Genetic Analysis of Photoreceptor Differentiation

描述(申请人提供)：光感受器是高度专门化的视网膜感光细胞，对视觉感知至关重要。由于遗传原因导致的人眼光感受器的丧失是一种常见的失明原因。虽然对光感受器细胞的研究投入了大量的努力，但对其分化和功能的一些基本方面仍然知之甚少。特别是，导致组装复杂的感光细胞形态特征的分子机制，如光敏外层片段，在很大程度上仍然未知。这些机制的缺陷经常导致光感受器死亡，并导致人类失明。要深入了解人眼光感受器退化的遗传原因，一个非常有成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。利用斑马鱼的突变方法，我们已经鉴定和表征了几个导致光感受器死亡的突变。一种新发现的突变jj203会导致杆状感光器的丢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研究，发现它编码一种分子马达--动蛋白。这一分析首次证明了动蛋白在视杆和视锥中的不同功能，提出了关于它们的货物专一性以及与纤毛运输机械相互作用的重要问题。我们正计划利用化学诱导的突变等位基因，通过正向和反向遗传方法恢复，来表征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Kinesin突变体对光感受器表型的哪些方面产生影响，以及不同的Kinesin是否可以相互替代。我们还将研究动蛋白如何与鞭毛内运输相互作用，这是一个对外节形成至关重要的过程。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。 公共卫生相关性：我们将使用动物模型斑马鱼来研究负责脊椎动物分化的基因，包括人类的感光细胞。这些研究将揭示导致人眼感光细胞退化，从而导致失明的机制。

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.