Defense Date

2014

Document Type

Thesis

Degree Name

Master of Science

Department

Biology

First Advisor

Gregory Walsh

Abstract

Planar cell polarity (PCP) is a developmental signaling mechanism that establishes a polarity within the plane of an epithelium. PCP has been shown to play a role in guiding numerous neurodevelopmental processes such as convergent extension, neuron migration, and axon pathfinding. Certain commissural neurons in the dorsal spinal cord make a series of guidance decisions en route to the brain: first, a ventral projection along the D-V axis, followed by a midline crossing, and after exiting the floorplate, a dorso-anterior turn along the A-P axis. Here, we provide in vivo evidence that the axons of the Commissural Primary Ascending (CoPAs) neurons in zebrafish require the PCP genes fzd3a, vangl2, and scribble for rostral pathfinding both before and after crossing the midline. Dorsoventral guidance of CoPA axons is unaltered in fzd3a, vangl2, and scribble mutants, suggesting that the PCP signaling pathway only controls A-P guidance of CoPAs. Our results have provided evidence for two potential non- mutually exclusive models: (i) A-P axon guidance is achieved by cell-autonomous Wnt-Frizzled signaling or that (ii) A-P axon guidance is achieved by non-cell-autonomous PCP signaling in the neuroepithelial environment. The single-cell nature of the CoPA axon system allows for simple genetic manipulation and visualization, which will potentially elucidate the validity of either model. Scribble (Scrib), a member of the LAP family, plays a critical role in establishing and regulating cell polarization in epithelia and during cell migration. In zebrafish, Scrib mutants have defects in convergent extension (CE) cell movements and facial branchiomotor neuron (FBMN) migration. Despite our understanding of Scrib’s genetic role in neurodevelopment, little is known about the subcellular localization of endogenous Scrib in vivo during CE and FBMN migration. We have generated a monoclonal antibody against the C-terminus of zebrafish Scrib and have shown that this antibody is specific against endogenous Scrib in both western blot and immunocytochemical applications. Confocal microscopy of Scrib immunocytochemistry shows that at various developmental stages, Scrib distinctly localizes to basolateral membranes of non polarized epithelium, to the membrane in mesodermal cells undergoing CE, and to the membrane of migrating FBMNs. Furthermore, the distribution of Scrib puncta along membranes of FBMN- FBMN contact is significantly altered in the PCP mutant pk1b. Further application of our newly generated Scrib antibody will potentially lead to new insight on Scrib’s role in neurodevelopment.

Rights

© The Author

Is Part Of

VCU University Archives

Is Part Of

VCU Theses and Dissertations

Date of Submission

May 2014

Included in

Biology Commons

Share

COinS