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In contrast, we demonstrate that the individual dsRBDs behave in a noncooperative fashion. Application of multiple nucleic acid lattice models to our data suggests the microstates accessed by an individual dsRBD binding to RNA are
indeed different from those accessed by the tandem dsRBD construct; furthermore, allosteric effects may be present in the tandem construct.
IMPAIRED METABOLISM OF THE ABNORMAL GLYCOGEN IN LAFORIN KNOCKOUT MICEChristopher J. Contreras, Dyann M. Segvich, Anna A. DePaoli-Roach, Peter J. Roach.
Indiana University School of Medicine, Indianapolis, IN.
Lafora disease (LD) is a rare, fatal, early onset form of myoclonus epilepsy that is characterized by the formation of Lafora bodies (LB) in many tissues, including the brain, heart, and skeletal muscle. Laforin is a dual specificity phosphatase that is mutated in about 50% of LD patients and has been shown to be a glycogen phosphatase that is responsible for maintaining low levels of glycogen phosphate. The absence of laforin results in the formation of LB, which are composed of abnormal glycogen that is poorly branched, insoluble, and hyperphosphorylated. The goal of this study was to determine whether such glycogen could be metabolized normally. Mice lacking laforin form LB and display myoclonus. However, the symptoms are less severe than in humans and occur later in life. Twelve-month-old laforin knockout (LKO) and wild-type (WT) mice were exercised to exhaustion to deplete skeletal muscle glycogen.
After exercise, WT mice degraded 75% of their skeletal muscle glycogen while the LKO mice had a small, statistically insignificant decrease in total glycogen levels. However, the possible decrease in LKO glycogen correlated with an increase in glycogen phosphate content. Interestingly, the soluble glycogen in low speed supernatants of tissue extracts did decrease in both the WT and LKO mice after exercise, while the abnormal glycogen in the low speed pellet of the LKO mice did not decrease. This project is ongoing but the data suggest that the abnormal glycogen accumulated in LKO mice is metabolically inert and not subject to normal degradation pathways.
BOTANY Room 207 A
TABLE BEET (BETA VULGARIS) AS THE MODEL SYSTEM TO STUDY THE TYROSINE BIOSYNTHETIC
PATHWAY AND ITS REGULATION IN PLANTSSamuel Lopez Nieves, Irwin Goldman, Hiroshi Maeda.
University of Wisconsin-Madison, Madison, WI.
Tyrosine (Tyr) is a precursor of important secondary metabolites in plants (i.e., alkaloids, betalains, vitamins, etc.). Animals are unable to synthesize Tyr and thus must uptake Tyr from external sources such as plants. While most of our knowledge of Tyr biosynthesis is derived from microbial studies, limited research on Tyr synthesis has been conducted in plants. Previous studies reported that Tyr can be produced via two different pathways, the 4-hydroxyphenylpyruvate and arogenate pathways, in microbes. The objectives of this study are to clarify the main biosynthetic pathway of Tyr and to investigate its regulation in plants. Here, we use the table beet (Beta vulgaris) as a model system that produces high levels of nitrogen-containing Tyr-derived pigments called betalains. We aim to first identify and characterize B. vulgaris genes and enzymes involved in Tyr biosynthesis. We have detected arogenate dehydrogenase (ADH) activity in the root extracts of the table beet, suggesting that the main production of Tyr in Graduate
previously-reported Arabidopsis ADH genes have been identified. In addition, we have successfully transformed beet roots using Agrobacterium rhizogenes, which can now be used to study the in vivo function of ADH genes through gene silencing. ADH suppression in table beet can alter Tyr production and lead to change of color derived from betalains, which will allow us to clarify the main biosynthetic pathway of Tyr and begin to investigate its regulation in plants.
329 ORAL ABSTRACTS
FLORISTIC STUDY OF THE TULE RIVER SOUTH-FORK WATERSHEDJessica Orozco, Travis Columbus.
Claremont Graduate University, Claremont, CA.
