| During development, axons need to make specific connections with their targets to form a functional nervous system. Axons are guided towards these targets by responding to a variety of guidance cues, which are integrated into behavioral responses by the motile tip of the growth cone. The simple scaffold of axon tracts in the zebrafish provides and ideal model to study how guidance cues collaborate to guide axon in vivo. In this thesis, I use these pathways to investigate how various guidance cues influence growth cone behaviors to affect pathfinding decisions. In Chapter 2, I show that an extracellular matrix molecule, laminin-alpha1, affects the direction of axon growth at choice points, axon extension, cell polarity and cell survival. In Chapter 3, I provide evidence that muscle contractions help guide overlying sensory axons in the direction of growth and the interaxonal behaviors. Collectively, this work shows the requirements for specific cues in the guidance of a variety of axons throughout the zebrafish embryo, as well as a novel in vivo mechanism of axon guidance. |
