Regulation of border specification in the developing forebrain by Gcn5-mediated r

描述(申请人提供)：长期以来，了解哺乳动物前脑发育的机制一直是神经生物学家的目标，因为前脑通常被称为结构，其复杂性使人类有别于其他高级生物体。到目前为止，许多信号通路都与前脑原基--前脑的正常模式和发育有关。然而，这些途径是如何在分子水平上受到调控的，在很大程度上还不清楚。维甲酸(RA)信号通路就是其中之一。虽然维甲酸信号显然是前脑正常发育所必需的，但尚不清楚特定细胞类型对RA的反应是如何调节的。此外，由于RA合成酶和RA受体分子的冗余性，很难研究RA依赖基因转录的区域性丢失的影响。本研究的目的是利用一个缺乏组蛋白乙酰转移酶Gcn5(Gcn5hat)活性的小鼠系来更好地了解RA信号在发育中的前脑边界指定中的作用。Gcn5hat突变体在背侧端脑中显示了表达丘脑标记的异位结构，表明背侧间脑在嘴端大规模扩张。Gcn5已被认为参与调节RA信号，并被认为发育中丘脑的吻部扩张受限于RA的背部局部产生。初步数据表明，Gcn5通过非表观遗传机制调节RA信号，这对Gcn5介导组蛋白乙酰化是促进RA依赖基因表达的主流假说提出了质疑。本研究旨在解决与Gcn5相关的两个基本问题及其在RA介导的前脑发育中的作用。首先，我将研究Gcn5hat突变体的前脑模式和分化，以确定Gcn5在前脑发育中的确切作用。更具体地说，它将确定Gcn5乙酰转移酶活性的要求，以确定前脑结构之间的适当边界，并还将确定这些结构是否继续产生其适当的神经元亚型。其次，这项研究将验证Gcn5乙酰转移酶活性是发育中的前脑中适当的RA信号所必需的假设，并将确定发育表型是否可以被饮食中RA水平的变化所调节。最后，本研究将探讨Gcn5调控RA信号的分子机制。我将测试这一新的假设，即Gcn5通过TACC1的乙酰化促进RAR？介导的信号传递。这项研究将拓宽我们对Gcn5如何通过新颖的、非表观遗传机制引发组织特异性信号反应的理解。总之，这些实验将阐明一种对发育至关重要的乙酰基转移酶的新功能，增加我们对RA信号在前脑发育中的理解，并确定需要Gcn5的特定神经发育过程，可能与人类发育、认知和神经精神疾病有关。

DESCRIPTION (provided by applicant): It has long been a goal of neurobiologists to understand the mechanisms that regulate development of the mammalian forebrain, as the forebrain is often referred to as the structure whose complexity sets humans apart from other higher-order organisms. To date, numerous signaling pathways have been implicated in the proper patterning and development of the forebrain primordium, the prosencephalon. However, how these pathways are regulated at the molecular level is largely unclear. The retinoic acid (RA) signaling pathway is one such pathway. Though it is clear that retinoic acid signaling is required for proper development of the forebrain, it is unclear how cell type-specific responses to RA are modulated. Additionally, because of redundancy in RA-synthesizing enzymes and RA receptor molecules, it has been difficult to investigate the effects of regional loss of RA-dependent gene transcription. The goal of this study is to utilize a mouse line lacking enzymatic activity of the histone acetyltransferase Gcn5 (Gcn5hat) to better understand the role of RA signaling in border specification in the developing forebrain. Gcn5hat mutants display ectopic structures in the dorsal telencephalon that express thalamic markers, suggesting a massive rostral expansion of the dorsal diencephalon. Gcn5 has been previously implicated in regulating RA signaling and it has been hypothesized that rostral expansion of the developing thalamus is limited by localized dorsal production of RA. Preliminary data suggests that Gcn5 regulates RA signaling through non-epigenetic mechanisms, which calls into question the prevailing hypothesis that Gcn5-mediated histone acetylation is required to promote RA-dependent gene expression. This study aims to address two fundamental questions relating to Gcn5 and its role in RA-mediated forebrain development. First, I will investigate patterning and differentiation in the forebrains of Gcn5hat mutants to determine the exact role of Gcn5 in forebrain development. More specifically, it will determine the requirement of Gcn5 acetyltransferase activity for specifying the proper borders between forebrain structures and will also determine whether these structures go on to produce their appropriate neuronal subtypes. Second, this study will test the hypothesis that Gcn5 acetyltransferase activity is required for proper RA signaling in the developing forebrain and I will determine whether the developmental phenotypes can be modulated by changes in dietary RA levels. Lastly, this study will investigate the molecular mechanism by which Gcn5 regulates RA signaling. I will test the novel hypothesis that Gcn5 promotes RAR¿-mediated signaling via acetylation of TACC1. This investigation will broaden our understanding of how Gcn5 elicits tissue-specific signaling responses through novel, non-epigenetic mechanisms. Together, these experiments will shed light on new functions of a developmentally critical acetyltransferase, increase our understanding of RA signaling in forebrain development, and identify specific neurodevelopmental processes that require Gcn5, potentially implicating Gcn5 in human developmental, cognitive, and neuropsychiatric diseases.