Schonthaler Helia B, Lampert Johanna M, Isken Andrea, Rinner Oliver, Mader Andreas, Gesemann Matthias, Oberhauser Vitus, Golczak Marcin, Biehlmaier Oliver, Palczewski Krzysztof, Neuhauss Stephan C F, von Lintig Johannes
University of Zurich, Institute of Zoology, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
Eur J Neurosci. 2007 Oct;26(7):1940-9. doi: 10.1111/j.1460-9568.2007.05801.x. Epub 2007 Sep 14.
An enzyme-based cyclic pathway for trans to cis isomerization of the chromophore of visual pigments (11-cis-retinal) is intrinsic to vertebrate cone and rod vision. This process, called the visual cycle, is mostly characterized in rod-dominated retinas and essentially depends on RPE65, an all-trans to 11-cis-retinoid isomerase. Here we analysed the role of RPE65 in zebrafish, a species with a cone-dominated retina. We cloned zebrafish RPE65 and showed that its expression coincided with photoreceptor development. Targeted gene knockdown of RPE65 resulted in morphologically altered rod outer segments and overall reduced 11-cis-retinal levels. Cone vision of RPE65-deficient larvae remained functional as demonstrated by behavioural tests and by metabolite profiling for retinoids. Furthermore, all-trans retinylamine, a potent inhibitor of the rod visual cycle, reduced 11-cis-retinal levels of control larvae to a similar extent but showed no additive effects in RPE65-deficient larvae. Thus, our study of zebrafish provides in vivo evidence for the existence of an RPE65-independent pathway for the regeneration of 11-cis-retinal for cone vision.
基于酶的视觉色素（11-顺式视黄醛）发色团从反式到顺式异构化的循环途径是脊椎动物视锥和视杆视觉所固有的。这个过程称为视觉循环，主要在视杆主导的视网膜中得到表征，并且基本上依赖于RPE65，一种全反式到11-顺式视黄醛异构酶。在这里，我们分析了RPE65在斑马鱼（一种视锥主导视网膜的物种）中的作用。我们克隆了斑马鱼RPE65，并表明其表达与光感受器发育一致。对RPE65进行靶向基因敲低导致视杆外段形态改变，并且11-顺式视黄醛水平总体降低。行为测试和类视黄醇代谢物分析表明，RPE65缺陷幼虫的视锥视觉仍然正常。此外，视杆视觉循环的有效抑制剂全反式视黄胺将对照幼虫的11-顺式视黄醛水平降低到类似程度，但对RPE65缺陷幼虫没有叠加效应。因此，我们对斑马鱼的研究为视锥视觉中存在独立于RPE65的11-顺式视黄醛再生途径提供了体内证据。
