Patterning Genes in Retinal Development

描述(申请人提供)：拟议研究的长期目标是确定导致脊椎动物视网膜中特定细胞类型分化的细胞和分子事件。目前应用的主要目标是评估Hedgehog(HH)信号和维甲酸(RA)信号如何控制光感受器发育的机制模型。在这个模型中，这些信号系统是共同调节的，并且是并行作用的：HH信号传播锥体分化并调节RA信号，RA信号传播视杆分化并调节光感受器表型。我们假设HH和RA通过影响转录因子CRX和RXL/2的表达而起作用，而转录因子CRX和RXL/2反过来调节光感受器特异性基因的表达。我们的研究使用了斑马鱼，一个强大的活体系统来研究脊椎动物光感受器发育的机制。通过使用允许操纵HH和RA信号系统的遗传和分子工具，我们将(1)识别光感受器分化过程中HH信号的细胞和分子靶点，(2)确定光感受器分化过程中RA信号的细胞和分子靶点，以及(3)确定HH和RA信号协调的机制。除了测试机理模型的这些组成部分外，我们的实验还将确定HH和RA是否影响光感受器细胞的命运。 以正确的比例产生多种神经细胞类型的机制是神经生物学中的重要和具有挑战性的问题。这项拟议的研究有望阐明HH和RA在体内调节特定光感受器类型发育中的各自作用。此外，维甲酸治疗正在进行积极的测试，作为视网膜疾病的治疗方法，HH已被建议作为一种潜在的治疗特定视力障碍的方法。更好地理解HH和RA的作用机制对于重新评估当前的治疗方法和设计未来的治疗方法将是有价值的。

DESCRIPTION (provided by applicant): The long-range objective of the proposed research is to determine the cellular and molecular events that lead to the differentiation of specific cell types in the vertebrate retina. The primary goal of the current application is to evaluate a mechanistic model for how Hedgehog (Hh) signaling and retinoic acid (RA) signaling control photoreceptor development. In this model, these signaling systems are co-regulated and act in parallel: Hh signaling propagates cone differentiation and regulates RA signaling, and RA signaling propagates rod differentiation and regulates photoreceptor phenotype. We hypothesize that Hh and RA act by influencing expression of the transcription factors crx and rxl/2, which in turn regulate photoreceptor-specific gene expression. Our research uses the zebrafish, a powerful, in vivo system for studying the mechanisms of vertebrate photoreceptor development. Through the use of genetic and molecular tools that allow the manipulation of the Hh and RA signaling systems, we will (1) identify cellular and molecular targets of Hh signaling during photoreceptor differentiation, (2) identify cellular and molecular targets of RA signaling during photoreceptor differentiation, and (3) determine the mechanism by which Hh and RA signaling are coordinated. In addition to testing these components of the mechanistic model, our experiments will determine whether Hh and RA influence photoreceptor cell fate. The mechanisms that generate multiple neuronal cell types in the correct ratios present important and challenging issues in neurobiology. The proposed research is expected to elucidate the respective roles of Hh and RA in regulating development of specific photoreceptor types in vivo. Furthermore, retinoid treatment is under active testing as a therapy for retinal disease, and Hh has been suggested as a potential treatment for specific visual disorders. An improved understanding of the mechanisms of action of Hh and RA will be valuable for reassessing current treatments, and for designing future therapies.