Poster 94 - Investigating Axonal Dysfunction in Alzheimer’s Disease: A Live Cell Imaging Approach

Saturday, October 26, 2024

10:00 AM - 12:00 PM EST

Location: Exhibit Hall E, F & G

Presenting Author(s)

Ali Fehmi

High School Intern
UCSD Institute of Engineering in Medicine
San Diego, California, United States

Co-Author(s)

JS

Jiyeon Song

Intern
UCSD Institute of Engineering in Medicine, United States
Crystal Zhang (she/her/hers)

Intern
UCSD Institute of Engineering in Medicine, United States

Co-Author(s)

Jinho Bae

High School Intern
UCSD Institute of Engineering in Medicine, United States

Co-Author(s)

Alexander Chin (he/him/his)

High School Intern
UCSD Institute of Engineering in Medicine
San Diego , California, United States
MM

Mihir Mandapaka

High School Intern
UCSD Institute of Engineering in Medicine, United States
Melody Chen

High School Intern
UCSD Institute of Engineering in Medicine, United States
Evan Zhu (he/him/his)

High School Intern
UCSD Institute of Engineering in Medicine
Irvine, California, United States
AL

Amy Li

High School Intern
UCSD Institute of Engineering in Medicine, United States

Primary Investigator(s)

Linda Shi, PhD (she/her/hers)

OPALS Program Director, Project Scientist, Co-director IEM
University of California, San Diego: Institute of Engineering in Medicine
La Jolla, California, United States

Last Author(s)

CW

Chengbiao Wu

Professor
UCSD School of Medicine Dept of Neuroscience, Outreach Program for Advancing Learning in STEM (OPALS), United States

Introduction: Alzheimer’s disease is a neurocognitive disorder that is characterized by progressive mental decline. Neurodegeneration is preceded by axonopathy, or axonal dysfunction, which is an early cellular manifestation where problems occur with the axons that carry electrical impulses between neurons. In Alzheimer’s, axonal dysfunction is correlated with the aggregation of neurotoxic proteins, such as amyloid-beta and tau, resulting in disruption of axonal transport. Axonal transport includes the travel of neurotrophic factors along microtubules that are essential for the survival of the neuron, so obstructions and pauses in this transport could lead to atrophy or cell death. As an effective cure for Alzheimer’s is yet to be discovered, it is crucial to understand the critical role and the differences of axonal dysfunction in a healthy brain versus an Alzheimer’s brain. Thus, our experiment aimed to investigate differences in axonal transport by analyzing live cell images of neurons in wild-type and Alzheimer’s disease mouse models. Our findings are expected to build upon previous literature by looking at specific disruptions in axonal transport which will allow us to determine the impact of Alzheimer’s on the efficiency of axonal transport for further investigations on potential new therapeutic strategies.

Materials and

Methods: To study the contrasts between Alzheimer’s and wild-type mouse neurons, our research analyzed two live cell imaging videos, one of wild-type neurons and the other of Alzheimer’s disease neurons. Both live cell images utilized mono-biotinylated brain-derived neurotrophic factor (mBtBDNF). These proteins have biotin and a quantum dot attached, which allows each molecule to fluoresce under imaging so that they could be tracked. We then created a novel MATLAB code that employed a variety of imaging techniques. The code was used to convert the live cell images to grayscale, set thresholds as to what can be recognized as proteins, create masks to specify certain areas, and construct kymographs to track the overall movement. Each protein was labeled with an individual ID to adjust for the blinks and pauses. Once the code was run on each video, data regarding velocity and pauses was generated. This would allow us to look for contrasts in the average number of pauses per cargo, the average pause duration, and the average velocity at which they traveled.

Results, Conclusions, and Discussions: We were able to make comparisons using the data in Figure 1. The average velocity of the Alzheimer’s disease proteins was slower at 15.57 pixels/frame compared to the average velocity of the wild type proteins, which was 21.32 pixels/frame. Additionally, the wild type model had an average pause count of 6.60 times per cargo, while the Alzheimer’s disease model had around double this quantity, at 12.67 times per cargo. The average pause duration for Alzheimer’s diseased cargo was longer than that of the wild type cargo, at 28.67 frames and 18.40 frames respectively. At this stage of our research, we conclude that axonal transport is less efficient in Alzheimer’s neurons compared to wild-type neurons. According to our data, axonal dysfunction in Alzheimer’s is characterized by an increased number of pauses per cargo, pause duration per cargo, as well as a decrease in average velocity. The data suggests that the decrease in overall average velocity can be predominantly attributed to the increased frequency and duration of pauses of individual cargo, rather than their movement speed. These findings indicate that preventing increased pauses in axonal transport in Alzheimer’s disease is critical to neuronal survival and treatment of the disease. We will continue to do more research with more live cell imaging videos. Future studies should target their research toward the potential causes of the increased pauses in axonal transport that we have identified, and how this is related to the aggregation of neurotoxic proteins.

Acknowledgements (Optional): This work was supported by a generous gift from Beckman Laser Institute Inc. to LS. The high school students (*) participated in the UCSD IEM OPALS internship. Special thanks to Dr. Shu Chien from UCSD Bioengineering and Dr. Lizhu Chen from CorDx Inc. for their donations.

References (Optional): K Sung. J. Neurosci. Methods. 2011; 200(2): 121-128