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D. Chakraborty, S. J. Fliesler, M. I. Naash; The Role of Rds Oligomerization in Cone Outer Segment Assembly and Maintenance. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4654.
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© ARVO (1962-2015); The Authors (2016-present)
Cysteine at position 150 (Cys150) of Rds has been suggested to mediate intermolecular disulfide bonding necessary for Rds oligomerization and large complex assembly. Here, was investigated the role of Cys150 in cone outer segment (COS) morphogenesis in wild-type (WT) and Neural Retina Leucine Zipper knockout (Nrl-/-) (which lack rod photoreceptors) mice.
Transgenic mice were generated using an RDS cDNA construct containing a C150S mutation under the control of the human red/green opsin promoter (COPS) to direct cone-specific expression. These were crossed onto WT, Rds+/- and Rds-/- genetic backgrounds and also onto Nrl-/-, Nrl-/-/Rds+/- and Nrl-/-/Rds-/- backgrounds. Transgene expression was verified by immunoprecipitation (IP) and western blotting, with correlative immunocytochemistry (ICC) to determine the localization of Rds and other OS-specific proteins. Retinal morphology was assessed by light and electron microscopy (EM). Electroretinography (ERG) was used to evaluate retinal function at postnatal day 30.
Significantly diminished photopic b-wave amplitudes were observed in COPS-C150S transgenic mice on both WT and Rds+/- backgrounds. In comparison to non-transgenic controls, COPS-C150S mice with either the Nrl-/- or Nrl-/-/Rds+/- background revealed significant reduction in photopic responses. Biochemical and ICC analyses revealed that the mutant protein is stable, lost its association with Rom-1, but can make it to cone OSs of transgenic retinas on Nrl-/-/Rds-/- background.
The C150S Rds mutation exerts a dominant negative effect on cone photoreceptors. OS structural differences between rods and cones may render cones more susceptible to abolishing the C150S-mediated intermolecular disulfide bonding necessary for Rds oligomerization. Further analyses are underway to elucidate the role of Rds in cone OS morphogenesis and maintenance.
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