TIP60 and APP in Neuronal Development

描述(申请人提供)：Tip60是一个关键的组蛋白乙酰转移酶(HAT)酶，在染色质介导的多种生物学过程中发挥重要作用，包括基因调节、细胞凋亡、细胞周期调节、DNA重组和修复。Tip60是一个多蛋白复合体的一部分，它被转录因子招募到某些基因的启动子中，在那里它通常会乙酰化周围的组蛋白来激活基因表达。因此，Tip60的招募参与了表观遗传基因的调控。虽然Tip60显然在转录调控中起着核心作用，但对于需要Tip60发挥作用的特定组织和细胞类型的发育途径和靶基因仍不清楚。为了研究Tip60在多细胞发育中的作用，我们实验室在果蝇中鉴定并克隆了人Tip60同源物(Dmel\Tip60)。我们已经在转基因果蝇中开发了一种系统，该系统允许在特定组织、细胞类型和发育阶段选择的特定组织、细胞类型和发育阶段中靶向和诱导地过表达野生型或显性阴性HAT缺陷的Dmel\Tip60和Dmel\Tip60基因。利用这个系统，我们已经确定了Dmel-Tip60在神经系统发育早期的形成中是必不可少的。我们表明，Dmel\Tip60在苍蝇脑中的丢失会导致大量神经元丢失和致命性。与我们的发现一致，其他小组已经证明Tip60 HAT活性在通过淀粉样前体蛋白(APP)介导的参与神经元发育的细胞信号通路转录激活目标基因中发挥重要作用。有趣的是，年轻的阿尔茨海默病(AD)模型小鼠在获得代表该疾病的A2斑块、神经毒性和行为异常之前很久，其大脑中过度产生APP的Tip60水平就大幅增加。这些发现为我们的中心假设提供了基础，即APP的扰动导致内源性Tip60的上调，导致Tip60/APP和独有的Tip60染色质介导的神经元通路的错误调节，这两个通路与发育和神经退化都相关。为了验证这一假设，将实现以下具体目标。Aim 1将确定参与不同神经元发育过程的Tip60表观遗传调控的靶基因，Aim 2将确定Tip60染色质介导的神经元突起和靶基因在体内受到APP，过度表达的影响程度。这些知识对基于染色质的治疗Tip60相关疾病的新疗法的开发具有重要意义。公共卫生相关性：我们的目标是破译Tip60和APP在神经元发育中的作用，这应该会深刻地增强我们对神经系统发育和神经退行性疾病的理解。这些知识对基于表观遗传学的新疗法的发展具有重要意义。

DESCRIPTION (provided by applicant): Tip60 is a key histone acetyltransferase (HAT) enzyme that plays essential roles in diverse chromatin- mediated biological processes, including gene regulation, apoptosis, cell-cycle regulation, DNA recombination and repair. Tip60 is part of a multi-protein complex that is recruited by transcription factors to the promoters of certain genes where it generally acetylates surrounding histones to activate gene expression. Thus, Tip60 recruitment is involved in epigenetic gene regulation. While it is evident that Tip60 plays a central role in transcriptional control, it remains unclear as to the tissue and cell type-specific developmental pathways and target genes that require Tip60 to function. To investigate the role of TIP60 in multicellular development, our laboratory has identified and cloned the human TIP60 homolog in Drosophila (Dmel\TIP60). We have developed a system in transgenic flies that allows for targeted and inducible overexpression of wild-type or dominant negative HAT defective Dmel\TIP60 and Dmel\TIP60 knockdown in specific tissues, cell types and developmental stages of choice. Using this system, we have determined that Dmel\TIP60 is essential for nervous system formation during early development. We show that loss of Dmel\TIP60 in the fly brain leads to substantial neuronal loss and lethality. Consistent with our finding, other groups have documented an essential role for Tip60 HAT activity in the transcriptional activation of target genes via amyloid precursor protein (APP) mediated cell signaling pathways proposed to be involved in neuronal development. Intriguingly, TIP60 levels dramatically increase in the brains of young Alzheimer's disease (AD) model mice overproducing APP long before they acquire the A2 plaques, neurotoxicity and behavioral abnormalities representative of the disease. These findings provide the basis for our central hypothesis that APP perturbation causes upregulation of endogenous TIP60, leading to misregulation of both TIP60/APP and exclusive TIP60 chromatin-mediated neuronal pathways that is relevant in both development and neurodegeneration. To test this hypothesis, the following specific aims will be carried out. Aim 1 will identify TIP60 epigenetically regulated target genes that participate in distinct neuronal developmental processes and Aim 2 will determine the extent to which TIP60 chromatin-mediated neuronal processes and target genes are affected by overexpression of APP, in vivo. Such knowledge has important implications for the development of novel chromatin-based therapeutics in TIP60 associated disorders. PUBLIC HEALTH RELEVANCE: Our goal of deciphering the role of Tip60 and APP in neuronal development should profoundly enhance our understanding of nervous system development and neurodegenerative disorders. Such knowledge has important implications for the development of novel epigenetic-based therapeutics.