No description available.

Position Effect Variegation (PEV) is the mosaic expression of a gene that has been moved out of its optimal environment and into a different area on the chromosome. Changing a gene’s environment may have profound effects on its eligibility for proper expression, which is a complicated process regulated by many factors. The PEV phenomenon is used as an assay to study gene expression as regulated by chromatin structure. In this study, the Drosophila melanogaster white gene was used as a reporter to study the various effects of CHD1, a chromatin regulating factor, on PEV gene expression. Inspired by preliminary data generated by the Armstrong Lab where overexpression of CHD1 resulted in suppression of gene silencing of the brown gene and loss of CHD1 resulted in enhancement of gene silencing, this study uses PEV as an assay to examine whether loss of function chd1 mutant alleles function dominantly to enhance silencing of the white gene when it is placed in a repressive chromatin environment. Surprisingly, I found that a chd1 loss of function mutant allele dominantly suppressed gene silencing (meaning I saw an increase in gene expression), suggesting that the CHD1 protein is normally required for effective silencing. The results demonstrated that CHD1 is a dominant modifier of PEV gene expression. CHD1 significantly modifies gene expression by suppressing silencing of the white gene inserted into pericentric heterochromatin on the second and fourth chromosomes and an insertion into the medial region of the fourth chromosome, while it shows no significant modification of the white gene inserted into telomeric heterochromatin of the fourth chromosome. Together, these intriguing results regarding varying gene expression at different chromosomal sites show that PEV is a dynamic phenomenon meriting further research and studying the effects of CHD1 as a modifier of PEV may be influential to understanding the mechanism and characteristics of gene expression.

Chromatin structure is a fundamental determinant of eukaryotic gene expression and it is composed of two chromatin environments, euchromatin and heterochromatin. Euchromatin provides an accessible platform for transcription factors; hence it is permissive for gene expression. Heterochromatin on the other hand is highly compacted and inaccessible, which in most cases leads to transcriptional repression. A locus that is composed of both of these environments is the ribosomal DNA (rDNA). In eukaryotes the rDNA is composed of hundreds to thousands of tandemly repeated genes where maintaining both silent and active copies is fundamental for the stability of the genome. The aim of this research was to investigate the role of the rDNA in gene expression in Drosophila melanogaster. In D. melanogaster the rDNA loci are present on the X and Y chromosomes. This research used the Y-linked rDNA array to investigate the role of this locus on gene expression. A genetic and molecular strategy was designed to create and quantify specific, graded and isogenic Y- linked rDNA deletions. Then the deletions were used to address the effect of rDNA deletions on gene expression using reporter genes sensitive to Position Effect Variegation (PEV). In addition, the effect of the deletions in nucleolus size and structure as well as the effect of spontaneous rDNA deletions on gene expression were tested in this study. This research found that changes in rDNA size change the chromatin balance, which resulted in increased expression of the reporter genes, decreased nucleolus volume, and altered nucleolus structure. These findings prompted a further research question on whether this effect on gene expression occured globally in the genome. This was addressed by performing microarray analysis where the results showed that rDNA deletions affect about half of the genes on the genome. Presented in this dissertation is evidence that suggest a novel role for the rDNA is a global modulator of gene expression and also is a contributor to the gene expression variance observed in natural populations.

Parkinson’s disease is an incurable neurodegenerative disease characterized by motor deficits, owing to dopaminergic denervation in the nigrostriatal pathway. The abnormal formation of hallmark Lewy bodies underlies the disease process. The pre-synaptic protein alpha- synuclein (⍺-syn) has prion-like properties arising from its propensity to propagate, seed misfolding, and self-aggregate. Pathogenesis is postulated to arise in olfactory and enteric regions, exploiting connected neuronal pathways to ultimately propagate to the substantia nigra pars compacta. There is little known about the earliest stages of ⍺-syn aggregation and its prion-like propagation mechanisms. Bimolecular fluorescence complementation of ⍺-syn aggregates has allowed us to directly visualize aggregation in transgenic mice and mice transduced with an adeno-associated virus vector. Although our transgenic mice expressed BiSyn in a mosaic fashion that limited utility, we were successful in transducing neurons in the mouse striatum. This work has validated the AAV2/9-CMV-BiSyn approach as groundwork for future systematic studies.

No description available.

No description available.