Use of Computer-Aided Screening for Detection of Motility Mutants in Zebrafish Embryos
T he zebrafish (Danio rerio) is an exquisite vertebrate model system for the study of developmental mechanisms. The unraveling of these developmental processes at the molecular level will allow design of new treatments for a myriad of diseases, including birth defects and other genetic disorders. This paper is centered on developing new techniques for screening genetic mutants in zebrafish, especially those affecting development of motility in this interesting vertebrate animal. Motility arises during development by the expression of genes encoding factors such as cytoskeletal proteins, ion channels and pumps, and neurotransmitter receptors. Use of computer-aided screening (CAS) provides objectivity and high-throughput which are major advantages compared to traditional phenotyping screens. In addition, CAS has the potential to be more sensitive than the traditional approach. For example, CAS analysis has revealed that embryonic motility defects are present in chordino and knypek, however, these defects were missed in previous traditional screens of these otherwise well-characterized mutants. Another important feature of this technology is the ability to provide a distributable library of image stacks, generated by NIH-image, of the embryonic development period for both new and previously characterized motility mutants. It is anticipated that these image stacks could be analyzed in the future as new image analysis programs are devised to take advantage of the vast amount of raw information in the longitudinal time arrays of mutant zebrafish development. The vertebrate zebrafish shares a basic body plan with other vertebrates, including man, and yet has many of the biological properties of invertebrate models such as rapid generation time, small size, cost-effective rearing, and optical clarity of embryos. Zebrafish has an important advantage over mammalian models such as the mouse, since in the zebrafish, development occurs outside the mother thus providing ready observation of embryonic formation. CAS, which couples modern digital imaging technology with a longitudinal temporal design, can be applied to identify a large number of motility mutations which will provide a research resource for workers in the fields of neuromuscular functioning and development in both normal and disease states. In addition, CAS may be useful to those working in the areas of toxicology and pharmacology, since CAS may be adapted to obtain quantitative data (i.e. LD50 or ED50 vs. time) on necrosis and death during embryonic development.