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C.M. Craft, B. Brown, K. Wu, L. Rife, X. Zhu; Cone Arrestin Knockout: Structure and Potential Function in Cone Photoreceptors . Invest. Ophthalmol. Vis. Sci. 2006;47(13):4315.
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© ARVO (1962-2015); The Authors (2016-present)
Visual arrestins, arrestin1 (ARR1/S–antigen/rod) and cone arrestin (CARR/Arr4/X–Arr), are co–expressed in cone photoreceptors with light–dependent translocation to outer segments (Invest. Ophthalmol. Vis. Sci. 2005 46:E–abstract 1179). Although CARR binds to photoactivated, phosphorylated S– and M–opsins (J. Neurosci. 2003, 23:6152), its function in cone phototransduction shutoff is not resolved. We hypothesize that CARR plays a role in the recovery of S– and M–opsins, analogous to ARR function in phosphorylated rhodopsin shutoff.
The X–linked Carr–/– founder mice were created, Carr–/– was backcrossed onto the Arr1–/– background (provided by Jeannie Chen, Nature 1997, 389:505), and PCR genotyped. To examine the knockout phenotypes, paired flash electroretinography (ERG) with different inter–stimulus intervals was used under photopic conditions to measure the photoresponse recovery of the knockout mice, followed by immunoblot analysis and immunofluorescence microscopy with specific antibodies for ARR1 (Mab D9F2, L.A. Donoso) or CARR (Pab LUMIj).
Successful germline transmission of Car and Arr1 backcross onto the Car–/– were verified. Photopic ERG analysis of the Carr–/– mice to measure cone response showed a delay in recovery, while the Arr1–/– photopic ERG was similar to control. The Carr–/–Arr1–/– photopic ERG phenotype was similar to Carr –/– alone. Immunoblot analysis and immunocytochemistry of Car+/– cones had reduced expression levels and dual immunolocalization of ARR1 and CAR confirmed cone expression that was absent in the retinas of Carr–/–Arr1–/–.
Carr–/– knockout mice were successfully created and backcrossed to Arr1–/–. Although both visual arrestins are co–expressed in mouse cone photoreceptors, only Carr–/– mice have a delay in the photopic ERG recovery and provides evidence that CARR is involved in the recovery of cone response. Although ARR1 is co–expressed in cone photoreceptors, it may have other functions.
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