Many of our neuroscience students apply for and conduct funded research through Pomona's Summer Undergraduate Research Program. Below are recent summer projects.


Syndecan23 Mutation in Drosophila melanogaster Affects Odor Response as well as Learning and Memory Capabilities

Dena Arizanovska ’18; Advisor: Karl Johnson; Collaborator: Jonathan King ’18

Syndecan (Sdc) is a transmembrane heparan sulfate proteoglycan that plays a role in axon guidance during development in Drosophila melanogaster. To better understand the effect of syndecan on behavior, we used Sdc23 mutant D. melanogaster larvae to examine odor preference and the capacity for learning and memory. To do this, we performed a series of olfaction assays in both wild type and mutant larvae to characterize naive odor response before adding a training period to identify the ability for associative learning. Our results showed that Sdc23 larvae prefer odors that wild type larvae do not respond to, suggesting a difference in odor receptor pathways and wiring. In addition, associative learning has been documented in wild type larvae, yet we did not find evidence of associative learning in Sdc23 larvae, which suggests that the syndecan mutation interferes with learning and memory capacity in D. melanogaster larvae.
Funding Provided By: The Elgin Fund for Summer Student Research and The Summer Undergraduate Research Program (SURP)

GREAT Knee Pain Reduction Trial

Cassandra Palmer ’18; Advisor: Matthew Sazinsky

Total knee arthroplasty (TKA) surgeries are becoming increasingly popular as general population lives longer. TKAs are great options for patients that suffer from severe osteoarthritis, however, with this procedure often comes postoperative pain that can last as long as 3-4 years. Acute postoperative pain puts patients at higher risk of developing chronic pain. Resulting from postoperative pain and other issues, there is a dissatisfaction that many patients feel after TKA surgeries. Genicular nerve radiofrequency ablation (RFA) is a procedure commonly performed in chronic knee osteoarthritic nonsurgical patients and has been found to vastly improve pain symptoms. The aim of this prospective, randomized, double-blinded clinical trial is to determine the efficacy of genicular nerve RFA in improving acute and chronic postoperative pain. TKA patients that fit the criteria will be randomly assigned either a treatment group receiving the RFA procedure or a control group without treatment (placebo). Exactly 60 patients (30 in each group) will be followed preoperatively and postoperatively with a series of surveys and tests including an 11-point Pain Intensity Numerical Rating Scale (PI-NRS). The main analysis will look at the difference between the experimental and control group PI-NRS mean score; significant difference has been determined to be 2 points of the mean. Unfortunately, due to funding issues, the study has not begun.
Funding Provided By: Dale N. Robertson Fund for Undergraduate Research

Identifying CSPGs in Drosophila Melanogaster

German Rojas ’18; Advisor: Karl Johnson

Chondroitin sulfate proteoglycans (CSPGs) are extracellular proteins involved in neural development and glial scar formation following CNS injury. During development, CSPGs have been shown to help guide axons; however, in spinal cord injury, CPSGs inhibit axonal regeneration. However, the mechanisms behind their actions are not yet fully understood. CSPGs have yet to be identified in Drosophila melanogaster, but there is evidence to suggest they exist, including the presence of CS in flies, and the presence of highly conserved CS biosynthetic enzymes in the fly genome. In this study, we are using syndecan, a heparan sulfate proteoglycan (HSPG) and biochemistry techniques, and we have found a potential way to identify and study the mechanisms underlying CSPG function in D. melanogaster.
Funding Provided By: Rose Hills Foundation SURP Grant

Metabolic labeling of Drosophila S2 cells with N-acetylgalactosamine and N-acetylglucosamine

Lauren Callans ’18; Advisor: Karl Johnson

Chondroitin sulfate proteoglycans (CSPGs) have been previously implicated in both neural development and spinal cord injury as repulsive growth molecules. CSPGs have not yet been identified in Drosophila melanogaster despite containing the highly-conserved sequences for necessary biosynthetic enzymes. Furthermore, the conservation of chondroitin and its function in related organisms, such as Caenorhabditis elegans, and the evidence suggesting the addition of chondroitin sulfate in syndecan over-expressing cells strongly suggest that Drosophila produce CSPGs. In this study, metabolic labeling was used to incorporate azide-tagged N-acetylgalactosamine or N-acetylglucosamine, sugars necessary for glycosylation of CSPGs and heparan sulfate proteoglycans (HSPGs) respectively, into Drosophila S2 cell proteins. Cells were incubated with the azide-tagged sugars for 48 hours to allow for incorporation. After incubation, a Click Chemistry reaction involving biotin alkyne was used to selectively draw CSPGs out of solution. Further optimization of the incorporation and reaction protocols is necessary before definitive conclusions can be made regarding the utility of metabolic labeling to identify CSPGs in Drosophila.
Funding Provided By: Fletcher Jones Foundation

The Effect of Reading Intervention on the Structure of the Dyslexic Brain

Mark Penrod ’18; Advisor: Nicole Weekes

Reading and language processing are two of the most fundamental cognitive tasks our brains carry out. However, certain reading disabilities, such as dyslexia, interfere with the brain’s ability to perform those tasks. Despite the growing number of cases of reading disability, there is not much consensus on the neural correlates of the disease or its effect on the development of the brain. In order to tackle these concerns, we studied a group of reading disabled children from ages 8-12 as they underwent 160 hours of intensive reading training. Before, during, and after the intervention, information on the structure of the brain was collected via magnetic resonance imaging (MRI). Children in the program unanimously improved significantly in various reading measures throughout the intervention. Additionally, a concurrent study suggests that changes in white matter between areas known to be involved in reading occur simultaneously. In this study, changes in cortical thickness were tracked and analyzed across the cerebral cortex throughout the intervention program. Preliminary results suggest a correlation between reading ability and cortical thickness in primary auditory and visual processing areas, as well as areas (such as the fusiform gyrus) known to be associated with the integration of phonological and visual information. Furthermore, longitudinal analysis indicates that cortical thickness decreases in these areas as reading-disabled children undergo intervention.
Funding Provided By: General SURP Fund

How do you see me? How age, emotion, and individual differences influence face processing and the N170.

Morgan Berlin ’19; Advisor: Jonathan King

With aging, our ability to process information changes: some processing improves with increased expertise while other processing, which relies on speed and working memory, may worsen. We investigated how aging affects the neural processing of human faces by comparing the N170 event-related potential across younger and older age groups. One experiment examines how age, anxiety, depression, and cognitive processing speed influence the amplitude and latency of the N170 when categorizing visual stimuli as faces or cars. The second experiment examines the interaction of facial emotional expressing and the "own-age" effect on the N170 component. The "own age" effect refers to our ability to preferentially process faces of people our own age (i.e., younger people recognize other younger people better than older people). We use a 1-back paradigm in which participants determine whether a face is the same face as shown in the previous trial or if an emotional expression is the same expression as shown in the previous trial. Participants then complete a memory task and social experience questionnaires. We predict that the interaction of age and emotion on the amplitude of the N170 will be mediated by social experience and cognitive processing abilities. Comparing the results from these two experiments will tell us how different processes involved in face processing may be maintained and changed with aging.
Funding Provided By: Paul K. Richter and Evalyn E. Cook Richter Memorial Fund

CRISPR/Cas9 Knockout of Biosynthetic Enzymes for CSPGs

Eric Smith ’19; Advisor: Karl Johnson

Chondroitin sulfate proteoglycans (CSPGs) are extracellular matrix molecules known for their role in nervous system development in vertebrates. Although they have been identified in humans and other species, CSPGs have yet to be identified in Drosophila melanogaster. Close relatives to CSPGs, heparan sulfate proteoglycans (HSPGs), have been shown in Drosophila to be key regulators of central nervous system development. The aim of this study is to explore whether CSPGs are present in Drosophila by knocking out the candidate CSPG biosynthetic enzymes using the CRISPR/Cas9 mutagenesis method.
Funding Provided By: Evelyn B. Craddock McVicar Memorial Fund

