Tomorrow's Health, Today's Research

Trainees in Biomedical Research Seminar Series Abstracts

 17 Feb 2014
Trevor Barss,
School of Exercise Science, Physical & Health Education
“Amplification of interlimb reflexes evoked by stimulating the hand simultaneously with conditioning from the foot during locomotion”
The common ancestor of the salmonids is thought to have undergone a whole-genome duplication event approximately 65 million years ago, resulting in an unstable tetraploid genome that has gradually reverted to a pseudo-diploid state in most salmonid species.  I am interested in examining the interaction between the whole-genome duplication event and a massive proliferation of transposable element DNA sequences that occurred in the same time period.  This proliferation has contributed to at least 55% of the Atlantic salmon genome being composed of transposable element sequences.  Both transposable elements and whole-genome duplications are important evolutionary forces; they each contribute to the development of novel gene functions, signaling network restructuring and genomic reorganization.  I hypothesize that these two processes have contributed to the stabilization of the salmonid genome following the whole-genome duplication as well as to the resulting rapid speciation of the salmonid lineage.  In this talk I will discuss how I am investigating this hypothesis using high-performance computing systems, phylogenetics and other bioinformatics tools.

20 January 2014
David Minkley, Department of Biology
Transposable element proliferation and the salmonid whole-genome duplication

The common ancestor of the salmonids is thought to have undergone a whole-genome duplication event approximately 65 million years ago, resulting in an unstable tetraploid genome that has gradually reverted to a pseudo-diploid state in most salmonid species.  I am interested in examining the interaction between the whole-genome duplication event and a massive proliferation of transposable element DNA sequences that occurred in the same time period.  This proliferation has contributed to at least 55% of the Atlantic salmon genome being composed of transposable element sequences.  Both transposable elements and whole-genome duplications are important evolutionary forces; they each contribute to the development of novel gene functions, signaling network restructuring and genomic reorganization.  I hypothesize that these two processes have contributed to the stabilization of the salmonid genome following the whole-genome duplication as well as to the resulting rapid speciation of the salmonid lineage.  In this talk I will discuss how I am investigating this hypothesis using high-performance computing systems, phylogenetics and other bioinformatics tools.

25 November 2013
Jordan Poley, Molecular Genetics, Atlantic Veterinary College, Prince Edward Island University
"Molecular pathways involved in sea lice (Lepeophtheirus salmonis) resistance to chemotherapeutants commonly used in aquaculture."

Sea lice (Lepeophtheirus salmonis) are an ectoparasitic copepod affecting salmonid aquaculture in Canada, Norway, Scotland and the United Kingdom.  They impose a financial burden of close to $500 million per year, feeding on the blood, mucus and skin of salmonids causing severe skin lesions, increased stress, and mortality. The aquaculture industry depends on a limited number of chemotherapeutants for sea lice control which has led to overuse, and consequently problems with drug resistance. An effective pesticide, emamectin benzoate (EMB; SLICE®) was widely used until resistant strains of the lice developed, causing the treatment to be administered in triple-dose formulations or, in some cases, abandoned completely. The objectives of this study were to identify molecular mechanisms involved or associated with EMB-resistance and to characterize these mechanisms using a series of in vitro and in vivo trials.  Quantitative polymerase chain reaction (qPCR) was used to compare differential gene expression between genders, life stages, drug concentrations, and populations using genes of interest targeting drug metabolism, xenobiotic transport, chemical stress, immunity, and ligand-gated receptors. EC50 values (half maximal effective concentration) were calculated for all populations assayed in vitro while infection levels were monitored for all sampling times in the in vivo trials. Trends in the present study suggest a concentration threshold may exist whereby minimum doses of EMB are required for pathway stimulation.  Other pathways however are down-regulated in response to the drug, suggesting potential trade-off mechanisms. These findings have characterized general mechanisms in sea lice when exposed to EMB, showing a diverse range of EMB responses which are highly dependent on a population’s EMB sensitivity.

04 November 2013
Amy Montgomery, Department of Mechanical Engineering
"Neural Differentiation Of Induced Pluripotent Stem Cells In 3d Matrices."

