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L.J. Robles, T. Taylor, S. Kelly; Timed Study of S–Crystallin Protein Expression in Light– and Dark–Adapted Octopus Photoreceptors . Invest. Ophthalmol. Vis. Sci. 2006;47(13):2835.
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Recent studies show that S–crystallin is present in greater amounts in dark–adapted octopus retinas and that it binds to F–actin, while in light–adapted retinas, S–crystallin is greatly reduced with no apparent F–actin binding (Zuniga et al., 2004). To further understand the kinetics of S–crystallin expression, we are investigating whether the expression of S–crystallin is time sensitive and varies with increasing time in the light or dark.
Octopi were light or dark adapted 3–4 hours after which the eyecups of one octopus were dissected for controls. The remaining octopi were transferred to the opposing lighting condition and sacrificed at 15 minute intervals for a period of two hours. At each time point, the octopus was anesthetized on ice, the eyes dissected and the retinas homogenized in buffer. Protein concentrations in the homogenates were determined and equal amounts of protein from each interval were loaded onto SDS gels. The proteins were separated and translational differences in S–crystallin quantified. Translational differences in actin were also analyzed.
Preliminary results indicate initially increased levels of S–crystallin, from 5.36% to 10.4%, in the first 15 to 30 minutes in animals moved to the dark after which the levels decrease slightly and remain constant in the second hour. Translation levels of actin are constant. Levels of S–crystallin in animals moved to the light show cyclically increasing and decreasing levels while actin expression remains constant.
Increases in S–crystallin levels during the first 30 minutes in the dark and cyclical levels in the light suggest that the possible involvement of S–crystallin in the reorganization of the rhabdomeric actin cytoskeleton may change over time.
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