Document Type

Honors Paper

Publication Date

May 2006

Abstract

The Notch pathway, a crucial developmental signaling system, acts to direct the fates of individual cells in many organisms and has also been implicated in a wide range of human diseases. Notch signaling plays a vital role in cell fate decisions in almost every tissue type ranging from the skin to the nervous and vascular systems. Aberrant Notch signaling has been implicated as a cause of many diseases, including a variety of cancers. Activation of the Notch receptor releases a Notch intracellular domain into the nucleus, where it binds with a transcription factor, Suppressor of Hairless (Su(H))to create an active complex which upregulates expression of target genes. In Drosophila the primary targets of Notch activation are the Enhancer of Split [E(spl)] genes. The E(spl) genes encode a family of basic-helix-loop-helix (bHLH) transcription factors, which exhibit overlapping functions throughout developmental stages. In order to determine the mechanisms through which E(spl) gene expression is controlled, I used three approaches to study E(spl) regulation. First, Bioinformatics analysis of the upstream regulatory regions of the E(spl) genes reveals binding sites for transcription factors that may act to regulate E(spl) gene expression. Evolutionary conservation of sites in the regulatory region lends support to their importance in the regulation of gene expression. Second, Real Time PCR quantification of the expression of three E(spl) genes at different stages of Drosophila metamorphosis suggest roles for some of these genes. Third, a reporter vector with the upstream region of one of the E(spl) genes cloned upstream of the firefly luciferase gene was constructed and used in Drosophila tissue culture experiments to further analyze the regulation of gene expression. Results from these three approaches will help to better understand the process of gene regulation and to characterize the mechanisms involved in controlling gene expression. Specific understanding of Notch target genes will elucidate how the Notch pathway functions in both normal and disease cells.

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The views expressed in this paper are solely those of the author.