Molecular Networks Controlling Subtype Specification of Color Photoreceptors

描述（由申请人提供）：神经元规格的精确控制是形成高度复杂神经系统的先决条件。此外，神经系统损伤和退化涉及特定神经元群的丢失，因此，了解神经元亚型规范的机制与人类健康有关。我的实验室和其他人已经确定了许多关键的命运决定因素，涉及指定不同的光感受器神经元亚型，使用遗传上可顺从的果蝇眼睛作为模型系统。最近，我们发现四个保守的转录因子[Otd（脊椎动物中的OTX/CRX）， Tj (MAF/NRL), Senseless （GFI1）和Pph13 (ARX)]在蓝色和绿色光感受器（pr）的二元命运选择中起着至关重要的作用。此外，我们证明了这些PR命运决定因素对Hippo肿瘤抑制通路的两个关键组分Wts和Yki的表达和/或活性的差异调节，以控制蓝色PR和绿色PR中细胞类型特异性基因的表达。虽然Hippo通路以其在生长控制中的作用而闻名，但我们的研究揭示了Hippo通路如何控制有丝分裂后细胞命运规范的新的机制见解。在这里，我们提出了实验来扩展我们对Hippo通路如何控制细胞命运规范的认识，验证了PR命运决定因素和Hippo通路介质之间的串音对于蓝色和绿色PR之间精确的二元细胞命运选择至关重要的中心假设。利用遗传、生化和分子方法，我们提出定义PR命运决定因素和Hippo通路之间的关键串扰节点，并阐明其潜在的分子机制。这些节点包括a) Hippo通路效应物Sd在蓝色和绿色pr中的差异作用（目的1）；b)蓝色和绿色pr中Hippo通路调控因子- melt和wts的调控（目标2）；c) Hippo和smad依赖信号之间的串扰，以确保二元命运决定（目标3）。本研究的结果将为未来研究Hippo通路在其他生物PR规范中的作用以及一般的神经元规范提供重要指导。

DESCRIPTION (provided by applicant): Precise control of neuronal specification is a prerequisite for the formation of a highly complex nervous system. Moreover, nervous system injury and degeneration involves a loss of specific groups of neurons, and therefore, understanding the mechanisms underlying neuronal subtype specification has relevance to human heath. My lab and others have identified numerous key fate determinants involved in specifying distinct photoreceptor neuron subtypes, using the genetically amenable Drosophila eye as a model system. Recently, we showed that four conserved transcription factors - [Otd (OTX/CRX in vertebrates), Tj (MAF/NRL), Senseless (GFI1), and Pph13 (ARX)] - play crucial roles in binary fate choices between blue and green photoreceptors (PRs). Moreover, we demonstrated that these PR fate determinants differentially regulate the expression and/or activity of two key components of the Hippo tumor suppressor pathway - Wts and Yki - to control cell type-specific gene expression in blue vs green PRs. While the Hippo pathway is well known for its role in growth control, our study revealed novel mechanistic insights into how the Hippo pathway controls cell fate specification in postmitotic cells. Here, we propose experiments to expand our knowledge on how the Hippo pathway controls cell fate specification, testing the central hypothesis that cross-talk between PR fate determinants and Hippo pathway mediators is critical for precise binary cell fate choices between blue and green PRs. Using genetic, biochemical and molecular approaches, we propose to define key crosstalk nodes between the PR fate determinants and the Hippo pathway and elucidate their underlying molecular mechanisms. These nodes include a) differential actions of the Hippo pathway effector Sd in blue vs green PRs (Aim 1); b) regulation of the Hippo pathway regulators - melt and wts - in blue and green PRs (Aim 2); and c) crosstalk between Hippo and Smad-dependent signaling to ensure a binary fate decision (Aim 3). Outcomes of this study will serve as an important guide for future studies on the role of the Hippo pathway in PR specification in other organisms, and for neuronal specification in general.