Disentangling apathy subtypes in Huntington’s Disease: a white matter biomarker of disease profile and progression

Audrey DePaepe ’18; Advisor: Ruth Diego-Balaguer

Along with motor and cognitive deterioration, neuropsychiatric symptoms form a common feature of Huntington’s disease (HD). Of these, apathy has been shown to highly correlate with disease progression, often emerging prior to clinical diagnosis. However, due to the multidimensional nature of apathy, its elusive etiology, and the lack of operative diagnostic criteria, treatment options are limited. In the present study, the global apathy measures of the short-form Lille Apathy Rating Scale (LARS) and the short Problem Behavior Assessment (PBA-s) correlated when assessed in pre-manifest and Stage I patients. Both apathy measures also correlated with Total Functional Capacity (TFC), a measure of disease severity. In addition, factor analysis of the LARS generated a dimensionalization of measured apathy into its three subtypes: emotional, cognitive, and auto-activation deficit. Further analysis by diffusion tensor imaging (DTI) revealed a significant relationship between global apathy and diffusion measures corresponding to a bilateral decrease in white matter (WM) integrity of the frontostriatal tract (FST). Moreover, higher levels of subtype-specific apathy correlated with a right-lateralized decrease in structural connectivity in the FST for the cognitive domain and in the uncinate (UC) for the emotional domain of apathy. That apathy subtypes are associated with distinct WM substrates supports the importance of an individualized approach to its diagnosis and treatment.
Funding Provided By: N/A


Chronic Mild Stress and Environmental Enrichment Modulate Novel Location Recognition Memory and Synaptic Plasticity

Angela Bi; Mentor: Jonathan King; Collaborators: Molly Cole ’16, Nathalie Guevara ‘19

Chronic Mild Stress (CMS) is a series of unpredictable stressors that is linked to depression and cognitive dysfunction. CMS induces anhedonia (measured by sucrose preference test, SPT) and impairs synaptic plasticity (hippocampal long-term potentiation). Environmental enrichment (EE) has been shown to reduce stress-induced behavioral deficits, enhance synaptic plasticity, and promote neurogenesis. Performance on several hippocampal-dependent memory assays including the novel location recognition (NLR) task is impaired by stress. Our study examined the effects of 4 weeks of CMS on SPT, NLR, and synaptic plasticity, and whether EE can counteract changes caused by CMS. Our results show that sucrose preference was not affected by 4 weeks of CMS, but was affected by CMS paired with EE. Short-term memory was impaired by CMS, as measured in the NLR task. EE did not counteract the effects of stress in short-term memory but did enhance long-term memory. Synaptic plasticity was not affected by CMS. However, there was a slight increase in long-term potentiation in the CMS/EE group above the control group. Rat strain and social interactions could be factors in stress reactivity.
Funding Provided By: Richter (Cole), Rose Hills (Bi), HAP (Guevara)

Effect of Cognitive Load on Frameswitching in Biculturals vs. Monoculturals

Julia Shay Kim ’16; Mentors: Richard Lewis and Sharon Goto; Collaborators: Goeun Park '17, Kevin Wei '15, Maryann Zhao '18

Asian American biculturals must navigate between Asian (interdependent) cultural and European American (independent) cultural frameworks (Fong et al., 2014) through frame-switching— changing their thinking and behavior to match their present cultural framework. We investigate whether frameswitching is an effortful (due to coping with more information) or effortless (due to practice) process. To do this, we use a concurrent cognitive load when performing the Navon letters task. Previous research has demonstrated that Asian Americans display relatively greater global perceptual processing on the Navon letters task, which measures local and global perceptual processing, when primed with collectivistic cultural values (McCone et al., 2010). 58 participants (17 Filipino Chinese, 20 Chinese, and 21 Asian Americans) were first primed with home or work settings using an unscrambling sentence task, hypothesized to prime interdependent and independent cultural schemas, respectively. Then, they completed the Navon letters task which measured their reaction time to global and local processing. From our results, we found that high cognitive load slows down frameswitching as demonstrated by mean reaction time (ms). Hence, our findings suggest that frameswitching is effortful in Asian American biculturals. However, Chinese and Filipino monoculturals showed a contrasting pattern of results. Implications for bicultural cognition and frameswitching are discussed.
Funding Provided By: Fletcher Jones (Park), Pomona Unrestricted (Zhao), Rose Hills (Kim), Pomona College Psychology Department (Wei)

Effects of Increased Handling and Habituation on Hyperactive (ADHD) High Running Mice

Katherine Forston ’16; Mentor: Karen Parfitt; Collaborator: Isaac Solomon ‘17

In 2003, Rhodes and Garland proposed that a line of high runner mice (HR mice), selectively bred for increased voluntary running, exhibited behavioral symptoms similar to humans affected by ADHD. HR mice indeed run a greater distance and for longer periods of time than controls (NS), but Rhodes and Garland's model was most strongly supported by the observation that Ritalin, a popular ADHD drug, decreased wheel running in HR mice while having a minimal effect on the control/NS lines (Garland et al 2005). Rhodes and Garland also argued that working memory was “impaired” in HR mice, whereas studies conducted by Pomona College students Ayabe and Guan in 2014 suggest that these mice are too hyperactive to function, let alone to exhibit learning in behavioral tasks such as the radial arm water maze (RAWM). Our 2015 study subjected both HR and NS mice to longer periods of handling and habituation in order to avoid an anxiety response to the novel environments associated with 3 different behavioral tasks: novel object location, social recognition, and the Morris water maze. Together, these tasks assess both social and spatial/working memory as a depiction of ADHD patients’ realistic impairments. If increased handling and habituation improve learning in both the NS and HR lines, the next step for our investigation will be to determine whether the drug Ritalin rescues the learning deficit between the two breeding lines, in order to deem HR mice a legitimate model for ADHD.
Funding Provided By: Rose Hills (Fortson)

Elucidating the neural basis for food odor preference in Caenorhabditis elegans

Cecilia Hollenhorst ’16; Mentor: Elizabeth Glater; Collaborator: Erik Vanstrum ‘16

More than one third of U.S. adults are obese, leading to increasing rates of heart disease, type two diabetes, stroke, and a multitude of other health issues. The biological basis of decisions regarding food remains largely unknown. Using the nematode Caenorhabditis elegans as a model organism, we aim to characterize both the neurons and the neural activity involved in food choice. Behavioral assays with genetic mutants that have disrupted function in specific sensory neurons allow quantitative measurement of the mutants’ preferences for bacteria eaten in the organism’s natural environment. Preference for each bacterium appears to employ a different set of sensory neurons, but specific ones, like the AWC neurons, are more commonly used in C. elegans’ food choice. Due to the AWC neurons’ importance, we are beginning to use a C. elegans mutant strain with a calcium-dependent fluorescent indicator in AWC(ON), allowing us to visualize real-time activity of the neuron during food choice behavior in a freely-moving organisms.
Funding Provided By: Fletcher Jones (Hollenhorst), Rose Hills (Vanstrum)

Food Odor Preference in C. elegans

Raquel Valdes ’17; Mentor: Elizabeth Glater

The organism Caenorhabditis elegans is used as an animal model to study the neuronal and genetic basis of behavior due to its simple nervous system and completely sequenced genome. Although the neurons required for the detection of specific, simple stimuli have been well-defined, less is known about the sensory circuits underlying the discrimination among complex stimuli, such as the mixtures of odors released by different kinds of bacteria, the worm’s major food source. To study the behavior involved in food odor preference, behavioral assays were conducted with both wildtype and mutant worms that were defective in sensory neurons found to have an important role in olfaction. In these assays, the C. elegans had to choose between E. coli and the test strain bacteria JUb38. The neurons that appear to play a role in the choice are ADF, AWB, and AWCon. Future studies will examine how these neurons work together to produce choice behavior.
Funding Provided By: Pomona College Neuroscience Department

