Date of Award

Spring 5-2013

Degree Type

Masters Thesis

Degree Name

Master of Science (MS)

Department

Biological Sciences

Committee Chair

Sandra Leal

Committee Chair Department

Biological Sciences

Committee Member 2

Glenmore Shearer

Committee Member 2 Department

Biological Sciences

Committee Member 3

Janis O'Donnell

Committee Member 3 Department

Biological Sciences

Committee Member 4

Yanlin Guo

Committee Member 4 Department

Biological Sciences

Abstract

The Drosophila melanogaster T-box transcription factor Midline (Mid) exhibits a high degree of structural and functional conservation with its vertebrate homolog Tbx-20. Both Mid and Tbx-20 regulate cell-fate specification with in diverse tissues including the central nervous system (CNS) and heart. Although, some important studies reported that Tbx-20 transcripts express in a wide range of developing mammalian eye tissues including those of the human fetus, the function of this transcription factor is unknown in the development of eye tissue. This current study is the first attempt to show that Mid and its para log H15 are expressed within distinct ommatidial cell types including photoreceptor neurons and sensory organ precursor (SOP) cells during early stages of pupal eye imaginal disc morphogensis and also identities a Mid transcription factor network regulating eye development. Reducing the expression of mid transcripts within eye disc tissues using RNA interference (mid-RNAi) results in the loss of interommatidial bristles (JOBs) in the adult eye due to the misspecification of sensory organ precursor (SOP) cells and increased levels of apoptosis induced during earlier stages of pupal development. Since the Notch-Delta signaling pathway specifies the SOP cell fate, we sought to place mid within the Notch-Delta genetic hierarchy specifying SOP cell fates.

We determined that Mid functions downstream of the Notch receptor and upstream of the Enhancer of Split gene complex [E(Spl)]. We also discovered mid collaborates with two Notch pathway members also implicated in the regulation of cell survival, extramacrochaetae (emc) and senseless (sens). Moreover, toward identifying the Mid regulatory transcription factor network specifying cell fate, we found that mid collaborates with dFOXO. The dFOXO transcription factor is distinct in that it regulates cell proliferation and homeostasis within Insulin regulated stress induced pathway. The culmination of these studies suggests that Mid regulates cell fate specification in collaboration with Notch-Delta signaling pathway and also play important role in cell survival pathways essential for maintaining homeostasis.

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