Date of Award

Summer 8-2015

Level of Access Assigned by Author

Campus-Only Thesis

Degree Name

Master of Arts (MA)

Department

Mathematics

Advisor

Andre Khalil

Second Committee Member

David Bradley

Third Committee Member

William Halteman

Abstract

Huntington's disease (HD) is a hereditary genetic neurological disorder which causes neuronal death. It affects muscular coordination and mental state, and can lead to premature death. HD is unique in the respect that in addition to the neurons, it affects gene expression in other tissues, including brain, blood and peripheral tissue. It is thought that HD's destructive behavior has an impact at the nuclear level, specifically the morphology of the chromosomes.

During the interphase, chromosomes tend to position themselves in a non-random way which allows them to perform their functions in tandem with the rest of the nucleus. Gene-rich chromosomes on average are elongated and occupy regions which are closer to the centroid of the nucleus. Since disease states such as cancer and laminopathies have been shown to impact the positioning and shapes of interphase chromosomes, it was hypothesized that similar traits may occur in HD. This thesis explores the effect HD has upon the architecture of the cell nucleus from human samples.

Data for this analysis was collected from blood samples from three groups of participants: individuals with early HD, moderate HD, and a control group. Samples were stained using florescence markers and imaged using the cryoFISH method, a high-resolution Fluorescence In Situ Hybridization microscopy applied to cryosections which were approximately 150nm thick. DNA florescence probes were used to mark the nuclei, chromosomes 4, and 19 for one set of cells, chromosomes 5, and 22 for the other set of cells. The images collected for the experiment were segmented and analyzed using a combination of machine learning, thresholding, and detection algorithms. The geometrical analysis revealed measurable changes in the structure and organization of chromosomes. The progression of HD causes overall elongation of the nucleus. Chromosome 4 becomes smaller and more compact in early HD and larger and more elongated in moderate HD. Chromosome 5 is larger in only early HD. Chromosomes 19 and 22 become more compact as the disease state progresses. These changes in chromosome structure and organization could provide a new avenue for diagnosis of HD.

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