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稳态的能力下降-可能伴随着神经精神疾病患者皮质回路组织和功能的改变。然而，目前尚不清楚皮层回路发育过程中抗氧化防御和活性氧积累（ROS）的减少是否导致了异常回路的形成及其后果。22q11缺失综合征（22q11DS）患者比其他人群更容易患精神疾病；因此，22q11DS已被建议作为研究神经精神疾病的神经发育起源的模型。大约有四分之一的基因位于22q11DS中常见的缺失区域，它们编码的蛋白质定位于线粒体。我建议在22q11DS小鼠模型中描述由于线粒体功能改变而导致的皮质神经元发育能力的变化，并确定这些变化如何影响回路的形成。在22q11线粒体基因中，硫氧还蛋白还原酶（TxnRd2）在皮质回路分化期间表达最多，编码线粒体初级H2O2清除剂。因此，我将研究TxnRd2清除活性的破坏如何影响线粒体抗氧化防御和改变皮层神经元的发育。我将验证一个假设，即在神经元发育后期，由于TxnRd2剂量减少，线粒体抗氧化防御能力下降，破坏了皮层神经元建立最佳连接的能力。为了验证这一假设，将使用可诱导的Cre-recombinase系统（Cux2GFP-Cre）在皮质投射神经元发育过程中特异性地产生一系列TxnRd2突变等位基因。将分析神经元生长、分化和细胞器分布的完整性，以评估皮层神经元参与正常回路发育的能力的变化。在txnrd2缺失的神经元中，ROS代谢将进一步被操纵，从而将抗氧化防御与单个神经元构建回路的能力联系起来。我的研究将定义由于抗氧化防御减弱而导致的线粒体ROS积累对神经元完整性的影响，并将确定锥体神经元分化改变在22q11DS回路形成中的作用。具有基因控制的酶抗氧化防御的同质神经元群体允许在具有相同代谢需求的细胞中比较氧化还原平衡的调节，并分析优化皮质回路发育的神经元能力的改变。我的数据将确立抗氧化防御在单个神经元构建回路能力中的作用，并将深入了解氧化还原失衡在各种行为障碍中异常回路连接中的作用。

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.