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1st appeared
2 November
1999 Genes and Visual Perception – Through the Eyes of the Zebrafish
Geneticists generally don't waste much time on zebras either, but scores of laboratory teams around the world -- up from a handful just a few years ago -- now are focusing their gene sleuthing on the black-and-white striped zebrafish, a denizen of India's Ganges River that for decades has been available in most pet shops. In fact, the Packard Foundation, which each year recognizes some of the most talented young faculty members nationwide, has just awarded $625,000 to UCSF for Herwig Baier’s zebrafish studies. Baier came to UCSF from the Max Planck Institute in Tübingen, Germany, less than a year ago. The assistant professor of physiology and his students are searching for genes that play a role in visual perception. As a pioneer of zebrafish research at UCSF, Baier joins Didier Stainier, who is also a Packard Foundation fellow and for several years has been studying zebrafish to learn about the development of the heart. Of his own research Baier says, "The idea is to approach a complex, innate ability of the brain--like visual perception--in a reductionist manner," Baier says. "We mutate genes one at a time. We look for an effect -- disturbed color vision, for instance -- that indicates a role for a gene in visual perception." The goal is to build a catalog of genes. By matching different defects with the mutated genes that cause them, Baier hopes to develop a picture of how normal genes and their corresponding proteins affect the nerve pathways and circuits that control visual perception. Since both humans and zebrafish are vertebrates, insight into the workings of the zebrafish visual system may shed light on similar mechanisms operating in humans. The zebrafish make good subjects for this research. They need no training to exhibit several easily recognized behaviors in response to visual cues in their watery surroundings. Baier first will look for genes affecting two different behaviors that can easily be elicited by exposing the fish to computer videos. The first behavior is an "opto-motor" response that enables the fish to use visual cues to remain stationary in a moving stream by swimming in place, something like a treadmill runner in the gym. Baier simulates a moving stream on video with a field of vertical stripes that moves across the screen. The second behavior Baier will monitor in his search for telltale genetic abnormalities is the so-called "optokinetic" tracking behavior -- the movement of the eye to follow an object. There are several additional reasons why developmental biologists of many stripes like to study the genetics of zebrafish. The fish are small, one to two inches long, and easy to care for. They produce many offspring in a short time. The eggs are externally fertilized and the embryos develop quickly. And most importantly, the embryos are transparent -- observers can see organs develop right before their eyes. Abnormally behaving clutches of embryos are examined for genetic abnormalities. With an optical microscope, Baier can view changes in calcium levels that signal nerve activity. He also uses dyes to highlight networks of nerves in the developing fish brain. Eventually, Baier hopes to figure out how a variety of genes play specific roles in visual perception. "The beauty and elegance of this approach is that it is not biased in favor of finding particular classes of genes," Baier says. "We don't know what kinds of genes we are going to find beforehand. It's very likely that we will find novel genes or unsuspected functions for known genes." Packard Fellowship money may be spent on any research the recipient wants to pursue. The awardees are nominated by their university presidents and recommended by a panel of nationally recognized scientists and engineers. Links: Source: Jeffrey Norris
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In
tracking down illness, medical students often are advised to consider
everyday diagnostic possibilities before the more exotic ones -- the
horse before the zebra.