Anas Abou-Ismail |
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Research Advisor & Department
Robert Thorne
Name of Project:
The Effect of Drop Characteristics on the Parameters of Protein Crystals
Abstract:
Identifying protein structure is critical to understanding its function and manipulating its behavior. One way to determine protein structure is to crystallize the protein, subject the crystals to x-ray, and then use the x-ray diffraction patterns to determine its electron map and atomic structure. A key step in this procedure is to obtain suitable crystals of the protein. In my lab, we fabricated micro-patterns that can hold drops of various parameters. The goal of my research project is to study the impact of changing these parameters on the properties of lysozyme crystals. Then we will identify the drop characteristics that produce desirable crystals. A key variable in our study is the surface area to volume ratio of the drops and how it affects evaporation and crystallization. So far we have identified the correlation between drop radius and the number of crystals per drop and the time required for the initial nucleation. Other factors are being investigated. Inthe long run this project will help determine the stucture of various proteins crucial to biology, medicine, and evolution.
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Anas Ahmad |
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Research Advisor & Department
Pat Rivlin
Name of Project:
Characterization of two genes that suppressor the oxidative stress resistance in Drosophila ether-a-go-go shaker double mutants.
Abstract:
Oxidative stress is thought to be the main cause of ageing and death. We are going to be conducting a screen for certain genes that expresses themselves in neurons and thought to decrease oxidative stress sensitivity in drosophila. In my lab, 17 genes have been characterized so far. We will be working in another two, lola and CH6751. While lola is known to encode for a transcription factor, CG6751 is thought to encode for an RNA polymerase active protein. In our study, we will be using potassium channels mutant drosophila. These mutants, carrying ethe-a-go-go and shaker mutations, have an impaired A-type potassium current, and high sensitivity to stimuli and most importantly oxidative stress. We will obtain flies that carry the potassium channel mutations along side one of the two genes being either over or misexpressed using Gal4/ UAS we will selectivily express one of the two genes to be studied in the potassium channels mutants and characterize how the misexpression of these genes alters the neural development and oxidative stress sensitivity. This study is particulary important because high oxidative stress sensitivity is the cause of certain neurodegenerative diseases in humans such as Alzheimer and Parkinsons disease.
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Mohammed Al-Hijji |
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Research Advisor & Department
Chip Aquadro
Name of Project:
An investigation of Positive Selection in the mei-p26 loci of Drosophila melanogaster and Drosophila simulans
Abstract:
Germline stem cells (GSCs) are special kind of stem cells; they are capable of self-renewal and asymmetric cell division and differentiation to give cystoblast cells, precursor of oocytes and nurse cells, in females and gonialblast cells, precursor of spermatids, in males. Cystoblast cells undergo four rounds of mitotic divisions to give rise to a 16-cell cyst where one of the cells will undergo meiosis and become an oocyte and the others will become nurse cells. Like cystoblast cells, gonialblast cells give rise to 16-cell cyst; however, all of those cells will undergo meiosis and end up producing spermatids. The process of self-renewal and differentiation of GSCs is controlled by many genes including bag of marbles (bam) and bengin gonial cell neoplasm (bgcn). When they are expressed, Bam and Bgcn initiate GSCs differentiation to cystoblast cells in females and to gonialblast cells in males. Recent discoveries show evidence of positive selection in the bam and bgcn genes of Drosophila melanogaster and Drosophila simulans. Statistical tests based on synonymous and non-synonymous polymorphism and divergence data showed deviation from neutrality, leading to a conclusion that this deviation is the result of non-synonymous fixation. To understand the evolution of the genes controlling the GSC differentiation, we will continue the survey on other genes that are involved in GSC renewal and differentiation and we will try to find evidence of positive selection. The first gene of focus is the mei-p26 locus. Like Bam, Mei-P26 has important role in GSCs differentiation. In addition to that, it helps regulate the frequency of exchange during the process of meiotic exchange. We will sequence mei-p26 in Zimbabwe population of D. melanogaster and we will test for positive selection using this polymorphism and also divergence data from D.simulans. By identifying mei-p26 or other genes GSC related genes that are undergoing positive selection, this may lead us toward determining the force of selection in this system.
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Brett Alcott |
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Research Advisor & Department
Rick Cerione - Molecular Medicine
Name of Project:
Characterizing the role of Tissue Transglutaminase in Epidermal Growth Factor-mediated migration and invasion of human cancer cell lines
Abstract:
The goal of my research project is to further elucidate the role tissue transglutaminase (TGase) plays in epidermal growth factor (EGF)-mediated migration and invasion of human cancer cell lines. EGF is a well-established oncogenic factor - yet the exact mechanisms by which EGF-coupled signaling events cause cancer progression are not fully understood. We have recently reported the novel finding that TGase, a GTP-binding protein (G-protein) with enzymatic transamidation activity, is potently activated by EGF in several human cancer cell lines, and that this activation of TGase promotes chemoresistance.
As a continuation of the work linking TGase to cancer, our laboratory has set out to determine whether EGF-induced TGase activity has a role (or roles) in oncogenesis. Other than promoting chemosresistance, we have found that EGF-induced TGase activation in the HeLa cervical carcinoma cell line was accompanied with a translocation of TGase to the leading edge of the plasma membrane. We followed up this observation and showed that in cell migration assays, TGase was recruited to the leading edge portion of the plasma membrane in response to EGF, and that the EGF-stimulated migration of HeLa cells could be compromised by blocking TGase activation. Taken together, these data indicate for the first time that TGase plays an important role in regulating EGF-mediated cell motility in human cancer cells.
