Date of Graduation

5-2025

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Cell & Molecular Biology (PhD)

Degree Level

Graduate

Department

Cell & Molecular Biology

Advisor/Mentor

Evans, Timothy A.

Committee Member

Lewis, Jeffrey A.

Second Committee Member

Pare, Adam

Third Committee Member

Nelson, Christopher E.

Keywords

Axon Guidance; CRISPR; Drosophila; Gene replacement; Tribolium; UAS GAL4

Abstract

Axon guidance in bilaterians is often controlled by various signaling pathways in the nervous system, which determine the fate of the axons if they cross the midline or not. One such pathway involved is the ligand-receptor pair Netrin (Net) and Frazzled (Fra), which is also known as the attractive pathway that promotes midline crossing axons in insects and other bilaterians. Orthologs of the pathway ligand Netrins and their receptors Frazzled [Fra] in insects and Deleted in Colorectal cancer [DCC] in vertebrates are widely conserved in bilaterians. How well these regulatory roles of the protein are conserved is poorly understood. In fruit flies or Drosophila melanogaster, fra guides axons to cross the midline via Netrin, and is also involved in regulating transcription of the gene commissureless or “comm” via a non-canonical pathway, which in turn regulates the gene roundabout (robo). The primary aim of this thesis was to compare the direct evidence of midline attractive roles of the gene fra and its abilities to guide axons in fruit flies or Drosophila melanogaster) using a CRISPR-Cas9-mediated gene replacement approach. In this project, we rescue the midline regulatory roles of Drosophila fra (DmFra) in promoting midline crossing guidance using the fra gene of the flour beetle, Tribolium castaneum (TcFra).

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