurons with AAV one week after SCI and NSC transplantation; 6 weeks later, growth of GFP+ axons into the graft will be assessed. Positive results will provide a novel and promising new strategy for CST regeneration. Moreover, we will gain a greater understanding of the intrinsic molecular mechanisms that can enhance regeneration of adult, injured CNS axons.
Advisor : FRED GAGE, PH.D.
Abstract Title : Phenotypical Characterization of iPSC-derived Neurons from Monozygotic Twins Discordant for Schizophrenia
Abstract : Schizophrenia (SCZD) is a debilitating neurodevelopmental disorder with a worldwide prevalence of approximately 1%. To examine the morphology and connectivity of SCZD neurons on a cellular level, human-induced pluripotent stem cells (hiPSCs) were used to develop neurons from monozygotic twins discordant for SCZD. Neural components of the hippocampal circuit were generated from the hiPSC twin lines and characterized in order to investigate SCZD pathology originating in the hippocampus. The efficacy with which hiPSC-derived neural progenitor cells differentiated into dentate granule (DG) neurons as well as the branching complexity and neurite length of the DG neurons were compared across monozygotic twin lines. There was no significant difference in the ability of healthy and SCZD MZ twin lines to generate PROX 1 positive DG neurons. The analysis of the neurite tracing paradigm is currently underway; however, the neurons have expressed the requisite fluorescent markers to demonstrate neural connectivity within the cultures.
Abstract Title : Physiologic Soft Tissue Connections Affect Strain Distribution in Rat Sciatic Nerves
Abstract : Peripheral nerve entrapment neuropathies, such as carpal tunnel syndrome, are well-established phenomena in which nerve compression leads to nerve injury. Associated symptoms include pain, weakness, paresthesias, or numbness. Although in some cases the cause of entrapment is plainly evident (eg. a space occupying lesion such as a tumor), in the majority of cases the mechanical cause of symptoms is less certain [1]. One potential explanation for symptoms without a clear anatomic cause is tethering of the nerve by abnormal soft tissue connections, resulting in regions of increased tensile deformation during joint movement. These deformations may lead to nerve injury by redistributing and disrupting the normal deformation pattern in nerves, which experience comparatively higher strains at articulating joints and lower strains away from joints [2-4]. At later stages of entrapment, surgical decompression, entailing lysis of nerve soft tissue connections, is frequently performed to untether (release) nerves, with generally positive clinical outcomes [1]. However, due to the surgery, normal tethers between the nerve and its environment are also broken, raising two questions. First, what is the normal role for neural soft tissue connections in the context of regional nerve deformation? Second, what impact does releasing these connections, such as during surgery, have on deformation? In this study we used a rat sciatic nerve model with rat knee and ankle motion to measure average strain, maximum strain, and proximal to distal distribution of strain before and after lysis of normal soft tissue connections. Our findings demonstrate that prior to surgical decompression, rat sciatic nerves demonstrate higher strain distally than proximally (P<0.001). Following decompression, this heterogeneity in strain is lost and distal strain decreases (P<0.001). These important and novel findings show that soft tissue connections significantly affect neural strain distribution. The fact that normal soft tissue connections alter the anatomic course of a nerve at the cost of increasing regional nerve strain suggests a possible protective function for these connections in certain anatomic locations. Loss of this normal heterogeneity due to scarring/adhesion formation (for eg., from overuse or trauma) may be an etiology of entrapment symptoms. Currently, we are in the process of studying abnormal adhesions in rat sciatic nerves, and performing histologic analysis to determine the effect of adhesions on nerve structure. [1]Mackinnon S, Hand Clin. 2002; 18:231-241. [2] Phillips et. al, J Phys 2004; 879-887 [3] Mason et al. JPNS 2011;16:261-269. [4] Wall et. al. JBJS Br. 1992; 74:126-129.
