During development, axons are guided by various environmental factors to reach their appropriate targets. Throughout this process, axonal growth cones require the presence of proper cell surface receptors and the execution of the signal pathways inside the growth cones in order to correctly respond to these cues.

Our research focuses on two axon guidance events: axon pruning and axon repulsion. These two events are important "regressive" processes that occur not only during development of the nervous system but also in many neurological diseases.

We use both mouse genetics and C. elegans genetics to study the in vivo functions of axon guidance molecules that are involved in axon pruning and axon repulsion. Specifically, we study mutant mice to understand the functions of a group of environmental guidance cues, semaphorins, and their receptors, plexins and neuropilins. These studies have provided insights into the specific roles of each ligand-receptor pairs in axon repulsion and axon pruning. In order to understand the signaling pathways inside the axon and the dynamic changes of axonal growth cones at single axon level, we study the repulsion of a subset of motor axons in C. elegans. Our studies have contributed significantly in understanding how the signaling molecules regulate the behavior of the axonal growth cone.

Taken together, we have used these two genetic systems to improve our understanding of the molecular and cellular mechanisms of axon repulsion and axon pruning. We are continuing this research and are also trying to use these two systems to study the mechanisms that may cause human diseases.

Dorsal turning of motor corticospinal axons at the pyramidal decussation requires plexin signaling
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Plexin signaling selectively regulates the stereotyped pruning of corticospinal axons from visual cortex
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