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Dissertation/Thesis Abstract

Modification and nuclear organization of the Drosophila melanogaster genome
by Wesolowska, Natalia, Ph.D., The Johns Hopkins University, 2013, 198; 3575013
Abstract (Summary)

The success of Drosophila as a system for genetic analysis is closely linked to its amenability to genetic manipulation. Part 1 of the dissertation elucidates a novel scheme for long-range targeted manipulation of genes. We integrated an 80-kb genomic fragment at its endogenous locus, utilizing a targeted attP attachment site for the phiC31 integrase. We achieved single-copy reduction of the resulting region duplication by inducing recombinational DNA repair. We showed that this two-step scheme of integration and reduction is efficient and useful for delivering modifications. We established a vector configuration that facilitates the recovery of modifications. The integrating genomic fragment allowed for delivery of a new attachment site at 70 kb from the existing attP into a new locus, making it susceptible to targeted mutagenesis. We extrapolate that with this scheme, only 1 200 lines bearing att-sites throughout the genome would suffice to render all Drosophila genes amenable to targeted mutagenesis. Excitingly, this method should be readily applicable to other systems.

In Part 2 of the dissertation, I explored the question of telomere organization in Drosophila. Telomeres demarcate the ends of linear chromosomes to distinguish them from broken ends. In yeast, they cluster at the periphery of the nucleus establishing a compartment of silent chromatin. To bring insight into telomere organization in a higher organism, we followed EGFPlabeled Drosophila telomeric protein HOAP in vivo and found that the 16 telomeres cluster into 4-6 foci per nucleus in somatic tissues. Interestingly, HOAP signal intensity in the clusters doubles in interphase, potentially due to loading of HOAP to newly replicated telomeres. We tested several predictions about rules governing clustering. First, by inspecting mutant embryos that develop as haploids, we found that clustering is not mediated by associations between homologs. Second, by demonstrating clustering capability for a telomere of novel sequence, we eliminated DNA sequence homology and identity as important factors. Third, by marking both ends of a chromosome, we ruled out predominance of intra-chromosomal interactions. We propose that clustering is indiscriminate of sequence and is likely maintained by a yet undetermined factor.

Indexing (document details)
Advisor: Rong, Yikiang
Commitee: Lilly, Mary, Van Doren, Mark, Zappulla, David
School: The Johns Hopkins University
Department: Cell, Molecular, Developmental Biology and Biophysics
School Location: United States -- Maryland
Source: DAI-B 75/02(E), Dissertation Abstracts International
Subjects: Molecular biology, Genetics, Cellular biology
Keywords: Gene targeting, Genome engineering, Nuclear biogenesis, Telomere organization
Publication Number: 3575013
ISBN: 978-1-303-52412-7
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