The Actin Cytoskeleton of Photoreceptor Inner Segments

描述（由申请人提供）：本项目的目标是了解光感受器内节的肌动蛋白细胞骨架如何有助于光感受器的形态发生，维持和存活，从而促进视觉。光感受器内节细胞骨架由平行的肌动蛋白丝束组成，终止于围绕外节基部的指状花萼突起。本研究验证了这一假设，即这些束是至关重要的感光细胞形态发生，内，外段对齐，并对齐的内段与瞳孔。它还检查了假设，这些束提供轨道肌球蛋白依赖的货物之间的核周肌样区域和外段的运输。几种蛋白质专门定位于这些结构，包括两种肌动蛋白交联剂肌成束蛋白和肌纤维蛋白，以及一种III类肌球蛋白Myo 3A。肌成束蛋白突变的患者患有青少年视网膜炎，Myo 3A过表达也会导致感光细胞肌动蛋白细胞骨架异常。虽然尚未研究肌成束蛋白突变的细胞缺陷的性质及其如何导致视网膜功能障碍，但它说明了视网膜内段肌动蛋白细胞骨架的重要性。这项研究测试的假设，肌动蛋白丝束的交联和调节成核协调其正确的组装和维护，因此需要维持健康的光感受器。本研究将首先关注肌成束蛋白、肌纤维蛋白和Myo 3A。为了研究光感受器的肌动蛋白纤维束，将采用两种动物模型系统，鱼和爪蟾，每一种都是唯一适合回答某些问题的。将使用鳟鱼视网膜研究发育过程中内节肌动蛋白丝束和花萼突起的形态发生，因为它们具有包含感光细胞发育所有阶段的增殖区。我们还将使用鱼（鲈鱼和绿色翻车鱼）鉴定光感受器内/外节细胞骨架的其他蛋白质组分，因为可以使用光感受器内/外节的均质制备物，并且鱼的大小使得生物化学易于处理。这些研究将提供新的信息的成分，组装和功能的内节丝束和萼过程，从而增加或了解感光细胞形态发生，功能和生存的基本机制。

DESCRIPTION (provided by applicant): The goal of this project is to understand how the actin cytoskeleton of the photoreceptor inner segment contributes to the morphogenesis, maintenance and survival of photoreceptors, and hence to vision. The photoreceptor inner segment cytoskeleton is comprised of parallel bundles of actin filaments terminating in fingerlike calycal processes that surround the base of the outer segment. This research tests the hypothesis that these bundles are critical to photoreceptor morphogenesis, to inner and outer segment alignment, and to alignment of the inner segment with the pupil. It also examines the hypothesis that these bundles provide tracks for myosin-dependent transport of cargo between the perinuclear myoid region and the outer segment. Several proteins localize specifically to these structures including two actin cross-linkers fascin and fimbrin and Myo3A, a class III myosin. Patients with a mutation in fascin suffer from retinitis pimentosa, and Myo3A over-expression also causes abnormalities in the photoreceptor actin cytoskeleton. While the nature of the cellular defect and how it contributes to retinal dysfunction has not been studied yet for the fascin mutation, it illustrates the importance of the inner segment actin cytoskeleton in the retina. This research tests the hypothesis that the cross-linking and regulated nucleation of actin filament bundles orchestrates their proper assembly and maintenance, and thus is required for maintenance of healthy photoreceptors. This study will initially focus on fascin, fimbrin and Myo3A. In order to study the actin filament bundles of photoreceptors, two animal model systems will be employed, fish and Xenopus, each of which is uniquely suited to answer certain questions. The morphogenesis of the inner segment actin filament bundles and calycal processes during development will be studied using trout retinas, since they possess a proliferative zone containing all stages of photoreceptor development. We will also identify other protein components of the photoreceptor inne/outer segment cytoskeleton using fish (Bass and green sunfish), because homogeneous preparations of photoreceptor inner outer segments can be used, and the size of the fish makes biochemistry tractible. These studies will provide new information about the constituents, assembly and functions of the inner segment filament bundles and calycal processes and will thereby increase or understanding of mechanisms fundamental to photoreceptor morphogenesis, function and survival.