The role of TxnRd2 in cortical circuit formation

描述（由申请人提供）：线粒体氧化还原失衡和抗氧化防御能力下降-细胞维持细胞呼吸产生的自由基和酶自由基解毒之间的稳态能力下降-可能伴随神经精神疾病患者皮质回路组织和功能的改变。然而，它是未知的，如果减少抗氧化防御和活性氧簇积累（ROS）在发展过程中的皮层电路有助于异常电路的形成及其后果。22 q11缺失综合征（22 q11 DS）患者比其他人群更易患精神疾病，因此，22 q11 DS已被建议作为研究神经精神疾病的神经发育起源的模型。大约四分之一的基因位于22 q11 DS中通常缺失的区域，编码定位于线粒体的蛋白质。我建议的特点，在发展中的皮层神经元的发育能力的变化，由于改变线粒体功能的小鼠模型中的22 q11 DS，并确定这些变化可能会损害电路的形成。在22 q11线粒体基因，硫氧还蛋白还原酶（TxnRd 2），最大限度地表达在皮层电路分化，编码的主要线粒体过氧化氢清除剂。因此，我将研究如何破坏TxnRd 2清除活性影响线粒体抗氧化防御和改变皮层神经元发育。我将测试的假设，减少线粒体抗氧化剂防御在神经元发育的后期阶段，由于减少剂量的TxnRd 2，破坏皮层神经元建立最佳连接的能力。为了验证这一假设，一个等位基因系列TxnRd 2突变将产生专门在发展皮层投射神经元，使用诱导型Cre重组酶系统（Cux 2GFP-Cre）。将分析神经元生长、分化和细胞器分布的完整性，以评价皮质神经元参与正常回路发育的能力的变化。ROS代谢将在TxnRd 2耗尽的神经元中进一步操纵，以将抗氧化防御与单个神经元构建电路的能力联系起来。我的研究将确定由于抗氧化防御减少对神经元完整性造成的ROS线粒体积累的影响，并将确定改变锥体神经元分化在22 q11 DS回路形成中的作用。具有遗传控制的酶促抗氧化防御的神经元的同质群体允许比较具有相等代谢需求的细胞中的氧化还原平衡的调节，并分析改变的神经元能力用于最佳皮层回路开发。我的数据将确立抗氧化防御在单个神经元构建电路能力中的作用，并将提供对氧化还原失衡在广泛的行为障碍中异常电路连接中的作用的深入了解。

DESCRIPTION (provided by applicant): Mitochondrial redox imbalance and decreased antioxidant defense-a decline in a cell's ability to maintain homeostasis between free radicals generated from cellular respiration and enzymatic free radical detoxification-may accompany altered cortical circuit organization and function in patients with neuropsychiatric disorders. However, it is unknown if decreased antioxidant defense and reactive oxygen species accumulation (ROS) during development of cortical circuits contributes to aberrant circuit formation and its consequences. Patients with 22q11 deletion syndrome (22q11DS) are more susceptible to psychiatric disorders than the rest of the population; therefore, 22q11DS has been suggested as a model for studying the neurodevelopmental origins of neuropsychiatric disorders. About one quarter of the genes located in the commonly deleted region in the 22q11DS encode proteins that localize to mitochondria. I propose to characterize changes in the developmental capacity of cortical neurons that develop due to altered mitochondrial function in mouse models of 22q11DS and determine how these changes could compromise circuit formation. Among 22q11 mitochondrial genes, thioredoxin reductase (TxnRd2), maximally expressed during cortical circuit differentiation, encodes a primary mitochondrial H2O2 scavenger. Thus, I will investigate how disrupted scavenging activity of TxnRd2 impacts mitochondrial antioxidant defense and alters cortical neuron development. I will test the hypothesis that diminished mitochondrial antioxidant defense during late stages of neuronal development, due to diminished dosage of TxnRd2, disrupts the capacity of cortical neurons to establish optimal connections. To test this hypothesis, an allelic series of TxnRd2 mutations will be generated specifically in developing cortical projection neurons, using an inducible Cre-recombinase system (Cux2GFP-Cre). Integrity of neuronal growth, differentiation and organelle distribution will be analyzed to evaluate changes in the capacity of cortical neurons to engage in normal circuit development. ROS metabolism will be further manipulated in TxnRd2-depleted neurons to link antioxidant defense to the capacity of individual neurons to build circuits. My studies will define the effects of mitochondrial accumulation of ROS due to diminished antioxidant defense on neuronal integrity, and will establish the role of altered pyramidal neuron differentiation in the formation of circuits in 22q11DS. A homogenous population of neurons with genetically controlled enzymatic antioxidant defense permit comparison of regulation of redox balance in cells with equal metabolic demand, and analysis of altered neuronal capacity for optimal cortical circuit development. My data will establish a role for antioxidant defense in the capacity of individual neurons to build circuits and will provide insight into the role of redox imbalance in aberrant circuit connectivity in a wide range of behavioral disorders.