Our laboratory investigates the behavior of induced pluripotent stem cells inside of 3D fibrin scaffolds. Fibrin is a natural protein-based biomaterial commonly used for tissue engineering applications. We are interested  in optimizing the production of neurons from induced pluripotent stem cells in these 3D fibrin scaffolds, specifically focussing on differentiation protocols  involving chemical and physical cues. This is part of ongoing work to develop efficient and reproducible protocols for the engineering of neural tissue for spinal cord injury treatment.

21 October 2013
Kevin Daze, Department of Chemistry
"Chemical tools that probe protein-protein interactions important in epigenetic pathways."

Lysine can exist in three different methylation states and each triggers a unique protein-protein interaction. Increasingly these interactions are being implicated as factors in the increased proliferation and invasiveness of numerous cancers.  My research focuses on chemical inhibitors of this interaction. Through the synthesis of antagonists that disrupt both sides of this important protein-protein interaction we hope to better understand this important cancer pathway.

30 September 2013
Graham Garnett, Department of Chemistry

"Small molecule hosts as enrichment reagents for post-translationally modified proteins."

The N-terminal tails of histones, the core protein component of the nucelosome, are frequently decorated with post translational modifications. The biological relevance of these kinds of N-terminal modifications, especially lysine methylation and acetylation, as epigenetic regulatory signals has been the subject of much recent research. Calixarenes are small molecule macrocycles that have been known to form host-guest complexes with various cationic species. Recently, research in the Hof lab at UVic has shown that a class of sulfonated calix[4]arenes are effective discriminators of post translationally modified amino acids, especially lysine and its methylation states.
Immobilization of these calix[4]arenes onto a solid matrix provides a reagent suitable for the enrichment of proteins bearing post-translational modifications.

16 September 2013
Taryn Klarner, School of Exercise Science, Physical & Health Education
“More Connected than your Social Network: Communicative Pathways of the Nervous System”

While the brain is the body’s command center, connections within the spinal cord control rhythmic activities like walking. The brain contributes to such movements, but spinal cord circuits can coordinate muscle activity on their own, relying on feedback from moving limbs to regulate the pattern. When these connections are lost or altered due to injury to the brain or spinal cord, movement in the arms and legs may be greatly reduced depending on the location and severity of the injury. A major focus of the research in the Rehabilitation Neuroscience Laboratory is on understanding how coordinated muscle activity in arms and legs can be improved after neurotrauma. Studies are conducted in participants who are neurologically intact as well as with individuals who have had strokes or spinal cord injuries to determine the extent to which enhanced sensory feedback techniques can retrain spinal cord circuits and improve limb coordination. Additionally projects aimed at examining targeted, training induced plastic adaptation of function after neurotrauma are ongoing. New knowledge gained from this research may lead to more effective methods of improving motor coordination following brain or spinal cord injury. These therapies could be used to help improve walking recovery after neurotrauma.

17 June 2013
Sammy Weiser-Novak, Division of Medical Sciences, Neuroscience Program
" Effects of prenatal ethanol exposure on dentate gyrus ultrastructure”

The brain is composed of many billions of neurons that are connected through trillions of discrete biochemical and electrical connections – synapses. Dendritic spines are nanoscopic membrane protrusions studding neuronal dendritic arbours, much like buds on the branches of trees, which serve as the loci of about 90% of the excitatory synapses in the brain. As the first postsynaptic elements encountered by excitatory neurotransmitters, dendritic spines represent the earliest sites of signal integration for a given neuron.

Synapses in the rat hippocampus are integral in learning and memory functions including the formation of spatial memories and pattern discrimination. In rodent models of prenatal ethanol exposure (PNEE) – an experimental emulation of the teratogenic conditions responsible for fetal alcohol spectrum disorders – behavioural and functional deficits have been reported extensively. However, the structural and ultrastructural substrates of these changes have not been adequately addressed in the literature. Furthermore, a variety of dendritic spine morphological pathologies have been reported in diseases associated with behavioural and functional deficits similar to those observed in animals treated with PNEE. In order to better understand the structural substrate of the functional and behavioural pathologies, electron microscopic investigations of ultrastructural changes to the hippocampus associated with PNEE are performed with special attention given to the dentate gyrus (DG) subregion, remarkable in both its capacity for the brain plasticity phenomena of long term potentiation and depression and as a locus of adult neurogenesis.

