Amyotrophic Lateral Sclerosis (ALS) is a progressive neurodegenerative disease characterized by the death of both upper and lower motor neurons. One hallmark of ALS is its rapid progression; 80% of patients die within the first 5 years of onset. The disease has some treatments, however, they only slow the disease progression by a few months. Although the cell types that are affected are known, the mechanism that causes the selective vulnerability of these cells remains unclear. Most genes associated with ALS are expressed through all cells, however; only specific cell populations degenerate. A better understanding of these genes and mechanisms crucial to generating specific therapies that could stop the progression of the disease. Research on ALS has been challenging since spinal-cord-projecting upper motor neurons are incredibly difficult to distinguish from other cell types. This has left the cause of their degeneration a mystery. This study aims to quantify the percentage of cells lost throughout disease progression of ALS. In order to do this, mice will be injected with an adeno associated virus (AAV) containing TOM-mcherry or TOM-tag. TOM-tag will be injected into the thalamus, staining resilient cells, and TOM-mcherry will be injected into the spinal cord, staining vulnerable cells. These cells will be quantified at different stages in ALS and be compared to wild type mice (mice not containing SOD mutation). This will help provide a more in depth timeline into ALS, including the percentage of cells degenerating at specific stages of ALS.