Autosomal recessive retinitis pigmentosa E150K opsin mice exhibit photoreceptor disorganization
Ning Zhang, … , Vladimir J. Kefalov, Krzysztof Palczewski
Ning Zhang, … , Vladimir J. Kefalov, Krzysztof Palczewski
Published December 10, 2012
Citation Information: J Clin Invest. 2013;123(1):121-137. https://doi.org/10.1172/JCI66176.
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Research Article Ophthalmology

Autosomal recessive retinitis pigmentosa E150K opsin mice exhibit photoreceptor disorganization

Abstract

The pathophysiology of the E150K mutation in the rod opsin gene associated with autosomal recessive retinitis pigmentosa (arRP) has yet to be determined. We generated knock-in mice carrying a single nucleotide change in exon 2 of the rod opsin gene resulting in the E150K mutation. This novel mouse model displayed severe retinal degeneration affecting rhodopsin’s stabilization of rod outer segments (ROS). Homozygous E150K (KK) mice exhibited early-onset retinal degeneration, with disorganized ROS structures, autofluorescent deposits in the subretinal space, and aberrant photoreceptor phagocytosis. Heterozygous (EK) mice displayed a delayed-onset milder retinal degeneration. Further, mutant receptors were mislocalized to the inner segments and perinuclear region. Though KK mouse rods displayed markedly decreased phototransduction, biochemical studies of the mutant rhodopsin revealed only minimally affected chromophore binding and G protein activation. Ablation of the chromophore by crossing KK mice with mice lacking the critical visual cycle protein LRAT slowed retinal degeneration, whereas blocking phototransduction by crossing KK mice with GNAT1-deficient mice slightly accelerated this process. This study highlights the importance of proper higher-order organization of rhodopsin in the native tissue and provides information about the signaling properties of this mutant rhodopsin. Additionally, these results suggest that patients heterozygous for the E150K mutation should be periodically reevaluated for delayed-onset retinal degeneration.

Authors

Ning Zhang, Alexander V. Kolesnikov, Beata Jastrzebska, Debarshi Mustafi, Osamu Sawada, Tadao Maeda, Christel Genoud, Andreas Engel, Vladimir J. Kefalov, Krzysztof Palczewski

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Figure 5

Single-cell suction electrode responses of WT, EK, and KK rods from 3- to 5-week-old mice.

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Single-cell suction electrode responses of WT, EK, and KK rods from 3- t...
(A) Families of single-cell responses from representative WT (left), EK (middle), and KK (right) rods. Flash strengths were increased from 0.9 to 706 photons/μm2, by single steps of 0.5 log units each (500 nm light). Red traces show responses to the identical light intensity (20 photons/μm2) for comparison. In these 3 cells, dark currents were 14.2, 13.0, and 8.9 pA, respectively. Absolute (B) and normalized (C) single-cell response amplitudes are shown as a function of flash strength. Points were fitted with Naka-Rushton hyperbolic functions. WT (n = 19), EK mutant (n = 19), KK mutant (n = 18) I1/2 levels are shown in Table 2. (D) Normalized single-cell dim flash responses (to light intensities of 7.6 photons/μm2) from dark-adapted WT, EK, and KK opsin mutant rods. Phototransduction activation was unaffected, but broadening of the response peak and acceleration of dim flash recovery (see Table 2) were observed in KK rods, whereas EK cells displayed an intermediate phenotype. (E) τD values from a series of supersaturating flashes. Linear fits through the data yielded τD values of 385 ± 23 ms (WT, n = 19), 292 ± 24 ms (EK, n = 19), and 152 ± 14 ms (KK, n = 18). Recovery from saturating flashes was also accelerated in mutant photoreceptor cells. Data are mean ± SEM.