Historically, field studies that involve Indian reservation lands have been few and far between, and seldom are floristic inventories carried out. This past summer, we used the Consortium of California Herbaria (CCH) database to identify herbarium collections from Indian reservation lands in California and mapped them using Google Earth and 2010 US Census tract maps. Overall, many reservation lands appear to be undercollected. We identified the Tule River Indian Reservation to be of particular interest as it occupies the majority of the Tule River South Fork watershed, yet there are only 50 collections from that area in the CCH. For this study, we are conducting a floristic study of the watershed.
The objectives of our floristic study are to document all vascular plant species that occur within the watershed;
create an annotated, vouchered checklist of the flora; and assess the status of rare and culturally significant plants to determine if protection under existing laws or guidelines is warranted. Plant samples will be taken across a variety of habitats and will involve removal of only enough plant material to be representative and necessary for identification and that can be preserved or vouchered on herbarium sheets. We are working with the elders and community members of the reservation to understand the cultural importance of these plants. This project is motivated by a desire to call attention to the poorly documented botanical diversity on California Indian lands, where native plants have great cultural significance.
EVALUATION OF THE SYSTEMIC INFLAMMATORY REACTION TO ANTIHELMINTIC TREATMENT IN PONIESAlejandra Betancourt, John Stewart, Eugene Lyons, David Horohov, Martin Nielsen.
University of Kentucky, Lexington, KY.
Grazing horses are widely exposed to parasite infections, which can largely be controlled with administration of anthelmintic formulations. However, treatment can inadvertently induce inflammatory reactions and clinical disease.
Little research has been performed evaluating the inflammatory response to anthelmintic treatment. In this study, we explored the differences in inflammatory response following treatment with 3 different anthelmintic drugs: moxidectin, pyrantel pamoate, and oxibendazole. A population (n = 30) of healthy, naturally parasitized ponies were divided into 3 treatment groups based on age and worm fecal egg counts. All ponies received the labeled anthelmintic dosage.
Treatment efficacy was evaluated using the fecal egg count reduction test over 8 weeks, with weekly egg counts.
The inflammatory response was assessed 4 times post treatment. Measurements involved characterization of cytokine gene expression and systemic inflammatory reaction. The objective of this study was to determine the effect of deworming treatment on proinflammatory cytokine gene expression in the peripheral blood and to evaluate any correlation between the expression of inflammatory cytokines with levels of acute phase proteins and inflammatory markers. Fecal egg counts from the study confirmed resistance levels in the parasite population. Treatment with oxibendazole and pyrantel pamoate was unsuccessful in the elimination of luminal parasites. Moxidectin, however, was very effective and egg counts of 0 persisted for several weeks. Preliminary analysis of cytokine gene expression data shows a trend towards elevated levels of Interleukin-1beta in the moxidectin group; acute phase protein levels did not follow this trend, thereby negating the correlation between the 2 measurements of systemic inflammation.
THE DYNEIN ADAPTOR, PAC1P/LIS1, IS REGULATED BY SUMO AND UBIQUITINAnnabel Alonso, Rita Miller.
Oklahoma State University, Stillwater, OK.
The function of Pac1p, the yeast homologue of Lis1, is closely associated with the minus-end directed motor protein, dynein. Mutations in Lis1 result in lissencephaly, a developmental brain syndrome caused by defects in neuronal migration. Pac1p is important for recruiting dynein to the plus-end of the microtubule. Dynein is subsequently offloaded to the cortex where it pulls on cytoplasmic microtubules to move the mitotic spindle across the bud neck, a key step in positioning the mitotic spindle. Although Pac1p plays a vital role in microtubule function, little is known about how it is regulated. Sumoylation is a post-translational modification that covalently attaches the small ubiquitin-like
330 ORAL ABSTRACTS
modifier (SUMO) protein to target substrates. Whereas sumoylation regulates many cellular processes, it has only recently been shown to regulate spindle positioning. Pac1p displayed an accumulation of higher molecular weight bands in an ubiquitin-like-protease (Ulp1) temperature sensitive strain, suggesting that SUMO can accumulate on Pac1p. Pull-down assays suggest that Pac1p is modified by both ubiquitin and SUMO. We have identified two sites of modification on Pac1p. Mutation of these sites created the Pac1p double mutant, pac1-2K→R. Analysis of the pac1K→R mutant revealed that it was only partially able to suppress the nuclear positioning defect observed in largebudded cells of pac1Δ. Of the large-budded pac1Δ cells containing the pac1-2K→R mutant, 12% displayed binucleate mother cells, in contrast to 2% containing WT-PAC1. The pac1Δ strains containing an empty vector displayed 18% aberrant cells. This data suggest that dynein is regulated by the ubiquitin and/or ubiquitin-like modifications on Pac1p.
