Retina: The control of photoreceptor cell fate

P_.提供。PdnUNRInvestigator/Program Director（Last，First，Middle）：Tomlinson，Andrew 视网膜发育中的一个关键问题是不同类型的感光细胞是如何指定和定位的 在视网膜内。果蝇的眼睛是解决这个问题的一个有价值的模型系统。苍蝇 眼睛是由数百个称为小眼的亚单位组成的复合集合体。在每个小眼内 是不同的光感受器类型，小眼作为包含不同光感受器的不同类别出现 类型光感受器的类型因其视蛋白表达、轴突投射和位置而不同 在小眼内。我们在这里解决的主要问题是：（一）光感受器如何在 每一个小眼都是独一无二的(ii)不同类型的小眼是如何区分的？ (I)R7光感受器的特徴：每个小眼中的UV敏感光感受器是R7细胞。 来自不同光感受器的信号，这些光感受器接触假定的R7并激活两个不同的内- 细胞内的信号-Ras和Notch（N）途径。我们希望了解这两个 通路相互作用以指定R7细胞。它们是否共同作用，为R7前体提供 独特的发展线索，还是他们以不同的方式行事？例如，N途径激活 允许激活Ras通路而没有其他功能？一旦这些问题得到解答， 将检查分子相互作用的性质，和/或两个途径的整合。 (2)小眼内的不对称性：每个小眼内的感光器排列成 与眼睛的光学特性密切相关的非对称方式。Ommatidia解码分级 信息传递到视网膜以建立初始不对称性，然后将其传递到视网膜的其他细胞。 小眼这里的问题是分级信息是如何建立的，以及它是如何解码的， 传达到单位的所有细胞。 (3)背缘的规格：背缘小眼是偏振光检测细胞， 眼的背侧末端，并且包含R7和R8细胞的特化。信号从 邻近的头部组织仅在背部组织中诱导这些小眼。我们希望了解信号 从头部组织组织的背缘小眼和其他相关的视网膜专业化。

P_.ROVIDED. Pdncipal Investigator/Program Director (Last, first, middle): Tomlinson, Andrew A critical question in retinal development is how different photoreceptor types are specified and positioned within a retina. The Drosophila eye is a valuable model system with which to address this question. The fly eye is a compound aggregate of many hundred sub-units called ommatidia. Within each ommatidium there are distinct photoreceptor types and ommatidia occur as different classes containing varying photoreceptor types. The photoreceptor types differ by their opsin expressions, their axonal projections, and their positions within the ommatidia. The major questions we are addressing here are: (i) how the photoreceptors within each ommatidium are uniquely specified? (ii) How the different types of ommatidia are specified? (I) Specification of the R7photoreceptor: The UV sensitive photoreceptor in each ommatidium is the R7 cell. Signals from differentiating photoreceptors that contact the presumptive R7 and activate two distinct intra- cellular signals within the cell - the Ras and Notch (N) pathways. We wish to understand how these two pathways interact to specify the R7 cell. Do they act combinatorially to provide the R7 precursor with a unique developmental cue, or do they act in a different manner? For example could N pathway activation allow the activation of the Ras pathway and have no other function? Once these questions are answered we will examine the nature of the molecular interaction, and or integration of the two pathways. (2) Specification of asymmetry within the ommatidia: The photoreceptors in each ommatidium are arrayed in an asymmetric manner that is critically related to the optical properties of the eye. Ommatidia decode graded information the retina to establish an initial asymmetry that is then communicated to the other cells of the ommatidium. The questions here are how the graded information is established, and how it is decoded and communicated to all cells of the unit. (3) The specification of the dorsal rim: The dorsal rim ommatidia are polarized light detectors cells found in the dorsal extreme of the eye and contain specializations of the R7 and R8 ceils. Signals emanating from the neighboring head tissue induce these ommatidia in only dorsal tissues. W e wish to understand how signals from the head tissue organize the dorsal rim ommatidia and other associated retinal specializations.