Researchers track paths in brain cells
Recent research by Associate Professor of molecular and computational biology Don Arnold and molecular biology doctoral candidate Sarmad Al-Bassam successfully videotaped the movement of proteins within a brain cell, allowing scientists to study the inner workings of the brain — live.
The project initially made use of green fluorescent protein, which is responsible for causing certain jellyfish to glow, to record the workings of the brain. Scientists have been using GFPs to view protein movement in cells for many years.
Other members of the team included USC postdoctoral fellow Min Xu, who helped develop algorithms for analyzing the data, and Thomas J. Wandless, a professor of chemical and systems biology at Stanford University. The project was funded by a grant from the National Institute of Health, and the findings of the project were published in Cell Reports in July.
As a continuation of the study, Arnold is now working on imaging the structure that turns the proteins around when they enter each cell’s axon. He turned in a paper for publishing which is currently undergoing academic review.
Arnold said the idea of GFP kick-started his research.
“In 1995, GFP came along and all of a sudden you could look at things live,” Arnold said.
At the time, however, GFP alone could not produce any useful data for scientists aside from allowing scientists to view protein movement.
“We wanted to look at proteins moving around in the cells, and the problem is that these proteins move along pathways, and all these pathways are moving simultaneously in the same space,” Arnold said. “When you see a vesicle moving along, it is impossible to tell which part of the pathway it’s in.”
Arnold and his team began working on this project in 2008 to resolve this problem. The project aimed to block the pathway and then release all the proteins at once, in effect synchronizing protein movement.
“We came up with the idea of halting this pathway and seeing everything go through at once,” he said.
Al-Bassam was responsible for developing the techniques for synchronizing movement within the brain.
“We adapted a chemical-genetic strategy that was originally devised to control the secretion of small peptides such as insulin and the human growth hormone for synchronizing the proteins,” Al-Bassam said. “The challenge was finding the unique conditions for visualizing the movement of vesicles containing fluorescent membrane proteins within neurons, which are some of the most difficult cells to work with.”
The footage led scientists to discover some interesting facts about the inner workings of the brain.
“We found that rather than being targeted specifically to the dendrites, vesicles carrying proteins initially enter both compartments, but then are stopped and prevented from moving beyond the initial segment of the axon,” Arnold said.
The footage of a brain lit up with GFP stirred up interest among students as well as scientists.
Isabel Shen, a sophomore majoring in neuroscience, said the video encouraged her to persue her own research.
“It’s easy to be told about protein movement in lecture; it’s hard to visualize the process,” Shen said. “Not only does this video demonstrate the technology available to USC faculty, it deals with a topic relevant to everyone in every stage of aging and brain development.”