Preliminary results suggest that PNEE treated rats may have fewer synapses and spines, which may underlie the functional and  behavioural deficits observed in living animals. Abnormal ultrastructure may be indicative of etiopathophysiology, which in turn may provide the basic science required to inform clinical approaches and advances in remedial treatments.

 

15 May 2013
Sara Tabet, Department of Chemistry
"Supramolecular hosts that bind methylated lysines: new assays and structure-function relationships"

Covalent modifications on the amino-terminal tails of histones are important epigenetic marks that participate in many gene regulation pathways. Methylation of lysine 27 on histone 3 causes gene repression, and is a marker for transcriptionally silent regions of chromatin. My research focuses on a family of supramolecular hosts that bind methyllysine residues in a variety of structural contexts. We have created a diverse set of structural analogs in order to explore their ability to bind selectively to different methylated residues in different structural contexts. To study their affinities and selectivities, I have developed a new, high-throughput dye-displacement assay that measures the binding of multiple methylated peptides to a collection of synthetic receptors. This new 96-well format binding assay requires a very small amount of sample relative to NMR determinations, and has allowed a rapid buildup of data on structure-function relationships that would not be possible with traditional one-at-a-time determinations of association constants.

06 May 2013
Akina Umemoto, Department of Psychology

"An electrophysiological (event-related potential, ERP) study of reward processing in children with Attention Deficit Hyperactivity Disorder".

 Increasing evidence from the behavioral, genetic, and neurophysiological study suggest that an abnormality in the midbrain dopamine system underlies Attention Deficit Hyperactivity Disorder (ADHD). A previous study in our laboratory found that children with ADHD showed increased sensitivity to the salience of reward (i.e., monetary acquisition) as observed in an electrophysiological measure (event-related potentials, ERPs) of reward processing, which was not the case in typically developing children (Holroyd, Baker, Kerns, & Mueller, 2008). However there were shortcomings that needed to be addressed. Our goal in the current study was to replicate and expand the previous study using ERPs recorded at the scalp from typically developing children and children with ADHD while they were engaged in a simple reinforcement task. This task involved children to navigate a “virtual T-Maze” in two reward conditions that differed on reward saliency. By examining an ERP component that is sensitive to reward processing believed to reflect the impact of the midbrain dopamine system, we show that children with ADHD performed similarly to their typically developing counterparts when they were receiving salient reward (i.e., monetary bonus). However, when working to receive less salient reward (i.e., points), children with ADHD showed reduced reward activity compared to children in the control group. Consistent with our hypothesis, our results suggest an altered midbrain dopamine system underlying ADHD, and that children with ADHD are unusually sensitive to the salience of reward.

15 April 2013
Connor O'Sullivan, Department of Biochemistry and Microbiology

"Ars2 as a Critical Factor for Myogenic Progenitor Proliferation and Differentiation"

 Ars2 is an essential gene required for early embryonic development in mice. Our group has shown that Ars2 -/- embryos die peri-implantation, shortly after the formation of epiblast and trophoblast lineages. Recent work by others has implicated Ars2 in the disparate functions of miRNA biogenesis and replication-dependent histone mRNA processing.  Within the miRNA biogenesis pathway, Ars2 has been shown to interact with Drosha and help stabilize pri-miRNA. For processing replication-dependent histone transcripts, Ars2 has been shown to interact with FLASH, a protein critical for the endonucleolytic cleavage of histone pre-mRNAs during S phase. This raises the question: Which functions of Ars2 are necessary for early embryonic development?  

