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Chi-Bin Chien

Professor of Neurobiology and Anatomy

B.A. Johns Hopkins University

Ph.D. California Institute of Technology

Research

References

chi-bin.chien@hsc.utah.edu

 

Research

For the developing brain to function properly, it must acquire the correct shape, pattern itself, and produce differentiated neurons, which then extend axons and form synaptic connections with each other. We study the cellular and molecular bases of neural development, using the zebrafish visual system as a model. These embryos develop quickly and are transparent, allowing us to observe cell behavior within the living embryo. Furthermore, we can perturb retinal development and axon guidance using embryological, genetic, and molecular biological tools.

We have cloned several axon guidance mutants and are intensively studying how they function in axons in vivo. For instance, we find that the Astray/Robo2 axon guidance receptor helps to guide retinal axons in at least three distinct guidance choices along their pathway. In the optic chiasm, timelapse analysis shows that Robo2 helps both to prevent and to correct guidance errors. We are currently studying guidance of axons in the optic tract by Slit ligands; signaling downstream of Robo2; and possible roles of robo2 alternative splicing.

Recently we have started expanding our interests beyond axon guidance, in three directions. First, we are studying how the optic cup forms and is patterned early during development, using a combination of 4D timelapse imaging and genetic manipulations. These studies are complemented by a forward genetic screen looking for new genes involved in eye development. Second, we are starting a large-scale Gal4 enhancer trap screen to generate genetic reagents that we can use to label and manipulate neuronal cohorts that may be involved in higher-order visual processing. Third, we have an ongoing collaboration with Dean Li’s lab to study how guidance ligands and receptors act in formation of the vasculature.

Confocal projection of wildtype (top) and astray mutant (bottom) zebrafish embryos, injected with diI in the dorsonasal quadrant of the left eye. The wildtype axons project only to contralateral optic tectum, while mutant axons make drastic pathfinding errors, projecting to both tecta, telencephalon and diencephalon, with multiple midline crossings.

References