Gaining genetic access to anterolateral tract projection neurons: characterization of candidate mouse molecular genetic tools

Jennifer Jia ’16; Mentors: Elizabeth Glater, David Ginty (Harvard Medical School), and Sebastian Choi (Harvard Medical School)

Noxious stimuli such as high or low temperatures and pain are detected by nociceptor free nerve endings, which relay information to the brain via anterolateral tract (ALT) projection neurons. These long-range neurons are largely excitatory and release glutamate to depolarize postsynaptic cells. ALT neurons span the length of the spinal cord and mostly reside in the superficial lamina of the dorsal horn. In order to study their involvement in pain perception, mouse molecular genetic tools are needed for their visualization and functional manipulation. AP staining of knock-in mouse line Robo3-ires-CreERT2 was used to visualize single cell morphology of neurons transiently expressing Robo3 in the developing spinal cord, of which some are projection neurons. Five transgenic GFP mouse lines from the GENSAT project (Gpr83-gfp, Nr5a1-gfp, Dlk1-gfp, Galr3-gfp, and Pde1c-gfp) were screened to have high GFP expression in the superficial lamina. These lines were crossed with vGlut2-ires-Cre; Rosa26-LSL-tdTomato and vGat-ires-Cre; Rosa26-LSL-tdTomato to determine whether they are excitatory or inhibitory. Furthermore, in situ hybridization was used to confirm that the Gpr83-gfp transgenic mouse line recapitulates endogenous Gpr83 gene expression in the spinal cord, allowing for the generation of Cre or Flp knock-in mouse lines. Using these tools, we hope to elucidate the roles of these neurons in conveying discriminative and affective somatosensation from the periphery to the brain.
Funding Provided By: Howard Hughes Medical Institute

Hand Me Down Hormones? Prenatal Effects of Siblings on Gender Identity & Sexual Orientation

Cal McMilllan ’17; Mentor: Rachel Levin

Previous studies have linked nonheterosexual orientations and transgender identities to greater numbers of older brothers, later birth order, and high concordance among siblings. In this study, we aimed to reexamine these questions in a more diverse population and a less clinical setting. Questionnaires from over 1300 people of all races, genders, and sexual orientations were collected and analyzed. We questioned what effect, if any, the number of older siblings or brothers had on sexual orientation and gender identity and examined the concordance of both nonheterosexual orientations and transgender identity among siblings. We found no effect of older brothers or older siblings on either gender identity or sexual orientation. However, we did find a higher degree of concordance of both transgender identity and nonheterosexual orientation among both twin and non-twin siblings than would be expected independently. All of our analyses yielded the same results whether or not nonbinary people were included.
Funding Provided By: Pomona Unrestricted

Investigating the Influence of Cytokine Signaling and Differentiation on Glioblastoma Molecular Subtype and Dissemination in a Novel Dot Migration Assay

Alicia Mizes ’16; Mentor: Michael Barish (City of Hope); Collaborator: Christine Brown (City of Hope)

Glioblastoma multiforme (GBM) is a highly aggressive WHO Grade IV astrocytoma with an expected median survival of only one year for affected patients. GBM possesses notable tumor heterogeneity and can be classified into four distinct subtypes: proneural, neural, classical, and mesenchymal, with different molecular expression profiles on account of variations in mutations, promoter methylation, and gene amplification. Mesenchymal subtypes display increased necrosis, inflammation, angiogenesis, recruitment of immune infiltrates, and endothelial-to-mesenchymal transition (EMT) that contribute to its elevated aggressiveness, radio-resistant phenotype, and poorer patient prognosis. The interaction of GBM with the tumor microenvironment, which includes microglia, macrophages, blood vessels, secreted cytokines and the extracellular matrix (ECM), plays an important role in its molecular expression profile and resulting invasive characteristics. Addition of the cytokine TNF-α to proneural GBM causes upregulation of CD44 and other mesenchymal markers. We have designed a novel in vitro dot migration culture system to study the dissemination of patient-derived proneural and mesenchymal GBM cells across an artificial ECM. We have investigated the ability of TNF-α to promote a proneural to mesenchymal transition and 10% fetal bovine serum (FBS) to induce differentiation in GBM stem-like cells through mediating a change in antigen expression that correlates with invasive potential.
Funding Provided By: Claremont Colleges Neuroscience Summer Research Fellowship and City of Hope Eugene and Ruth Roberts Summer Student Academy

Local VTA-CRF Signaling and Stress-Escalated Dependent-Like Alcohol Consumption

Olivia Onyilagha ’18; Mentors: Klaus Miczek (Tufts University) and Laura Darnieder (Tufts University)

One environmental factor that has an impact on alcohol use disorders (AUD) is stress. The neuropeptide corticotrophin releasing factor (CRF) mediates our body’s responses to stress and drugs of abuse. Peripherally, CRF governs the hypothalamic-pituitary-adrenal (HPA) axis and has actions within the brain by activating both CRF-R1 and CRF-R2 receptor subtypes (Boyson et al. 2014). In addition to the HPA axis, CRF also activates other regions of the brain such as the ventral tegmental area which is an area integral to reward circuitry. The objective of this study is to identify whether local release of CRF in the VTA can alter dependence-like alcohol drinking. Previous research in out lab has shown that mice that undergo a series of social defeat stress later have escalated levels of alcohol consumption (Hwa et. al, 2013) therefore in order to confirm CRF’s role in this stress escalated consumption we will manipulate it’s release optogenetically and hypothesize that this local release will also escalate alcohol consumption. Channelrhodopsin-CRF mice were to be optically stimulated intermittently for ten days, and put on a two-bottle choice intermittent alcohol access protocol with 20% ethanol (v/v) and water for two weeks. Preliminary results showed no escalating trend in alcohol consumption early on in the drinking protocol, however the continuation of the study in the coming weeks may show more conclusive results.
Funding Provided By: Tufts University Building Diversity in Biomedical Sciences Program

LTP deficits in selectively-bred High Runner mice are reversed with access to a running wheel

Ailene Nguyen ’16; Mentor: Karen Parfitt; Collaborator: Katherine Taylor Fortson ‘16

High Runner (HR) mice have been selectively bred for high running traits and are a proposed animal model for Attention-Deficit/Hyperactivity Disorder (ADHD). We studied the effects of wheel access in HR mice on a neurobiological analog of learning and memory, long-term potentiation (LTP), in the CA1 area of hippocampal slices prepared from these mice. We used single or triple theta-burst stimulation (1xTBS or 3xTBS) protocols and measured changes in electrophysiological responses following these high-frequency stimulation patterns to compare sensitivities to theta burst stimulation in mice with vs without access to a running wheel. The 1xTBS protocol assesses differences in the threshold of LTP induction, while the 3xTBS protocol assesses differences in maximal LTP. Previous studies by Asia Ayabe ’15 and Kevin Guan ’15 have shown that LTP induced by 1xTBS is significantly reduced for HR mice that do not have wheel access compared to those that can exercise freely, demonstrating that running has a rescue effect on LTP for HR mice. Our results are consistent with those of Ayabe and Guan (2015), allowing us to now investigate the mechanisms that may cause the high running traits of these mice. We are interested in further elucidating potential differences in dopamine neurotransmission of the HR mice, since the dopamine receptor system is implicated in hippocampal LTP as well as in ADHD in humans.
Funding Provided By: Pomona College SURP(Nguyen), Rose Hills Foundation(Fortson)

Murine Hippocampi Long-term Potentiation Facilitated by Peptide

Sam Crawford ’16; Mentor: Karen Parfitt; Collaborator: Kevin Knox ’16, Alyssa Cook ‘16

