Date of Award

12-2014

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

Hao Xu

Committee Member 2 Department

Biological Sciences

Committee Member 3

Janis O'Donnell

Abstract

From a genetic and allelic modifier screen, we report that the Drosophila melanogaster T-box transcription factor midline (mid), a homolog to the human TBX20 gene, interacts with dFOXO within the insulin receptor (InR) and the c-Jun-N-terminal kinase (JNK) signaling pathways to regulate interommatidial bristle (IOB) formation. Previous studies have identified mid’s role in cell fate specification of sensory organ precursor cells in conjunction with the Notch-Delta signaling pathway (Das et al., 2013). The Notch, InR, and JNK signaling pathways regulate dFOXO activity under conditions of stress. Thus, we determined the effects of oxidative stress and metabolic stress by exposing mid-RNAi flies to paraquat and starvation conditions, respectively. We found that oxidative stress suppressed the mid-RNAi phenotype while starvation had no significant effect. We next assayed Mid and H15, a paralog of Mid, via Western blot analysis and report that Mid exhibits a nucleocytoplasmic distribution pattern that is altered within the mid-RNAi mutant while H15 was found exclusively within the cytoplasmic fraction. This opens the possibility that Mid and/or H15 may regulate cytoplasmic targets upstream of dFOXO. The evidence suggests that Mid utilizes the InR, JNK, and Notch signaling pathways to regulate cell fate specification, differentiation, and survival during third instar larval development.

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