by Alison Chan
This summer, I spent ten weeks at the Gotoh lab at the University of Tokyo, conducting research focusing on neuronal migration.
For my main research project, I focused on how the knockdown of certain genes might affect neuronal migration. Neurons are generated from neural progenitor cells and migrate from the ventricular zone, through the intermediate ventricular zone, to the cortical plate during brain development. For the first few weeks of my time at the Gotoh lab, I focused on learning in utero electroporation (IUE), a technique that allows researchers to study the function of a gene in a specific cortical area. I utilized IUE to study the function of two genes of interest, gene X and gene Y, electroporating a DNA construct into the neural progenitor cells of the ventricular zone of the embryonic brain on embryonic day 14, then allowing the neural progenitor cells to mature, migrate, and differentiate (Figure 1). On embryonic day 17, I dissected the brains from the embryos, later slicing the brains with the cryostat machine and conducting immunohistochemistry with green fluorescent protein (GFP) staining on the brain slices. Finally, I imaged these brain slices with the confocal microscope to visualize the migrating neurons (Figure 2).
From this work, I found that the two vectors of gene X had likely little to no effect on neuronal migration, as the knockdowns showed little change in neuronal migration. For gene Y, however, the first vector showed possible neuronal migration defect, whereas the second vector showed minimal effect. Therefore, there may be an off-target gene of the first vector that caused this observed defect in neuronal migration, but there is not enough information to come to a conclusion, so a next step would be to increase n to better quantify results.
I also completed an additional behavior experiment in the last few weeks, which focused on the brain lipidome, or the distribution of lipids during brain development. For this behavior experiment, I studied how the deletion of enzyme Z, involved in lipid synthesis, might impact neuronal maturation in the context of behavior. I conducted open-field behavior tests, which run for thirty minutes per mouse and can elucidate information on the activity, motor, and anxiety levels of mice based on various parameters, such as total distance traveled, moving duration and speed, and percentage of time spent in the center of the chamber (Figure 3).
In the first trial with two mice, the wildtype mouse spent 34.17% of time in the center region whereas the enzyme knockdown mouse spent 87.19% of time in the center region, which was a surprisingly distinct result and may suggest that enzyme knockdown mice exhibit decreased anxiety levels (Figure 4). In my second trial with four mice, however, the exhibited behavior of the wildtype and knockdown mice were less distinct; the first enzyme knockdown mouse did not travel much and the second enzyme knockdown mouse only spent slightly more time (18.86%) in the center region as compared to the wildtype mice (16.83% and 13.36%, respectively) (Figure 5). Therefore, increasing n would be a next step to better quantify results.
Outside of lab, I had a fruitful experience exploring the city and learning more about Japanese culture. I was able to try out many local delicacies, such as grilled eel, seabream chazuke, and tuna cutlet. On weekends, I went on day trips to nearby towns, such as Kawaguchiko, where I saw Mount Fuji (Figure 6), and Enoshima Island, a spot known for the Iwaya caves and sea views. One of the members of my lab also kindly organized a trip to Kamakura as well, where we visited popular spots, such as the Great Buddha statue (Figure 7) and Hachimangu Shrine, and ended the day with a fireworks show in Yokohama. I was also able to do some longer trips with friends from Harvard, such as a weekend trip to Osaka and Kyoto and one to Okinawa (Figure 8), which were wonderful experiences, as I was able to note regional differences in cuisine, character, and atmosphere.
One of my favorite parts about this summer was meeting the Gotoh lab members, who were all incredibly welcoming, inviting me to daily lunches at the university cafeteria and events such as a farewell gathering at a barbeque beach in Toyosu (Figure 9). I also enjoyed getting to explore Tokyo together with the other Harvard students, from doing karaoke to going to summer street food festivals. Even though I traveled to Japan alone for the summer, I was lucky to meet many kind individuals who I hope to stay in touch with.
I am extremely grateful to have had the opportunity to spend ten weeks in Japan, and I not only learned a myriad of laboratory techniques and scientific concepts but also made lasting connections that made my time abroad truly memorable.