Genetic Analysis of Photoreceptor Differentiation

描述（申请人提供）：光感受器是视网膜上高度特化的光敏细胞，对视觉感知至关重要。由于遗传原因，人眼中光感受器的丧失是导致失明的常见原因。尽管对光感受器细胞的研究已经投入了大量的精力，但对其分化和功能的一些基本方面仍然知之甚少。特别是，导致光感受器形态复杂特征（如光敏外段）组装的分子机制在很大程度上仍是未知的。这些机制的缺陷经常导致光感受器死亡并导致人类失明。深入了解人眼光感受器退化的遗传原因的一个非常有效的方法是研究光感受器丧失的动物模型。斑马鱼是用于研究视网膜疾病遗传原因的主要动物模型之一。利用斑马鱼的诱变方法，我们已经确定并描述了几种导致光感受器死亡的突变。一种新发现的突变，jj203，导致杆状光感受器的缺失和锥体外节分化的延迟。我们对jj203基因座的分子性质进行了表征，发现它编码一种分子马达，即运动蛋白。这一分析首次证明了运动蛋白在视杆细胞和视锥细胞中的功能不同，提出了关于它们的货物特异性和与纤毛运输机械相互作用的重要问题。我们计划通过正向和反向遗传方法，利用化学诱导的突变等位基因，来表征运动蛋白在光感受器分化和存活中的作用。我们将询问不同的激酶突变体影响光感受器表型的哪些方面，以及不同的激酶是否可以相互替代。我们还将研究运动蛋白如何与鞭毛内运输相互作用，这是外节形成所必需的过程。这些研究将为驱动光感受器分化的分子机制提供基本的见解。

DESCRIPTION (provided by applicant): Photoreceptors are highly specialized light-sensitive cells of the retina, essential for visual perception. The loss of photoreceptors in the human eye due to genetic causes is a frequent cause of blindness. Although a lot of effort has been devoted to the studies of the photoreceptor cell, some essential aspects of its differentiaton and function remain poorly understood. In particular, molecular mechanisms that lead to the assembly of the sophisticated features of photoreceptor morphology, such as the photosensitive outer segment, remain to a large extend unknown. Defects of these mechanisms frequently cause photoreceptor death and lead to blindness in humans. A very productive way to gain insight into the genetic causes of photoreceptor degeneration in the human eye is to study animal models of photoreceptor loss. The zebrafish is one of the leading animal models used to study the genetic causes of retinal disease. Using a mutagenesis approach in zebrafish, we have identified and characterized several mutations that lead to photoreceptor death. A newly discovered mutation, jj203, causes a loss of rod photoreceptors and a delay in the differentiation of cone outer segments. We characterized the molecular nature of the jj203 locus and found that it encodes a molecular motor, kinesin. This analysis demonstrated for the first time that kinesins function differently in rods and cones, raising important questions regarding their cargo specificity and the interaction with ciliary transport machinery. We are planning to characterize the role of kinesins in photoreceptor differentiation and survival using chemically-induced mutant alleles recovered both via forward and reverse genetic approaches. We will ask what aspects of photoreceptor phenotype are affected in different kinesin mutants and whether different kinesins can substitute each other. We will also study how kinesins interact with the intraflagellar transport, a process essential for outer segment formation. These studies will provide fundamental insights into the molecular mechanisms that drive photoreceptor differentiation. PUBLIC HEALTH RELEVANCE: We will use animal model, the zebrafish, to study genes responsible for the differentiation of vertebrate, including human, photoreceptor cells. These studies will reveal mechanisms that contribute to photoreceptor degeneration in the human eye, and consequently blindness.