Our long range goal is to integrate the complex architecture of the cephalopod photoreceptor with the effects of light and dark on rhabdomere structure, the visual cycle and transport processes. The objective of this application is to further sort-out the effects of light and dark on photoreceptor cytoskeletal proteins. Our central hypothesis is that light regulates the expression and distribution of cytoskeletal proteins in adult and embryonic retinas. To test our hypothesis we will pursue three specific aims: 1) we will identify and characterize lighting-condition-specific actin-binding proteins in rhabdomere microvilli using F-actin affinity chromatography and generate probes to screen a light/dark retinal cDNA library and to use in situ hybridization and Northern blot analysis, 2) we will determine the effects of light on the presence and distribution of tubulin mRNA within the octopus retina using quantitative RT-PCR, Northern blot analysis and in situ hybridization and 3) using c onfocal microscopy, immunocytochemistry and standard molecular techniques, we will map the appearance and distribution of cytoskeletal proteins in light- and dark-adapted embryonic retinas and correlate the appearance of cytoskeletal proteins with the construction of the rhodopsin-retinochrome system. Our results will further elaborate the components of the photoreceptor cytoskeleton and investigate a mechanism, light, involved in regulating its organization. The cytoskeleton is critical to normal photoreceptor processes and is thought to direct disk morphogenesis and to coordinate the transport of materials within photoreceptor compartment. Disruption of cytoskeletal systems through mutations in critical protein components is devastating to photoreceptor function and is linked to retinal degeneration in both vertebrate and invertebrate species. Understanding the mechanisms that regulate cytoskeletal organization, such as light, is crucial to our basic understanding of photoreceptor fu nction and to understanding of how abnormalities in cytoskeletal proteins may lead to blindness and other degenerative retinal diseases.
