Identification and Quantification of Neurodegeneration in DRPLA

Dentatorubral Pallidoluysian Atrophy (DRPLA) is a neurodegenerative disease that results from an accumulation of a polyglutamine-expansion mutated protein: Atrophin-1. This protein’s toxic accumulation in neuronal and glial cells, but also its specific characteristics cause neurodegeneration in specific areas of the brain: the Nucleus Ruber, the Dentate Nucleus, and the Globulus Pallidus. It is interesting that only these areas experience neurodegeneration, as the At-1 accumulation occurs in other areas of the brain as well. Cells in these areas induce autophagy as a protective measure to rescue the cell from further degeneration; however, this process is truncated as the Atrophin-1 protein creates a “block” in autophagy. Neurodegeneration therefore continues in these areas. It is necessary to quantify the neurodegeneration of the specific brain structures affected by DRPLA in order to create a timeline for investigation of the disease’s mechanism. So far, this disease’s mechanism has only been studied using the model Drosophila Melanogaster, however pioneering work has begun in the mouse model system. Should neurodegeneration be seen at a specific age in the mouse model, then the autophagy process has already begun, and behavioral experiments should be shifted to earlier time points. An immunohistochemical method of indirect fluorescence staining was employed to tag cell bodies, neuronal nuclei, and nonspecific nuclei. These stainings were visualized using microscopy, and the images were analyzed to count the number of cells, and more specifically, the number of neurons in the Nucleus Ruber. The cell count would reveal how neurodegeneration progressed in mice of different ages, thus shaping the timeline for characteristic cell death in DRPLA mice. Though still preliminary, results show that neurodegeneration is evident in mice at the end stages of DRPLA when compared to mice in earlier points. Mice at three weeks had little difference between sick and healthy phenotypes, meaning neurodegeneration was not evident at this time point, and data for mice at ages in between these two time points was still under analysis at the time of this abstract submission. In conclusion, immunohistochemical methods allowed for quantification of neurodegeneration in DRPLA mice in a way that the timeline of neurodegeneration could be confirmed or shifted based on experimental results. Neurodegeneration results indicated the progression of the disease, and could be used as a basis for further experimentation of the implications of neurodegeneration on the structure of the Nucleus Ruber.