Margaret Ferris
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Research Advisor & Department
David Lin - Vet Biomedical Sciences
Name of Project:
Genomic Screen for Axonal Targeting Cues in the Olfactory Bulb
Abstract:
The brain is made up of ten billion neurons and during fetal development trillions of connections must be made between these neurons. In vertebrates, the olfactory receptor neurons are located in the nose in the olfactory epithelium. Axons of the OSNs (olfactory sensory neurons) project to the front of the brain and innervate their target, the olfactory bulb. More specifically, in the olfactory system, OSNs in the mammalian nose must grow to specific targets called glomeruli within the olfactory bulb. One hypothesis on how this process of connectivity occurs is that the targets of these axons, the glomeruli, produce differentially expressed cues. These cues, in turn, let the axons which target them distinguish between their eventual synaptic partner and all other possible partners. Thus, based on our hypothesis, we believe that there will be differential expression of genes within the glomeruli themselves. While working in the Lin lab, I will seek to find these cues that distinguish among the targets in the olfactory system. My project will be to search for new targeting cues by developing a refined map of the olfactory bulb. First I will isolate RNA from specific areas of the bulb. Then, using microarray analysis, I will compare the RNA samples to each other to find differential expression of genes within the bulb. I will then use in situ hybridization to confirm any differential expression that is found. Once these genetic differences are confirmed we can then move on to creating knockout mice and studying the specific effects of each gene of axonal targeting.
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Jessica Finn
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Research Advisor & Department
Joseph Peters - Microbiology
Name of Project:
Mutational analysis of a protein required for movement of the DNA element called transposon Tn7
Abstract:
The bacterial transposon Tn7 encodes for five proteins that are required in order for it to complete its transposition pathways: TnsA, TnsB, TnsC, TnsD, and TnsE. While TnsABC are required for all of Tn7’s transposition pathways, TnsD and TnsE each cause Tn7 to enter a different pathway. The transposition pathway involving TnsABC+D causes Tn7 to insert into the host cell’s genome at a site called attTn7, while the pathway involving TnsABC+E causes Tn7 to insert into one of two broader classes of sites. The first site, which is preferred by Tn7, is that which is located on plasmid DNAs that can move between cells, and the second site can be found in the Escherichia coli chromosome in regions where DNA replication terminates. No matter the site chosen, Tn7 always shows signs of transposition immunity, a property that implies that Tn7 does not attempt to insert itself into DNA that already contains a copy of Tn7. The exact nature of Tn7’s targeting system can be examined by utilizing the filamentous bacteriophage M13, a bacteriophage known to have a closed circular DNA genome that replicates inside a host cell through rolling circle replication. The insertion of attTn7 into an M13mp18 cloning vector, a genetically engineered derivative of phage M13 that contains the lacZ gene, the lacI gene, and the pLAC promoter, allows one to transform strains of E. coli with a plasmid-like bacteriophage genome that contains a safe insertion site for Tn7. The three different E. coli strains that will be transformed with the manipulated version of M13mp18 are: (1) a strain that contains the machinery for Tn7 to enter the TnsABC+D pathway, (2) a strain in which Tn7 is known to utilize the TnsABC+E pathway, and (3) a mutant strain that inserts Tn7 at random due to the absence of either TnsD or TnsE. Transformation of these three different strains will allow one to determine the levels of transposition into the phage genome that coincide with the presence or absence of specific pathways, and from this one can draw conclusions about Tn7’s preference for insertion into phage M13. In addition, the E. coli strain with the TnsABC+D machinery, which has now been transformed, can be used to prove the notion of transposition immunity, for, in the cases where transposition occurred, Tn7 should have inserted itself at the attTn7 site. The level of transposition into the phage DNA (which now contains a copy of Tn7) can now be determined, allowing the idea of transposition immunity to be either supported or refuted.
