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Christopher C. Tan, Han na Park, B M. Brown, Jane Abey, P M. Iuvone, Cheryl Craft, Machelle T. Pardue; Visual Arrestins Influence Refraction and Ocular Biometry. Invest. Ophthalmol. Vis. Sci. 2012;53(14):3450.
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© ARVO (1962-2015); The Authors (2016-present)
Mice have two visual arrestins, Arr1, which is expressed in rods, cones and pineal, and Arr4, which is cone and pineal specific. Arrestins are involved in desensitization and recovery of G protein-coupled receptor activity, including opsins. Arr1 is needed for normal light adaptation (Brown et al., IOVS 2010;51:2372), while Arr4 is needed for contrast sensitivity (Brown et al., ARVO 2012). Based on the novel roles of visual arrestins in regulating visual responses, we examined refractive error and ocular biometry in Arr1-/-, Arr4-/-, and Arr1-/-Arr4-/- (DKO) mice and investigated the potential involvement of dopamine (DA) (Craft et al., ARVO 2012).
Refraction and corneal radius of curvature (CRC) were measured with automated photorefractor and keratometer at postnatal day 60-70, respectively. Ocular biometry of anterior chamber depth (ACD), posterior chamber depth (PCD), corneal thickness (CT), retinal thickness (RT), lens thickness (LT), and axial length (AL) were collected from 1310nm spectral-domain optical coherence tomography images. Mice were dark-reared and retinas were collected under light and dark conditions to determine dopamine levels by high-performance liquid chromatography with coulometric detection.
Arrestin knockouts were significantly less hyperopic than wild-type (WT) controls. Arr1-/- and DKOs had significantly shorter AL and smaller LT. DKO mice had significantly steeper CRC and deeper ACD. The absence of Arr1 or Arr4 resulted in smaller CT, but DKOs were similar to WT. DA levels were similar between light and dark conditions in all genotypes. Arr1-/- mice had significantly higher DA levels than all other genotypes.
DA levels in arrestin knockout mice did not show a consistent relationship to refractive or ocular parameters. However, the absence of both Arr1 and Arr4 influenced anterior chamber development. It is unclear if these changes are due to the alterations in visual regulation and contrast sensitivity in the absence of arrestins (Brown et al., ARVO 2012) or if the expression loss of arrestin proteins has a direct role on regulating eye size.
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