Autosomal recessive retinitis pigmentosa E150K opsin mice exhibit photoreceptor disorganization

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

Subretinal fibrosis in Stargardt's disease

A

Falco : tooneelspel

Om. K. de Lae

The contribution of stereo vision to the control of braking

Introduction To be successful in the confusion of daily traffic, executing appropriate brake manoeuvres is an important skill. When following a car, a driver needs to be alert in order to quickly register and act upon decelerations of a leading vehicle. From the literature, it can be concluded that monocular information sources like the optical variable tau play an important role in the visual control of braking, but that several other visual cues, such as depth information from stereo vision, might have a supplement impact on brake behaviour. In present experiment, the contribution of stereo vision was investigated when performing a braking task Methods 26 female participants with normal (≤ 40 arcsec on a Grade Circle Test; StereoN; N = 13) or weak (≥ 800 arcsec; StereoW; N = 13) stereo vision performed braking tasks when driving at a speed of approximately 11 km/h on a go-cart. Subjects could start braking at 4, 7 or 10 meters from a target vehicle when a red lamp on the rear of this vehicle lit. The momentanuous position of the go-cart was measured at 200Hz with a laser (Noptel CMP2-30) and velocity and acceleration were calculated. From these data, time and distance of brake initiation, and time of maximal deceleration were calculated as principal dependent variables and submitted to a 3 (conditions of distance: 4m vs. 7m vs. 10m) x 2 (group conditions: stereoW, stereoN) ANOVA with repeated measures on the first factor. Results StereoW group started braking earlier in time than StereoN (p≤.05). In the braking adjustment phase, maximal deceleration occurred closer in time to contact for StereoN group than StereoW (p<.01). This effect increased up to 2596 msec in the 10m-condition, as the interaction effect showed up (p<.01). StereoN group reached standstill on a greater distance than StereoW group (p<.05). Conclusions From this experiment, it can be concluded stereo vision contributes to the initiation as well as to the control of a braking manoeuvre. However, this does not mean that people with a lack of stereo vision may cause greater risks in traffic negotiation, in particular situations in which rear-end collisions may occur. The lack of good stereo vision is even associated with more prudent brake behaviour, i.e. an earlier brake initiation and an earlier maximal deceleration