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Kasey Fowler-Finn
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Research Advisor & Department
Ronald Hoy - Neurobiology and Behavior
Name of Project:
The Battle Begins: A Behavioral Investigation of Communication in Male-Male Interactions of a Non-visual Specialist, Phignus marginemaculatus (order Amblypggi)
Abstract:
Communication is present in all interactions between individuals, and it is a topic that can be studied in many different systems and at many different levels. One extremely prevalent context of communication is male-male interactions, which are characterized as ritualized, and often highly visual displays. My project aims at studying communication, specifically male-male interactions, in a non-visual specialist, an amblypygid (Class Arachnida, Order Amblypygi). Amblypygids are ideal organisms to use in explorations of sensory modalities other than vision since their major means of interacting is through modified antenniform legs, which are covered with sensory receptors for chemical, tactile, olfactory, and vibratory cues. Using this system to characterize male-male interactions and the use of non-visual signaling is possible through examination of highly ritualized displays and the escalation to battles, presumably for competition to female access, which means there is sexual selection acting upon male weaponry and signal use in intrasexual selection. The main objective of my research is to characterize these male-male interactions in the amblypygid Phrynus marginemaculatus. I will determine what signals are used in male-male interactions and what determines the outcome of male fights. After running several trials of males paired to other males of similar size and different sizes, video analysis of the ritualized displays and battles remains to be completed. Scoring of the videos is aimed at characterizing the battles. Patterns I hope to uncover are what non-visual cues are important in decision-making by opposing males, what characteristics of an individual will help determine the outcome of the battles, and characterization of different phases of the battles. My ultimate goal is to put this study in an evolutionary context, as sexual selection is apparent in this system.
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Jessica Fox
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Research Advisor & Department
Cole Gilbert - Entomology
Name of Project:
Convergent Evolution of a Flight Control Organ in Insects
Abstract:
It has been noted that some members of the beetle family Scarabaeidae, among them the Green June Beetle, Cotinus mutabilis, have a distinct manner of flight that is more controlled than the flight of other members of the family. These beetles have the peculiar habit of raising and twirling the middle pair of legs as they fly. This interesting behavior is found in conjunction with a specific morphology: the beetles possess a row of eight to ten sensory hairs on the distal part of the tibia, which may be stimulated by the tarsal motion during flight. This arrangement of a moving appendage with basal sense organs is similar to the halteres of flies, which provide stabilization for their acrobatic fight. To examine the function of these hairs in scarabs, I will remove or cover them on several C. mutabilis, and compare the flight behaviors of these altered beetles to that of control animals. I expect that the beetles whose hairs have been altered will not be able to fly with the same degree of control as unaltered beetles. I will quantify this by measuring the time required for the beetles to fly to a light stimulus. Also, to provide evidence that these hairs are used for flight and not simply for walking, I will map the neurons extending from the hairs with a fluorescent dye. I predict that the neurons will project dorsally in the thoracic CNS, where neural processing for the control of the wings occurs, rather than project ventrally, where neural processing for walking occurs. Once these hairs have been demonstrated to influence flight behavior, further experiments can be done to explore the precise mechanisms of control.
