, 1993). He went on to produce some of the most stunning in vivo movies U0126 cell line of navigating axons ( Hutson and Chien, 2002) and morphogenetic eye movements ( Kwan et al., 2012) and some of the finest anatomical images of the developing visual system (see Figure 1). Striving to find the best system and approach to make progress into the molecular mechanisms of neural wiring in vivo, Chi-Bin did a second postdoc with Friedrich Bonhoeffer at the Max Planck Institute in Tübingen. Christianne Nusslein-Volhard and

Friedrich had just done a major screen for developmental mutants of zebrafish, and Bonhoeffer’s laboratory concentrated on those that affect the retinotectal projection. At the time Chi-Bin went to the Bonhoeffer laboratory, they had already identified over a 100 mutants in genes that disrupted the retinotectal

pathway. Some of these had pathfinding errors, and some had topographic mapping errors (Karlstrom et al., 1996 and Trowe et al., 1996). This, it seemed, was the opportunity for which Chi-Bin had long been preparing himself, and it was his work on the development of the zebrafish retinotectal system that shone so brightly on the developmental neurobiological community. In 1998, at the age of 32, Chi-Bin learn more joined the Department of Neurobiology and Anatomy at the University of Utah. There he met and quickly fell in love with Niki Hack, who became his wife. But within a year he received devastating news. He had advanced much colon cancer that required surgery and chemotherapy. This did not dissuade Chi-Bin from pursuing the most challenging scientific problems. In the Bonhoeffer laboratory, Chi-Bin had decided to focus on the astray mutant, which caused severe axon pathfinding defects in the brain. Identifying the molecule encoded by the astray gene was the task that Chi-Bin

next set for himself. In 2001, he produced a landmark paper ( Fricke et al., 2001) showing that the astray gene codes for the Robo2 receptor. Robo had recently been shown to act as a guidance receptor for Slit in Drosophila, and it had just been shown that mammalian Slit2 repelled RGC axons in vitro. Chi-Bin’s study brought together the in vitro studies in mammals and the genetic studies in Drosophila and showed that, in the vertebrate visual system, there was a conserved role for this ligand-receptor system. Importantly, Chi-Bin went beyond simply identifying the molecule; he did amazing eye transplants between normal and mutant fish embryos—the first person to get such incredibly difficult transplants to work, though several had tried before—to show that the Robo2 phenotype was autonomous to the navigating retinal axons. This extra effort is what made the paper a great achievement. It set a high standard for the zebrafish work in this area.