To address this question, we have been comparing the phenotypic contributions of Ars2, Drosha, and FLASH to the proliferation and differentiation of myoblast cells using RNAi and dominant negative expression studies.  We have found that Ars2 is necessary for the proliferation and differentiation of myogenic progenitors. Specifically, knockdown or overexpression of Ars2 perturbs myoblast progenitor cell cycle progression, formation of differentiated myotubes, and the biogenesis of miRNAs essential for myogenesis. Interestingly, Ars2 knockdown or overexpression phenocopies Drosha, but not FLASH knockdown, indicating that Ars2’s requirement for myogenesis is dependent on its role in miRNA biogenesis and independent of its role in histone transcript processing. Finally, overexpression of Ars2 point mutants has demonstrated that residues within the Zn Finger and RNA Recognition Motif are required for the biogenesis of specific miRNAs, as well as progression through the cell cycle.

18 March 2013
Andrew Boyce, Neuroscience
"Stroke alters large-pore Pannexin-1 channel localization: Implications for neural cell viability?"

“Pannexin-1 (Panx1) is a large pore ion and metabolite-permeable channel. It is expressed abundantly in the brain and has received considerable attention in molecular stroke research. Panx1 is activated by elevated extracellular potassium and oxygen-glucose deprivation (OGD), stimuli that are present in the post-stroke brain. Current models point primarily to a role for plasma membrane Panx1 and ATP release in mediating neuron vulnerability to these stimuli. However, we recently identified intracellular expression of Panx1 in a large proportion of cells in the peri-infarct region following stroke. Our preliminary data from cellular fractionation with complementary immuno-electron microscopy and live cell and fixed cell confocal microscopy suggest that this increase in Panx1 expression is occurring predominantly at the nucleus, a novel localization for this well-characterized plasma membrane protein. As previous evidence has shown that the ionic permeability is sensitive to changes in ATP concentration and membrane potential, phenomena associated with Panx1 activation. We hypothesize that upregulation of Panx1 nuclear trafficking in response to post-stroke stimuli may provide a mechanism to enhance neuronal survival, in two cooperative ways: (1) through a decrease in plasma membrane Panx1-mediated ATP release and calcium influx at the plasma membrane, reducing anoxic depolarization; and (2) through the elevation of nuclear calcium concentrations allowing for an increase in a well-characterized form of activity-sensitive, calcium-CREB-CBP-dependent gene repression, linked to increased long-term plasticity and neuronal survival.”

21 February 2013
Ralph McWhinnie, Department of Biochemistry & Microbiology
“Transcription control in prokaryotes: creating synthetic promoters”

"Control of gene expression at the transcriptional level is an important tool in molecular and synthetic biology. Many promoter-repressor systems are known in model organisms, such as E. coli, but these are often not functional in other bacterial species due to differences in transcriptional machinery. Here I describe a method for the selection of promoters that function in the intracellular pathogen, Francisella tularensis from a library of semi-random DNA sequence. Promoters are created by ligating a mixture of synthetic DNA fragments, consisting of the tetracycline operator flanked by random sequence, into an expression plasmid upstream of a chloramphenicol (Cm) resistance gene. Clones that survive on Cm have received a functional promoter. Promoters identified in this way are tested for controlled expression in a Francisella host that expresses the tetracycline repressor (TetR).Twenty promoters of various strengths and capacity for repression were chosen to be measured quantitatively, sequenced, and have their transcription start sites determined. I will describe the properties of these synthetic genetic control elements and how they will serve as tools to study the molecular mechanisms of pathogenicity in Francisella. More generally, this method could allow for the development promoters of various transcriptional strengths, with binding sites for various transcription factors, in various organisms of potential biotechnological importance, but for which genetic control elements are underdeveloped.

 07 February 2013
Ben Sutherland, Department of Biology
"Sea lice and salmon - using gene expression to understand parasite stress and host susceptibility"

Sea lice Lepeophtheirus salmonis infections of farmed salmon continue to be a burden for the salmon aquaculture industry through both direct harvest losses and treatment costs, and due to potential negative consequences for wild salmon being infected by increased numbers of lice spread from farms. The recent development of genomic tools for salmon and sea lice have allowed for the investigation of several components of both sides of this host-parasite interaction. First, the transcriptomic responses of the free-swimming louse to acute changes in environmental temperature and salinity have increased our understanding of this copepods cellular stress response. Second, the characterization of the transcriptomic responses of three closely related Pacific and Atlantic salmon species begins to elucidate the wide variation in the susceptibility of hosts to the infection.

