Searching for the Mechanisms of ALS
“The Iron Horse” — this was the nickname given to Lou Gehrig, a legendary baseball player. Not only did he win six World Series championships, but he was also a seven-time All-Star. He once held the record for most consecutive games played — over 2000. However, in 1938, Gehrig’s ability to play baseball suddenly deteriorated. He lost strength, speed, and coordination, and experienced great fatigue. Gehrig had developed amyotrophic lateral sclerosis (ALS) — a neurodegenerative muscle disorder that affects voluntary muscle movement. Using his fame as an athlete, Gehrig helped spread greater awareness of ALS, and the disease became commonly known as Lou Gehrig’s disease in America. In 1941, just two years after he was diagnosed with ALS, Gehrig passed away. Because ALS has no cure, most patients die within three to five years after diagnosis. Due to its severity as a neurodegenerative disease, ALS has become a commonly researched disease in neuroscience; its biological mechanisms are the focal point of undergraduate researcher Stanley Yuan’s senior thesis.
Originally from California, Yuan is a molecular biology major pursuing a certificate in neuroscience. Yuan first became involved in this project during his freshman spring semester, when he started working with Professor Elizabeth Gould in the Department of Neuroscience. He wanted to explore research, and, combined with his interest in medicine, he found this project to be a great fit because of its clinical applications. As a molecular biology major, Yuan focuses on the genetic mechanisms affecting two groups of brain cells in patients with ALS — he is researching the as-of-yet unknown cause of the disease. Because ALS is a neuromuscular degeneration disease, it mainly affects motor neurons — a type of neuron in the body that controls both voluntary and involuntary movement. However, not all motor neurons degenerate in patients with ALS. It turns out that there are some motor neurons that die when someone has the disease — a degenerative group — and some motor neurons that remain alive for the duration of the time that the person with the disease stays alive—a resistant group. An example of the degenerative group of neurons is the neurons that control limb movement, while examples of resistant groups of neurons are those that control eye movement, the bladder, and the rectum. Yuan is studying these two groups in the brain stem and spinal cord. Comparing the genetics of the two groups of neurons can give insight into how the disease works because it may show why one group of cells is more vulnerable to the disease than another.
Yuan’s experiments are mainly done with the brains and spinal cords of rats, but after gathering results from rat neurons, Yuan uses human brains to see if the results match up. So far, Yuan has found two genes that are differentially expressed between the two groups of neurons. Differential expression is measured by the amount of proteins produced by specific genes — a gene that produces more protein is expressed more. Bex1 and MSK1 are the two genes that were initially identified by doing a microarray analysis, a lab technique that looks at the expression of all the genes in one cell. By comparing the microarray analysis of a resistant cell with a degenerative cell and looking at scientific literature for the genes that are connected to neurodegenerative disease, it was determined that Bex1 and MSK1 were genes that merited further research. Yuan then found that Bex1 is expressed more in the motor neurons resistant to the disease, suggesting that the proteins made from Bex1 are somehow extending the life of the motor neurons. On the other hand, MSK1 is expressed more in the neurons that degenerate with ALS, suggesting that greater expression of this protein is leading to the degeneration of these neurons. The exact mechanism of how the Bex1 and MSK1 proteins are functioning in relation to ALS is still unknown and is something to look into with further research.
To determine the location of the expression of these genes in the two groups of neurons, Yuan used a technique known as immunofluorescence. After harvesting the brain and spinal cords from rats, he sliced the brain into thin tissue pieces and tagged the slices with fluorescent markers. If the gene is expressed, the fluorescent markers bind to the protein and fluoresce. The brightness of fluorescence is proportional to the level at which the gene is expressed — higher expression levels lead to brighter fluorescence. Immunofluorescence not only helps determine levels of gene expression but also helps identify exactly which cells exhibit higher gene expression. This leads directly to the next major step of the project — gene therapy. In this case, gene therapy would involve injecting these two specific genes into populations of either cells or rats to see the effect of the inserted genes. Will injecting the resistant gene into degenerating cells slow down the degeneration process?
Currently, the underlying mechanism of ALS is not known — what are the biological factors leading to ALS, and why does the disease arise? Furthermore, there is no cure for the disease. The only way to treat it is to slow the progression of the disease and help the affected muscles, such as by taking medicine for muscle cramping. Yuan is excited about the clinical application of this project because his results can aid in answering these major questions. His research can help elucidate a mechanism that may be a factor in causing ALS as well as other neurodegenerative diseases. By understanding how the mechanism works, better treatments can be developed because they will be more localized and specific to the cause of the disease, rather than simply treating the symptoms of the disease. Looking into the future, Yuan’s research may even contribute to a cure for ALS. Yuan’s senior thesis is exciting undergraduate research with a strong clinical connection that may alleviate the morbidity of an ALS diagnosis.