Memory loss noted in Alzheimer’s disease (AD) patients is linked to β-amyloid proteins formed through cleavage of Amyloid Precursor Protein (APP). In contrast, secreted Amyloid Precursor Protein α (sAPPα), another APP derivative, is neuroprotective, able to lower the threshold needed to induce long term potentiation (LTP). sAPPα can rescue LTP and memory deficits in an AD mouse model but its clinical impact is limited by its inability to cross the blood brain barrier. We studied a shorter peptide fragment of sAPPα that seems capable of permeating the blood brain barrier. Hippocampal slices were prepared from male mice. Baseline excitatory post-synaptic potentials (EPSPs) measured in area CA1 of the slices did not change when normal artificial cerebral spinal fluid (ACSF) was switched to a bath containing ACSF and 10 nM of our peptide fragment, both the diastereomeric (DX) and non-diastereomeric forms (NDX), or 10 nM of a control polypeptide (CY). Half-theta-burst stimulation (0.5TBS) induced similar levels of post-tetanic potentiation (PTP) in hippocampal slices bathed in normal ACSF, 10 nm NDX and 10 nm CY. A 0.5TBS induced higher levels of PTP in slices bathed in 10 nm DX. DX and NDX [KP1] facilitated larger amounts of LTP in slices compared to CY and normal ACSF (responses for 10 minutes, 50 minutes after 0.5TBS = 144.2 ± 2.5% vs. 118.9 ± 1.8% vs. 107.7 ± 2.5% vs. 110.0 ± 1.7%). Future work will focus on the potential metaplastic effects of DX and the mechanisms of action.
Funding Provided By: Norris (Knox), Pomona Unrestricted (Crawford), Rose Hills (Cook)

Studying chemosensory behavior in C. elegans through CRISPR-Cas9

Christopher Song ’16; Mentor Elizabeth Glater

Funding Provided By: Rose Hills

The Novel Object Location Task is Ineffective at Showing Behavioral Impairments in APPswe/PS1delta9 Transgenic Mice Compared to Littermate Controls

Kevin Knox ’16; Mentor: Karen Parfitt; Collaborators: Sam Crawford ’16, Isaac Solomon ‘17

There are numerous mouse models of Alzheimer’s disease (AD) available today, particularly those that produce abundant amounts of beta amyloid (Aβ), a protein that has been shown to be heavily involved in the disease. APPswe/PS1delta9 transgenic mice have mutations found in human AD patients and start producing excess Aβ at six months of age. They have been shown to have significant decreases in spatial learning and memory when compared to wild type C57 littermate control mice. This includes their inability to correctly distinguish novel objects as well as novel locations for objects. We have begun investigating potential spatial memory impairment in the transgenic mice compared to w/t C57 mice, both bred in our lab. In order to characterize whether our transgenic mice are spatially impaired, indicating the onset of typical AD-like symptoms, we performed a novel location recognition test with 5 five transgenic mice and 5 five wild type mice. The basis of this test is that mice will spend more time with an object placed in a new location, if they remember its original location. In our assays, as expected, the mice spent equivalent times exploring two identical objects. But the transgenic and wild type mice also spent similar amounts of time exploring the object that had been moved to the new location (7.85 +/- 2.15 s vs 7.17 +/- 1.24; p>0.05, Students unpaired T test). In addition, in both genotypes the amount of time spent exploring the moved object was not significantly different from time spent exploring the unmoved object. These unexpected results could be due to our low sample sizes or inaccuracy in measuring the time spent with the objects.
Funding Provided By: Norris (Knox), Pomona Unrestricted (Crawford)

Using GC-MS to identify volatiles in bacteria

Soleil Worthy ’18; Mentors: Elizabeth Glater and Charles Taylor

Funding Provided By: Howard Hughes Medical Institute


C. Elegans show altered food preferences after exposure to several bacterial strains

Ryan Ota (2015); Student Collaborator(s): Emily Kan (2015 CMC); Mentor(s): Elizabeth Glater

Funding Provided by: Sherman Fairchild Foundation (OR)

Studying chemosensory behavior in C. elegans through CRISPR-Cas and RNAi silencing of f-box genes

Christopher Song (2016); Student Collaborator(s): Patrick Liu (2014); Mentor(s): Elizabeth Glater

Funding Provided by: Kenneth T. and Eileen L. Norris Foundation (CS)

Impact of short-term voluntary and forced exercise on long-term potentiation in the rat hippocampus

Asia Ayabe (2015); Student Collaborator(s): Kevin Guan (2015); Mentor(s): Jonathan King

Abstract: Forced and voluntary exercise regimens have been well established as separate means of promoting cognitive function. Prior studies that directly compare the effects of forced and voluntary exercise have shown that both forms of exercise increase levels of brain-derived neurotrophic factor, but effects on spatial memory tasks and synaptic plasticity have been variable. The current investigation compares the effects of forced and voluntary exercise on hippocampal synaptic plasticity as determined by long-term potentiation (LTP). Our exercise paradigm was designed to minimize the impact of stress and pain, and standardized equipment and housing environments. The voluntary exercise group had free access to freely rotating running wheels and the forced exercise group used a motorized running wheel. Additionally, the voluntary exercise group ran quickly, and for shorter periods of time, when compared to forced exercisers. Our results show a significant increase in hippocampal LTP for the forced, but not voluntary, rats in comparison to the control. These findings suggest that periods of low intensity, longer duration exercise may be more beneficial to synaptic plasticity than high intensity, short duration regimens. Overall, voluntary and forced running are two distinct models that produce different effects on LTP, and should be treated as such.
Funding Provided by: Paul K. Richter and Evalyn E. Cook Richter Memorial Fund

Ginsenoside metabolite Compound K enhances hippocampal LTP but does not protect or repair Aβ25-35-induced deficits on LTP

Yuni Kay (2015); Student Collaborator(s): Ariana Tribby (2017); Mentor(s): Jonathan King

Abstract: Amyloid beta (Aβ) peptides are implicated in cognitive deficits associated with Alzheimer's disease. Buildup of Aβ deposits in the hippocampus is thought to contribute to cognitive decline. Research suggests that the active components of ginseng roots called ginsenosides, such as Rb1, may ameliorate the effects of some forms of neurodegeneration. Additionally, Rb1 is metabolized in the body and Compound K (ComK), its final metabolite, is present at the highest concentrations in the blood. Preliminary data in the lab has indicated ComK's potential ability to counteract the detriments caused by Aβ25-35. This experiment further investigated ComK's role in LTP modulation and studied its potential mechanism by investigating variable temporal application. Our results show that compared to the control, ComK facilitates LTP and Aβ attenuates LTP. However, ComK does not protect against attenuation caused by Aβ. Furthermore, ComK attenuates LTP if applied after Aβ perfusion. Thus, while 5nM ComK increases LTP compared to the control, it is not an effective treatment against Aβ-induced impairments in hippocampal synaptic plasticity.
Funding Provided by: Sherman Fairchild Foundation (AT); Rose Hills Foundation (YK)

Who Learns, Wins: Predicting Success and Stimulating Learning via Observation

Julianne Shrieve (2015); Additional Collaborator(s): Emily Cross (Bangor University), Dace Apshvalka (Bangor University); Mentor(s): Jonathan King

Abstract: The objective of this study is to gain a better understanding of how individual differences amongst subjects affects the efficacy of observational learning. The study, which is ongoing, consists of three parts. During an 8-week period, we ran a pilot study for the first part of the experiment. Subjects learned three different button pushing sequences through physical practice, observation of another person performing the action, and from a “ghost” performing the action (buttons lit up in sequence but no hand was seen pressing them). Subjects also completed questionnaires and working memory tests. During the pilot period, we worked on perfecting the button-pushing program before beginning to officially collect data, so no results have yet been obtained. The future of the study will be an in- subject design comparing the speeds at which the subjects perform the sequences they learned with the three different learning methods as well as one unlearned sequence. The researchers will then look at those individuals who learned best through observation and see what they have in common based on the personality questionnaires and working memory tasks. The second part of the experiment will involve fMRI analysis of these individuals, and using the fMRI data, the third part of the experiment will determine whether transcranial direct-current stimulation (TDCS) can be used to stimulate observational learning.
Funding Provided by: Pomona College SURP