06 December 2012
Nima Khadem Mohtaram, Department of Mechanical Engineering
"Development of Micro and Nano-structured Neural Tissue Engineering Scaffolds"

This work focuses on developing micro and nano-structured biomaterial scaffolds to replicate the neural tissue found in the spinal cord. Poly (-caprolactone) (PCL) microspheres and electrospun PCL nanofibers were fabricated to serve as biocompatible and biodegradable drug delivery systems and tissue engineered scaffolds respectively.  PCL microspheres serve as a novel drug delivery system to control the release of protein molecules that promote neural tissue repair. The PCL nanofiber scaffolds can serve as substrates for stem cell cultures. We hypothesized that electrospun PCL fibers can promote induced pluripotent stem cell (iPS) differentiation into the desired neural phenotypes through their nanostructure.

22 November 2012
Leigh Wicki-Stordeur, Neuroscience 
"Pannexin 1 regulates stem cells within the brain"

In a region of the postnatal brain called the ventricular zone (VZ), multipotent neural stem and progenitor cells (NSC/NPCs) continually generate new olfactory bulb neurons, via a multi-step, highly regulated process called neurogenesis. This process is essential for the development of social memories and behaviours and also plays an important role in brain repair following injury. The cell behaviours associated with neurogenesis include proliferation, differentiation, migration and maturation. Although the mechanisms driving progression through these cellular stages are still poorly understood, there is growing consensus that ion channels play a vital role through regulating ion and metabolite fluxes. Furthermore, evidence is emerging to support channel-independent signaling effects by anchoring multiprotein complexes at sub-membrane domains. My work has recently revealed that pannexin 1 (Panx1), a large-pore ion and metabolite permeable channel, is a key regulator of NSC/NPCs. I discovered Panx1 expression in postnatal VZ NSC/NPCs, and demonstrated its role in the positive regulation of proliferation of these cells in part through mediating the release of ATP, an important regulator of NSC/NPC proliferation. Furthermore, I have new evidence for a role of Panx1 in NSC/NPC differentiation. Panx1 activity appears to be necessary to keep these cells active within the cell cycle and thereby avoid differentiation. As NSC/NPCs are highly responsive to neurological injury and disease, and are gaining attention as putative targets for brain repair, understanding the fundamental role of Panx1 channels in their regulation is of critical importance for brain health and disease.

01 November 2012
Oliver Krupke, Department of Biochemistry/Microbiology
"Regulating cell shape change in the developing embryo"

Early in embryonic development, sea urchin embryos form a specialized region of ectoderm, the ciliary band.  This continuous strip 4-5 cells wide forms a raised ridge encircling the oral ectoderm and functions as the principal swimming and feeding organ of the larva.  Cells of this region are elongated with a narrow apical end bearing a single cilium and occur as a simple sheet of epithelial cells overlying a basement membrane.  During its differentiation, a dramatic and coordinated apical constriction occurs in all cells of the ciliary band.  Inhibiting actomyosin contractility prevents this constriction and blocks ciliary band formation.  Apical constriction of these cells is also perturbed in the absence of Ephrin forward signaling through Eph and knocking down expression of either Eph or Efn or inhibiting Eph kinase function results in a significant reduction in apical constriction.  This shape change appears to depend on phosphorylation of focal adhesion kinase that requires Ephrin signaling through Eph.  Concomitant with this cell shape change is an outward buckling of the entire cell sheet to form a ridge that becomes the ciliary band.  This contrasts starkly to widely studied models where apical constriction results in an inward buckling of a cell sheet.  We hypothesize that apical constriction is not the principle force underlying shape change in the cell sheet that forms the ciliary band.  We further hypothesize that this change in cell shape is controlled in part by forward signaling by Ephrin through Eph.  The simplicity of this system provides an excellent model to study the contribution of apical constriction to cell shape change.