This proposal is to study the content and isoforms of myosin in the retina of green sunfish and zebrafish. These teleost fish contain three well-defined types of cells: rods, cones, and RPEs (retinal pigmented epithelial cells). All three cell types show well-defined changes in response to light, darkness, and certain chemicals. These shape changes occur both in the intact retina and in isolated cells, and are known as retinomotor movements. Some of the motility changes have been shown to be actin-dependent, so it is likely that myosin is also involved. Myosin K/EDTA ATPase activity will be measured by standard techniques. Myosin will be immunolocalized using monoclonal or polyclonal antibodies against three types of non-muscle myosin, and monoclonal antibodies against retinal myosin will also be prepared. Myosin isoform synthesis and deposition will be determined in the developing retina; because of the way the retina develops, the age and state of morphogenesis of the various cell types can be easily determined. %%% Fish retinas change more in response to light, darkness, and other stimuli than mammalian retinas do. They provide a convenient system for studying the possible role of myosin in the changes in cell shape. Actin has already been identified in fish retinal cells. In non-muscle tissues, at least three types of myosin have been identified, which have markedly different properties. Antibodies to these isoforms have been prepared. They will be used to determine which form of myosin is present in each cell type, and where it is localized. If retinal myosin is different from the known types, monoclonal antibodies will be prepared against it. Since the location of cells is well-characterized during retinal development, the antibodies will be used to see whether isoforms change during this time. Since myosin-based cell motility is important for many life processes, it is likely that the results will apply to other systems as well.