Higher concentrations of Mg++ inhibit the formation of long term potentiation in mouse hippocampal area CA1

Samuel Crawford (2016); Student Collaborator(s): Vinay Srinivasan (2016), Isaac Soloman (2017), Julie Necarsulmer (2015), Leah Bleichner (2015); Mentor(s): Karen Parfitt

Abstract: An important excitatory neurotransmitter in the brain is the simple amino acid, l-glutamate. Some receptors for glutamate, e.g the N-methyl-D- aspartate (NMDA) receptors, are ion channels that are blocked by magnesium ions (Mg++) at normal resting membrane potentials. We used low (0.85 mM) and high (2.8 mM) concentrations of Mg++ to determine the influence of Mg++ on paired pulse facilitation (PPF) and induction of long-term potentiation (LTP) via the NMDA receptor-- mediated pathway. LTP and PPF were measured in the CA1 area of hippocampal slices prepared from C57 Bl 6N mice. The magnitude of LTP was significantly greater in the low Mg++ concentration. PPF was not affected by the Mg++ concentration, suggesting that Mg++ influences LTP via a postsynaptic role. Future studies will involve a concentration of Mg++ similar to that which occurs naturally in cerebrospinal fluid, in an effort to establish appropriate controls when altering concentrations of other LTP–affecting molecules (e.g. Aβ, the oligomer responsible for forming plaques in the brain, which lead to Alzheimer’s related symptoms.)
Funding Provided by: Paul K. Richter and Evalyn E. Cook Richter Memorial Fund (SC, JN, VS); Howard Hughes Medical Institute HAP (IS); Evelyn B. Craddock-McVicar Memorial Fund (LB)

Morris Water Maze, Radial Arm Water Maze, and Novel Object Recognition Tasks detect spatial learning and memory deficits in mice

Julie Necarsulmer (2015); Student Collaborator(s): Leah Bleichner (2015), Isaac Soloman (2017), Vinay Srinivasan (2016), Sam Crawford (2016), Vy Doan (2018); Mentor(s): Karen Parfitt

Abstract: Alzheimer's Disease (AD) is characterized by a progressive loss of cognitive function, notably the impairment of spatial learning and memory. The present study examined three tasks commonly used to test hippocampal-dependent spatial learning and memory—the Morris Water Maze (MWM), Radial Arm Water Maze (RAWM) and the Novel Object Recognition (NOR) tasks, as potentially viable assays for future experiments that will utilize an AD transgenic mouse model. Spatial learning and memory requires the glutamate NMDA receptor. We used the NMDA antagonist MK-801 to examine whether performance on these tasks is impaired, as has been shown by previous groups in this and other rodent strains. For each task, MK-801 (0.05 mg/kg; 5mL/kg in 0.9% saline vehicle) or vehicle alone was administered to C57B/6N mice 30 minutes prior to testing. Deficits in spatial learning and memory were demonstrated by all three tasks when comparing MK-801-treated mice to vehicle- treated controls, indicating that the MWM, RAWM, and NOR task are all viable assays for use in future studies.
Funding Provided by: Paul K. Richter and Evalyn E. Cook Richter Memorial Fund (LB, SC, JN, VS); Howard Hughes Medical Institute HAP (VD, IS)

A-Beta 25-35 modestly reduces hippocampal long term potentiation in vitro

Vinay Srinivasan (2016); Student Collaborator(s): Samuel Crawford (2016), Julie Necarsulmer (2015), Leah Bleichner (2015), Isaac Solomon (2017); Mentor(s): Karen Parfitt

Abstract: Alzheimer's disease (AD), characterized by severe memory loss and progressively worsening neurocognitive deficits, is one of the most pressing concerns for the aging population of the 21st century. At a molecular level, extracellular oligomerization of beta-amyloids (A-Beta), ~40 amino acid peptides produced by beta and gamma secretase cleavage of the Alzheimer's precursor protein, is thought to be responsible for the pathology. However, much is still unknown about the specific mechanisms underlying the peptide's neurotoxic effects within the brain. Previous work has examined hippocampal long-term potentiation (LTP), an accepted molecular basis of learning and memory, to investigate the role of A-Beta in mediating AD symptoms. The results of these studies have suggested a selective, post-synaptic receptor-mediated mechanism of interaction between A-Beta and the modulators of LTP. As the basis for future work demonstrating the efficacy of neuroprotective compounds, our project sought to demonstrate the purportedly clear inhibitory effect of A-Beta (25-35) on theta burst-induced hippocampal LTP by recording excitatory post- synaptic potentials in the CA1 region. We observed only marginal inhibition of LTP in treated slices compared to control, which differs from the more stark differences found in previous LTP work. However, low [Mg2+] in our baths and/or an overly- strong theta burst protocol might account for the absence of significant inhibition of LTP.
Funding Provided by: Paul K. Richter and Evalyn E. Cook Richter Memorial Fund (LB, SC, JN, VS); Howard Hughes Medical Institute HAP (IS)

Biochemical Purification of Chondroitin Sulfate Proteoglycans in Drosophila melanogaster

Jennifer Jia (2016); Student Collaborator(s): Melina Mastrodimo (2016); Mentor(s): Karl Johnson, Sara Olson

Abstract: CSPGs, or chondroitin sulfate proteoglycans, belong to a class of proteoglycans (PGs) modified by chondroitin sulfate (CS) glycosaminoglycan (GAG) side chains. These PGs have diverse neurological functions: specifically, they act as repulsive guidance cues for axons. High concentrations of CSPGs in perineuronal nets and glial scars prevent the creation of new synapses and the regeneration of axons in the central nervous system (CNS). Evidence suggests that CS exists in higher quantity in Drosophila than heparan sulfate (HS), a similar GAG chain present in the well-studied heparan sulfate proteoglycan (HSPG), and overexpression of HSPGs causes CS modification. In addition, CS and HS share the same protein-to-chain linker region. Although CSPGs are ubiquitous in the animal kingdom and robust evidence support CSPGs’ existence in Drosophila, they have never been identified or isolated. Previous α-CS antibody assays failed to identify the presence of CSPGs. Using the highly negative property of CS chains, a large scale biochemical purification was performed to extract potential candidates from wild type 3rd instar larvae. Following tandem mass spectrometry analysis, only the highly expressed perlecan, troll (HSPG), was isolated. Further experiments involving overexpressed syndecan in Drosophila muscles and treatments with heparinase may increase the chance of CSPG isolation.
Funding Provided by: Sherman Fairchild Foundation (JJ); Paul K. Richter and Evalyn E. Cook Richter Memorial Fund (MM)

Identification of Chondroitin Sulfate Proteoglycans (CSPGs) in Drosophila Melanogaster and Slit as a Possible CSPG.