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Zekeriyya Gemici
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Research Advisor & Department
Eric Alani - Molecular Biology & Genetics
Name of Project:
Incompatibility betweeen Alleles of Mismatch Repair Genes in different Strains of Saccharomyces cerevisiae
Abstract:
The MLH1 and PMS1 genes in the yeast S. cerevisiae play important roles in mismatch repair (MMR). MMR is the process by which cells can correct base pair mismatches that arise as the result of DNA replication errors. Both MLH1 and PMS1 genes have to be effective for MMR to take place, because Mlh1p and Pms1p form a heterodimeric complex in MMR. Argueso et al. (MCB 23:873) discovered three mlh1 alleles derived from the S288C yeast strain that had negligible effects on MMR in a S288C yeast strain, but completely disrupted MMR in a related SK1 yeast strain. The two related yeast strains have polymorphisms in the MLH1 and PMS1 genes that are clustered around specific regions along the genes. We hypothesize that phenotypic variation is due to the different PMS1 polymorphisms that exist in the different strains. Detailed studies suggest that the MLH1 and PMS1 genes are co-evolving with respect to each other. In addition, we are attempting to suggest a model on how a mismatch repair defective phenotype can spread in human populations based on the strain background effects we observed in yeast. My more immediate goal is to characterize the particular polymorphisms responsible for the phenotypic variation in different strain backgrounds, as well as to identify the cause of MMR deficiency observed when particular mlh1/PMS1 combinations are tested. I will also clone out the PMS1 and MLH1 genes from more distantly related yeast strains or species and test these genes for MMR functionality in S288C and SK1 strain backgrounds.
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Carly Gomes
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Research Advisor & Department
Ralph Obendorf - Crop and Soil Sciences
Name of Project:
Transport of Phloem Unloading of myo-inositol, D-chiro-inositol and D-pinitol in Soybean Seed Coat Cups
Abstract:
Galactosyl cyclitols are galactose derivatives of free cyclitols, which include myo-inositol, D-pinitol and D-chiro-inositol in soybean plants. They are harmless forms of seed storage products that accumulate after the onset of desiccation tolerance, and contribute to the structural stability of membranes, proteins, enzymes, organelles, and other macromolecules. Although it is known that myo-inositol is produced in soybean embryos, the location of D-pinitol and D-chiro-inositol biosynthesis remains unknown. In the first phase of experimentation, soybean explants were used to test for transport of myo-inositol, D-pinitol and D-chiro-inositol from leaves to seeds. The results of the experiment were consistent with the interpretation that both D-pinitol and D-chiro-inositol are biosynthesized in maternal tissue and afterwards transported to soybean embryos. The objective of current research is to obtain further evidence that D-pinitol and D-chiro-inositol biosynthesis occurs in leaves, seed coats, or other maternal tissue. Phloem unloading in seed coats of developing soybeans will be analyzed using in planta techniques. Embryos will be surgically removed from seeds, leaving seed coat cups to be filled with buffer solutions for collection of downloaded cyclitols. D-Pinitol, D-chiro-inositol, and myo-inositol (unlabeled or alternatively 2D- or 13C-labeled) will be fed to soybean plants via the leaf midvein (or 13CO2 by photosynthesis) and will be given enough time to be transported to and downloaded from the seed coat. Buffer samples will then be dried, derivitized, and analyzed by gas chromatography or GC-MS to determine which cyclitols are unloaded from seed coats to embryos.
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Kamilla Greenidge
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Research Advisor & Department
Barbara Finlay - Psychology
Name of Project:
The Role of the Thalamus in Regulating Normal Thalamocortical Projection Patterns
Abstract:
The thalamus acts as a major relay station in the brain. It receives impulses from all sensory areas (except the olfactory) and transmits them to the cerebral cortex. In development, the thalamus is the first extracortical input to the cortex and is central in the regulation of survival and lamination of cortical neurons, and in other features of neuronal organization, like neurotransmitter expression. In this study, we examine the effect of reduction or absence of the thalamus on the development of intracortical connections. Hamsters are one of the most immature mammals at birth, and the development of their intracortical connections occurs entirely postnatally, thus, they are a good species for studies of early developmental events. Portions of the thalamus, specifically somatosensory thalamic nuclei, are lesioned electrolytically at birth. 2-3 days later, a tracer is placed in the cortex to label the growing thalamic axons. Preliminary results suggest a decrease in total axon growth and a large decline in long range projections, though the general pattern appeared normal. Thus far, results suggest that the thalamus influences the rate/extent of axon outgrowth. We hope to verify, and further describe this phenomenon and will survey the literature to see in what way reduction of input to a neuron might influence the rate of growth of its axons.
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