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Hoon Shim, Ching-Kang J. Chen; Delayed ERG b-wave In A True RGS7 Knockout Mouse. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1178.
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The post-photoreceptoral loss of Gβ5-S in the Gβ5 knockout (Gβ5-/-) mouse results in the loss of the ERG b-wave. The protein levels of R7 subfamily of Regulators of G-protein Signaling (RGS): RGS6, RGS7, RGS9 and RGS11 are reduced in Gβ5-/- mice to near or below the threshold of detection. We have previously shown that RGS7 and RGS11 are co-localized on the dendritic tips of depolarizing bipolar cells (DBCs). In a RGS7 mutant mouse line termed SG7, which expresses a truncated RGS7 protein in reduced amounts compared to wild-type, no differences were detected in ERG recordings compared to controls; however, in RGS11 knockout (RGS11-/-) mice, the ERG b-wave was delayed. When SG7 and RGS11-/- mice were mated to generated the double mutant mouse line termed SG711, the ERG b-wave was further delayed. Since the SG7 mouse represents a hypomorph, we sought to generate a true RGS7 null mouse (RGS7-/-) to investigate the effect of a complete loss of RGS7 has on the ERG b-wave generation.
The RGS7-/- mouse is generated by homologous recombination replacing exons 6-8 with a Neo cassette. The electroretinogram (ERG) is recorded under both scotopic and photopic conditions, bridged by a 10-minute light adaptation period at 30 cd/m2 background intensity. The implicit times and amplitudes of both a- and b-waves are analyzed at the various flash intensities. Protein levels are determined by Western blotting and protein localization is determined by immunohistochemistry.
RGS7-/- mice are viable and fertile; however, have a runty phenotype. Western blot analysis of retinal protein extracts from RGS7-/- mice show complete lack of RGS7 protein. Gβ5-S protein levels are reduced in RGS7-/- mice and ERG recordings demonstrate a delayed b-wave.
The data indicates RGS7 has a substantial role in the generation of the ERG b-wave. In the RGS11-/- mouse, protein levels of Gβ5-S do not change possibly due to the up-regulation of RGS7 to compensate for the loss of RGS11. However, in RGS7-/- mice, Gβ5-S protein levels decrease indicating RGS11 cannot fully compensate for the role of RGS7 throughout the retina. By mating the complete null RGS7-/- to the RGS11-/- mouse, to generate the double knockout mouse, we will be able to resolve whether loss of both RGS7 and RGS11 are the main reason for the lack of the ERG b-wave in Gβ5-/- mice.
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