Lauren Kershberg (2015); Mentor(s): Karl Johnson

Abstract: Chondroitin sulfate proteoglycans (CSPGs) are extracellular matrix molecules involved in several neural processes. CSPGs, a protein core with a specific glycosaminoglycan (GAG) sugar side chain attached, serve as repulsive guidance cues during neuronal cell migration in early development. Furthermore, CSPGs have been implicated in a loss of brain plasticity and in the permanence of spinal cord injury. CSPGs have never been identified in Drosophila despite evidence of their existence. Drosophila possess genes for the enzymes to make CSPGs in their genome. Using immunohistochemistry, we have removed the enzymes required to make CSPGs and have found axon guidance defects at the midline. Therefore, CSPGs appear to function in the neural development of Drosophila. As a secondary project, we have begun to determine whether the critical repulsive axon guidance cue, Slit is chondroitin sulfate modified based on previous bioinformatics studies suggesting it may be.
Funding Provided by: Rose Hills Foundation

The Effect of Cognitive Load on Frameswitching Measured by N400 Brain Activity

Juliah Shay Kim (2016); Student Collaborator(s): Kevin Wei (2015), Goeun Park (2017) ; Mentor(s): Richard Lewis; Sharon Goto

Abstract: Many people who have been exposed to multiple cultures may spontaneously alter their thinking and behavior to match their setting. In social neuroscience, the term for this ability is coined "frameswitching." The aim of this study was to determine if cognitive load had an effect on people's ability to frameswitch. Asian-Americans are generally identified as interdependent and collectivist. Hence, Asian-Americans would show greater N400 brain activity, which measures one's awareness of social incongruity, compared to other populations. However, stress or pressure can alter an individual's ability to frameswitch, also altering N400 activity. We hypothesized that a high cognitive load would affect frameswitching in Asian- Americans while low cognitive load would have less of an effect. Another important factor of this study was priming participants with work setting and family setting. The data collected so far suggests that any amount of cognitive load may affect frameswitching. We hope to further examine this effect in future studies by comparing the effects of different levels of cognitive load in Asian- Americans, Chinese bi-culturals, and European- Americans.
Funding Provided by: Paul K. Richter and Evalyn E. Cook Richter Memorial Fund (JK)

Using fNIRS to study activity of the right temporal parietal junction in response to Theory of Mind task

Amy Ragsdale (2015); Student Collaborator(s): Shannon Burns (2015); Mentor(s): Richard Lewis, Sharon Goto

Abstract: When humans infer the mental states of others in order to better predict and understand another’s behavior, we engage in the cognitive process known as ‘Theory of Mind (ToM) or mentalization. Recognition of false beliefs in others requires a mental representation beyond that involved in processing non-social, physical reality. Therefore, false belief tasks have been used as standard measures of mentalization. Several fMRI studies have demonstrated that the right temporal- parietal junction (rTPJ) plays an important role in false belief recognition and activation of Theory of Mind cognition. Functional near infrared spectroscopy (fNIRS) is an emerging technology to measure brain function. In comparison to fMRI, fNIRS has the advantages of being less costly, less sensitive to movement artifacts, and portable. To date, no study has been published using fNIRS in order to investigate mentalization. We adapted a false belief task (Saxe et al., 2003) and presented it to adult college students. Preliminary results indicate that neural activity in the rTPJ is greater in response to the false belief condition relative to the control condition as measured by fNIRS.
Funding Provided by: Paul K. Richter and Evalyn E. Cook Richter Memorial Fund

Effects of childhood adversity on addiction-related function and circuitry

Julie Fedorko (2016); Additional Collaborator(s): Elliot Stein (NIH - National Institute on Drug Abuse); Mentor(s): Vani Pariyadath (NIH - National Institute on Drug Abuse)

Abstract: Previous studies suggest that childhood exposure to severe or chronic trauma leads to elevated risk of addiction, through alterations in key regions of reward circuitry, such as the striatum. Here, we combined avoidance/approach learning tasks and neuroimaging to explore the effects of adversity on addiction-related reward circuit function among nonsmokers. From our behavioral analysis we find that avoidance learning negatively correlates with childhood adversity in nonsmokers. From our FMRI results we find that adult stress does have an effect on striatal function, while childhood adversity appears to show non-significant effects. Furthermore, activation in the ACC seems to be affected by childhood adversity. These results suggest that, while avoidance learning correlates with childhood adversity, this relationship cannot be attributed to striatal function.
Funding Provided by: National Institute on Drug Abuse, National Institute of Health

Understanding Synapse Rearrangement in the Developing Cerebellum using Serial Section Scanning Electron Microscopy

Jasmine Lopez (2017); Additional Collaborator(s): Alyssa Wilson (Harvard University); Mentor(s): Jeff Lichtman (Harvard Medical School)

Abstract: The brain is the only organ associated with various incurable illnesses such as autism, where it is known that neural connections appear to function incorrectly. Understanding the relation between the structure of the central nervous system and its function may provide better insight about how the healthy brain works and how to fix it when it does not. In our study, we focused on the developing cerebellum, a sub-system of the central nervous system, with a particular interest in understanding synapse rearrangement between purkinje cells and climbing fibers. HYPOTHESIS: Synapse rearrangement in the developing cerebellum may resemble that of other parts of nervous system in which existing literature is present. METHODS: Large blocks of cerebellar tissue from 3-, 5-, and 7-day-old mice (P3, P5, and P7) were reconstructed using serial section scanning electron microscopy (ssSEM). This technique provided the resolution needed to visually distinguish cerebellar ultrastructure. After ssSEM, the data was generated into digital images and automated segmentations. This was followed by the utilization of Mojo (software) for the revision of automated segmentations and identification of synapses. RESULTS: Ongoing study- we need more completed revisions of automated segmentations to acquire an understanding of synapse rearrangement in the cerebellum. CONCLUSIONS: More time is needed to complete the editing of image tissue blocks from P3, P5, and P7 in order to obtain an exact and detailed description of synapse numbers, sizes, positions, and strengths.
Funding Provided by: National Institute of Health (Harvard University); National Institute of Diabetes and Digestive and Kidney Diseases (NIDDK) STEP-UP

Early Internalizing Symptoms Correlated with Later Decreases in Academic Achievement for Boys with ADHD

Warren Szewczyk (2015); Additional Collaborator(s): Elizabeth Owens (University of California, Berkeley); Mentor(s): Megan Norr (University of California, Berkeley)

Abstract: It has been well established that children with ADHD and externalizing problems have poorer academic achievement outcomes than unimpaired peers. The relationship between internalizing symptoms, ADHD, and long-term academic achievement is less well understood. Furthermore, gender differences in ADHD symptomatology and academic achievement have not been well characterized. Here we utilized correlational analysis on a longitudinal sample of 79 boys and 180 girls with ADHD to examine the effect of early internalizing and externalizing symptoms on future math and reading ability. For boys with ADHD, internalizing symptoms in childhood (mean age = 8.25) were negatively correlated with both math and reading achievement ten years later. This trend did not hold for girls with ADHD. These results suggest a need for further exploration of the relationship between internalizing, gender, and academic achievement.
Funding Provided by: Claremont Colleges 5C Neuroscience Fellowship


Serotonin has a context-specific ability to modulate altruistic punishment

Yi Li (2014); Mentor(s): Jorge Barraza; Karl Johnson

Abstract: Serotonin plays a crucial role in facilitating cooperative behavior, but in the case of third party punishment, its effect is heavily context dependent. Recent research suggests that serotonin reduces punishment when the individual is personally harmed, but not when others are harmed. Here, we further investigate how the role of serotonin in cooperative behavior differs depending on the group identification of the individuals involved using an acute tryptophan depletion treatment, minimal group paradigm, ultimatum game, and third party punishment tasks. We found that serotonin modulates punishment of unfair behavior both by reducing punishment of fair behavior and by facilitating punishment of unfair behavior in a context-dependent way. While serotonin did not mediate differential punishment of ingroup and outgroup participants engaging in the same behavior, the effects of serotonin on altruistic punishment were sensitive to group identification: Serotonin reduced punishment of fair offers when members of their own ingroup were involved, but exacerbated punishment of unfair behavior when the sender or receiver was a member of the outgroup. Taken in totality, the results suggest that serotonin’s ability to modulate third-party punishment is context-specific.
Funding Provided by: Paul K. Richter and Evelyn E Cook Richter Memorial Fund; Pomona College Department of Neuroscience

Increased Insular Volume is Associated with a Reduced Future Oriented Time Perspective

