Tag: Poster 43

The Role of Chromatin Remodeling Complex in Valve Development

Presenter: Maithri Sarangam

Mentor: Kryn Stankunas

AM Poster Presentation

Poster 43

Congenital heart diseases are one of the most common types of birth defects. Studying the development of this complex organ may provide insight into the causes of such defects. It has been shown that chromatin remodeling complexes play a role in directing developmental processes. They affect expression of genes by modifying chromatin, the DNA-protein complex in the nucleus. One particular chromatin remodeling complex, the BAF complex, has been shown to be important in heart development. We believe the BAF complex is required during the remodeling and elongation phase of aortic valve development. The aortic valve controls blood flow from the heart through the aorta. We used mouse models and complex genetic techniques to study the role of the BAF complex in mammalian heart valve development. Using a crelox system, we induced a loss of function of the BAF complex in endocardial cells, which make up the lining the heart, by knocking out Brg1, the key ATP-ase required for the complex to function. We then used various histological and immunofluorescence stains to study the resulting phenotype at different time points during the elongation and remodeling phase. The aortic valve phenotypes in the mutant embryos deviated from that of their wild type litter-mates, suggesting that the BAF complex does have a role in this phase of valve development.

Aging Effects on Perceptual and Conceptual Memory: Transformations from Short-term to Long-term Memory

Presenter: Anisha Adke

Faculty Mentor: Dasa Zeithamova-Demircan

Presentation Type: Poster 43

Primary Research Area: Science

Major: Biology

Funding Source: UROP Mini-Grant, University of Oregon, $1,000

Conceptual and precision memory are two functions of healthy and adaptive memory. Conceptual memory retains the gist of events. Precision memory allows memory of specific perceptual details of events, contrasting them from other similar experiences. Precision and conceptual memory may be differentially important for short-term memory and long-term memory. Long-term memories may have a tendency to retain meaning but lose details. This is adaptive in daily life, but may be a problem in certain situations, like during eyewitness testimonies, where details rather than generalities are essential. Loss of memory precision also characterizes normal aging, but it is unclear whether this occurs because details are lost in long-term memory or they are not encoded in short-term memory. The purpose of the study was to determine if memories transform from perceptual to conceptual over time and identify the effect of aging on this relationship.

Subjects’ memory were tested for general meaning (conceptual memory) or specific details (perceptual memory) either immediately (short-term) or after thirty minutes (long-term). Preliminary results show that short-term memory supports quicker and more accurate judgments of perceptual details, whereas long-term memory supports quicker and more accurate judgments of meaning. Future testing will assess whether older adults are quicker and more accurate in judgments of meaning in both long and short-term memory, suggesting that older adults process events on a conceptual level even when information is maintained over very short delays.

Forebrain Control Of Social Behavior In Zebrafish Model

Presenter(s): Adeline Fecker − Biology

Faculty Mentor(s): Sarah Stednitz

Poster 43

Research Area: Natural Sciences

The zebrafish animal model provides valuable insight into social behavior and social impairments. Zebrafish exhibit a stereotyped orienting pattern called shulling when they interact with another fish. Our goal is to identify the neurons involved in this social behavior. We control the shulling behavior by placing one fish on each side of a clear divider. This assay allows
us to track their shulling pattern and control the duration of the interaction. After running a social behavior test in zebrafish, the brain is immediately dissected, cleared and stained for activity. This procedure labels the neurons that were recently active during the social behavior condition. Activity was labeled on three channels: GFP, ERK, and phospho ERK. We used zebrafish bred with the GFP transgene and stained the dissected brains with ERK and phospho ERK antibodies. The brains of fish who received no social stimulation were also dissected and stained as a control. The lateral septum of the forebrain is highly active in the stimulated condition. In a follow-up experiment, ablations of the lateral septum revealed social deficits in the behavior tests. This suggests the lateral septum is important for social behavior. Similar research on mammalian models supports the importance of the forebrain in social behavior. Our finding not only strengthens the validity of the fish model but also has implications for the localization of social deficits in autism and schizophrenia.

Determining Lipid Specificity Using Alpha-Hemolysin

Presenter(s): Grant Klausen

Faculty Mentor(s): Jim Prell & Jesse Wilson

Poster 43

Session: Sciences

Many therapeutic drugs target membrane proteins, many of which likely have specific lipid interactions that effect their oligomerization, structure, and function. However, only a small fraction of the proteins in the Protein Data Bank are characterized with bound lipids. Membrane protein-lipid complexes are often extremely difficult to characterize due to protein instability in solution and to the high degree heterogeneity that makes crystallization challenging.

Here, we use state-of-the-art native mass spectrometry to quantify stoichiometries and specific lipid interactions of alpha-hemolysin (AHL) toxin from Staphylococcus aureus. AHL is a well studied transmembrane toxin that shares many similarities in structure and function with other membrane toxins, such as anthrax. AHL causes host cell death by forming pores in host cell plasma membranes that lead to cell lysis. AHL is secreted as a monomer, and we have shown it oligomerizes as both a hexamer and a heptamer in detergent micelles. Our end goal is to determine if this toxin binds specifically to sphingolipids (SL) or phosphatidylcholines (PC). For this purpose, AHL is oligomerized in stable detergent micelles to which various types of lipids are titrated at specific concentrations to measure differences in binding and determine lipid specificity.. Detergents C8E4, C10E6, C12E8, DDM, OG, LDAO, and FOS-14 were tested for their ability to form AHL pores, and initial results show that both SL and PC bind strongly to the pore, but phosphatidic acid lipids do not. Results from these experiments have relevance in developing therapeutic drugs to block these interactions and neutralize the toxins.