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Date of Graduation
Master of Science (MS)
Dr. Marquis Walker
Retinal degenerative diseases (RDD’s) are a diverse group of retinal disorders that cause visual impairment. While RDD prevalence is high, little is known about the molecular mechanisms underlying the pathogenesis within some of these disorders. Here we are trying to elucidate the molecular mechanisms that drive early onset photoreceptor function loss in the RDD, Mucolipidosis type IV (MLIV). MLIV is a lysosomal storage disorder that results from loss of function mutations in the MCOLN1 gene and leads to a disruption of autophagy. The MCOLN1 gene encodes a lysosomal cation channel called Trpml1. Based on previous data from our lab, we hypothesized that a loss of Trpml1 expression in photoreceptors causes a disruption in protein trafficking and intracellular signaling, which results in decreased light activation, and is exacerbated in light stress conditions. To test this hypothesis, we measured retinal function in 6-week-old control and Mcoln1-/- mice under normal light and light stress conditions. In these experiments we find that the Mcoln1-/- mice have a significantly decreased photoresponse when compared to control at all light conditions. We also used immunohistochemistry and western analysis to reveal reduction in expression and observed mislocalization of phototransduction proteins such as rhodopsin and cyclic nucleotide gated (CNG) channels. We saw changes in protein expression and localization that were consistent with the decrease in Mcoln1-/- mouse photoresponses. These observations in physiological response and protein expression lead us to test for changes in gene expression within the Mcoln1-/- mice. To do this we used RNA sequencing on both control and Mcoln1-/- mice that were raised under normal and stressed light conditions. We used differential expression analysis to identify changes in gene expression across all light conditions. In this data, we saw subtle decreases in rod photoreceptor proteins of Mcoln1-/- mice under all light conditions that were consistent with functional and expression changes measured through ERG and western analysis. In addition, we looked at differentially expressed genes that were significant in fold change difference and we found 4 commonly upregulated across all light conditions, which all function in the cellular immune response within the Mcoln1-/- retina. This data suggests that in the Mcoln1-/- retina, there is chronic inflammation that may be inducing increased cell stress on photoreceptors therefore contributing to the decreased photoreceptor responses. These findings provide novel information about the molecular changes that occur during the onset of photoreceptor function loss and the impact of light-stress in the RDD, Mucolipidosis type IV.
Cistulli, Rebecca, "Characterizing the effects of light on the early onset photoreceptor function loss in Mucolipidosis type IV" (2023). Masters Theses, 2020-current. 234.
Available for download on Thursday, April 10, 2025