Date of Award

Spring 2023

Degree Type

Thesis

Department

Biological Sciences

Director of Thesis

Dr. Kristy Welshhans

First Reader

Nikita Kirkise

Second Reader

Nikita Kirkise

Abstract

During cellular migration, fibroblasts sense extracellular cues through membrane complexes at their leading edge and can respond to these cues via local translation. Local translation is the process in which mRNAs are transported to subcellular regions and translated in response to specific cues. There is evidence that local translation may be dysregulated in the neurodevelopmental disorder, Down syndrome, which is caused by the triplication of chromosome 21 and results in genome-wide dysregulation of protein expression. To determine if dysregulated local translation contributes to Down syndrome, we used three sets of primary fibroblasts from individuals with Down syndrome and apparently healthy individuals. Because of the extra copy of chromosome 21, we hypothesized that local translation would be increased in Down syndrome fibroblasts. A starve and stimulate puromycin assay was used to label and fluorescently visualize locally translated proteins. Although we anticipated an increase in local translation, which was the case in one of the Down syndrome fibroblast cell lines, we found a decrease in local translation in the other two Down syndrome fibroblast cell lines. One location where local translation occurs is focal adhesions, which are present at the leading edge of fibroblasts. Focal adhesions link the extracellular matrix to the intracellular actin cytoskeleton and regulate many cellular processes, including motility and signaling. We examined a key member of the focal adhesion protein complex, paxillin, in the leading edge of Down syndrome fibroblasts and find that it is downregulated in all 3 Down syndrome cell lines. This decrease in adhesion likely impacts local translation, cell motility, and cell signaling in Down syndrome, thus contributing to the phenotypes of this disorder. Taken together, we show that local translation and focal adhesions are altered in Down syndrome fibroblasts. This provides insight into the slow wound healing phenotype of Down syndrome. Furthermore, the cellular and molecular mechanisms occurring in the leading edge of fibroblasts are very similar to the tips of developing neurons; therefore, these studies also suggest that future studies examine whether these same mechanisms may be altered during neural development in Down syndrome and contribute to the intellectual disability phenotype.

First Page

1

Last Page

31

Rights

© 2023, Ashlyn Gotberg, Nikita Kirkise, and Kristy Welshhans

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