ONCOGENIC K-RAS PROMOTES BASAL EXTRUSION OF EPITHELIAL CELLSGloria Slattum, Yapeng Gu, Jody Rosenblatt.
University of Utah, Salt lake City, UT.
Epithelia provide a protective barrier for the organs they encase, yet the cells comprising the epithelia are constantly turning over via cell death and cell division. To maintain a protective barrier during homeostasis, epithelia extrude cells destined to die by contracting a band of actin and myosin. Although extrusion can remove cells triggered to die by apoptotic stimuli, during homeostasis, epithelia extrude live cells, which then die by anoikis. Because transformed cells may override anoikis and survive after extrusion, the direction of extrusion has important consequences for the extruded cell’s fate. As most cells extrude apically, they are eliminated through the lumen, however, cells with upregulated survival signals that extrude basally could potentially invade the underlying tissue and migrate to other sites in the body. We found oncogenic K-Ras cells extruded basally, rather than apically, in a cell-autonomous manner and can survive and proliferate following extrusion. Expressing oncogenic K-RasV12 downregulates the bioactive lipid sphingosine 1 phosphate (S1P) and its receptor S1P2, both of which are required for apical extrusion. Surprisingly, the S1P biosynthetic pathway is not affected, as the S1P precursor, sphingosine kinase, and the degradative enzymes S1P lyase and S1PP phosphatase are not altered. Instead, we found that S1P is degraded by autophagy, which is highly pronounced in extruding RasV12 cells. Disruption of autophagy chemically or genetically in K-RasV12 cells rescues S1P localization and apical extrusion. We propose that basal cell extrusion provides a novel mechanism for cells to exit the epithelium and initiate invasion of the surrounding tissues.
IDENTIFYING THE ROLE OF CODANIN IN ERYTHROID DIFFERENTIATIONLinette Bosques, Gary Kupfer.
Yale University, School of Medicine, New Haven, CT.
Improving understanding of rare diseases has historically led to major advances in medical science. Our studies with the rare red blood cell disorder, congenital dyserythropoietic anemia type 1 (CDA-1), have similar potential outcomes.
CDA-1 is an autosomal recessive disorder marked by specific morphological abnormalities of erythroblasts in the bone marrow, resulting in ineffective erythropoiesis and anemia. Light microscopy of bone marrow shows binucleated erythroblasts connected by internuclear bridges. Electron microscopy of bone marrow shows erythroblasts with spongy heterochromatin and invagination of the nuclear membrane. The gene responsible for causing CDA-1, CDAN1, encodes a ubiquitous protein, codanin, with unknown function. Our goal is to understand how codanin regulates erythropoiesis because codanin deletion mutants are embryonic lethal in mice and null alleles do not occur in humans. Preliminary data shows that codanin binds to erythroid-specific promoters and its expression is maintained during erythropoiesis. We chose to analyze how the founder mutation (R1040W) in CDAN1 affects erythroid differentiation. Expression of the R1040W mutant in human erythroleukemia cells deficient for endogenous codanin phenocopies the CDA-1 spongy heterochromatin and retards KLF1 and β-globin expression. Conversely, wild-type codanin overexpression stimulates erythropoiesis, increasing expression of erythroid genes. These studies suggest codanin regulates the expression of key erythroid genes. Determining the pathophysiology of CDA-1, and thus better Graduate Oral understanding normal erythropoiesis, will have a broad impact as we can translate our findings to improve treatment for rare blood disorders.
IDENTIFICATION OF POTENTIAL BIOMARKERS AND THERAPEUTIC TARGETS FOR MULTIPLE SCLEROSISBY M2 PROTEOMICS Itay Raphael, William E. Haskins, Thomas Forsthuber.
University of Texas at San Antonio, San Antonio, TX.