Analyses of roles of nutritional factors in brain function using mouse genetics and application for the treatment of brain disease

为了了解营养因素在脑功能中的作用和开发脑疾病的治疗方法，我们研究了维生素A(维甲酸)和必需氨基酸色氨酸(Trp)在脑功能中的作用：(1)转基因小鼠的建立和分析，使其能够调节前脑中野生型或显性负性视黄酸受体(RAR)的表达。先前的研究表明，RA缺陷小鼠和RARs基因敲除小鼠都表现出海马LTP和空间记忆的损害，这表明RARs在学习和记忆中发挥着重要作用。为了进一步阐明RAR在学习和记忆中的作用，我们建立了条件突变小鼠，使其能够使用四环素系统调节前脑特异性RAR-α的过度表达或RAR-α的显性负突变(DN)。生化分析显示，RAR-α过表达导致RAR-…表达增加前脑中有更多的靶基因，提示这些突变小鼠的视黄醇信号通路被激活。重要的是，行为分析显示，RAR-α过度表达的小鼠表现出增强了空间、社会识别和背景恐惧记忆的形成。综上所述，我们认为RAR-α对学习和记忆具有积极的调节作用。(2)Trp在脑功能中的作用以及Trp在焦虑相关行为治疗中的应用。全身性Trp的耗竭是研究减少5-HT对认知影响的重要工具。我们首先研究了长期食用低色氨酸饮食对小鼠记忆形成的影响。Trp限制的小鼠表现出海马体依赖的情景恐惧记忆的形成受损。相比之下，这些小鼠表现出正常的海马体依赖的空间记忆，以及线索恐惧和条件性味觉厌恶记忆，这是杏仁核依赖的记忆过程。因此，限制饮食色氨酸似乎会导致小鼠海马区依赖的情景恐惧记忆形成的选择性损害。我们已经表明，限制摄取色氨酸也影响小鼠的情绪行为。为了开发焦虑相关行为的治疗方法，我们接下来检测了Trp限制对在前脑过度表达alplaCaMKII的转基因小鼠中观察到的焦虑相关行为的影响。Trp限制导致CaMKII转基因小鼠焦虑相关行为的改善，增加了Trp限制用于治疗焦虑相关疾病的可能性。较少

To understand roles of nutritional factors in brain function and develop the treatment for brain diseases, we have investigated roles of Vitamin A (Retinoic Acid) and essential amino acid tryptophan (TRP) in brain function.(1) Generation and Analyses of Transgenic mice that enable to regulate expression of wild type or dominant negative Retinoic Acid Receptor (RAR) in forebrain.Retinoic acid receptors (RARs) ubiquitously and highly express in brain. Previous studies have shown that RA-deficient mice and RARs knock out mice exhibit impairments of both hippocampal LTP and spatial memory, suggesting an essential role of RARs in learning and memory. To further clarify the roles of RARs in learning and memory, we generated conditional mutant mice that enable to regulate forebrain-specific overexpression of RAR-alpha or dominant negative mutant (dn) of RAR-alpha using tetracycline system. Biochemical analyses showed that overexpression of RAR-alpha leads to an increase in expression of RARs- … More target gene in forebrain, suggesting the activation of retinoid signaling pathway in these mutant mice. Importantly, behavioral analyses revealed that RAR-alpha overexpression mice show enhancement of formation of spatial, social recognition and contextual fear memories. Taken together with previous findings, we suggest that RAR-alpha functions as a positive regulator for learning and memory.(2) Roles of TRP in brain function and the application of TRP on the treatment for anxiety-related behavior.The depletion of systemic TRP is an important tool to study the effects of reduced 5-HT on cognition. We first examined the effects of chronic consumption of a low TRP diet on memory formation in mice. TRP-limited mice showed impaired formation of contextual fear memory that is hippocampus-dependent. In contrast, these mice showed normal hippocampus-dependent spatial memory, as well as in cued fear and conditioned taste aversion memories, which are amygdala-dependent memory processes. Thus, dietary TRP restriction appears to result in selective impairments in hippocampus-dependent contextual fear memory formation in mice.We have shown that limitation of TRP-intake also affect emotional behaviors in mice. To develop the treatment of anxiety-related behavior, we next examined effects of TRP-limitation on anxiety related behavior observed in transgenic mice overexpressing alplaCaMKII in forebrain. TRP-limitation leads to the improvement of anxiety-related behavior in CaMKII transgenic mice, raising the possibility that TRP-limitation is applicable for the treatment of anxiety-related disease. Less