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Undergraduate Research in Biology

Student-faculty research is an essential part of Pomona's educational mission. In biology, the research process teaches students how to think like a scientist. Students engaged in research work closely with faculty to develop the skills needed to form a biological question and answer it in a rigorous way.

All biology majors either carry out an original experimental or field research project or develop an original research proposal for their senior capstone experience, but students are encouraged to engage in research before their senior year. Some students first become engaged with a research lab as an assistant — helping the faculty member and advanced students with their projects and carrying out lab support tasks. The department also encourages students to spend a summer or a semester involved in biological research, either working with a faculty member on campus or through one of many available research internship programs or biological field station programs.

Students interested in research or laboratory assistant positions in the biology department should contact the potential faculty mentor.

Potential Role of Sonic Hedgehog in Tissue Fibrosis during Chronic Graft vs Host Disease

Ash Maria ’22; Advisor: Elizabeth Glater

Sonic hedgehog (SHH) is a protein involved in cell growth, tissue specialization, and body patterning pathways. Chronic graft vs. host disease (cGvHD) is an immune condition which can occur after allogeneic hematologic stem cell transplants (HCT). In cGvHD the donor graft sees the recipient as foreign, causing malignant immune response in recipient. SHH may promote unregulated fibrosis in many recipient organs. Preliminary evidence suggests that SHH is overexpressed early after HCT in vivo. Given this, we hypothesized that SHH is critical in unregulated fibrosis of various organs during cGvHD. To determine patient SHH levels, we examined plasma samples from HCT patients with or without cGVHD, and healthy donors, for abundance of SHH through an ELISA assay. An ELISA is where a plate is pre-coated with the capture antibody, then the following are added in order: plasma samples/standard, biotinylated secondary antibody, Streptavidin-HRP, and finally TMB colorimetric substrate. We found a leaning-towards significant positive trend between SHH abundance and active plasma samples. Further supporting our hypothesis, in a recent Phase 1 clinical trial, SHH pathway inhibitor sonidegib was effective in fighting some cGvHD symptoms, but patients found worse quality of life from harmful side effects, leading to early trial termination. Thus, our goal of this project was to get a better understanding of the SHH pathway to aid in development of safe and effective inhibitors to treat cGvHD.

Nitrogen Excretion during Embryonic Development in the Terrestrial Isopod Genera Ligidium and Ligia

Stephanie Yu ’22; Advisor: Jonathan Wright

This study aimed to isolate the modes of nitrogen excretion in terrestrial and marine-littoral isopod crustaceans of the family Ligiidae, Ligidium and Ligia, and determine whether the form of waste nitrogen changes during embryonic development. Previous studies performed on embryos of the fully terrestrial Armadillidium vulgare, found increasing ammonia excretion until the manca stage, in which ammonotelism was supplanted by uric acid storage. In this study, ammonia and uric acid assays were conducted across all stages of development. Embryos of Ligia occidentalis were found to excrete increasing levels of ammonia with each transition to a later embryonic stage, suggesting ammonotelism in all stages. Levels of uric acid production did not change significantly during embryonic development and remained low, demonstrating that Ligia embryos do not store uric acid as a primary mode of nitrogen excretion in any stage. This contrasts with the findings of research on A. vulgare. Specifically, in A. vulgare , marsupial fluid in the closed marsupium is provisioned from the maternal blood, with limited capacity for replenishment; therefore, the shift to uric acid storage could protect the mancae from ammonia toxicity. In Ligia, the marsupial fluid in the open marsupium is provisioned from external seawater and can be replenished regularly, preventing long-term accumulation of ammonia and rendering uric acid storage unnecessary.

The reversal in orientation of a C. elegans migratory cell does not require the presence of nicotinic receptors

Amy Kaneshiro ’22; Advisor: Mihoko Kato

We are studying cell migration using Caenorhabditis elegans, a small, transparent nematode. In the male, an epithelial cell, the linker cell (LC), leads the gonad migration from the mid body region to the posterior. This migration uses acetylcholine signaling which can occur through two plasma membrane localized receptor types: muscarinic and nicotinic. The LC expresses one muscarinic receptor and multiple nicotinic receptors. The drug aldicarb increases the amount of extracellular acetylcholine and causes the LC to reverse its orientation. GAR-3, a muscarinic receptor, was previously found to be important for LC reversals to occur, but the role of nicotinic receptors is unknown. We tested whether LC reversals depend on two of the LC nicotinic receptors by creating null mutants of acr-15 and acr-16 using CRISPR/Cas9 genome editing. We found that this double mutant resulted in 12.19% reversal and 53.66% no reversal which is not statistically different from the number of reversals in the control that expresses both receptors. We conclude that acr-15 and acr-16 are not required for LC reversal to occur since there was a normal number of reversals without these receptors. For future studies, we developed a marker that expresses red fluorescent protein (RFP) in the LC nucleus and green fluorescent protein (GFP) in the mitochondria. Since the mitochondria is normally in front of the nucleus during LC migration, this marker will be used to more accurately determine LC orientation.

Investigating the movement of the dancing plant Codariocalyx motorius

Jason Lu ’22; Advisor: Fabien Jammes

Codariocalyx motorius, the dancing plant also known as the telegraph plant is a species that is native to India and China. The telegraph plant possesses terminal and lateral leaflets. Remarkably, its lateral leaflets move in an elliptical shape at a speed visible to the naked eye. While light and sound have been reported to affect the movement of the dancing plant, no one knows how plants could benefit from it. Our goals this summer were to (i) optimize the germination and growth of this tropical plant (ii) observe and quantify its movement in response to environmental cues and (iii) develop a protocol for the transformation, tissue culture and regeneration of the dancing plant. We show that the poor germination rate of Codariocalyx motorius seeds can be improved by scarification of the seed coats. By testing different types of soil, we optimized the growing conditions that allowed us to grow 3-4-week old healthy plants showing moving lateral leaflets. By analyzing video recordings, we then tried to characterize, in a quantitative manner, the elliptical movement of the leaflets in order to further understand how environmental stimuli can affect it. Finally, we optimized a protocol of dancing plant transformation, tissue culture and regeneration. This tool will allow us to generate transgenic plants in which particular cellular compartments or signaling pathways contributing to the movement could be tracked by fluorescence microscopy.