Molecular Networks Controlling Subtype Specification of Color Photoreceptors

描述(申请人提供)：精确控制神经元规格是形成高度复杂的神经系统的先决条件。此外，神经系统的损伤和退化涉及特定神经元组的丢失，因此，了解神经元亚型指定的机制与人类健康相关。我的实验室和其他实验室已经确定了许多关键的命运决定因素，这些决定因素涉及到指定不同的光感受器神经元亚型，使用遗传上可听从基因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)，无意义(GFI1)和Pph13(ARX)]在蓝色和绿色光感受器(PR)之间的二元命运选择中发挥关键作用。此外，我们还证明了这些PR命运决定因素对河马肿瘤抑制途径的两个关键成分WTS和YKI的表达和/或活性的不同调控，从而控制蓝色PR和绿色PR中细胞类型特异性基因的表达。虽然河马途径以其在生长控制中的作用而闻名，但我们的研究揭示了河马途径如何控制有丝分裂后细胞命运的新的机制见解。在这里，我们提议进行实验，以扩大我们关于河马途径如何控制细胞命运规范的知识，测试核心假设，即PR命运决定因素和河马通路介体之间的相互作用对于在蓝色和绿色PR之间精确地选择细胞命运至关重要。利用遗传学、生物化学和分子生物学方法，我们建议确定PR命运决定因素和河马途径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)河马途径效应器SD在蓝色和绿色PR中的不同作用(目标1)；b)在蓝色和绿色PR中对河马途径调节因子Melt和WTS的调节(目标2)；以及c)河马和Smad依赖的信号之间的串扰，以确保二元命运决定(目标3)。这项研究的结果将为未来研究河马通路在其他生物的PR规范中的作用以及一般的神经元规范提供重要的指导。

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.