Cesia Dominguez Lopez (2014); Mentor(s): Louise Cosand

Abstract: In the past few decades, the insula has become the focus point of investigation for representation of bodily states and is thought to play a role in maintaining addiction, making decisions (based on present vs. future outcomes), and in interoceptive abilities. Notably, lesions to insula have been associated with abrupt cessation of smoking and cravings. The present study examined insular volume in cigarette smokers. Because aberrant decision making in addiction generally favors the present, insula volume was compared with present/future orientation as measured by self-report questionnaire (Zimbardo Time Perspective Iventory; Zimbardo, 1999) in 17 male cigarette smokers. Anatomical region of interest volumes were drawn on structural MRI images for each participant. Insular volume was inversely related to future oriented thinking (r=-.504, p= .039). These results may suggest that larger insular cortices correspond to a sensitivity to present visceral states, such as craving, at the cost of sensitivity to long-term outcomes.
Funding Provided by: Kenneth T. and Eileen L. Norris Foundation

The Role of Copy Number Variation in fbxc-5, an F-box protein, on Food Choice Preference in C. elegans

Patrick Liu (2014); Student Collaborator(s): Lillian Haynes (2013 HMC); Mentor(s): Elizabeth Glater

Abstract: A key question in neuroscience is how genetic and biological variation can ultimately influence behavioral phenotypes. The Glater Lab is currently interested in the genetic and neuronal basis for bacterial food choice preference in C. elegans. Two strains of C. elegans demonstrate a marked difference in their naïve preference for S. marscecens, a pathogenic bacteria, and E. coli. Specifically, the N2 strain shows a strong preference for S. marscecens over E. coli whereas the Hawaiian strain shows a much weaker preference. Through genomic substitution lines, the fbxc-5 genes, a set of F-box proteins which differ in copy number between the N2 (5 copies) and Hawaiian (3 copies) strains, have been implicated in mediating this difference. To study the effect of copy number variation of the fbxc-5 gene on the choice preference between N2 and Hawaiian, we utilize a technique called Mos-1 mediated single copy insertion (MoSCI) (Jorgenson 2008) to introduce a single copy of the fbxc-5 gene into the Hawaiian genome and observe its effects on the worm’s choice behavior. Better understanding of these effects will help us understand the role of genetic variation in mediating difference in food choice behavior.
Funding Provided by: Howard Hughes Medical Institute

Identification of Chondroitin Sulfate Proteoglycans (CSPGs) in Drosophila melanogaster

Kevin Guttenplan (2014); Mentor(s): Karl Johnson

Abstract: Proteoglycans are a class of large, negatively-charged proteins with many sugar side-chain modifications. Heparan Sulfate Proteoglycans (HSPGs) are well characterized in Drosophila and are implicated in nervous system development. Chondroitin Sulfate Proteoglycans, proteins similar to HSPGs but with CS rather than HS sugar side chains, have been identified in animals ranging from humans to C. Elegans. Nevertheless, though CS and HS sugars have identical attachment sites and CS sugars are known to exist in Drosophila, no Drosophila CSPGs have been definitively found. Thus, we sought to identify novel CSPGs in Drosophila.
Funding Provided by: National Science Foundation #IOS-0841551

Characterization and Identification of Chondroitin Sulfate Proteoglycans in Drosophila melanogaster

Lauren Kershberg (2015); Student Collaborator(s): Estela Sanchez (2017); Mentor(s): Karl Johnson

Abstract: Chondroitin sulfate proteoglycans (CSPGs) are sugar modified proteins found in a variety of organisms. They affect neural development and axon growth. However, CSPGs have never been found in Drosophila despite evidence of their existence. The identification of CSPGs in Drosophila would allow for an in depth study of the neural mechanisms of CSPGs. In this two part project, bioinformatics approaches were first used to identify four candidate Drosophila CSPGs in three genes: slit, collagen, and tok. Next, experimental techniques are being utilized to locate, identify, and characterize the CSPGs. These experiments are still in progress.
Funding Provided by: National Science Foundation #IOS-0841551

The Role of DAD in Syndecan Localization at the Drosophila Synapse

Tafadzwa Mtisi (2015); Mentor(s): Karl Johnson

Abstract: The precise regulation of synaptic growth is critical for the proper formation of neural circuits. Previous studies have identified a number of molecular signals involved in the regulation of synaptic growth in the Drosophila neuromuscular junction (NMJ). The heparan sulfate proteoglycans (HSPGs) Syndecan (Sdc) and Dallylike interact with the receptor phosphatase LAR to regulate synaptic development. Sdc is a transmembrane protein with highly conserved cytoplasmic domains about which, little is known. Past Johnson lab students conducted a yeast two-hybrid screen on Drosophila embryonic cDNA to identify potential binding partners for the cytoplasmic domains of Sdc (SdcCD). Among the target interactors was Daughters Against Decapentaplegic (DAD), an inhibitory Smad protein in the decapentaplegic signaling pathway. It was hypothesized that DAD’s Pdz domain binds to Sdc’s C2 EFYA cytoplasmic domain. This research was aimed at identifying the role of DAD in localizing Sdc at Drosophila NMJ synapse. A dose-dependent knockout of DAD was used by means of RNA interference and the temperature sensitive Gal 4 system. We hypothesized that the more time third instar larvae spend at 25°C the more DAD is knocked out and the less Sdc localizes at the synapse. Immunoflorescent images of DAD knockout after 3 days at 25°C showed some Sdc still localized at the synapse. Further imaging and quantifying are yet to be done for larvae with higher dose of DAD knockout under the confocal microscope.
Funding Provided by: Koe Family Fund

The Effect of Hey on Axon Guidance in Drosophila melanogaster

Ryan Randle (2014); Mentor(s): Karl Johnson

Abstract: During the development of the CNS in Drosophila, axons rely on conserved guidance cues in order to innervate their appropriate targets. In a forward genetic screen of the 8941 and 7537 deletions, mutants that cause axons to ectopically cross the midline, we attempted to identify novel contributors to axon guidance at the Drosophila midline. Within these deletions lie the transcription factor Hey, previously described as a target of Notch signaling. The midline defects present in the Heyf06656 loss of function mutant are similar to those found in the genetic screen. In light of this, we hypothesized that Hey may have a novel role in canonical midline crossing during CNS development. In order to determine whether Hey was a novel contributor to axon guidance at the Drosophila midline, we scored stage 17 embryos for the number of midline crossing defects (ectopic crossings) in crosses between these mutants, and assayed for the distribution of key guidance molecules. Statistical analysis of the number of defects between each cross showed that Hey indeed is responsible for the defects seen in the screen. However, due to the presence of both Slit and Robo, it is unlikely the defects are accomplished through some previously uncharacterized interaction between Hey and these two guidance molecules. We concluded that it is likely the defects are caused by Hey's role as a target of notch delta signaling. Specifically, the Hey mutant acts to suppress asymmetric differentiation of midline glial cells. Continuing this research may confirm Hey's indirect effect on axon guidance.
Funding Provided by: Fletcher Jones Foundation

Environmental Enrichment Restores Chronic Mild Stress Induced Impairments in Synaptic Plasticity but not Behavior

Hannah DeWeerth (2014); Student Collaborator(s): Jenny He (2014); Yuni Kay (2015); Mentor(s): Jonathan King

Abstract: Stress and depression have a profound effect on cognitive performance. Chronic mild stress (CMS), a series of unpredictable mild stressors, has been shown to induce depressive-like behaviors and impair synaptic plasticity. Environmental enrichment (EE) has been shown to rescue depressive-like behaviors, enhance plasticity and promote neurogenesis. In the current study, we examined whether EE could counteract impairments caused by stress. Rats were subjected to 5 weeks of CMS or assigned as control rats and divided into EE or non-EE conditions. The forced swim test (FST) and the novelty suppressed feeding test (NSF) were used to assess the effects of CMS and EE on behavior. Anhedonia was measured by sucrose preference. Electrophysiological recordings from hippocampal slices were used to examine differences in synaptic plasticity as measured by long-term potentiation (LTP). Our results show that CMS had an effect on food consumption as measured by the NSF test. Rats that were subjected to CMS and EE together showed a higher level of LTP than rats subjected to CMS alone. These data show that EE facilitated recovery of CMS induced impairments in synaptic plasticity. Other parameters measured by the FST and NSF tests were not sensitive enough to detect differences using this paradigm. This study provides evidence that chronic mild stress and environmental enrichment may modulate similar circuits in the brain that affect synaptic plasticity and EE may be beneficial for cognitive function.
Funding Provided by: Paul K. Richter and Evelyn E. Cook Richter Memorial Fund

