Tag: Poster 47

Analyzing Time of Chromosomal Rearrangment in Glioblastoma

Presenter: Anna Streitz

Mentor: Hui Zong

AM Poster Presentation

Poster 47

Glioblastoma is the most common and aggressive type of malignant brain tumor. Due to the tumor cell’s ability to disperse through- out the brain, their resistance to traditional chemotherapy and high rate of tumor relapse, current research is focusing on determining and designing therapies against the tumor cell-of-origin. In order to determine the cell of origin in these tumors, labeled mutant cells were generated through the use of mosaic analysis with double markers (MADM) allowing our lab to track the entire tumorigenic process in vivo and determine which cell types were giving rise to tumors. It was found that oligodendrocyte precursor cells (OPCs) were the primary cell type to show overexpansion and eventually give rise to a malignant tumor. It was hypothesized that by ablating the OPC cell population, using a genetic tool, one could prevent tumor formation or slow tumor growth. OPC specific thymidine kinase (TK) in conjunction with the drug Ganciclovir (GCV) was used in the hopes of causing OPC death. However, when end stage tumors were analyzed it was found that TK expression had been lost within the tumor cells, but not mutant OPCs outside of the tumor region. DNA analysis showed that the loss of the TK transgene had occurred on a genomic level, suggesting that a region of genomic DNA had been lost. The goal of this study is to characterize when the loss of TK occurs. Analysis of small tumors will reveal if TK loss is necessary for tumor growth or if it is lost as a function of tumor growth.

An Interspecific Comparison of Variance in Sex-Based Developmental Markers

Presenter: Kyle Morley

Mentors: Andrea Eller and Frances White, Anthropology

Poster: 47

Major: Anthropology 

Sexual dimorphism varies with the degree of male-male competition among primates. Changes in body size of both sexes are well known during ontogeny, but less is known about how osteological developmental markers vary under differing levels of sexual selection. Male-male competition is reflected in a species’ body size sex ratio: humans are reported to have a 1.2 ratio, while rhesus macaques have a 1.6 ratio. We predict greater results for larger bodies and canines in macaque males compared to macaque females and humans as well as greater growth marker variation among macaque males than in these other groups. We documented dental eruption and epiphyseal fusion in 292 macaque skeletal specimens and compared the data to over 25,000 individuals using published human population data. Two-way ANOVAs without replication were used to test whether species had similar variation in dental eruption and fusion time. The two species had significantly different eruption variation (males F=33.71, df=15,1, p <0.0001; females F=119.06, df =15,1, p <0.0001) with macaques more variable than humans. Both species also had different ranges in fusion time (F=7.28, df=13,1, p <0.05) with macaque males more variable than human males. The results support our prediction that macaque males show the greatest variation in these growth markers. Interspecies comparisons of developmental plasticity, such as this study, allow for inferences on how growth variation is affected by sexual selection.

Sea Star Plasticity: Morphological Variation of Pisaster ochraceus in Response to Wave Exposure

Presenter: Alyssa Bjorkquist

Faculty Mentor: Richard Emlet, Kelly Sutherland

Presentation Type: Poster 47

Primary Research Area: Science

Major: Marine Biology, Psychology

Funding Source: Undergraduate Research Opportunity Mini-Grant, UROP, $1000

Pisaster ochraceus (the Ochre Sea Star) is a keystone species in the NE Pacific whose role as an ecological engineer influences intertidal diversity by predating on space-competing organisms. Individuals inhabit a broad range of habitats ranging from sheltered coves to exposed cliffs and experience large temporal and spatial variability in water flow throughout their lifetime. However, it is largely unknown how sea star body shape changes between wave- exposed and wave-sheltered environments throughout an organism’s lifetime. Wave exposure was measured at each study site near Charleston, OR using dissimilar metal dissolution and intertidal zonation of sessile organisms. Furthermore, I analyzed how aspects of juvenile and adult P. ochraceus morphology differed between sites as functions of wave exposure.

Sites with more wave exposure were associated with greater anode mass loss over time (F1,30 = 256.21, p < 0.001) and broader vertical zone boundaries relative to mean water level than sheltered sites (F2,8 = 3.03, p < 0.01). Adult sea star populations from wave-exposed sites had longer, narrower arms and smaller central discs relative to individuals from sheltered habitats for a given weight (F2,152 = 70.0, p < 0.001). Juveniles appeared to exhibit similar morphological trends but results were inconclusive. The relationship between wave exposure and sea star morphology indicate that hydrodynamic conditions play a large role in shaping sea star development and environmental adaptability post-larval metamorphosis.

Using 3D Visualization to Study Immune Cell Distribution in Larval Zebrafish 

Presenter(s): Jacob Bieker – Physics, Computer and Information Science

Faculty Mentor(s): Raghu Parthasarathy

Poster 47

Research Area: Physical Science

Funding: Presidential Undergraduate Research Scholarship

Advances in microscopy and data visualization are enabling fundamental insights into a wide variety of biological processes. During the early development of zebrafish, a popular model organism, immune cells grow and migrate. How the distribution of immune cells in the organism changes with age, however, has been unclear. We therefore used light-sheet microscopy to image fluorescent neutrophils, a type of immune cell, in larval zebrafish during the first few days of the cells’ development. We then combined the imaging data with new three-dimensional visualization techniques using virtual reality to develop insights into the spatial organization of these cells. The virtual reality system is widely applicable and accessible, with the ability to run on common cell phones and work with various input types of input data. The use of virtual reality coupled with live imaging data shows the promise of three-dimensional visualization as an avenue for exploring biological data.

Piwi-piRNA pathway protein PRG-1 represses in temperature-induced DNA damage in spermatocytes

Presenter(s): Fountane Chan

Faculty Mentor(s): Diana Libuda & Nicole Kurhanewicz

Oral Session 3 M

Poster 47

Session: Sciences

Half of infertility cases worldwide involve male-factor subfertility. As awareness and frequency of male infertility has grown, it is increasingly important to understand the underlying mechanisms of these major human health concerns. Developing sperm are particularly sensitive to fluctuations in temperature, requiring a narrow isotherm of 2-7°C below core body temperature. Although both oocytes and spermatocytes undergo meiosis, the specialized form of cell division that produces haploid sex cells, elevated gonadal temperatures have been shown both to impair only male fertility and produce excess DNA damage specifically in spermatocytes. Preliminary work using the powerful roundworm model Caenorhabditis elegans suggests the Piwi-piRNA pathway, a highly conserved genome maintenance pathway, is involved in temperature-induced DNA damage. Absence of worm-specific Argonaute proteins (WAGO), primary effector proteins of the Piwi pathway, results in considerably elevated DNA damage upon heat-shock. Interestingly, a panel of mutants deficient in the C. elegans Piwi protein, PRG-1, which functions upstream of WAGOs, demonstrate highly variable degrees of heat-induced DNA damage. This variability is likely due to acquired mutations stemming from inadequate germline surveillance over multiple generations. To circumvent this issue by controlling the number of generations a strain is without PRG-1, we generated a conditional knockdown mutant of PRG-1. Utilizing this mutant, we found that in the absence of PRG-1 after one generation, spermatocytes demonstrate exacerbated levels of heat-induced DNA damage, similar to WAGO null mutants. Taken together, my data suggest a key role for PRG-1 and male-specific components of the Piwi pathway in heat-induced DNA damage in spermatocytes.