While taking part in several aspects of the research outlined above, I became interested in trying to determine how EGF causes TGase to translocate to the plasma membrane. To answer this question, I started to perform immunoprecipitations of lysates from EGF-treated HeLa cells. Consistent immunoprecipitation results (phosphorylated protein bands associating exclusively with TGase) showed TGase may interact with several other proteins downstream of its activation/mobilization by EGF, including FAK (Focal Adhesion Kinase) and cool-2/Beta-pix. FAK in particular presents an interesting target, as it has been linked to the ability of cancer cells to form focal adhesions - membrane-ECM junctions which enable these cells to initiate coordinated intracellular actions such as migration. Protein co-localization studies, investigating the relative distributions of TG, FAK, cool and other identified partners will be critical to further understanding the range of interactions present in this system.
Immunoprecipitation and immunofluorescent studies will be coupled with cytological activity assays to better understand the relation of these protein-protein interactions to cell morphological and biochemical-functional changes. In-vitro assays with pure protein samples will also be performed to determine the extent and nature of the FAK/TGase/cool interaction(s). Once potential binding partners are determined, mutations and vector cloning/expression techniques will be used to definitively identify protein binding/interaction sites between TG and its partners in the proposed signaling scheme.
Identifying binding partners of TGase, determining their binding sites and, eventually, their broader effects on cancer cell motility and invasion capabilities represents an important effort towards better understanding how cancer works from a molecular perspective.
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Michael Avery |
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Research Advisor & Department
Linda Rayor - Entomology
Name of Project:
Chemical Communication and Colony Identity in a Social Australian Huntsman Spider: Delena cancerides
Abstract:
The vast majority of spider species are both solitary and cannibalistic. However, sociality among spiders has evolved in disparate families and in very different environments. Delena cancerides, an Australian social huntsman spider, lives in large, outbred colonies on the vertical surfaces between tree trunks and peeling bark. Individuals in laboratory colonies generally coexist peacefully, tend to aggregate, and share prey with infrequent instances of intraspecific aggression or cannibalism. Such a community confers major benefits to the participating individuals: postponing or eliminating dispersal from the protective retreat decreases mortality rate, while cooperative prey capture and sharing allow for more and larger prey items to be available for consumption by colony members than would be to similarly sized solitary spiders.
There is evidence from previous olfactory and introduction experiments performed in the lab that suggest that colony members can differentiate between individuals from their own and alien colonies, and that aggression occurs more frequently toward alien spiders. Additionally, the aggression observed in introductions involving aliens is context dependent, suggesting that colony demography and the character of the individual alien spider are important in determining the reaction to invasion by a conspecific. This phenomena of colony identity and differential reaction to alien D. cancerides evidences a greater complexity of social interaction than previously described in the spiders. I am conducting a series of experiments to determine the information regarding sex, age, and source colony that individual D. cancerides communicate about themselves to one another, and how this communication is mediated. To test for the use of volatiles in chemical communication, I have used a two-choice "Y" olfactometer to perform preliminary scent-preference testing in D. cancerides, and am working on an improved olfactometer design for the continuation of the project.
The olfactometer works by moving air unidirectionally over an ostensible stimulus (be it a whole spider or some dissolved extract or byproduct) and into a chamber occupied by an experimental animal. The stimuli are placed in chambers that are physically and visually inaccessible to the subject, and the behavioral responses and positional information of the subject in the presence of olfactory cues are recorded over a twelve hour period. I will vary the presence, type, and amount of stimuli and examine the differences in behavioral response among experimental spiders of various ages, sexes, and colonies. Finally, if an isolated extract elicits predictable behavioral responses among subject spiders, nuclear magnetic resonance analysis of the extract will be conducted to describe the candidate compounds for chemical communication in D. cancerides.
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Siddhartha Bajracharya |
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Research Advisor & Department
Matthias Hesse - Microbiology and Immunology
Name of Project:
The role of CD103+ regulatory T-cells and antigen-presenting B cells in helminth-induced chronic inflammation
Abstract:
In Dr. Hesse’s lab this summer, I’ll be continuing the project I began this academic year: investigating the immune regulation of inflammatory disease in a mouse model of schistosomiasis. Schistosomiasis is a tropical infectious disease caused by a trematode parasite. Infection with this pathogen causes a severe inflammatory response against trapped parasite eggs, particularly in the liver and intestine. In particular, we’re looking at the role and mechanism of T regulatory cells in downregulating the immune response to schistosome eggs in liver tissue caused by T effector cells. T regulatory cells are crucial in modulating the immune response to the eggs, as an uncontrolled immune response can rapidly result in severe morbidity and heightened mortality.
The mechanism by which the relatively small number of T regulatory cells found in schistosomiasis infections are able to downregulate the large number of T effector cells is still unknown. The model that we will be testing proposes that T regulatory cells and B cells effectively form a "trap" for T effector cells as they return to be restimulated by the antigen-presenting B cells, allowing the T regulatory cell to come into contact with and downregulate the T effector cells as they approach the B cells. We propose that activated T regulatory cells bind to egg-antigen-presenting B cells via the interaction of the surface antigen CD103 on T regulatory cells with its ligand e-cadherin on the surface of B cells.
Several methods will be used to test this hypothesis, including immunohistochemistry analysis of mouse liver sections to determine presence and location of target T and B cells, and use of CD103-deficient knockout mice to determine effects on schistosomiasis infection progress and survival.
This summer I will be developing an in vitro assay that allows me to determine e-cadherin expression by B cells activated in different cytokine millieus. I will use flow cytometry to determine surface marker expression and real-time PCR to determine gene expression, in order to analyze the mechanisms by which e-cadherin levels are regulated. Additionally, I will start to develop an in vitro suppression assay where we will test our hypothesis using e-cadherin expressing B cells, naive effector T cells, and CD103+ regulatory T cells. We propose that the presence of e-cadherin expressing B cells increases the suppression capacity of regulatory T cells.
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