Gender Identity, Sexual Orientation and the Prenatal Androgen Theory: Re-evaluating definitions, cognitive tests and somatic markers

Zachary Schudson (2013); Student Collaborator(s): Alexis Takahashi (2013); Zoey Martin-Lockhart (2014 PIT); Mentor(s): Rachel Levin

Abstract withheld upon request.
Funding Provided by: Rose Hills Foundation

Neuroplasticity-based cognitive training in schizophrenia: predicting patient responses using a neurological marker

Sean T. Pianka (2014); Additional Collaborator(s): Gregory A. Light (University of California, San Diego); Veronica B. Perez (University of California, San Diego); Mentor(s): Richard Lewis

Abstract: Prevailing pharmacologic treatment paradigms do little to address the neurocognitive deficits in memory, attention, and verbal information processing experienced by a majority of schizophrenia (SZ) patients. Recent studies show that neuroplasticity¬based, procognitive training interventions targeting early perceptual processes may help to ameliorate neurocognitive deficits in some SZ patients. Neurological biomarkers capable of predicting individual patient responses to procognitive training are needed to hone and efficiently implement these resource-intensive treatment protocols. The current study in a cohort of 22 SZ patients utilizes EEG and computational analyses to investigate the effects of a single dose of Targeted Cognitive Training (TCT) on an electrophysiological biomarker known as mismatch negativity (MMN). TCT is a neuroplasticity-based, procognitive training intervention designed to improve auditory information processing. MMN is an automatic, preattentive neurological response to deviant auditory stimuli presented amid a sequence of standard tones. Patterned changes in MMN response may serve as a dynamic index of auditory system neuroplasticity. MMN responses to several deviant stimuli were collected before and after a 1.5-hour session of TCT. Preliminary findings suggest that greater improvements in TCT performance correspond with enhanced MMN responses. Studies further elucidating the efficacy of MMN as a predictive biomarker for patient responses to TCT are currently under way.
Funding Provided by: Claremont Colleges Summer Research Fellowships in Neuroscience

Comparing Neurofibrillary Tangles in Alzheimer's Disease and Progressive Supranuclear Palsy

Alexandria (Ali) Valdrighi (2015); Mentor(s): Izumi Maezawa (UC Davis -Department of Pathology)

Abstract: Alzheimer’s disease is a prevalent neurodegenerative disorder in the United States affecting approximately 5.5 million Americans. Neurofibrillary tangles are a hallmark of Alzheimer’s disease created by hyperphosphorylation of 3R and 4R tau isoforms. Neurofibrillary tangles are also observed in the neurodegenerative disorder Progressive Supranuclear Palsy (PSP), but PSP is only associated with 4R tauopathies. Superresolution Microscopy is a newly developed microscopy technique that is able to resolve images at approximately 100 nm resolution. It can be used to generate detailed, 3D images of neurofibrillary tangles which offer clues to their structures. Superresolution microscopy can be used to image Alzheimer’s and PSP tangles. It is anticipated that the shapes can then be compared to develop a quantitative method of distinguishing the two types of tangles. Distinguishing the tangles quantitatively would allow post-mortem diagnosis of Alzheimer’s and PSP which would be beneficial in clinical research. It may also illuminate structural differences between 3R and 4R tauopathies. Alzheimer’s tangles were observed to have a greater curvature than PSP tangles. Alzheimer’s tangles were also more prevalent in the hippocampus and larger than PSP tangles. A quantitative method to distinguish the shapes of these tangles would need to be developed and statistically validated to apply these findings to the broader research setting.
Funding Provided by: Edmonson Fellowship Program (UC Davis-Health System)

Dopamine receptor 1 neurons mediate food timing on circadian time scales

Emily Meyer (2014); Student Collaborator(s): Mari Purpura (2015 PIT); Christina Chang (2016 CMC); Catherine Chiang (2016 SCR); Mentor(s): Andrew Steele (W.M. Keck Science Center of The Claremont Colleges)

Abstract: Mice, like humans, have a built-in timekeeping system – or circadian rhythm – that revolves around a 24-hour day. This system is dependent on light:dark cycles but also on feeding schedule. When fed a calorie-restricted diet consisting of one meal at the same time each day, mice show abnormally high activity for two to three hours before that meal. This behavior is commonly referred to as food anticipatory activity (FAA). In mice with genetically removed dopamine receptor 1 (D1R), this entrainment to scheduled feeding does not occur, indicating that dopamine is involved in the development of FAA. This summer, the relationship between dopamine and FAA will be further examined by both activating and blocking D1R receptors pharmacologically instead of genetically. Additionally, brain and tissue samples from D1R knockout mice will be investigated for signs of circadian rhythm entrainment. These studies may shed light on aberrant feeding behaviors in humans.
Funding Provided by: Howard Hughes Medical Institute; W.M. Keck Science Center of The Claremont Colleges; Claremont McKenna College

M1 and M2 genes in drosophila hemocytes: what are they doing?

Jennifer Chai (2015); Mentor(s): Junryo Watanabe

Abstract: Macrophages are professional phagocytes of the mammalian immune system, and they adjust their surface receptors as well as their secreted products in response to the environmental cues and local stimuli. Classically activated macrophages, or M1 macrophages, perform anti-microbial functions and secrete proinflammatory cytokines. In contrast, alternatively activated macrophages, or M2 macrophages, are involved in mechanisms such as tissue regeneration and release anti-inflammatory / cytokines. Macrophage-mediated clearance of apoptotic debris is crucial for regeneration of peripheral nervous system after injury. It is hypothesized that M2 macrophages are mediating this clearance much in the same way M2 macrophages aid in the repair and regeneration in muscle and liver organs. In Drosophila, hemocytes act as professional phagocytes, and they are responsible for disposal of all apoptotic and pathogenic microorganisms. The mechanism by which hemocytes recognize and engulf apoptotic debris is poorly understood and whether a similar or parallel M1/M2 phenotype exists in fly hemocytes is currently unknown. However, several genes, such as draper and croquemort, have been identified as been required for phagocytosis of apoptotic cells. Thus, it is hypothesized that hemocytes from M2 deficient flies can phagocytose pathogens but not apoptotic debris, and the reverse should hold for M1 gene deficient hemocytes. Here we investigate similarities and differences between signaling in mammalian M1 macrophages and hemocytes exposed to Escherichia coli using genomic and in vitro systems.
Funding Provided by: Pomona College SURP

Stress Reactivity and Depressive Symptomatology

Nicholas Lawson (2014); Student Collaborator(s): Stephanie Njau; (2014) Additional Collaborator(s): Roxanna Salim; Mentor(s): Nicole Weekes; Richard Lewis

Abstract: The purpose of this study was to investigate the relationship between depressive symptomatology and shifts in prefrontal asymmetry in response to a stressor. There is an abundance of evidence to suggest that individuals who have experienced high levels of childhood trauma and those who have experienced an accumulation of stressors are at higher risk for developing depression. Furthermore, there is evidence to suggest that a combination of higher stressor exposure and greater stress reactivity interact in producing higher risk of depression, such that individuals who are exposed to the highest levels of stressors and respond to such stressors with the highest levels of stress reactivity will experience the highest levels of risk. 75 subjects (15 of which were tested in the summer of 2013) have been tested. Each subject was exposed to a stressor protocol and had stress reactivity measures assessed before and after the stressor. Subjects also provided information about their levels of depressive symptomatology. Subjects testing will continue through the 2013-2014 academic year. We predict that those individuals who respond to a stressor with greater shifts toward right prefrontal activity will be at greater risk for depression. Research ongoing.
Funding Provided by: Rose Hills Foundation