Abstract Title : Repurposing glatiramer acetate for Huntington's disease therapeutics
Abstract : There is ample evidence that Huntington?s disease (HD) is linked to deficiency of striatal brain-derived neurotrophic factor (BDNF), which is essential to the development, function, and survival of neurons. Our study investigates the effects of an FDA-approved drug, glatiramer acetate (GA) or CopaxoneŽ , which is used in the treatment of multiple sclerosis. GA has been shown to increase BDNF levels in immune cells, and our previous studies found that GA could increase BDNF in striatal cells, as well. It is possible that increasing BDNF expression in affected cells will prevent or reduce HD phenotypes. In the current project, we tested whether chronic GA treatment could improve disease symptoms and elevate BDNF levels in an HD mouse model. We monitored HD phenotypes, such as motor dysfunction, cognitive ability, and behavioral changes, as well as BDNF expression in the brains of CAG140 knock-in HD mice in response to 18 weeks of GA treatment at a dose of 25 mg/kg. Slight motor skill improvement was seen in drug-treated homozygous HD mice compared to vehicle-treated mice in the climbing task, and improvements in cognition were observed in the T-maze test. There was minimal change in other behaviors, including rotarod and open field assessments. GA caused elevation of Bdnf mRNA, but no change in BDNF protein levels. These results revealed some beneficial effects of GA in the HD mice, but imply that a higher dosage of GA may be required for full therapeutic effects of drug treatment.
Abstract Title : Changes in Hippocampal CRF Signaling Components with Alzheimer's Disease Progression
Abstract : The main neuropathological hallmarks of Alzheimer's disease (AD) include β-amyloid plaques, neurofibrillary tangles, and neural loss. Chronic stress that mechanistically involves corticotropin-releasing factor receptor type 1 (CRFR1) is implicated as a contributing factor in AD. To determine the relevance of CRF signaling in the hippocampus to AD progression, this study utilized 22 post mortem human brain tissues from various AD stages. The analysis of CRF system intermediates was done by quantifying the relative levels of mRNA detected with in situ hybridization in individual hippocampal subregions. This study further used unbiased stereology to investigate possible neuronal loss due to increased CRF signaling and other factors. Results of this aim will provide a comprehensive study and comparison of the distribution of CRF signaling components in the human hippocampus, and of the extent to which such modifications may be associated with AD pathology and cognitive decline.
Advisor : HOLLIS T. CLINE, PH.D.
Abstract Title : Developing an in Vivo Disease Model to Study Fragile X Syndrome in Xenopus laevis Tadpoles.
Abstract : Fragile X Syndrome (FXS) is the leading known monogenic form of Autism and the most common form of inherited intellectual disability. FXS results from silencing the FMR1 gene during embryonic development, leading to loss of Fragile X Mental Retardation Protein (FMRP). Recent studies suggest that loss of FMRP results in aberrant neurogenesis, but neurogenic defects have been variable. We used in vivo time-lapse imaging of neural progenitor cells and their neuronal progeny to evaluate the effect of acute loss or over-expression of FMRP on neurogenesis in the developing optic tectum of Xenopus laevis tadpoles which express a homolog of FMR1. We report FMRP regulates neural progenitor cell proliferation, differentiation, neuronal maturation, and cell survival. We investigated behavioral abnormalities using two visually-guided behaviors, as well as susceptibility to seize. We show aberrant sensorimotor and schooling behavior, as well as increased seizure susceptibility. These studies demonstrate Xenopus as a system to study FXS.
Abstract Title : Identification of DNA methylation changes associated with inflammatory genes during the progression of Alzheimer's disease.
Abstract : Inflammation in the brain is a well-documented part of the pathology of Alzheimer's disease (AD). Emerging evidence associates epigenetic mechanisms, particularly DNA methylation alterations, with AD pathogenesis. This project investigates the role of DNA methylation on modulating the expression of genes involved in inflammation during AD progression. We analyzed data generated by genome-wide profiling of DNA methylation in postmortem brain samples from individuals with mild cognitive impairment or AD in comparison to healthy subjects. We identified inflammatory genes with altered methylation levels in the disease groups, then used an in vitro model of neuroinflammation to analyze the role of DNA methylation in modulating inflammation-related gene expression. Cultured immortalized human primary microglial cells were treated with compounds that induce or inhibit DNA methylation, and the effect of these compounds on transcription levels of inflammation-related genes was quantified using real-time PCR.